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<span class="Comment"># Chessboard program: you type in moves in algebraic notation, and it'll</span>
<span class="Comment"># display the position after each move.</span>

<span class="Comment"># recipes are mu's names for functions</span>
<span class="muRecipe">recipe</span> main [
  open-console  <span class="Comment"># take control of screen, keyboard and mouse</span>

  <span class="Comment"># The chessboard recipe takes keyboard and screen objects as 'ingredients'.</span>
<span class="Constant">  #</span>
  <span class="Comment"># In mu it is good form (though not required) to explicitly show the</span>
  <span class="Comment"># hardware you rely on.</span>
<span class="Constant">  #</span>
  <span class="Comment"># The chessboard also returns the same keyboard and screen objects. In mu it</span>
  <span class="Comment"># is good form to not modify ingredients of a recipe unless they are also</span>
  <span class="Comment"># results. Here we clearly modify both keyboard and screen, so we return</span>
  <span class="Comment"># both.</span>
<span class="Constant">  #</span>
  <span class="Comment"># Here the console and screen are both 0, which usually indicates real</span>
  <span class="Comment"># hardware rather than a fake for testing as you'll see below.</span>
  <span class="Constant">0/screen</span>, <span class="Constant">0/console</span><span class="Special"> &lt;- </span>chessboard <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>

  close-console  <span class="Comment"># cleanup screen, keyboard and mouse</span>
]

<span class="SalientComment">## But enough about mu. Here's what it looks like to run the chessboard program.</span>

<span class="muScenario">scenario</span> print-board-and-read-move [
  $close-trace  <span class="Comment"># administrivia: most scenarios save and check traces, but this one gets too large/slow</span>
  <span class="Comment"># we'll make the screen really wide because the program currently prints out a long line</span>
  assume-screen <span class="Constant">120/width</span>, <span class="Constant">20/height</span>
  <span class="Comment"># initialize keyboard to type in a move</span>
  assume-console [
    type <span class="Constant">[a2-a4</span>
<span class="Constant">]</span>
  ]
  run [
    screen:address, console:address<span class="Special"> &lt;- </span>chessboard screen:address, console:address
    <span class="Comment"># icon for the cursor</span>
    screen<span class="Special"> &lt;- </span>print-character screen, <span class="Constant">9251/␣</span>
  ]
  screen-should-contain [
  <span class="Comment">#            1         2         3         4         5         6         7         8         9         10        11</span>
  <span class="Comment">#  012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789</span>
   <span class="Constant"> .Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.         .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .8 | r n b q k b n r                                                                                                     .</span>
   <span class="Constant"> .7 | p p p p p p p p                                                                                                     .</span>
   <span class="Constant"> .6 |                                                                                                                     .</span>
   <span class="Constant"> .5 |                                                                                                                     .</span>
   <span class="Constant"> .4 | P                                                                                                                   .</span>
   <span class="Constant"> .3 |                                                                                                                     .</span>
   <span class="Constant"> .2 |   P P P P P P P                                                                                                     .</span>
   <span class="Constant"> .1 | R N B Q K B N R                                                                                                     .</span>
   <span class="Constant"> .  +----------------                                                                                                     .</span>
   <span class="Constant"> .    a b c d e f g h                                                                                                     .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .Type in your move as &lt;from square&gt;-&lt;to square&gt;. For example: 'a2-a4'. Then press &lt;enter&gt;.                               .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .Hit 'q' to exit.                                                                                                        .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .move: ␣                                                                                                                 .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .                                                                                                                        .</span>
  ]
]

<span class="SalientComment">## Here's how 'chessboard' is implemented.</span>

<span class="muRecipe">recipe</span> chessboard [
  <span class="Constant">local-scope</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>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>initial-position
  <span class="Comment"># hook up stdin</span>
  stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
  start-running send-keys-to-channel:<span class="muRecipe">recipe</span>, console, stdin, screen
  <span class="Comment"># buffer lines in stdin</span>
  buffered-stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
  start-running buffer-lines:<span class="muRecipe">recipe</span>, stdin, buffered-stdin
  <span class="Delimiter">{</span>
    msg:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.</span>
<span class="Constant">]</span>
    print-string screen, msg
    cursor-to-next-line screen
    print-board screen, board
    cursor-to-next-line screen
    msg<span class="Special"> &lt;- </span>new <span class="Constant">[Type in your move as &lt;from square&gt;-&lt;to square&gt;. For example: 'a2-a4'. Then press &lt;enter&gt;.</span>
<span class="Constant">]</span>
    print-string screen, msg
    cursor-to-next-line screen
    msg<span class="Special"> &lt;- </span>new <span class="Constant">[Hit 'q' to exit.</span>
<span class="Constant">]</span>
    print-string screen, msg
    <span class="Delimiter">{</span>
      cursor-to-next-line screen
      msg<span class="Special"> &lt;- </span>new <span class="Constant">[move: ]</span>
      print-string screen, msg
      m:address:move, quit:boolean, error:boolean<span class="Special"> &lt;- </span>read-move buffered-stdin, screen
      <span class="muControl">break-if</span> quit, <span class="Constant">+quit:label</span>
      buffered-stdin<span class="Special"> &lt;- </span>clear-channel buffered-stdin  <span class="Comment"># cleanup after error. todo: test this?</span>
      <span class="muControl">loop-if</span> error
    <span class="Delimiter">}</span>
    board<span class="Special"> &lt;- </span>make-move board, m
    clear-screen screen
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
<span class="Constant">  +quit</span>
]

<span class="SalientComment">## a board is an array of files, a file is an array of characters (squares)</span>

<span class="muRecipe">recipe</span> new-board [
  <span class="Constant">local-scope</span>
  initial-position:address:array:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Comment"># assert(length(initial-position) == 64)</span>
  len:number<span class="Special"> &lt;- </span>length *initial-position
  correct-length?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">64</span>
  assert correct-length?, <span class="Constant">[chessboard had incorrect size]</span>
  <span class="Comment"># board is an array of pointers to files; file is an array of characters</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>new location:type, <span class="Constant">8</span>
  col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>equal col, <span class="Constant">8</span>
    <span class="muControl">break-if</span> done?
    file:address:address:array:character<span class="Special"> &lt;- </span>index-address *board, col
    *file<span class="Special"> &lt;- </span>new-file initial-position, col
    col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> board
]

<span class="muRecipe">recipe</span> new-file [
  <span class="Constant">local-scope</span>
  position:address:array:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  index:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  index<span class="Special"> &lt;- </span>multiply index, <span class="Constant">8</span>
  result:address:array:character<span class="Special"> &lt;- </span>new character:type, <span class="Constant">8</span>
  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>equal row, <span class="Constant">8</span>
    <span class="muControl">break-if</span> done?
    dest:address:character<span class="Special"> &lt;- </span>index-address *result, row
    *dest<span class="Special"> &lt;- </span>index *position, index
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    index<span class="Special"> &lt;- </span>add index, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> result
]

<span class="muRecipe">recipe</span> print-board [
  <span class="Constant">local-scope</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">7</span>  <span class="Comment"># start printing from the top of the board</span>
  <span class="Comment"># print each row</span>
<span class="CommentedCode">#?   $print [printing board to screen ], screen, 10/newline</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>lesser-than row, <span class="Constant">0</span>
    <span class="muControl">break-if</span> done?
<span class="CommentedCode">#?     $print [printing rank ], row, 10/newline</span>
    <span class="Comment"># print rank number as a legend</span>
    rank:number<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    print-integer screen, rank
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ | ]</span>
    print-string screen, s
    <span class="Comment"># print each square in the row</span>
    col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    <span class="Delimiter">{</span>
      done?:boolean<span class="Special"> &lt;- </span>equal col:number, <span class="Constant">8</span>
      <span class="muControl">break-if</span> done?:boolean
      f:address:array:character<span class="Special"> &lt;- </span>index *board, col
      c:character<span class="Special"> &lt;- </span>index *f, row
      print-character screen, c
      print-character screen, <span class="Constant">32/space</span>
      col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    row<span class="Special"> &lt;- </span>subtract row, <span class="Constant">1</span>
    cursor-to-next-line screen
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># print file letters as legend</span>
<span class="CommentedCode">#?   $print [printing legend</span>
<span class="CommentedCode">#? ] #? 1</span>
  s<span class="Special"> &lt;- </span>new <span class="Constant">[  +----------------]</span>
  print-string screen, s
  screen<span class="Special"> &lt;- </span>cursor-to-next-line screen
<span class="CommentedCode">#?   screen &lt;- print-character screen, 97 #? 1</span>
  s<span class="Special"> &lt;- </span>new <span class="Constant">[    a b c d e f g h]</span>
  screen<span class="Special"> &lt;- </span>print-string screen, s
  screen<span class="Special"> &lt;- </span>cursor-to-next-line screen
<span class="CommentedCode">#?   $print [done printing board</span>
<span class="CommentedCode">#? ] #? 1</span>
]

<span class="Comment"># board:address:array:address:array:character &lt;- initial-position</span>
<span class="muRecipe">recipe</span> initial-position [
  <span class="Constant">local-scope</span>
  <span class="Comment"># layout in memory (in raster order):</span>
  <span class="Comment">#   R P _ _ _ _ p r</span>
  <span class="Comment">#   N P _ _ _ _ p n</span>
  <span class="Comment">#   B P _ _ _ _ p b</span>
  <span class="Comment">#   Q P _ _ _ _ p q</span>
  <span class="Comment">#   K P _ _ _ _ p k</span>
  <span class="Comment">#   B P _ _ _ _ p B</span>
  <span class="Comment">#   N P _ _ _ _ p n</span>
  <span class="Comment">#   R P _ _ _ _ p r</span>
  initial-position:address:array:number<span class="Special"> &lt;- </span>new-array <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">81/Q</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">113/q</span>, <span class="Constant">75/K</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">107/k</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>
<span class="CommentedCode">#?       82/R, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 114/r,</span>
<span class="CommentedCode">#?       78/N, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 110/n,</span>
<span class="CommentedCode">#?       66/B, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 98/b, </span>
<span class="CommentedCode">#?       81/Q, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 113/q,</span>
<span class="CommentedCode">#?       75/K, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 107/k,</span>
<span class="CommentedCode">#?       66/B, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 98/b,</span>
<span class="CommentedCode">#?       78/N, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 110/n,</span>
<span class="CommentedCode">#?       82/R, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 114/r</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>new-board initial-position
  <span class="muControl">reply</span> board
]

<span class="muScenario">scenario</span> printing-the-board [
  assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
  run [
    <span class="Constant">1</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
    screen:address<span class="Special"> &lt;- </span>print-board screen:address, <span class="Constant">1</span>:address:array:address:array:character/board
<span class="CommentedCode">#?     $dump-screen #? 1</span>
  ]
  screen-should-contain [
  <span class="Comment">#  012345678901234567890123456789</span>
   <span class="Constant"> .8 | r n b q k b n r           .</span>
   <span class="Constant"> .7 | p p p p p p p p           .</span>
   <span class="Constant"> .6 |                           .</span>
   <span class="Constant"> .5 |                           .</span>
   <span class="Constant"> .4 |                           .</span>
   <span class="Constant"> .3 |                           .</span>
   <span class="Constant"> .2 | P P P P P P P P           .</span>
   <span class="Constant"> .1 | R N B Q K B N R           .</span>
   <span class="Constant"> .  +----------------           .</span>
   <span class="Constant"> .    a b c d e f g h           .</span>
   <span class="Constant"> .                              .</span>
   <span class="Constant"> .                              .</span>
  ]
]

<span class="SalientComment">## data structure: move</span>

container move [
  <span class="Comment"># valid range: 0-7</span>
  from-file:number
  from-rank:number
  to-file:number
  to-rank:number
]

<span class="Comment"># result:address:move, quit?:boolean, error?:boolean &lt;- read-move stdin:address:channel, screen:address</span>
<span class="Comment"># prints only error messages to screen</span>
<span class="muRecipe">recipe</span> read-move [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  from-file:number, quit?:boolean, error?:boolean<span class="Special"> &lt;- </span>read-file stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="Comment"># construct the move object</span>
  result:address:move<span class="Special"> &lt;- </span>new move:type
  x:address:number<span class="Special"> &lt;- </span>get-address *result, from-file:offset
  *x<span class="Special"> &lt;- </span>copy from-file
  x<span class="Special"> &lt;- </span>get-address *result, from-rank:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-rank stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  error?<span class="Special"> &lt;- </span>expect-from-channel stdin, <span class="Constant">45/dash</span>, screen
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, error?
  x<span class="Special"> &lt;- </span>get-address *result, to-file:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-file stdin, screen
  <span class="muControl">reply-if</span> quit?:boolean, <span class="Constant">0/dummy</span>, quit?:boolean, error?:boolean
  <span class="muControl">reply-if</span> error?:boolean, <span class="Constant">0/dummy</span>, quit?:boolean, error?:boolean
  x:address:number<span class="Special"> &lt;- </span>get-address *result, to-rank:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-rank stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  error?<span class="Special"> &lt;- </span>expect-from-channel stdin, <span class="Constant">10/newline</span>, screen
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, error?
  <span class="muControl">reply</span> result, quit?, error?
]

<span class="Comment"># file:number, quit:boolean, error:boolean &lt;- read-file stdin:address:channel, screen:address</span>
<span class="Comment"># valid values for file: 0-7</span>
<span class="muRecipe">recipe</span> read-file [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    q-pressed?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">81/Q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    q-pressed?<span class="Special"> &lt;- </span>equal c, <span class="Constant">113/q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    empty-fake-keyboard?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">0/eof</span>
    <span class="muControl">break-unless</span> empty-fake-keyboard?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
    <span class="muControl">break-unless</span> newline?
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
    print-string screen, error-message
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  file:number<span class="Special"> &lt;- </span>subtract c, <span class="Constant">97/a</span>
  <span class="Comment"># 'a' &lt;= file &lt;= 'h'</span>
  <span class="Delimiter">{</span>
    above-min:boolean<span class="Special"> &lt;- </span>greater-or-equal file, <span class="Constant">0</span>
    <span class="muControl">break-if</span> above-min
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[file too low: ]</span>
    print-string screen, error-message
    print-character screen, c
    cursor-to-next-line screen
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    below-max:boolean<span class="Special"> &lt;- </span>lesser-than file, <span class="Constant">8</span>
    <span class="muControl">break-if</span> below-max
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[file too high: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> file, <span class="Constant">0/quit</span>, <span class="Constant">0/error</span>
]

<span class="Comment"># rank:number &lt;- read-rank stdin:address:channel, screen:address</span>
<span class="Comment"># valid values: 0-7, -1 (quit), -2 (error)</span>
<span class="muRecipe">recipe</span> read-rank [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    q-pressed?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">8/Q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    q-pressed?<span class="Special"> &lt;- </span>equal c, <span class="Constant">113/q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10</span>  <span class="Comment"># newline</span>
    <span class="muControl">break-unless</span> newline?
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
    print-string screen, error-message
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  rank:number<span class="Special"> &lt;- </span>subtract c, <span class="Constant">49/'1'</span>
  <span class="Comment"># assert'1' &lt;= rank &lt;= '8'</span>
  <span class="Delimiter">{</span>
    above-min:boolean<span class="Special"> &lt;- </span>greater-or-equal rank, <span class="Constant">0</span>
    <span class="muControl">break-if</span> above-min
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[rank too low: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    below-max:boolean<span class="Special"> &lt;- </span>lesser-or-equal rank, <span class="Constant">7</span>
    <span class="muControl">break-if</span> below-max
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[rank too high: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> rank, <span class="Constant">0/quit</span>, <span class="Constant">0/error</span>
]

<span class="Comment"># read a character from the given channel and check that it's what we expect</span>
<span class="Comment"># return true on error</span>
<span class="muRecipe">recipe</span> expect-from-channel [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  expected: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>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    match?:boolean<span class="Special"> &lt;- </span>equal c, expected
    <span class="muControl">break-if</span> match?
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[expected character not found]</span>
    print-string screen, s
  <span class="Delimiter">}</span>
  result:boolean<span class="Special"> &lt;- </span>not match?
  <span class="muControl">reply</span> result
]

<span class="muScenario">scenario</span> read-move-blocking [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Comment"># press 'a'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a']
    <span class="Comment"># press '2'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2']
    <span class="Comment"># press '-'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">45/'-'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> hyphen 'a2-']
    <span class="Comment"># press 'a'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a2-a']
    <span class="Comment"># press '4'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">52/'4'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2-a4']
    <span class="Comment"># press 'newline'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10</span>  <span class="Comment"># newline</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' now completes</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/completed?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">1/completed</span>
    assert <span class="Constant">4</span>:boolean/completed?, [
F read-move-blocking: routine failed to terminate on newline]
    trace <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
  ]
  trace-should-contain [
    test: reached end
  ]
]

<span class="muScenario">scenario</span> read-move-quit [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-quit: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Comment"># press 'q'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">113/q</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' completes</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/completed?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">1/completed</span>
    assert <span class="Constant">4</span>:boolean/completed?, [
F read-move-quit: routine failed to terminate on 'q']
    trace <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
  ]
  trace-should-contain [
    test: reached end
  ]
]

<span class="muScenario">scenario</span> read-move-illegal-file [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .file too low: 2     .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muScenario">scenario</span> read-move-illegal-rank [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .rank too high: a    .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muScenario">scenario</span> read-move-empty [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10/newline</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .that's not enough   .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muRecipe">recipe</span> make-move [
  <span class="Constant">local-scope</span>
  b:address:array:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  m:address:move<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  from-file:number<span class="Special"> &lt;- </span>get *m, from-file:offset
  from-rank:number<span class="Special"> &lt;- </span>get *m, from-rank:offset
  to-file:number<span class="Special"> &lt;- </span>get *m, to-file:offset
  to-rank:number<span class="Special"> &lt;- </span>get *m, to-rank:offset
  f:address:array:character<span class="Special"> &lt;- </span>index *b, from-file
  src:address:character/square<span class="Special"> &lt;- </span>index-address *f, from-rank
  f<span class="Special"> &lt;- </span>index *b, to-file
  dest:address:character/square<span class="Special"> &lt;- </span>index-address *f, to-rank
  *dest<span class="Special"> &lt;- </span>copy *src
  *src<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
  <span class="muControl">reply</span> b/same-as-ingredient:<span class="Constant">0</span>
]

<span class="muScenario">scenario</span> making-a-move [
  assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
  run [
    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
    <span class="Constant">3</span>:address:move<span class="Special"> &lt;- </span>new move:type
    <span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, from-file:offset
    *<span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
    <span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, from-rank:offset
    *<span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">1/'2'</span>
    <span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, to-file:offset
    *<span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
    <span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, to-rank:offset
    *<span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">3/'4'</span>
    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>make-move <span class="Constant">2</span>:address:array:address:array:character/board, <span class="Constant">3</span>:address:move
    screen:address<span class="Special"> &lt;- </span>print-board screen:address, <span class="Constant">2</span>:address:array:address:array:character/board
  ]
  screen-should-contain [
  <span class="Comment">#  012345678901234567890123456789</span>
   <span class="Constant"> .8 | r n b q k b n r           .</span>
   <span class="Constant"> .7 | p p p p p p p p           .</span>
   <span class="Constant"> .6 |                           .</span>
   <span class="Constant"> .5 |                           .</span>
   <span class="Constant"> .4 |             P             .</span>
   <span class="Constant"> .3 |                           .</span>
   <span class="Constant"> .2 | P P P P P P   P           .</span>
   <span class="Constant"> .1 | R N B Q K B N R           .</span>
   <span class="Constant"> .  +----------------           .</span>
   <span class="Constant"> .    a b c d e f g h           .</span>
   <span class="Constant"> .                              .</span>
  ]
]
</pre>
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<pre id='vimCodeElement'>
<span class="Comment"># Chessboard program: you type in moves in algebraic notation, and it'll</span>
<span class="Comment"># display the position after each move.</span>

<span class="Comment"># recipes are mu's names for functions</span>
<span class="muRecipe">recipe</span> main [
  open-console  <span class="Comment"># take control of screen, keyboard and mouse</span>

  <span class="Comment"># The chessboard recipe takes keyboard and screen objects as 'ingredients'.</span>
<span class="Constant">  #</span>
  <span class="Comment"># In mu it is good form (though not required) to explicitly show the</span>
  <span class="Comment"># hardware you rely on.</span>
<span class="Constant">  #</span>
  <span class="Comment"># The chessboard also returns the same keyboard and screen objects. In mu it</span>
  <span class="Comment"># is good form to not modify ingredients of a recipe unless they are also</span>
  <span class="Comment"># results. Here we clearly modify both keyboard and screen, so we return</span>
  <span class="Comment"># both.</span>
<span class="Constant">  #</span>
  <span class="Comment"># Here the console and screen are both 0, which usually indicates real</span>
  <span class="Comment"># hardware rather than a fake for testing as you'll see below.</span>
  <span class="Constant">0/screen</span>, <span class="Constant">0/console</span><span class="Special"> &lt;- </span>chessboard <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>

  close-console  <span class="Comment"># cleanup screen, keyboard and mouse</span>
]

<span class="SalientComment">## But enough about mu. Here's what it looks like to run the chessboard program.</span>

<span class="muScenario">scenario</span> print-board-and-read-move [
  $close-trace  <span class="Comment"># administrivia: most scenarios save and check traces, but this one gets too large/slow</span>
  <span class="Comment"># we'll make the screen really wide because the program currently prints out a long line</span>
  assume-screen <span class="Constant">120/width</span>, <span class="Constant">20/height</span>
  <span class="Comment"># initialize keyboard to type in a move</span>
  assume-console [
    type <span class="Constant">[a2-a4</span>
<span class="Constant">]</span>
  ]
  run [
    screen:address, console:address<span class="Special"> &lt;- </span>chessboard screen:address, console:address
    <span class="Comment"># icon for the cursor</span>
    screen<span class="Special"> &lt;- </span>print-character screen, <span class="Constant">9251/␣</span>
  ]
  screen-should-contain [
  <span class="Comment">#            1         2         3         4         5         6         7         8         9         10        11</span>
  <span class="Comment">#  012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789</span>
   <span class="Constant"> .Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.         .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .8 | r n b q k b n r                                                                                                     .</span>
   <span class="Constant"> .7 | p p p p p p p p                                                                                                     .</span>
   <span class="Constant"> .6 |                                                                                                                     .</span>
   <span class="Constant"> .5 |                                                                                                                     .</span>
   <span class="Constant"> .4 | P                                                                                                                   .</span>
   <span class="Constant"> .3 |                                                                                                                     .</span>
   <span class="Constant"> .2 |   P P P P P P P                                                                                                     .</span>
   <span class="Constant"> .1 | R N B Q K B N R                                                                                                     .</span>
   <span class="Constant"> .  +----------------                                                                                                     .</span>
   <span class="Constant"> .    a b c d e f g h                                                                                                     .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .Type in your move as &lt;from square&gt;-&lt;to square&gt;. For example: 'a2-a4'. Then press &lt;enter&gt;.                               .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .Hit 'q' to exit.                                                                                                        .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .move: ␣                                                                                                                 .</span>
   <span class="Constant"> .                                                                                                                        .</span>
   <span class="Constant"> .                                                                                                                        .</span>
  ]
]

<span class="SalientComment">## Here's how 'chessboard' is implemented.</span>

<span class="muRecipe">recipe</span> chessboard [
  <span class="Constant">local-scope</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>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>initial-position
  <span class="Comment"># hook up stdin</span>
  stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
  start-running send-keys-to-channel:<span class="muRecipe">recipe</span>, console, stdin, screen
  <span class="Comment"># buffer lines in stdin</span>
  buffered-stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
  start-running buffer-lines:<span class="muRecipe">recipe</span>, stdin, buffered-stdin
  <span class="Delimiter">{</span>
    msg:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.</span>
<span class="Constant">]</span>
    print-string screen, msg
    cursor-to-next-line screen
    print-board screen, board
    cursor-to-next-line screen
    msg<span class="Special"> &lt;- </span>new <span class="Constant">[Type in your move as &lt;from square&gt;-&lt;to square&gt;. For example: 'a2-a4'. Then press &lt;enter&gt;.</span>
<span class="Constant">]</span>
    print-string screen, msg
    cursor-to-next-line screen
    msg<span class="Special"> &lt;- </span>new <span class="Constant">[Hit 'q' to exit.</span>
<span class="Constant">]</span>
    print-string screen, msg
    <span class="Delimiter">{</span>
      cursor-to-next-line screen
      msg<span class="Special"> &lt;- </span>new <span class="Constant">[move: ]</span>
      print-string screen, msg
      m:address:move, quit:boolean, error:boolean<span class="Special"> &lt;- </span>read-move buffered-stdin, screen
      <span class="muControl">break-if</span> quit, <span class="Constant">+quit:label</span>
      buffered-stdin<span class="Special"> &lt;- </span>clear-channel buffered-stdin  <span class="Comment"># cleanup after error. todo: test this?</span>
      <span class="muControl">loop-if</span> error
    <span class="Delimiter">}</span>
    board<span class="Special"> &lt;- </span>make-move board, m
    clear-screen screen
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
<span class="Constant">  +quit</span>
]

<span class="SalientComment">## a board is an array of files, a file is an array of characters (squares)</span>

<span class="muRecipe">recipe</span> new-board [
  <span class="Constant">local-scope</span>
  initial-position:address:array:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Comment"># assert(length(initial-position) == 64)</span>
  len:number<span class="Special"> &lt;- </span>length *initial-position
  correct-length?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">64</span>
  assert correct-length?, <span class="Constant">[chessboard had incorrect size]</span>
  <span class="Comment"># board is an array of pointers to files; file is an array of characters</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>new location:type, <span class="Constant">8</span>
  col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>equal col, <span class="Constant">8</span>
    <span class="muControl">break-if</span> done?
    file:address:address:array:character<span class="Special"> &lt;- </span>index-address *board, col
    *file<span class="Special"> &lt;- </span>new-file initial-position, col
    col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> board
]

<span class="muRecipe">recipe</span> new-file [
  <span class="Constant">local-scope</span>
  position:address:array:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  index:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  index<span class="Special"> &lt;- </span>multiply index, <span class="Constant">8</span>
  result:address:array:character<span class="Special"> &lt;- </span>new character:type, <span class="Constant">8</span>
  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>equal row, <span class="Constant">8</span>
    <span class="muControl">break-if</span> done?
    dest:address:character<span class="Special"> &lt;- </span>index-address *result, row
    *dest<span class="Special"> &lt;- </span>index *position, index
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    index<span class="Special"> &lt;- </span>add index, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> result
]

<span class="muRecipe">recipe</span> print-board [
  <span class="Constant">local-scope</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">7</span>  <span class="Comment"># start printing from the top of the board</span>
  <span class="Comment"># print each row</span>
<span class="CommentedCode">#?   $print [printing board to screen ], screen, 10/newline</span>
  <span class="Delimiter">{</span>
    done?:boolean<span class="Special"> &lt;- </span>lesser-than row, <span class="Constant">0</span>
    <span class="muControl">break-if</span> done?
<span class="CommentedCode">#?     $print [printing rank ], row, 10/newline</span>
    <span class="Comment"># print rank number as a legend</span>
    rank:number<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    print-integer screen, rank
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ | ]</span>
    print-string screen, s
    <span class="Comment"># print each square in the row</span>
    col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
    <span class="Delimiter">{</span>
      done?:boolean<span class="Special"> &lt;- </span>equal col:number, <span class="Constant">8</span>
      <span class="muControl">break-if</span> done?:boolean
      f:address:array:character<span class="Special"> &lt;- </span>index *board, col
      c:character<span class="Special"> &lt;- </span>index *f, row
      print-character screen, c
      print-character screen, <span class="Constant">32/space</span>
      col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    row<span class="Special"> &lt;- </span>subtract row, <span class="Constant">1</span>
    cursor-to-next-line screen
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># print file letters as legend</span>
<span class="CommentedCode">#?   $print [printing legend</span>
<span class="CommentedCode">#? ] #? 1</span>
  s<span class="Special"> &lt;- </span>new <span class="Constant">[  +----------------]</span>
  print-string screen, s
  screen<span class="Special"> &lt;- </span>cursor-to-next-line screen
<span class="CommentedCode">#?   screen &lt;- print-character screen, 97 #? 1</span>
  s<span class="Special"> &lt;- </span>new <span class="Constant">[    a b c d e f g h]</span>
  screen<span class="Special"> &lt;- </span>print-string screen, s
  screen<span class="Special"> &lt;- </span>cursor-to-next-line screen
<span class="CommentedCode">#?   $print [done printing board</span>
<span class="CommentedCode">#? ] #? 1</span>
]

<span class="Comment"># board:address:array:address:array:character &lt;- initial-position</span>
<span class="muRecipe">recipe</span> initial-position [
  <span class="Constant">local-scope</span>
  <span class="Comment"># layout in memory (in raster order):</span>
  <span class="Comment">#   R P _ _ _ _ p r</span>
  <span class="Comment">#   N P _ _ _ _ p n</span>
  <span class="Comment">#   B P _ _ _ _ p b</span>
  <span class="Comment">#   Q P _ _ _ _ p q</span>
  <span class="Comment">#   K P _ _ _ _ p k</span>
  <span class="Comment">#   B P _ _ _ _ p B</span>
  <span class="Comment">#   N P _ _ _ _ p n</span>
  <span class="Comment">#   R P _ _ _ _ p r</span>
  initial-position:address:array:number<span class="Special"> &lt;- </span>new-array <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">81/Q</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">113/q</span>, <span class="Constant">75/K</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">107/k</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>
<span class="CommentedCode">#?       82/R, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 114/r,</span>
<span class="CommentedCode">#?       78/N, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 110/n,</span>
<span class="CommentedCode">#?       66/B, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 98/b, </span>
<span class="CommentedCode">#?       81/Q, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 113/q,</span>
<span class="CommentedCode">#?       75/K, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 107/k,</span>
<span class="CommentedCode">#?       66/B, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 98/b,</span>
<span class="CommentedCode">#?       78/N, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 110/n,</span>
<span class="CommentedCode">#?       82/R, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 114/r</span>
  board:address:array:address:array:character<span class="Special"> &lt;- </span>new-board initial-position
  <span class="muControl">reply</span> board
]

<span class="muScenario">scenario</span> printing-the-board [
  assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
  run [
    <span class="Constant">1</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
    screen:address<span class="Special"> &lt;- </span>print-board screen:address, <span class="Constant">1</span>:address:array:address:array:character/board
<span class="CommentedCode">#?     $dump-screen #? 1</span>
  ]
  screen-should-contain [
  <span class="Comment">#  012345678901234567890123456789</span>
   <span class="Constant"> .8 | r n b q k b n r           .</span>
   <span class="Constant"> .7 | p p p p p p p p           .</span>
   <span class="Constant"> .6 |                           .</span>
   <span class="Constant"> .5 |                           .</span>
   <span class="Constant"> .4 |                           .</span>
   <span class="Constant"> .3 |                           .</span>
   <span class="Constant"> .2 | P P P P P P P P           .</span>
   <span class="Constant"> .1 | R N B Q K B N R           .</span>
   <span class="Constant"> .  +----------------           .</span>
   <span class="Constant"> .    a b c d e f g h           .</span>
   <span class="Constant"> .                              .</span>
   <span class="Constant"> .                              .</span>
  ]
]

<span class="SalientComment">## data structure: move</span>

container move [
  <span class="Comment"># valid range: 0-7</span>
  from-file:number
  from-rank:number
  to-file:number
  to-rank:number
]

<span class="Comment"># result:address:move, quit?:boolean, error?:boolean &lt;- read-move stdin:address:channel, screen:address</span>
<span class="Comment"># prints only error messages to screen</span>
<span class="muRecipe">recipe</span> read-move [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  from-file:number, quit?:boolean, error?:boolean<span class="Special"> &lt;- </span>read-file stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="Comment"># construct the move object</span>
  result:address:move<span class="Special"> &lt;- </span>new move:type
  x:address:number<span class="Special"> &lt;- </span>get-address *result, from-file:offset
  *x<span class="Special"> &lt;- </span>copy from-file
  x<span class="Special"> &lt;- </span>get-address *result, from-rank:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-rank stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  error?<span class="Special"> &lt;- </span>expect-from-channel stdin, <span class="Constant">45/dash</span>, screen
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, error?
  x<span class="Special"> &lt;- </span>get-address *result, to-file:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-file stdin, screen
  <span class="muControl">reply-if</span> quit?:boolean, <span class="Constant">0/dummy</span>, quit?:boolean, error?:boolean
  <span class="muControl">reply-if</span> error?:boolean, <span class="Constant">0/dummy</span>, quit?:boolean, error?:boolean
  x:address:number<span class="Special"> &lt;- </span>get-address *result, to-rank:offset
  *x, quit?, error?<span class="Special"> &lt;- </span>read-rank stdin, screen
  <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
  error?<span class="Special"> &lt;- </span>expect-from-channel stdin, <span class="Constant">10/newline</span>, screen
  <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, error?
  <span class="muControl">reply</span> result, quit?, error?
]

<span class="Comment"># file:number, quit:boolean, error:boolean &lt;- read-file stdin:address:channel, screen:address</span>
<span class="Comment"># valid values for file: 0-7</span>
<span class="muRecipe">recipe</span> read-file [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    q-pressed?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">81/Q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    q-pressed?<span class="Special"> &lt;- </span>equal c, <span class="Constant">113/q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    empty-fake-keyboard?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">0/eof</span>
    <span class="muControl">break-unless</span> empty-fake-keyboard?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
    <span class="muControl">break-unless</span> newline?
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
    print-string screen, error-message
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  file:number<span class="Special"> &lt;- </span>subtract c, <span class="Constant">97/a</span>
  <span class="Comment"># 'a' &lt;= file &lt;= 'h'</span>
  <span class="Delimiter">{</span>
    above-min:boolean<span class="Special"> &lt;- </span>greater-or-equal file, <span class="Constant">0</span>
    <span class="muControl">break-if</span> above-min
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[file too low: ]</span>
    print-string screen, error-message
    print-character screen, c
    cursor-to-next-line screen
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    below-max:boolean<span class="Special"> &lt;- </span>lesser-than file, <span class="Constant">8</span>
    <span class="muControl">break-if</span> below-max
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[file too high: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> file, <span class="Constant">0/quit</span>, <span class="Constant">0/error</span>
]

<span class="Comment"># rank:number &lt;- read-rank stdin:address:channel, screen:address</span>
<span class="Comment"># valid values: 0-7, -1 (quit), -2 (error)</span>
<span class="muRecipe">recipe</span> read-rank [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    q-pressed?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">8/Q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    q-pressed?<span class="Special"> &lt;- </span>equal c, <span class="Constant">113/q</span>
    <span class="muControl">break-unless</span> q-pressed?
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">1/quit</span>, <span class="Constant">0/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10</span>  <span class="Comment"># newline</span>
    <span class="muControl">break-unless</span> newline?
    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
    print-string screen, error-message
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  rank:number<span class="Special"> &lt;- </span>subtract c, <span class="Constant">49/'1'</span>
  <span class="Comment"># assert'1' &lt;= rank &lt;= '8'</span>
  <span class="Delimiter">{</span>
    above-min:boolean<span class="Special"> &lt;- </span>greater-or-equal rank, <span class="Constant">0</span>
    <span class="muControl">break-if</span> above-min
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[rank too low: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    below-max:boolean<span class="Special"> &lt;- </span>lesser-or-equal rank, <span class="Constant">7</span>
    <span class="muControl">break-if</span> below-max
    error-message<span class="Special"> &lt;- </span>new <span class="Constant">[rank too high: ]</span>
    print-string screen, error-message
    print-character screen, c
    <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
  <span class="Delimiter">}</span>
  <span class="muControl">reply</span> rank, <span class="Constant">0/quit</span>, <span class="Constant">0/error</span>
]

<span class="Comment"># read a character from the given channel and check that it's what we expect</span>
<span class="Comment"># return true on error</span>
<span class="muRecipe">recipe</span> expect-from-channel [
  <span class="Constant">local-scope</span>
  stdin:address:channel<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  expected: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>
  c:character, stdin<span class="Special"> &lt;- </span>read stdin
  <span class="Delimiter">{</span>
    match?:boolean<span class="Special"> &lt;- </span>equal c, expected
    <span class="muControl">break-if</span> match?
    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[expected character not found]</span>
    print-string screen, s
  <span class="Delimiter">}</span>
  result:boolean<span class="Special"> &lt;- </span>not match?
  <span class="muControl">reply</span> result
]

<span class="muScenario">scenario</span> read-move-blocking [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Comment"># press 'a'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a']
    <span class="Comment"># press '2'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2']
    <span class="Comment"># press '-'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">45/'-'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> hyphen 'a2-']
    <span class="Comment"># press 'a'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a2-a']
    <span class="Comment"># press '4'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">52/'4'</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' still waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2-a4']
    <span class="Comment"># press 'newline'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10</span>  <span class="Comment"># newline</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' now completes</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number
    <span class="Constant">4</span>:boolean/completed?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">1/completed</span>
    assert <span class="Constant">4</span>:boolean/completed?, [
F read-move-blocking: routine failed to terminate on newline]
    trace <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
  ]
  trace-should-contain [
    test: reached end
  ]
]

<span class="muScenario">scenario</span> read-move-quit [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-quit: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Comment"># press 'q'</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">113/q</span>
    restart <span class="Constant">2</span>:number/routine
    <span class="Comment"># 'read-move' completes</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/completed?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">1/completed</span>
    assert <span class="Constant">4</span>:boolean/completed?, [
F read-move-quit: routine failed to terminate on 'q']
    trace <span class="Constant">[test]</span>, <span class="Constant">[reached end]</span>
  ]
  trace-should-contain [
    test: reached end
  ]
]

<span class="muScenario">scenario</span> read-move-illegal-file [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .file too low: 2     .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muScenario">scenario</span> read-move-illegal-rank [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .rank too high: a    .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muScenario">scenario</span> read-move-empty [
  assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
  run [
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move:<span class="muRecipe">recipe</span>, <span class="Constant">1</span>:address:channel, screen:address
    <span class="Comment"># 'read-move' is waiting for input</span>
    wait-for-routine <span class="Constant">2</span>:number
    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
    <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">2/waiting</span>
    assert <span class="Constant">4</span>:boolean/waiting?, [
F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10/newline</span>
    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
    restart <span class="Constant">2</span>:number/routine
    wait-for-routine <span class="Constant">2</span>:number
  ]
  screen-should-contain [
   <span class="Constant"> .that's not enough   .</span>
   <span class="Constant"> .                    .</span>
  ]
]

<span class="muRecipe">recipe</span> make-move [
  <span class="Constant">local-scope</span>
  b:address:array:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  m:address:move<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  from-file:number<span class="Special"> &lt;- </span>get *m, from-file:offset
  from-rank:number<span class="Special"> &lt;- </span>get *m, from-rank:offset
  to-file:number<span class="Special"> &lt;- </span>get *m, to-file:offset
  to-rank:number<span class="Special"> &lt;- </span>get *m, to-rank:offset
  f:address:array:character<span class="Special"> &lt;- </span>index *b, from-file
  src:address:character/square<span class="Special"> &lt;- </span>index-address *f, from-rank
  f<span class="Special"> &lt;- </span>index *b, to-file
  dest:address:character/square<span class="Special"> &lt;- </span>index-address *f, to-rank
  *dest<span class="Special"> &lt;- </span>copy *src
  *src<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
  <span class="muControl">reply</span> b/same-as-ingredient:<span class="Constant">0</span>
]

<span class="muScenario">scenario</span> making-a-move [
  assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
  run [
    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
    <span class="Constant">3</span>:address:move<span class="Special"> &lt;- </span>new move:type
    <span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, from-file:offset
    *<span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
    <span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, from-rank:offset
    *<span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">1/'2'</span>
    <span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, to-file:offset
    *<span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
    <span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, to-rank:offset
    *<span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">3/'4'</span>
    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>make-move <span class="Constant">2</span>:address:array:address:array:character/board, <span class="Constant">3</span>:address:move
    screen:address<span class="Special"> &lt;- </span>print-board screen:address, <span class="Constant">2</span>:address:array:address:array:character/board
  ]
  screen-should-contain [
  <span class="Comment">#  012345678901234567890123456789</span>
   <span class="Constant"> .8 | r n b q k b n r           .</span>
   <span class="Constant"> .7 | p p p p p p p p           .</span>
   <span class="Constant"> .6 |                           .</span>
   <span class="Constant"> .5 |                           .</span>
   <span class="Constant"> .4 |             P             .</span>
   <span class="Constant"> .3 |                           .</span>
   <span class="Constant"> .2 | P P P P P P   P           .</span>
   <span class="Constant"> .1 | R N B Q K B N R           .</span>
   <span class="Constant"> .  +----------------           .</span>
   <span class="Constant"> .    a b c d e f g h           .</span>
   <span class="Constant"> .                              .</span>
  ]
]
</pre>
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