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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Mu - edit.mu</title>
<meta name="Generator" content="Vim/7.4">
<meta name="plugin-version" content="vim7.4_v1">
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.muScenario { color: #00af00; }
.Delimiter { color: #a04060; }
.SalientComment { color: #00ffff; }
.Comment { color: #9090ff; }
.Constant { color: #00a0a0; }
.Special { color: #ff6060; }
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<body>
<pre id='vimCodeElement'>
<span class="Comment"># Environment for learning programming using mu.</span>

<span class="muRecipe">recipe</span> main [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  open-console
  initial-recipe:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe new-add [</span>
<span class="Constant">  x:number &lt;- next-ingredient</span>
<span class="Constant">  y:number &lt;- next-ingredient</span>
<span class="Constant">  z:number &lt;- add x:number, y:number</span>
<span class="Constant">  reply z:number</span>
<span class="Constant">]</span>]
  initial-sandbox:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[new-add 2:literal, 3:literal]</span>
  env:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0:literal/screen</span>, initial-recipe:address:array:character, initial-sandbox:address:array:character
  render-all <span class="Constant">0:literal/address</span>, env:address:programming-environment-data
  event-loop <span class="Constant">0:literal/screen</span>, <span class="Constant">0:literal/console</span>, env:address:programming-environment-data
]

container programming-environment-data [
  recipes:address:editor-data
  recipe-warnings:address:array:character
  current-sandbox:address:editor-data
  sandbox:address:sandbox-data
  sandbox-in-focus?:boolean  <span class="Comment"># false =&gt; focus in recipes; true =&gt; focus in current-sandbox</span>
]

<span class="muRecipe">recipe</span> new-programming-environment [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  initial-recipe-contents:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  initial-sandbox-contents:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  width:number<span class="Special"> &lt;- </span>screen-width screen:address
  height:number<span class="Special"> &lt;- </span>screen-height screen:address
  <span class="Comment"># top menu</span>
  result:address:programming-environment-data<span class="Special"> &lt;- </span>new programming-environment-data:type
  draw-horizontal screen:address, <span class="Constant">0:literal</span>, <span class="Constant">0:literal/left</span>, width:number, <span class="Constant">32:literal/space</span>, <span class="Constant">0:literal/black</span>, <span class="Constant">238:literal/grey</span>
  button-start:number<span class="Special"> &lt;- </span>subtract width:number, <span class="Constant">20:literal</span>
  button-on-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal button-start:number, <span class="Constant">0:literal</span>
  assert button-on-screen?:boolean, <span class="Constant">[screen too narrow for menu]</span>
  move-cursor screen:address, <span class="Constant">0:literal/row</span>, button-start:number/column
  run-button:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F10)  ]</span>
  print-string screen:address, run-button:address:array:character, <span class="Constant">255:literal/white</span>, <span class="Constant">161:literal/reddish</span>
  <span class="Comment"># dotted line down the middle</span>
  divider:number, _<span class="Special"> &lt;- </span>divide-with-remainder width:number, <span class="Constant">2:literal</span>
  draw-vertical screen:address, divider:number, <span class="Constant">1:literal/top</span>, height:number, <span class="Constant">9482:literal/vertical-dotted</span>
  <span class="Comment"># recipe editor on the left</span>
  recipes:address:address:editor-data<span class="Special"> &lt;- </span>get-address result:address:programming-environment-data/deref, recipes:offset
  recipes:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor initial-recipe-contents:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, divider:number/right
  <span class="Comment"># sandbox editor on the right</span>
  new-left:number<span class="Special"> &lt;- </span>add divider:number, <span class="Constant">1:literal</span>
  new-right:number<span class="Special"> &lt;- </span>add new-left:number, <span class="Constant">5:literal</span>
  current-sandbox:address:address:editor-data<span class="Special"> &lt;- </span>get-address result:address:programming-environment-data/deref, current-sandbox:offset
  current-sandbox:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor initial-sandbox-contents:address:array:character, screen:address, new-left:number, width:number
  <span class="Comment"># initialize cursor</span>
  update-cursor screen:address, recipes:address:address:editor-data/deref, current-sandbox:address:address:editor-data/deref, <span class="Constant">0:literal/focus-in-recipes</span>
  <span class="muControl">reply</span> result:address:programming-environment-data
]

<span class="muScenario">scenario</span> editor-initially-prints-string-to-screen [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
    new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="SalientComment">## In which we introduce the editor data structure, and show how it displays</span>
<span class="SalientComment">## text to the screen.</span>

container editor-data [
  <span class="Comment"># editable text: doubly linked list of characters (head contains a special sentinel)</span>
  data:address:duplex-list
  <span class="Comment"># location before cursor inside data</span>
  before-cursor:address:duplex-list

  <span class="Comment"># raw bounds of display area on screen</span>
  <span class="Comment"># always displays from row 1 and at most until bottom of screen</span>
  left:number
  right:number
  <span class="Comment"># raw screen coordinates of cursor</span>
  cursor-row:number
  cursor-column:number
]

<span class="Comment"># editor:address, screen:address &lt;- new-editor s:address:array:character, screen:address, left:number, right:number</span>
<span class="Comment"># creates a new editor widget and renders its initial appearance to screen.</span>
<span class="Comment">#   top/left/right constrain the screen area available to the new editor.</span>
<span class="Comment">#   right is exclusive.</span>
<span class="muRecipe">recipe</span> new-editor [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Comment"># no clipping of bounds</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
  result:address:editor-data<span class="Special"> &lt;- </span>new editor-data:type
  <span class="Comment"># initialize screen-related fields</span>
  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, left:offset
  x:address:number/deref<span class="Special"> &lt;- </span>copy left:number
  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, right:offset
  x:address:number/deref<span class="Special"> &lt;- </span>copy right:number
  <span class="Comment"># initialize cursor</span>
  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, cursor-row:offset
  x:address:number/deref<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/top</span>
  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, cursor-column:offset
  x:address:number/deref<span class="Special"> &lt;- </span>copy left:number
  init:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, data:offset
  init:address:address:duplex-list/deref<span class="Special"> &lt;- </span>push-duplex <span class="Constant">167:literal/§</span>, <span class="Constant">0:literal/tail</span>
  y:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, before-cursor:offset
  y:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
  <span class="Comment"># early exit if s is empty</span>
  <span class="muControl">reply-unless</span> s:address:array:character, result:address:editor-data
  len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
  <span class="muControl">reply-unless</span> len:number, result:address:editor-data
  idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
  <span class="Comment"># now we can start appending the rest, character by character</span>
  curr:address:duplex-list<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx:number, len:number
    <span class="muControl">break-if</span> done?:boolean
    c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, idx:number
    insert-duplex c:character, curr:address:duplex-list
    <span class="Comment"># next iter</span>
    curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
    idx:number<span class="Special"> &lt;- </span>add idx:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># initialize cursor to top of screen</span>
  y:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, before-cursor:offset
  y:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
  <span class="Comment"># initial render to screen, just for some old tests</span>
  _, screen:address<span class="Special"> &lt;- </span>render screen:address, result:address:editor-data
  <span class="muControl">reply</span> result:address:editor-data
]

<span class="muScenario">scenario</span> editor-initializes-without-data [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
  run [
    1:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">0:literal/data</span>, screen:address, <span class="Constant">2:literal/left</span>, <span class="Constant">5:literal/right</span>
    2:editor-data<span class="Special"> &lt;- </span>copy 1:address:editor-data/deref
  ]
  memory-should-contain [
    <span class="Comment"># 2 (data) &lt;- just the § sentinel</span>
    <span class="Comment"># 3 (before cursor) &lt;- the § sentinel</span>
    4<span class="Special"> &lt;- </span>2  <span class="Comment"># left</span>
    5<span class="Special"> &lt;- </span>4  <span class="Comment"># right  (inclusive)</span>
    6<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
    7<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor column</span>
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="Comment"># bottom:number, screen:address &lt;- render screen:address, editor:address:editor-data</span>
<span class="muRecipe">recipe</span> render [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="muControl">reply-unless</span> editor:address:editor-data, <span class="Constant">1:literal/top</span>, screen:address/same-as-ingredient:0
  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
  screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
  hide-screen screen:address
  <span class="Comment"># traversing editor</span>
  curr:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
  prev:address:duplex-list<span class="Special"> &lt;- </span>copy curr:address:duplex-list
  curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
  <span class="Comment"># traversing screen</span>
  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/top</span>
  column:number<span class="Special"> &lt;- </span>copy left:number
  cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
  cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
  before-cursor:address:address:duplex-list<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, before-cursor:offset
  move-cursor screen:address, row:number, column:number
  <span class="Delimiter">{</span>
<span class="Constant">    +next-character</span>
    <span class="muControl">break-unless</span> curr:address:duplex-list
    off-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number, screen-height:number
    <span class="muControl">break-if</span> off-screen?:boolean
    <span class="Comment"># update editor-data.before-cursor</span>
    <span class="Comment"># Doing so at the start of each iteration ensures it stays one step behind</span>
    <span class="Comment"># the current character.</span>
    <span class="Delimiter">{</span>
      at-cursor-row?:boolean<span class="Special"> &lt;- </span>equal row:number, cursor-row:address:number/deref
      <span class="muControl">break-unless</span> at-cursor-row?:boolean
      at-cursor?:boolean<span class="Special"> &lt;- </span>equal column:number, cursor-column:address:number/deref
      <span class="muControl">break-unless</span> at-cursor?:boolean
      before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>prev-duplex curr:address:duplex-list
    <span class="Delimiter">}</span>
    c:character<span class="Special"> &lt;- </span>get curr:address:duplex-list/deref, value:offset
    <span class="Delimiter">{</span>
      <span class="Comment"># newline? move to left rather than 0</span>
      newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
      <span class="muControl">break-unless</span> newline?:boolean
      <span class="Comment"># adjust cursor if necessary</span>
      <span class="Delimiter">{</span>
        at-cursor-row?:boolean<span class="Special"> &lt;- </span>equal row:number, cursor-row:address:number/deref
        <span class="muControl">break-unless</span> at-cursor-row?:boolean
        left-of-cursor?:boolean<span class="Special"> &lt;- </span>lesser-than column:number, cursor-column:address:number/deref
        <span class="muControl">break-unless</span> left-of-cursor?:boolean
        cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy column:number
        before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>prev-duplex curr:address:duplex-list
      <span class="Delimiter">}</span>
      <span class="Comment"># clear rest of line in this window</span>
      clear-line-delimited screen:address, column:number, right:number
      <span class="Comment"># skip to next line</span>
      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
      column:number<span class="Special"> &lt;- </span>copy left:number
      move-cursor screen:address, row:number, column:number
      curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
      prev:address:duplex-list<span class="Special"> &lt;- </span>next-duplex prev:address:duplex-list
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
    <span class="Delimiter">}</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
      <span class="Comment"># room for clicking on the cursor after it.</span>
      at-right?:boolean<span class="Special"> &lt;- </span>equal column:number, right:number
      <span class="muControl">break-unless</span> at-right?:boolean
      <span class="Comment"># print wrap icon</span>
      print-character screen:address, <span class="Constant">8617:literal/loop-back-to-left</span>, <span class="Constant">245:literal/grey</span>
      column:number<span class="Special"> &lt;- </span>copy left:number
      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
      move-cursor screen:address, row:number, column:number
      <span class="Comment"># don't increment curr</span>
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
    <span class="Delimiter">}</span>
    print-character screen:address, c:character
    curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
    prev:address:duplex-list<span class="Special"> &lt;- </span>next-duplex prev:address:duplex-list
    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># is cursor to the right of the last line? move to end</span>
  <span class="Delimiter">{</span>
    at-cursor-row?:boolean<span class="Special"> &lt;- </span>equal row:number, cursor-row:address:number/deref
    cursor-outside-line?:boolean<span class="Special"> &lt;- </span>lesser-or-equal column:number, cursor-column:address:number/deref
    before-cursor-on-same-line?:boolean<span class="Special"> &lt;- </span>and at-cursor-row?:boolean, cursor-outside-line?:boolean
    above-cursor-row?:boolean<span class="Special"> &lt;- </span>lesser-than row:number, cursor-row:address:number/deref
    before-cursor?:boolean<span class="Special"> &lt;- </span>or before-cursor-on-same-line?:boolean, above-cursor-row?:boolean
    <span class="muControl">break-unless</span> before-cursor?:boolean
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>copy row:number
    cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy column:number
    <span class="Comment"># line not wrapped but cursor outside bounds? wrap cursor</span>
    <span class="Delimiter">{</span>
      too-far-right?:boolean<span class="Special"> &lt;- </span>greater-than cursor-column:address:number/deref, right:number
      <span class="muControl">break-unless</span> too-far-right?:boolean
      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
      cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
      above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
      assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: wrapping cursor past bottom of screen]</span>
    <span class="Delimiter">}</span>
    before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy prev:address:duplex-list
  <span class="Delimiter">}</span>
  <span class="Comment"># clear rest of current line</span>
  clear-line-delimited screen:address, column:number, right:number
  <span class="muControl">reply</span> row:number, screen:address/same-as-ingredient:0
]

<span class="Comment"># row:number, screen:address &lt;- render-string screen:address, s:address:array:character, left:number, right:number, color:number, row:number</span>
<span class="Comment"># print a string 's' to 'editor' in 'color' starting at 'row'</span>
<span class="Comment"># leave cursor at start of next line</span>
<span class="muRecipe">recipe</span> render-string [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
  <span class="muControl">reply-unless</span> s:address:array:character, row:number/same-as-ingredient:5, screen:address/same-as-ingredient:0
  column:number<span class="Special"> &lt;- </span>copy left:number
  move-cursor screen:address, row:number, column:number
  screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
  len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
  <span class="Delimiter">{</span>
<span class="Constant">    +next-character</span>
    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i:number, len:number
    <span class="muControl">break-if</span> done?:boolean
    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number, screen-height:number
    <span class="muControl">break-if</span> done?:boolean
    c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, i:number
    <span class="Delimiter">{</span>
      <span class="Comment"># at right? wrap.</span>
      at-right?:boolean<span class="Special"> &lt;- </span>equal column:number, right:number
      <span class="muControl">break-unless</span> at-right?:boolean
      <span class="Comment"># print wrap icon</span>
      print-character screen:address, <span class="Constant">8617:literal/loop-back-to-left</span>, <span class="Constant">245:literal/grey</span>
      column:number<span class="Special"> &lt;- </span>copy left:number
      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
      move-cursor screen:address, row:number, column:number
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>  <span class="Comment"># retry i</span>
    <span class="Delimiter">}</span>
    i:number<span class="Special"> &lt;- </span>add i:number, <span class="Constant">1:literal</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># newline? move to left rather than 0</span>
      newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
      <span class="muControl">break-unless</span> newline?:boolean
      <span class="Comment"># clear rest of line in this window</span>
      <span class="Delimiter">{</span>
        done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
        <span class="muControl">break-if</span> done?:boolean
        print-character screen:address, <span class="Constant">32:literal/space</span>
        column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
        <span class="muControl">loop</span>
      <span class="Delimiter">}</span>
      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
      column:number<span class="Special"> &lt;- </span>copy left:number
      move-cursor screen:address, row:number, column:number
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
    <span class="Delimiter">}</span>
    print-character screen:address, c:character, color:number
    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># clear rest of current line</span>
    line-done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
    <span class="muControl">break-if</span> line-done?:boolean
    print-character screen:address, <span class="Constant">32:literal/space</span>
    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> row:number/same-as-ingredient:5, screen:address/same-as-ingredient:0
]

<span class="muRecipe">recipe</span> clear-line-delimited [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  column:number<span class="Special"> &lt;- </span>copy left:number
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
    <span class="muControl">break-if</span> done?:boolean
    print-character screen:address, <span class="Constant">32:literal/space</span>
    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muScenario">scenario</span> editor-initially-prints-multiple-lines [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .abc  .</span>
   <span class="Constant"> .def  .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-initially-handles-offsets [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
    new-editor s:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> . abc .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-initially-prints-multiple-lines-at-offset [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
    new-editor s:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> . abc .</span>
   <span class="Constant"> . def .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-initially-wraps-long-lines [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def]</span>
    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .abc ↩.</span>
   <span class="Constant"> .def  .</span>
   <span class="Constant"> .     .</span>
  ]
  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span> [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .    ↩.</span>
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-initially-wraps-barely-long-lines [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  ]
  <span class="Comment"># still wrap, even though the line would fit. We need room to click on the</span>
  <span class="Comment"># end of the line</span>
  screen-should-contain [
   <span class="Constant"> .     .</span>
<span class="Constant">    .abcd↩.</span>
   <span class="Constant"> .e    .</span>
   <span class="Constant"> .     .</span>
  ]
  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span> [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .    ↩.</span>
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-initializes-empty-text [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  run [
    1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
    2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor column</span>
  ]
]

<span class="SalientComment">## handling events from the keyboard, mouse, touch screen, ...</span>

<span class="muRecipe">recipe</span> event-loop [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
  sandbox-in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, sandbox-in-focus?:offset
  <span class="Delimiter">{</span>
    <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
<span class="Constant">    +next-event</span>
    e:event, console:address, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console:address
    <span class="muControl">loop-unless</span> found?:boolean
    <span class="muControl">break-if</span> quit?:boolean  <span class="Comment"># only in tests</span>
    trace <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
    <span class="Comment"># check for global events that will trigger regardless of which editor has focus</span>
    <span class="Delimiter">{</span>
      k:address:number<span class="Special"> &lt;- </span>maybe-convert e:event, keycode:variant
      <span class="muControl">break-unless</span> k:address:number
      <span class="Comment"># F10? load all code and run all sandboxes.</span>
      <span class="Delimiter">{</span>
        do-run?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65526:literal/F10</span>
        <span class="muControl">break-unless</span> do-run?:boolean
        run-sandboxes env:address:programming-environment-data
        <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
      <span class="Delimiter">}</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># 'touch' event - send to both editors</span>
    <span class="Delimiter">{</span>
      t:address:touch-event<span class="Special"> &lt;- </span>maybe-convert e:event, touch:variant
      <span class="muControl">break-unless</span> t:address:touch-event
      _<span class="Special"> &lt;- </span>move-cursor-in-editor screen:address, recipes:address:editor-data, t:address:touch-event/deref
      sandbox-in-focus?:address:boolean/deref<span class="Special"> &lt;- </span>move-cursor-in-editor screen:address, current-sandbox:address:editor-data, t:address:touch-event/deref
      <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># if it's not global, send to appropriate editor</span>
    <span class="Delimiter">{</span>
      <span class="Delimiter">{</span>
        <span class="muControl">break-if</span> sandbox-in-focus?:address:boolean/deref
        handle-event screen:address, console:address, recipes:address:editor-data, e:event
      <span class="Delimiter">}</span>
      <span class="Delimiter">{</span>
        <span class="muControl">break-unless</span> sandbox-in-focus?:address:boolean/deref
        handle-event screen:address, console:address, current-sandbox:address:editor-data, e:event
      <span class="Delimiter">}</span>
    <span class="Delimiter">}</span>
<span class="Constant">    +continue</span>
    <span class="Comment"># if no more events currently left to process, render</span>
    <span class="Comment"># todo: test this</span>
    <span class="Delimiter">{</span>
      more-events?:boolean<span class="Special"> &lt;- </span>has-more-events? console:address
      <span class="muControl">break-if</span> more-events?:boolean
      render-all screen:address, env:address:programming-environment-data
    <span class="Delimiter">}</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="Comment"># helper for testing a single editor</span>
<span class="muRecipe">recipe</span> editor-event-loop [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
<span class="Constant">    +next-event</span>
    e:event, console:address, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console:address
    <span class="muControl">loop-unless</span> found?:boolean
    <span class="muControl">break-if</span> quit?:boolean  <span class="Comment"># only in tests</span>
    trace <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
    <span class="Comment"># 'touch' event - send to both editors</span>
    <span class="Delimiter">{</span>
      t:address:touch-event<span class="Special"> &lt;- </span>maybe-convert e:event, touch:variant
      <span class="muControl">break-unless</span> t:address:touch-event
      move-cursor-in-editor screen:address, editor:address:editor-data, t:address:touch-event/deref
      <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># other events - send to appropriate editor</span>
    handle-event screen:address, console:address, editor:address:editor-data, e:event
<span class="Constant">    +continue</span>
    row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, editor:address:editor-data
    <span class="Comment"># clear next line, in case we just processed a backspace</span>
    left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
    right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
    row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
    move-cursor screen:address, row:number, left:number
    clear-line-delimited screen:address, left:number, right:number
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">recipe</span> handle-event [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">50:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  e:event<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="muControl">reply-unless</span> editor:address:editor-data
  <span class="Comment"># typing a character</span>
  <span class="Delimiter">{</span>
    c:address:character<span class="Special"> &lt;- </span>maybe-convert e:event, text:variant
    <span class="muControl">break-unless</span> c:address:character
    <span class="Comment"># unless it's a backspace</span>
    <span class="Delimiter">{</span>
      backspace?:boolean<span class="Special"> &lt;- </span>equal c:address:character/deref, <span class="Constant">8:literal/backspace</span>
      <span class="muControl">break-unless</span> backspace?:boolean
      delete-before-cursor editor:address:editor-data
      <span class="muControl">reply</span>
    <span class="Delimiter">}</span>
    insert-at-cursor editor:address:editor-data, c:address:character/deref, screen:address
    <span class="muControl">reply</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># otherwise it's a special key to control the editor</span>
  k:address:number<span class="Special"> &lt;- </span>maybe-convert e:event, keycode:variant
  assert k:address:number, <span class="Constant">[event was of unknown type; neither keyboard nor mouse]</span>
  d:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
  before-cursor:address:address:duplex-list<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, before-cursor:offset
  cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
  cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
  screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
  <span class="Comment"># arrows; update cursor-row and cursor-column, leave before-cursor to 'render'.</span>
  <span class="Comment"># right arrow</span>
  <span class="Delimiter">{</span>
    move-to-next-character?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65514:literal/right-arrow</span>
    <span class="muControl">break-unless</span> move-to-next-character?:boolean
    <span class="Comment"># if not at end of text</span>
    old-cursor:address:duplex-list<span class="Special"> &lt;- </span>next-duplex before-cursor:address:address:duplex-list/deref
    <span class="muControl">break-unless</span> old-cursor:address:duplex-list
    <span class="Comment"># scan to next character</span>
    before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy old-cursor:address:duplex-list
    <span class="Comment"># if crossed a newline, move cursor to start of next row</span>
    <span class="Delimiter">{</span>
      old-cursor-character:character<span class="Special"> &lt;- </span>get before-cursor:address:address:duplex-list/deref/deref, value:offset
      was-at-newline?:boolean<span class="Special"> &lt;- </span>equal old-cursor-character:character, <span class="Constant">10:literal/newline</span>
      <span class="muControl">break-unless</span> was-at-newline?:boolean
      cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
      <span class="Comment"># todo: what happens when cursor is too far down?</span>
      screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
      above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
      assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: moving past bottom of screen]</span>
      <span class="muControl">reply</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># if the line wraps, move cursor to start of next row</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># if we're at the column just before the wrap indicator</span>
      wrap-column:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
      at-wrap?:boolean<span class="Special"> &lt;- </span>equal cursor-column:address:number/deref, wrap-column:number
      <span class="muControl">break-unless</span> at-wrap?:boolean
      <span class="Comment"># and if next character isn't newline</span>
      new-cursor:address:duplex-list<span class="Special"> &lt;- </span>next-duplex old-cursor:address:duplex-list
      <span class="muControl">break-unless</span> new-cursor:address:duplex-list
      next-character:character<span class="Special"> &lt;- </span>get new-cursor:address:duplex-list/deref, value:offset
      newline?:boolean<span class="Special"> &lt;- </span>equal next-character:character, <span class="Constant">10:literal/newline</span>
      <span class="muControl">break-if</span> newline?:boolean
      cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
      <span class="Comment"># todo: what happens when cursor is too far down?</span>
      above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
      assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: moving past bottom of screen]</span>
      <span class="muControl">reply</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># otherwise move cursor one character right</span>
    cursor-column:address:number/deref<span class="Special"> &lt;- </span>add cursor-column:address:number/deref, <span class="Constant">1:literal</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># left arrow</span>
  <span class="Delimiter">{</span>
    move-to-previous-character?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65515:literal/left-arrow</span>
    <span class="muControl">break-unless</span> move-to-previous-character?:boolean
<span class="CommentedCode">#?     trace [app], [left arrow] #? 1</span>
    <span class="Comment"># if not at start of text (before-cursor at § sentinel)</span>
    prev:address:duplex-list<span class="Special"> &lt;- </span>prev-duplex before-cursor:address:address:duplex-list/deref
    <span class="muControl">break-unless</span> prev:address:duplex-list
    <span class="Comment"># if cursor not at left margin, move one character left</span>
    <span class="Delimiter">{</span>
      at-left-margin?:boolean<span class="Special"> &lt;- </span>equal cursor-column:address:number/deref, <span class="Constant">0:literal</span>
      <span class="muControl">break-if</span> at-left-margin?:boolean
<span class="CommentedCode">#?       trace [app], [decrementing] #? 1</span>
      cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-column:address:number/deref, <span class="Constant">1:literal</span>
      <span class="muControl">reply</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># if at left margin, there's guaranteed to be a previous line, since we're</span>
    <span class="Comment"># not at start of text</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># if before-cursor is at newline, figure out how long the previous line is</span>
      prevc:character<span class="Special"> &lt;- </span>get before-cursor:address:address:duplex-list/deref/deref, value:offset
      previous-character-is-newline?:boolean<span class="Special"> &lt;- </span>equal prevc:character, <span class="Constant">10:literal/newline</span>
      <span class="muControl">break-unless</span> previous-character-is-newline?:boolean
<span class="CommentedCode">#?       trace [app], [previous line] #? 1</span>
      <span class="Comment"># compute length of previous line</span>
      end-of-line:number<span class="Special"> &lt;- </span>previous-line-length before-cursor:address:address:duplex-list/deref, d:address:duplex-list
      cursor-row:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-row:address:number/deref, <span class="Constant">1:literal</span>
      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy end-of-line:number
      <span class="muControl">reply</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># if before-cursor is not at newline, we're just at a wrapped line</span>
    assert cursor-row:address:number/deref, <span class="Constant">[unimplemented: moving cursor above top of screen]</span>
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-row:address:number/deref, <span class="Constant">1:literal</span>
    cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>  <span class="Comment"># leave room for wrap icon</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># down arrow</span>
  <span class="Delimiter">{</span>
    move-to-next-line?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65516:literal/down-arrow</span>
    <span class="muControl">break-unless</span> move-to-next-line?:boolean
    <span class="Comment"># todo: support scrolling</span>
    already-at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal cursor-row:address:number/deref, screen-height:number
    <span class="muControl">break-if</span> already-at-bottom?:boolean
<span class="CommentedCode">#?     $print [moving down</span>
<span class="CommentedCode">#? ] #? 1</span>
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
    <span class="Comment"># that's it; render will adjust cursor-column as necessary</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># up arrow</span>
  <span class="Delimiter">{</span>
    move-to-previous-line?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65517:literal/up-arrow</span>
    <span class="muControl">break-unless</span> move-to-previous-line?:boolean
    <span class="Comment"># todo: support scrolling</span>
    already-at-top?:boolean<span class="Special"> &lt;- </span>lesser-or-equal cursor-row:address:number/deref, <span class="Constant">1:literal/top</span>
    <span class="muControl">break-if</span> already-at-top?:boolean
<span class="CommentedCode">#?     $print [moving up</span>
<span class="CommentedCode">#? ] #? 1</span>
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-row:address:number/deref, <span class="Constant">1:literal</span>
    <span class="Comment"># that's it; render will adjust cursor-column as necessary</span>
  <span class="Delimiter">}</span>
]

<span class="Comment"># process click, return if it was on current editor</span>
<span class="Comment"># todo: ignores menu bar (for now just displays shortcuts)</span>
<span class="muRecipe">recipe</span> move-cursor-in-editor [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  t:touch-event<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="muControl">reply-unless</span> editor:address:editor-data, <span class="Constant">0:literal/false</span>
  click-column:number<span class="Special"> &lt;- </span>get t:touch-event, column:offset
  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
  too-far-left?:boolean<span class="Special"> &lt;- </span>lesser-than click-column:number, left:number
  <span class="muControl">reply-if</span> too-far-left?:boolean, <span class="Constant">0:literal/false</span>
  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
  too-far-right?:boolean<span class="Special"> &lt;- </span>greater-than click-column:number, right:number
  <span class="muControl">reply-if</span> too-far-right?:boolean, <span class="Constant">0:literal/false</span>
  <span class="Comment"># update cursor</span>
  cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
  cursor-row:address:number/deref<span class="Special"> &lt;- </span>get t:touch-event, row:offset
  cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
  cursor-column:address:number/deref<span class="Special"> &lt;- </span>get t:touch-event, column:offset
  render screen:address, editor:address:editor-data
  <span class="Comment"># gain focus</span>
  <span class="muControl">reply</span> <span class="Constant">1:literal/true</span>
]

<span class="muRecipe">recipe</span> insert-at-cursor [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  c:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
<span class="CommentedCode">#?   $print [insert ], c:character, [ </span>
<span class="CommentedCode">#? ] #? 1</span>
  before-cursor:address:address:duplex-list<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, before-cursor:offset
  d:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
  insert-duplex c:character, before-cursor:address:address:duplex-list/deref
  before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>next-duplex before-cursor:address:address:duplex-list/deref
  cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
  cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
  <span class="Comment"># update cursor: if newline, move cursor to start of next line</span>
  <span class="Comment"># todo: bottom of screen</span>
  <span class="Delimiter">{</span>
    newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
    <span class="muControl">break-unless</span> newline?:boolean
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
    cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
    <span class="muControl">reply</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># if the line wraps at the cursor, move cursor to start of next row</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># if we're at the column just before the wrap indicator</span>
    wrap-column:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
<span class="CommentedCode">#?     $print [wrap? ], cursor-column:address:number/deref, [ vs ], wrap-column:number, [ </span>
<span class="CommentedCode">#? ] #? 1</span>
    at-wrap?:boolean<span class="Special"> &lt;- </span>greater-or-equal cursor-column:address:number/deref, wrap-column:number
    <span class="muControl">break-unless</span> at-wrap?:boolean
<span class="CommentedCode">#?     $print [wrap!</span>
<span class="CommentedCode">#? ] #? 1</span>
    cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-column:address:number/deref, wrap-column:number
    cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
    <span class="Comment"># todo: what happens when cursor is too far down?</span>
    screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
    above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
    assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: typing past bottom of screen]</span>
<span class="CommentedCode">#?     $print [return</span>
<span class="CommentedCode">#? ] #? 1</span>
    <span class="muControl">reply</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># otherwise move cursor right</span>
  cursor-column:address:number/deref<span class="Special"> &lt;- </span>add cursor-column:address:number/deref, <span class="Constant">1:literal</span>
]

<span class="muRecipe">recipe</span> delete-before-cursor [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  before-cursor:address:address:duplex-list<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, before-cursor:offset
  d:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
  <span class="Comment"># unless already at start</span>
  at-start?:boolean<span class="Special"> &lt;- </span>equal before-cursor:address:address:duplex-list/deref, d:address:duplex-list
  <span class="muControl">reply-if</span> at-start?:boolean
  <span class="Comment"># delete character</span>
  prev:address:duplex-list<span class="Special"> &lt;- </span>prev-duplex before-cursor:address:address:duplex-list/deref
  remove-duplex before-cursor:address:address:duplex-list/deref
  <span class="Comment"># update cursor</span>
  before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy prev:address:duplex-list
  cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
  cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-column:address:number/deref, <span class="Constant">1:literal</span>
<span class="CommentedCode">#?   $print [delete-before-cursor: ], cursor-column:address:number/deref, [ </span>
<span class="CommentedCode">#? ] #? 1</span>
]

<span class="Comment"># takes a pointer 'curr' into the doubly-linked list and its sentinel, counts</span>
<span class="Comment"># the length of the previous line before the 'curr' pointer.</span>
<span class="muRecipe">recipe</span> previous-line-length [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  curr:address:duplex-list<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  start:address:duplex-list<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  result:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
  <span class="muControl">reply-unless</span> curr:address:duplex-list, result:number
  at-start?:boolean<span class="Special"> &lt;- </span>equal curr:address:duplex-list, start:address:duplex-list
  <span class="muControl">reply-if</span> at-start?:boolean, result:number
  <span class="Delimiter">{</span>
    curr:address:duplex-list<span class="Special"> &lt;- </span>prev-duplex curr:address:duplex-list
    <span class="muControl">break-unless</span> curr:address:duplex-list
    at-start?:boolean<span class="Special"> &lt;- </span>equal curr:address:duplex-list, start:address:duplex-list
    <span class="muControl">break-if</span> at-start?:boolean
    c:character<span class="Special"> &lt;- </span>get curr:address:duplex-list/deref, value:offset
    at-newline?:boolean<span class="Special"> &lt;- </span>equal c:character <span class="Constant">10:literal/newline</span>
    <span class="muControl">break-if</span> at-newline?:boolean
    result:number<span class="Special"> &lt;- </span>add result:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> result:number
]

<span class="muRecipe">recipe</span> render-all [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
  sandbox-in-focus?:boolean<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox-in-focus?:offset
  <span class="Comment"># render recipes, along with any warnings</span>
  left:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, left:offset
  right:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, right:offset
  row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, recipes:address:editor-data
  recipe-warnings:address:array:character<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipe-warnings:offset
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> recipe-warnings:address:array:character
    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, recipe-warnings:address:array:character, left:number, right:number, <span class="Constant">1:literal/red</span>, row:number
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># no warnings? move to next lin</span>
    <span class="muControl">break-if</span> recipe-warnings:address:array:character
    row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># draw dotted line after recipes</span>
  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9480:literal/horizontal-dotted</span>
  <span class="Comment"># clear next line, in case we just processed a backspace</span>
  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
  move-cursor screen:address, row:number, left:number
  clear-line-delimited screen:address, left:number, right:number
  <span class="Comment"># render sandboxes along with warnings for each</span>
  left:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, left:offset
  right:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, right:offset
  row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, current-sandbox:address:editor-data
  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9473:literal/horizontal-double</span>
  sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox:offset
  row:number, screen:address<span class="Special"> &lt;- </span>render-sandboxes screen:address, sandbox:address:sandbox-data, left:number, right:number, row:number
  <span class="Comment"># clear next line, in case we just processed a backspace</span>
  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
  move-cursor screen:address, row:number, left:number
  clear-line-delimited screen:address, left:number, right:number
  update-cursor screen:address, recipes:address:editor-data, current-sandbox:address:editor-data, sandbox-in-focus?:boolean
  show-screen screen:address
  <span class="muControl">reply</span> screen:address/same-as-ingredient:0
]

<span class="muRecipe">recipe</span> render-sandboxes [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  sandbox:address:sandbox-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="muControl">reply-unless</span> sandbox:address:sandbox-data, row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
  screen-height:number<span class="Special"> &lt;- </span>screen-width screen:address
  at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number screen-height:number
  <span class="muControl">reply-if</span> at-bottom?:boolean, row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
  <span class="Comment"># render sandbox contents</span>
  sandbox-data:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, data:offset
  row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-data:address:array:character, left:number, right:number, <span class="Constant">7:literal/white</span>, row:number
  <span class="Comment"># render sandbox warnings or response, in that order</span>
  sandbox-response:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, response:offset
  sandbox-warnings:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, warnings:offset
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> sandbox-warnings:address:array:character
    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-warnings:address:array:character, left:number, right:number, <span class="Constant">1:literal/red</span>, row:number
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> sandbox-warnings:address:array:character
    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-response:address:array:character, left:number, right:number, <span class="Constant">245:literal/grey</span>, row:number
  <span class="Delimiter">}</span>
  <span class="Comment"># draw solid line after sandbox</span>
  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9473:literal/horizontal-double</span>
  <span class="Comment"># draw next sandbox</span>
  next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, next-sandbox:offset
  row:number, screen:address<span class="Special"> &lt;- </span>render-sandboxes screen:address, next-sandbox:address:sandbox-data, left:number, right:number, row:number
  <span class="muControl">reply</span> row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
]

<span class="muRecipe">recipe</span> update-cursor [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  recipes:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  current-sandbox:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  sandbox-in-focus?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> sandbox-in-focus?:boolean
<span class="CommentedCode">#?     $print [recipes in focus</span>
<span class="CommentedCode">#? ] #? 1</span>
    cursor-row:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, cursor-row:offset
    cursor-column:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, cursor-column:offset
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> sandbox-in-focus?:boolean
<span class="CommentedCode">#?     $print [sandboxes in focus</span>
<span class="CommentedCode">#? ] #? 1</span>
    cursor-row:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, cursor-row:offset
    cursor-column:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, cursor-column:offset
  <span class="Delimiter">}</span>
  move-cursor screen:address, cursor-row:number, cursor-column:number
]

<span class="muScenario">scenario</span> editor-handles-empty-event-queue [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console <span class="Constant">[]</span>
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-mouse-clicks [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 1  <span class="Comment"># on the 'b'</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor is at row 0..</span>
    4<span class="Special"> &lt;- </span>1  <span class="Comment"># ..and column 1</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 7  <span class="Comment"># last line, to the right of text</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 7  <span class="Comment"># interior line, to the right of text</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text-3 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 3, 7  <span class="Comment"># below text</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-column [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  <span class="Comment"># editor occupies only left half of screen</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    <span class="Comment"># click on right half of screen</span>
    left-click 3, 8
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># no change to cursor row</span>
    4<span class="Special"> &lt;- </span>0  <span class="Comment"># ..or column</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-into-empty-editor [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    type <span class="Constant">[abc]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    type <span class="Constant">[0]</span>
    left-click 1, 2
    type <span class="Constant">[d]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .0adbc     .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 5  <span class="Comment"># right of last line</span>
    type <span class="Constant">[d]</span>  <span class="Comment"># should append</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-3 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 3, 5  <span class="Comment"># below all text</span>
    type <span class="Constant">[d]</span>  <span class="Comment"># should append</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-4 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 3, 5  <span class="Comment"># below all text</span>
    type <span class="Constant">[e]</span>  <span class="Comment"># should append</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .de        .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-5 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 3, 5  <span class="Comment"># below all text</span>
    type <span class="Constant">[ef]</span>  <span class="Comment"># should append multiple characters in order</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .def       .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-wraps-line-on-insert [
  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  <span class="Comment"># type a letter</span>
  assume-console [
    type <span class="Constant">[e]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  <span class="Comment"># no wrap yet</span>
  screen-should-contain [
   <span class="Constant"> .     .</span>
   <span class="Constant"> .eabc .</span>
   <span class="Constant"> .     .</span>
   <span class="Constant"> .     .</span>
  ]
  <span class="Comment"># type a second letter</span>
  assume-console [
    type <span class="Constant">[f]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  <span class="Comment"># now wrap</span>
  screen-should-contain [
   <span class="Constant"> .     .</span>
<span class="Constant">    .efab↩.</span>
   <span class="Constant"> .c    .</span>
   <span class="Constant"> .     .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-after-inserting-characters [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    type <span class="Constant">[01]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .01ab      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    left-click 1, 4  <span class="Comment"># line is full; no wrap icon yet</span>
    type <span class="Constant">[f]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd↩     .</span>
   <span class="Constant"> .fe        .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor column</span>
  ]
]

<span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    left-click 1, 3  <span class="Comment"># right before the wrap icon</span>
    type <span class="Constant">[f]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcf↩     .</span>
   <span class="Constant"> .de        .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
    4<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor column</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    type <span class="Constant">[0</span>
<span class="Constant">1]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .0         .</span>
   <span class="Constant"> .1abc      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    type <span class="Constant">[0</span>
<span class="Constant">1]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> . 0        .</span>
   <span class="Constant"> . 1abc     .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-clears-previous-line-completely-after-inserting-newline [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  <span class="Comment"># press just a 'newline'</span>
  assume-console [
    type [
]
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd↩     .</span>
   <span class="Constant"> .e         .</span>
   <span class="Constant"> .          .</span>
   <span class="Constant"> .          .</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  <span class="Comment"># line should be fully cleared</span>
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd↩     .</span>
   <span class="Constant"> .e         .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-handles-backspace-key [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 1
    type <span class="Constant">[«]</span>
  ]
  3:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
  replace-in-console <span class="Constant">171:literal/«</span>, 3:event/backspace
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    5:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .bc        .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    4<span class="Special"> &lt;- </span>1
    5<span class="Special"> &lt;- </span>0
  ]
]

<span class="muScenario">scenario</span> editor-clears-last-line-on-backspace [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># just one character in final line</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
<span class="Constant">cd]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    left-click 2, 0  <span class="Comment"># cursor at only character in final line</span>
    type <span class="Constant">[«]</span>
  ]
  3:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
  replace-in-console <span class="Constant">171:literal/«</span>, 3:event/backspace
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-right-with-key [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    press 65514  <span class="Comment"># right arrow</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .a0bc      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow - next line</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .0d        .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow</span>
    press 65514  <span class="Comment"># right arrow - next line</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> . abc      .</span>
   <span class="Constant"> . 0d       .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  assume-console [
    left-click 1, 3
    press 65514  <span class="Comment"># right arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd↩     .</span>
   <span class="Constant"> .ef        .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>0
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># line just barely wrapping</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  <span class="Comment"># position cursor at last character before wrap and hit right-arrow</span>
  assume-console [
    left-click 1, 3
    press 65514  <span class="Comment"># right arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>0
  ]
  <span class="Comment"># now hit right arrow again</span>
  assume-console [
    press 65514
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>1
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-3 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">6:literal/right</span>
  assume-console [
    left-click 1, 4
    press 65514  <span class="Comment"># right arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> . abcd↩    .</span>
   <span class="Constant"> . ef       .</span>
   <span class="Constant"> .          .</span>
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>1
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow-at-end-of-line [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 3
    press 65514  <span class="Comment"># right arrow - next line</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .0d        .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-left-with-key [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 2
    press 65515  <span class="Comment"># left arrow</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .a0bc      .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize editor with two lines</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">d]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  <span class="Comment"># position cursor at start of second line (so there's no previous newline)</span>
  assume-console [
    left-click 2, 0
    press 65515  <span class="Comment"># left arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1
    4<span class="Special"> &lt;- </span>3
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-2 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize editor with three lines</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def</span>
<span class="Constant">g]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  <span class="Comment"># position cursor further down (so there's a newline before the character at</span>
  <span class="Comment"># the cursor)</span>
  assume-console [
    left-click 3, 0
    press 65515  <span class="Comment"># left arrow</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .def0      .</span>
   <span class="Constant"> .g         .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-3 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def</span>
<span class="Constant">g]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  <span class="Comment"># position cursor at start of text</span>
  assume-console [
    left-click 1, 0
    press 65515  <span class="Comment"># left arrow should have no effect</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .0abc      .</span>
   <span class="Constant"> .def       .</span>
   <span class="Constant"> .g         .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-4 [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize editor with text containing an empty line</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>

d]
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  <span class="Comment"># position cursor right after empty line</span>
  assume-console [
    left-click 3, 0
    press 65515  <span class="Comment"># left arrow</span>
    type <span class="Constant">[0]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
  ]
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abc       .</span>
   <span class="Constant"> .0         .</span>
   <span class="Constant"> .d         .</span>
   <span class="Constant"> .          .</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-across-screen-lines-across-wrap-with-left-arrow [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize editor with text containing an empty line</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
  screen-should-contain [
   <span class="Constant"> .          .</span>
   <span class="Constant"> .abcd↩     .</span>
   <span class="Constant"> .ef        .</span>
   <span class="Constant"> .          .</span>
  ]
  <span class="Comment"># position cursor right after empty line</span>
  assume-console [
    left-click 2, 0
    press 65515  <span class="Comment"># left arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1  <span class="Comment"># previous row</span>
    4<span class="Special"> &lt;- </span>3  <span class="Comment"># end of wrapped line</span>
  ]
]

<span class="muScenario">scenario</span> editor-moves-to-previous-line-with-up-arrow [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 2, 1
    press 65517  <span class="Comment"># up arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1
    4<span class="Special"> &lt;- </span>1
  ]
]

<span class="muScenario">scenario</span> editor-moves-to-next-line-with-down-arrow [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">def]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  <span class="Comment"># cursor starts out at (1, 0)</span>
  assume-console [
    press 65516  <span class="Comment"># down arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  <span class="Comment"># ..and ends at (2, 0)</span>
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>0
  ]
]

<span class="muScenario">scenario</span> editor-adjusts-column-at-previous-line [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
<span class="Constant">def]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 2, 3
    press 65517  <span class="Comment"># up arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>1
    4<span class="Special"> &lt;- </span>2
  ]
]

<span class="muScenario">scenario</span> editor-adjusts-column-at-next-line [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
<span class="Constant">de]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 3
    press 65516  <span class="Comment"># down arrow</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    3<span class="Special"> &lt;- </span>2
    4<span class="Special"> &lt;- </span>2
  ]
]

<span class="muScenario">scenario</span> point-at-multiple-editors [
  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize both halves of screen</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  <span class="Comment"># focus on both sides</span>
  assume-console [
    left-click 1, 1
    left-click 1, 17
  ]
  <span class="Comment"># check cursor column in each</span>
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
    4:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, recipes:offset
    5:number<span class="Special"> &lt;- </span>get 4:address:editor-data/deref, cursor-column:offset
    6:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, current-sandbox:offset
    7:number<span class="Special"> &lt;- </span>get 6:address:editor-data/deref, cursor-column:offset
  ]
  memory-should-contain [
    5<span class="Special"> &lt;- </span>1
    7<span class="Special"> &lt;- </span>17
  ]
]

<span class="muScenario">scenario</span> edit-multiple-editors [
  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
  <span class="Comment"># initialize both halves of screen</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  <span class="Comment"># type one letter in each of them</span>
  assume-console [
    left-click 1, 1
    type <span class="Constant">[0]</span>
    left-click 1, 17
    type <span class="Constant">[1]</span>
  ]
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
    4:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, recipes:offset
    5:number<span class="Special"> &lt;- </span>get 4:address:editor-data/deref, cursor-column:offset
    6:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, current-sandbox:offset
    7:number<span class="Special"> &lt;- </span>get 6:address:editor-data/deref, cursor-column:offset
  ]
  screen-should-contain [
   <span class="Constant"> .           run (F10)          .  # this line has a different background, but we don't test that yet</span>
   <span class="Constant"> .a0bc           ┊d1ef          .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .               ┊              .</span>
  ]
  memory-should-contain [
    5<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor column of recipe editor</span>
    7<span class="Special"> &lt;- </span>18  <span class="Comment"># cursor column of sandbox editor</span>
  ]
  <span class="Comment"># show the cursor at the right window</span>
  run [
    screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
  ]
  screen-should-contain [
   <span class="Constant"> .           run (F10)          .</span>
   <span class="Constant"> .a0bc           ┊d1␣f          .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .               ┊              .</span>
  ]
]

<span class="muScenario">scenario</span> multiple-editors-cover-only-their-own-areas [
  assume-screen <span class="Constant">60:literal/width</span>, <span class="Constant">10:literal/height</span>
  run [
    1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
    2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  ]
  <span class="Comment"># divider isn't messed up</span>
  screen-should-contain [
   <span class="Constant"> .                                         run (F10)          .</span>
   <span class="Constant"> .abc                           ┊def                          .</span>
   <span class="Constant"> .                              ┊                             .</span>
   <span class="Constant"> .                              ┊                             .</span>
   <span class="Constant"> .                              ┊                             .</span>
  ]
]

<span class="muScenario">scenario</span> editor-in-focus-keeps-cursor [
  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
  <span class="Comment"># initialize programming environment and highlight cursor</span>
  assume-console <span class="Constant">[]</span>
  run [
    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
    event-loop screen:address, console:address, 3:address:programming-environment-data
    screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
  ]
  <span class="Comment"># is cursor at the right place?</span>
  screen-should-contain [
   <span class="Constant"> .           run (F10)          .</span>
   <span class="Constant"> .␣bc            ┊def           .</span>
<span class="Comment"># artifact of fake console: no events = no render</span>
<span class="Comment">#   .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .               ┊              .</span>
  ]
  <span class="Comment"># now try typing a letter</span>
  assume-console [
    type <span class="Constant">[z]</span>
  ]
  run [
    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
    event-loop screen:address, console:address, 3:address:programming-environment-data
    screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
  ]
  <span class="Comment"># cursor should still be right</span>
  screen-should-contain [
   <span class="Constant"> .           run (F10)          .</span>
   <span class="Constant"> .z␣bc           ┊def           .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .               ┊              .</span>
  ]
]

<span class="SalientComment">## Running code from the editors</span>

container sandbox-data [
  data:address:array:character
  response:address:array:character
  warnings:address:array:character
  next-sandbox:address:sandbox-data
]

<span class="muScenario">scenario</span> run-and-show-results [
  $close-trace  <span class="Comment"># trace too long for github</span>
  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">12:literal/height</span>
  <span class="Comment"># recipe editor is empty</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[divide-with-remainder 11:literal, 3:literal]</span>
  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  <span class="Comment"># run the code in the editors</span>
  assume-console [
    press 65526  <span class="Comment"># F10</span>
  ]
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
  ]
  <span class="Comment"># check that screen prints the results</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F10)          .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊divide-with-remainder 11:literal, 3:literal      .</span>
   <span class="Constant"> .                                                  ┊3                                                .</span>
   <span class="Constant"> .                                                  ┊2                                                .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
  screen-should-contain-in-color <span class="Constant">7:literal/white</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                   divide-with-remainder 11:literal, 3:literal      .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
  ]
  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
   <span class="Constant"> .                                                  ┊3                                                .</span>
   <span class="Constant"> .                                                  ┊2                                                .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
  <span class="Comment"># run another command</span>
  assume-console [
    left-click 1, 80
    type <span class="Constant">[add 2:literal, 2:literal]</span>
    press 65526  <span class="Comment"># F10</span>
  ]
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
  ]
  <span class="Comment"># check that screen prints the results</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F10)          .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊add 2:literal, 2:literal                         .</span>
   <span class="Constant"> .                                                  ┊4                                                .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊divide-with-remainder 11:literal, 3:literal      .</span>
   <span class="Constant"> .                                                  ┊3                                                .</span>
   <span class="Constant"> .                                                  ┊2                                                .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
]

<span class="muRecipe">recipe</span> run-sandboxes [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
  <span class="Comment"># load code from recipe editor, save any warnings</span>
  in:address:array:character<span class="Special"> &lt;- </span>editor-contents recipes:address:editor-data
  recipe-warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, recipe-warnings:offset
  recipe-warnings:address:address:array:character/deref<span class="Special"> &lt;- </span>reload in:address:array:character
  <span class="Comment"># check contents of right editor (sandbox)</span>
  <span class="Delimiter">{</span>
    sandbox-contents:address:array:character<span class="Special"> &lt;- </span>editor-contents current-sandbox:address:editor-data
    <span class="muControl">break-unless</span> sandbox-contents:address:array:character
    <span class="Comment"># if contents exist, run them and turn them into a new sandbox-data</span>
    new-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>new sandbox-data:type
    data:address:address:array:character<span class="Special"> &lt;- </span>get-address new-sandbox:address:sandbox-data/deref, data:offset
    data:address:address:array:character/deref<span class="Special"> &lt;- </span>copy sandbox-contents:address:array:character
    <span class="Comment"># push to head of sandbox list</span>
    dest:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, sandbox:offset
    next:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address new-sandbox:address:sandbox-data/deref, next-sandbox:offset
    next:address:address:sandbox-data/deref<span class="Special"> &lt;- </span>copy dest:address:address:sandbox-data/deref
    dest:address:address:sandbox-data/deref<span class="Special"> &lt;- </span>copy new-sandbox:address:sandbox-data
    <span class="Comment"># clear sandbox editor</span>
    init:address:address:duplex-list<span class="Special"> &lt;- </span>get-address current-sandbox:address:editor-data/deref, data:offset
    init:address:address:duplex-list/deref<span class="Special"> &lt;- </span>push-duplex <span class="Constant">167:literal/§</span>, <span class="Constant">0:literal/tail</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># rerun other sandboxes</span>
  curr:address:sandbox-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox:offset
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> curr:address:sandbox-data
    data:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, data:offset
    response:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, response:offset
    warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, warnings:offset
    response:address:address:array:character/deref, warnings:address:address:array:character/deref<span class="Special"> &lt;- </span>run-interactive data:address:address:array:character/deref
    curr:address:sandbox-data<span class="Special"> &lt;- </span>get curr:address:sandbox-data/deref, next-sandbox:offset
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muScenario">scenario</span> run-updates-results [
  $close-trace  <span class="Comment"># trace too long for github</span>
  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">12:literal/height</span>
  <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
<span class="Constant">recipe foo [</span>
<span class="Constant">z:number &lt;- add 2:literal, 2:literal</span>
<span class="Constant">]</span>]
  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  <span class="Comment"># run the code in the editors</span>
  assume-console [
    press 65526  <span class="Comment"># F10</span>
  ]
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
  ]
  <span class="Comment"># check that screen prints the results</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F10)          .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
   <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .z:number &lt;- add 2:literal, 2:literal              ┊foo                                              .</span>
   <span class="Constant"> .]                                                 ┊4                                                .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
  <span class="Comment"># make a change (incrementing one of the args to 'add'), then rerun</span>
  assume-console [
    left-click 3, 28  <span class="Comment"># one past the value of the second arg</span>
    type <span class="Constant">[«3]</span>  <span class="Comment"># replace</span>
    press 65526  <span class="Comment"># F10</span>
  ]
  4:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
  replace-in-console <span class="Constant">171:literal/«</span>, 4:event/backspace
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
  ]
  <span class="Comment"># check that screen updates the result on the right</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F10)          .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
   <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .z:number &lt;- add 2:literal, 3:literal              ┊foo                                              .</span>
   <span class="Constant"> .]                                                 ┊5                                                .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
]

<span class="muScenario">scenario</span> run-instruction-and-print-warnings [
  $close-trace  <span class="Comment"># trace too long for github</span>
  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">10:literal/height</span>
  <span class="Comment"># left editor is empty</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
  <span class="Comment"># right editor contains an illegal instruction</span>
  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
  <span class="Comment"># run the code in the editors</span>
  assume-console [
    press 65526  <span class="Comment"># F10</span>
  ]
  run [
    event-loop screen:address, console:address, 3:address:programming-environment-data
  ]
  <span class="Comment"># check that screen prints error message in red</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F10)          .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊get 1234:number, foo:offset                      .</span>
   <span class="Constant"> .                                                  ┊unknown element foo in container number          .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
  screen-should-contain-in-color <span class="Constant">7:literal/white</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                   get 1234:number, foo:offset                      .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
  ]
  screen-should-contain-in-color, <span class="Constant">1:literal/red</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                   unknown element foo in container number          .</span>
   <span class="Constant"> .                                                                                                    .</span>
  ]
  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   <span class="Constant"> .                                                  ┊                                                 .</span>
  ]
]

<span class="muRecipe">recipe</span> editor-contents [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  buf:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80:literal</span>
  curr:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
  <span class="Comment"># skip § sentinel</span>
  assert curr:address:duplex-list, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
  curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
  <span class="muControl">reply-unless</span> curr:address:duplex-list, <span class="Constant">0:literal</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> curr:address:duplex-list
    c:character<span class="Special"> &lt;- </span>get curr:address:duplex-list/deref, value:offset
    buffer-append buf:address:buffer, c:character
    curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  result:address:array:character<span class="Special"> &lt;- </span>buffer-to-array buf:address:buffer
  <span class="muControl">reply</span> result:address:array:character
]

<span class="muScenario">scenario</span> editor-provides-edited-contents [
  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
  assume-console [
    left-click 1, 2
    type <span class="Constant">[def]</span>
  ]
  run [
    editor-event-loop screen:address, console:address, 2:address:editor-data
    3:address:array:character<span class="Special"> &lt;- </span>editor-contents 2:address:editor-data
    4:array:character<span class="Special"> &lt;- </span>copy 3:address:array:character/deref
  ]
  memory-should-contain [
    4:string<span class="Special"> &lt;- </span><span class="Constant">[abdefc]</span>
  ]
]

<span class="SalientComment">## helpers for drawing editor borders</span>

<span class="muRecipe">recipe</span> draw-box [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  top:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bottom:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># top border</span>
  draw-horizontal screen:address, top:number, left:number, right:number, color:number
  draw-horizontal screen:address, bottom:number, left:number, right:number, color:number
  draw-vertical screen:address, left:number, top:number, bottom:number, color:number
  draw-vertical screen:address, right:number, top:number, bottom:number, color:number
  draw-top-left screen:address, top:number, left:number, color:number
  draw-top-right screen:address, top:number, right:number, color:number
  draw-bottom-left screen:address, bottom:number, left:number, color:number
  draw-bottom-right screen:address, bottom:number, right:number, color:number
  <span class="Comment"># position cursor inside box</span>
  move-cursor screen:address, top:number, left:number
  cursor-down screen:address
  cursor-right screen:address
]

<span class="muRecipe">recipe</span> draw-horizontal [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  x:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> style-found?:boolean
    style:character<span class="Special"> &lt;- </span>copy <span class="Constant">9472:literal/horizontal</span>
  <span class="Delimiter">}</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  bg-color:number, bg-color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> bg-color-found?:boolean
    bg-color:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal/black</span>
  <span class="Delimiter">}</span>
  move-cursor screen:address, row:number, x:number
  <span class="Delimiter">{</span>
    continue?:boolean<span class="Special"> &lt;- </span>lesser-or-equal x:number, right:number  <span class="Comment"># right is inclusive, to match editor-data semantics</span>
    <span class="muControl">break-unless</span> continue?:boolean
    print-character screen:address, style:character, color:number, bg-color:number
    x:number<span class="Special"> &lt;- </span>add x:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">recipe</span> draw-vertical [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  col:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  x:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bottom:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> style-found?:boolean
    style:character<span class="Special"> &lt;- </span>copy <span class="Constant">9474:literal/vertical</span>
  <span class="Delimiter">}</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    continue?:boolean<span class="Special"> &lt;- </span>lesser-than x:number, bottom:number
    <span class="muControl">break-unless</span> continue?:boolean
    move-cursor screen:address, x:number, col:number
    print-character screen:address, style:character, color:number
    x:number<span class="Special"> &lt;- </span>add x:number, <span class="Constant">1:literal</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">recipe</span> draw-top-left [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  top:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  move-cursor screen:address, top:number, left:number
  print-character screen:address, <span class="Constant">9484:literal/down-right</span>, color:number
]

<span class="muRecipe">recipe</span> draw-top-right [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  top:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  move-cursor screen:address, top:number, right:number
  print-character screen:address, <span class="Constant">9488:literal/down-left</span>, color:number
]

<span class="muRecipe">recipe</span> draw-bottom-left [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bottom:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  move-cursor screen:address, bottom:number, left:number
  print-character screen:address, <span class="Constant">9492:literal/up-right</span>, color:number
]

<span class="muRecipe">recipe</span> draw-bottom-right [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bottom:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="Comment"># default color to white</span>
    <span class="muControl">break-if</span> color-found?:boolean
    color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
  <span class="Delimiter">}</span>
  move-cursor screen:address, bottom:number, right:number
  print-character screen:address, <span class="Constant">9496:literal/up-left</span>, color:number
]

<span class="muRecipe">recipe</span> print-string-with-gradient-background [
  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
  x:address:screen<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  color:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bg-color1:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  bg-color2:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
  color-range:number<span class="Special"> &lt;- </span>subtract bg-color2:number, bg-color1:number
  color-quantum:number<span class="Special"> &lt;- </span>divide color-range:number, len:number
<span class="CommentedCode">#?   close-console #? 2</span>
<span class="CommentedCode">#?   $print len:number, [, ], color-range:number, [, ], color-quantum:number, [ </span>
<span class="CommentedCode">#? ] #? 2</span>
<span class="CommentedCode">#? #?   $exit #? 3</span>
  bg-color:number<span class="Special"> &lt;- </span>copy bg-color1:number
  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i:number, len:number
    <span class="muControl">break-if</span> done?:boolean
    c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, i:number
    print-character x:address:screen, c:character, color:number, bg-color:number
    i:number<span class="Special"> &lt;- </span>add i:number, <span class="Constant">1:literal</span>
    bg-color:number<span class="Special"> &lt;- </span>add bg-color:number, color-quantum:number
<span class="CommentedCode">#?     $print [=&gt; ], bg-color:number, [ </span>
<span class="CommentedCode">#? ] #? 1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
<span class="CommentedCode">#?   $exit #? 1</span>
  <span class="muControl">reply</span> x:address:screen/same-as-ingredient:0
]
</pre>
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