10 files changed, 36 insertions, 36 deletions

diff --git a/sandbox/001-editor.mu b/sandbox/001-editor.mu
index 8855395a..963bb1cf 100644
--- a/sandbox/001-editor.mu
+++ b/sandbox/001-editor.mu
@@ -6,10 +6,10 @@ def main text:text [
   local-scope
   load-inputs
   open-console
-  clear-screen 0/screen  # non-scrolling app
+  clear-screen null/screen  # non-scrolling app
   e:&:editor <- new-editor text, 0/left, 5/right
-  render 0/screen, e
-  wait-for-event 0/console
+  render null/screen, e
+  wait-for-event null/console
   close-console
 ]
 
@@ -61,7 +61,7 @@ def new-editor s:text, left:num, right:num -> result:&:editor [
   *result <- put *result, cursor-row:offset, 1/top
   *result <- put *result, cursor-column:offset, left
   # initialize empty contents
-  init:&:duplex-list:char <- push 167/§, 0/tail
+  init:&:duplex-list:char <- push 167/§, null
   *result <- put *result, data:offset, init
   *result <- put *result, top-of-screen:offset, init
   *result <- put *result, before-cursor:offset, init
@@ -80,7 +80,7 @@ scenario editor-initializes-without-data [
   local-scope
   assume-screen 5/width, 3/height
   run [
-    e:&:editor <- new-editor 0/data, 2/left, 5/right
+    e:&:editor <- new-editor null/data, 2/left, 5/right
     2:editor/raw <- copy *e
   ]
   memory-should-contain [
diff --git a/sandbox/002-typing.mu b/sandbox/002-typing.mu
index a67fcf3c..ef3f25d2 100644
--- a/sandbox/002-typing.mu
+++ b/sandbox/002-typing.mu
@@ -6,10 +6,10 @@ def! main text:text [
   local-scope
   load-inputs
   open-console
-  clear-screen 0/screen  # non-scrolling app
+  clear-screen null/screen  # non-scrolling app
   editor:&:editor <- new-editor text, 5/left, 45/right
-  editor-render 0/screen, editor
-  editor-event-loop 0/screen, 0/console, editor
+  editor-render null/screen, editor
+  editor-event-loop null/screen, null/console, editor
   close-console
 ]
 
@@ -223,7 +223,7 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> go-render?:bool
   next:&:duplex-list:char <- next before-cursor
   {
     # at end of all text? no need to scroll? just print the character and leave
-    at-end?:bool <- equal next, 0/null
+    at-end?:bool <- equal next, null
     break-unless at-end?
     bottom:num <- subtract screen-height, 1
     at-bottom?:bool <- equal save-row, bottom
@@ -701,7 +701,7 @@ after <insert-character-special-case> [
     just-before-wrap?:bool <- greater-or-equal cursor-column, before-wrap-column
     next:&:duplex-list:char <- next before-cursor
     # at end of line? next == 0 || next.value == 10/newline
-    at-end-of-line?:bool <- equal next, 0
+    at-end-of-line?:bool <- equal next, null
     {
       break-if at-end-of-line?
       next-character:char <- get *next, value:offset
diff --git a/sandbox/003-shortcuts.mu b/sandbox/003-shortcuts.mu
index db19443d..c9e66d5b 100644
--- a/sandbox/003-shortcuts.mu
+++ b/sandbox/003-shortcuts.mu
@@ -113,7 +113,7 @@ def delete-before-cursor editor:&:editor, screen:&:screen -> go-render?:bool, ba
   data:&:duplex-list:char <- get *editor, data:offset
   # if at start of text (before-cursor at § sentinel), return
   prev:&:duplex-list:char <- prev before-cursor
-  return-unless prev, false/no-more-render, 0/nothing-deleted
+  return-unless prev, false/no-more-render, null/nothing-deleted
   trace 10, [app], [delete-before-cursor]
   original-row:num <- get *editor, cursor-row:offset
   move-cursor-coordinates-left editor
@@ -2353,7 +2353,7 @@ def delete-to-end-of-line editor:&:editor -> result:&:duplex-list:char, editor:&
   start:&:duplex-list:char <- get *editor, before-cursor:offset
   end:&:duplex-list:char <- next start
   {
-    at-end-of-text?:bool <- equal end, 0/null
+    at-end-of-text?:bool <- equal end, null
     break-if at-end-of-text?
     curr:char <- get *end, value:offset
     at-end-of-line?:bool <- equal curr, 10/newline
diff --git a/sandbox/004-programming-environment.mu b/sandbox/004-programming-environment.mu
index 1208d0e8..1454144b 100644
--- a/sandbox/004-programming-environment.mu
+++ b/sandbox/004-programming-environment.mu
@@ -3,10 +3,10 @@
 def! main [
   local-scope
   open-console
-  clear-screen 0/screen  # non-scrolling app
-  env:&:environment <- new-programming-environment 0/filesystem, 0/screen
-  render-all 0/screen, env, render
-  event-loop 0/screen, 0/console, env, 0/filesystem
+  clear-screen null/screen  # non-scrolling app
+  env:&:environment <- new-programming-environment null/filesystem, null/screen
+  render-all null/screen, env, render
+  event-loop null/screen, null/console, env, null/filesystem
 ]
 
 container environment [
diff --git a/sandbox/005-sandbox.mu b/sandbox/005-sandbox.mu
index ae4372a1..632a5df1 100644
--- a/sandbox/005-sandbox.mu
+++ b/sandbox/005-sandbox.mu
@@ -10,11 +10,11 @@
 def! main [
   local-scope
   open-console
-  clear-screen 0/screen  # non-scrolling app
-  env:&:environment <- new-programming-environment 0/filesystem, 0/screen
-  env <- restore-sandboxes env, 0/filesystem
-  render-all 0/screen, env, render
-  event-loop 0/screen, 0/console, env, 0/filesystem
+  clear-screen null/screen  # non-scrolling app
+  env:&:environment <- new-programming-environment null/filesystem, null/screen
+  env <- restore-sandboxes env, null/filesystem
+  render-all null/screen, env, render
+  event-loop null/screen, null/console, env, null/filesystem
 ]
 
 container environment [
@@ -160,7 +160,7 @@ def run-sandboxes env:&:environment, resources:&:resources, screen:&:screen -> e
     # needs to be before running them, in case we die when running
     save-sandboxes env, resources
     # clear sandbox editor
-    init:&:duplex-list:char <- push 167/§, 0/tail
+    init:&:duplex-list:char <- push 167/§, null
     *current-sandbox <- put *current-sandbox, data:offset, init
     *current-sandbox <- put *current-sandbox, top-of-screen:offset, init
   }
@@ -458,8 +458,8 @@ def restore-sandboxes env:&:environment, resources:&:resources -> env:&:environm
   load-inputs
   # read all scenarios, pushing them to end of a list of scenarios
   idx:num <- copy 0
-  curr:&:sandbox <- copy 0
-  prev:&:sandbox <- copy 0
+  curr:&:sandbox <- copy null
+  prev:&:sandbox <- copy null
   {
     filename:text <- append [lesson/], idx
     contents:text <- slurp resources, filename
@@ -668,7 +668,7 @@ def editor-contents editor:&:editor -> result:text [
   # skip § sentinel
   assert curr, [editor without data is illegal; must have at least a sentinel]
   curr <- next curr
-  return-unless curr, 0
+  return-unless curr, null
   {
     break-unless curr
     c:char <- get *curr, value:offset
@@ -817,15 +817,15 @@ after <global-keypress> [
 ]
 
 # sandbox belonging to 'env' whose next-sandbox is 'in'
-# return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox
+# return null if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox
 def previous-sandbox env:&:environment, in:&:sandbox -> out:&:sandbox [
   local-scope
   load-inputs
   curr:&:sandbox <- get *env, sandbox:offset
-  return-unless curr, 0/nil
+  return-unless curr, null
   next:&:sandbox <- get *curr, next-sandbox:offset
   {
-    return-unless next, 0/nil
+    return-unless next, null
     found?:bool <- equal next, in
     break-if found?
     curr <- copy next
diff --git a/sandbox/006-sandbox-copy.mu b/sandbox/006-sandbox-copy.mu
index 4b7222f3..0eae6cf7 100644
--- a/sandbox/006-sandbox-copy.mu
+++ b/sandbox/006-sandbox-copy.mu
@@ -194,7 +194,7 @@ def find-sandbox env:&:environment, click-row:num -> result:&:sandbox [
     curr-sandbox <- get *curr-sandbox, next-sandbox:offset
     loop
   }
-  return 0/not-found
+  return null/not-found
 ]
 
 def click-on-sandbox-area? click-row:num, env:&:environment -> result:bool [
diff --git a/sandbox/009-sandbox-test.mu b/sandbox/009-sandbox-test.mu
index 3fd4dafc..c22916a7 100644
--- a/sandbox/009-sandbox-test.mu
+++ b/sandbox/009-sandbox-test.mu
@@ -173,9 +173,9 @@ def find-click-in-sandbox-output env:&:environment, click-row:num -> sandbox:&:s
   }
   # return sandbox if click is in its output region
   response-starting-row:num <- get *sandbox, response-starting-row-on-screen:offset
-  return-unless response-starting-row, 0/no-click-in-sandbox-output, 0/sandbox-index
+  return-unless response-starting-row, null/no-click-in-sandbox-output, 0/sandbox-index
   click-in-response?:bool <- greater-or-equal click-row, response-starting-row
-  return-unless click-in-response?, 0/no-click-in-sandbox-output, 0/sandbox-index
+  return-unless click-in-response?, null/no-click-in-sandbox-output, 0/sandbox-index
   return sandbox, sandbox-index
 ]
 
@@ -186,7 +186,7 @@ def toggle-expected-response sandbox:&:sandbox -> sandbox:&:sandbox [
   {
     # if expected-response is set, reset
     break-unless expected-response
-    *sandbox <- put *sandbox, expected-response:offset, 0
+    *sandbox <- put *sandbox, expected-response:offset, null
   }
   {
     # if not, set expected response to the current response
diff --git a/sandbox/010-sandbox-trace.mu b/sandbox/010-sandbox-trace.mu
index 6d775322..d544dd8c 100644
--- a/sandbox/010-sandbox-trace.mu
+++ b/sandbox/010-sandbox-trace.mu
@@ -225,7 +225,7 @@ def find-click-in-sandbox-code env:&:environment, click-row:num -> sandbox:&:san
   click-on-sandbox-code?:bool <- and click-above-response?, click-below-menu?
   {
     break-if click-on-sandbox-code?
-    return 0/no-click-in-sandbox-output
+    return null/no-click-in-sandbox-output
   }
   return sandbox
 ]
diff --git a/sandbox/011-errors.mu b/sandbox/011-errors.mu
index 8678989f..2f59d1fe 100644
--- a/sandbox/011-errors.mu
+++ b/sandbox/011-errors.mu
@@ -253,7 +253,7 @@ scenario run-updates-errors-for-shape-shifting-recipes [
       |recipe foo x:_elem -> z:_elem [|
       |  local-scope|
       |  load-ingredients|
-      |  y:&:num <- copy 0|
+      |  y:&:num <- copy null|
       |  z <- add x, y|
       |]|
     ]
@@ -308,7 +308,7 @@ scenario run-avoids-spurious-errors-on-reloading-shape-shifting-recipes [
     ]
   ]
   # call code that uses other variants of it, but not it itself
-  test-sandbox:text <- new [x:&:list:num <- copy 0
+  test-sandbox:text <- new [x:&:list:num <- copy null
 to-text x]
   env:&:environment <- new-programming-environment resources, screen, test-sandbox
   render-all screen, env, render
diff --git a/sandbox/012-editor-undo.mu b/sandbox/012-editor-undo.mu
index 23448ea2..69afd207 100644
--- a/sandbox/012-editor-undo.mu
+++ b/sandbox/012-editor-undo.mu
@@ -204,7 +204,7 @@ def add-operation editor:&:editor, op:&:operation -> editor:&:editor [
   undo <- push op undo
   *editor <- put *editor, undo:offset, undo
   redo:&:list:&:operation <- get *editor, redo:offset
-  redo <- copy 0
+  redo <- copy null
   *editor <- put *editor, redo:offset, redo
 ]