2861 - 'maybe-convert' no longer returns address

9 files changed, 125 insertions, 121 deletions

diff --git a/sandbox/002-typing.mu b/sandbox/002-typing.mu
index 1c27ce98..d7624ccf 100644
--- a/sandbox/002-typing.mu
+++ b/sandbox/002-typing.mu
@@ -25,15 +25,15 @@ def editor-event-loop screen:address:shared:screen, console:address:shared:conso
     break-if quit?  # only in tests
     trace 10, [app], [next-event]
     # 'touch' event
-    t:address:touch-event <- maybe-convert e, touch:variant
+    t:touch-event, is-touch?:boolean <- maybe-convert e, touch:variant
     {
-      break-unless t
-      move-cursor-in-editor screen, editor, *t
+      break-unless is-touch?
+      move-cursor-in-editor screen, editor, t
       loop +next-event:label
     }
     # keyboard events
     {
-      break-if t
+      break-if is-touch?
       screen, editor, go-render?:boolean <- handle-keyboard-event screen, editor, e
       {
         break-unless go-render?
@@ -177,24 +177,24 @@ def handle-keyboard-event screen:address:shared:screen, editor:address:shared:ed
   save-column:number <- copy cursor-column
   # character
   {
-    c:address:character <- maybe-convert e, text:variant
-    break-unless c
+    c:character, is-unicode?:boolean <- maybe-convert e, text:variant
+    break-unless is-unicode?
     trace 10, [app], [handle-keyboard-event: special character]
     # exceptions for special characters go here
     <handle-special-character>
     # ignore any other special characters
-    regular-character?:boolean <- greater-or-equal *c, 32/space
+    regular-character?:boolean <- greater-or-equal c, 32/space
     go-render? <- copy 0/false
     return-unless regular-character?
     # otherwise type it in
     <insert-character-begin>
-    editor, screen, go-render?:boolean <- insert-at-cursor editor, *c, screen
+    editor, screen, go-render?:boolean <- insert-at-cursor editor, c, screen
     <insert-character-end>
     return
   }
   # special key to modify the text or move the cursor
-  k:address:number <- maybe-convert e:event, keycode:variant
-  assert k, [event was of unknown type; neither keyboard nor mouse]
+  k:number, is-keycode?:boolean <- maybe-convert e:event, keycode:variant
+  assert is-keycode?, [event was of unknown type; neither keyboard nor mouse]
   # handlers for each special key will go here
   <handle-special-key>
   go-render? <- copy 1/true
@@ -821,7 +821,7 @@ scenario editor-moves-cursor-down-after-inserting-newline [
 
 after <handle-special-character> [
   {
-    newline?:boolean <- equal *c, 10/newline
+    newline?:boolean <- equal c, 10/newline
     break-unless newline?
     <insert-enter-begin>
     editor <- insert-new-line-and-indent editor, screen
@@ -1003,7 +1003,7 @@ ef]
 
 after <handle-special-key> [
   {
-    paste-start?:boolean <- equal *k, 65507/paste-start
+    paste-start?:boolean <- equal k, 65507/paste-start
     break-unless paste-start?
     *editor <- put *editor, indent?:offset, 0/false
     go-render? <- copy 1/true
@@ -1013,7 +1013,7 @@ after <handle-special-key> [
 
 after <handle-special-key> [
   {
-    paste-end?:boolean <- equal *k, 65506/paste-end
+    paste-end?:boolean <- equal k, 65506/paste-end
     break-unless paste-end?
     *editor <- put *editor, indent?:offset, 1/true
     go-render? <- copy 1/true
diff --git a/sandbox/003-shortcuts.mu b/sandbox/003-shortcuts.mu
index f29773af..8ed01de7 100644
--- a/sandbox/003-shortcuts.mu
+++ b/sandbox/003-shortcuts.mu
@@ -25,7 +25,7 @@ cd]
 
 after <handle-special-character> [
   {
-    tab?:boolean <- equal *c, 9/tab
+    tab?:boolean <- equal c, 9/tab
     break-unless tab?
     <insert-character-begin>
     editor, screen, go-render?:boolean <- insert-at-cursor editor, 32/space, screen
@@ -68,7 +68,7 @@ scenario editor-handles-backspace-key [
 
 after <handle-special-character> [
   {
-    delete-previous-character?:boolean <- equal *c, 8/backspace
+    delete-previous-character?:boolean <- equal c, 8/backspace
     break-unless delete-previous-character?
     <backspace-character-begin>
     editor, screen, go-render?:boolean, backspaced-cell:address:shared:duplex-list:character <- delete-before-cursor editor, screen
@@ -339,7 +339,7 @@ scenario editor-handles-delete-key [
 
 after <handle-special-key> [
   {
-    delete-next-character?:boolean <- equal *k, 65522/delete
+    delete-next-character?:boolean <- equal k, 65522/delete
     break-unless delete-next-character?
     <delete-character-begin>
     editor, screen, go-render?:boolean, deleted-cell:address:shared:duplex-list:character <- delete-at-cursor editor, screen
@@ -415,7 +415,7 @@ scenario editor-moves-cursor-right-with-key [
 
 after <handle-special-key> [
   {
-    move-to-next-character?:boolean <- equal *k, 65514/right-arrow
+    move-to-next-character?:boolean <- equal k, 65514/right-arrow
     break-unless move-to-next-character?
     # if not at end of text
     next-cursor:address:shared:duplex-list:character <- next before-cursor
@@ -699,7 +699,7 @@ scenario editor-moves-cursor-left-with-key [
 
 after <handle-special-key> [
   {
-    move-to-previous-character?:boolean <- equal *k, 65515/left-arrow
+    move-to-previous-character?:boolean <- equal k, 65515/left-arrow
     break-unless move-to-previous-character?
     trace 10, [app], [left arrow]
     # if not at start of text (before-cursor at § sentinel)
@@ -963,7 +963,7 @@ def]
 
 after <handle-special-key> [
   {
-    move-to-previous-line?:boolean <- equal *k, 65517/up-arrow
+    move-to-previous-line?:boolean <- equal k, 65517/up-arrow
     break-unless move-to-previous-line?
     <move-cursor-begin>
     editor, go-render? <- move-to-previous-line editor
@@ -1193,7 +1193,7 @@ def]
 
 after <handle-special-key> [
   {
-    move-to-next-line?:boolean <- equal *k, 65516/down-arrow
+    move-to-next-line?:boolean <- equal k, 65516/down-arrow
     break-unless move-to-next-line?
     <move-cursor-begin>
     editor, go-render? <- move-to-next-line editor, screen-height
@@ -1324,7 +1324,7 @@ scenario editor-moves-to-start-of-line-with-ctrl-a [
 
 after <handle-special-character> [
   {
-    move-to-start-of-line?:boolean <- equal *c, 1/ctrl-a
+    move-to-start-of-line?:boolean <- equal c, 1/ctrl-a
     break-unless move-to-start-of-line?
     <move-cursor-begin>
     move-to-start-of-line editor
@@ -1337,7 +1337,7 @@ after <handle-special-character> [
 
 after <handle-special-key> [
   {
-    move-to-start-of-line?:boolean <- equal *k, 65521/home
+    move-to-start-of-line?:boolean <- equal k, 65521/home
     break-unless move-to-start-of-line?
     <move-cursor-begin>
     move-to-start-of-line editor
@@ -1496,7 +1496,7 @@ scenario editor-moves-to-end-of-line-with-ctrl-e [
 
 after <handle-special-character> [
   {
-    move-to-end-of-line?:boolean <- equal *c, 5/ctrl-e
+    move-to-end-of-line?:boolean <- equal c, 5/ctrl-e
     break-unless move-to-end-of-line?
     <move-cursor-begin>
     move-to-end-of-line editor
@@ -1509,7 +1509,7 @@ after <handle-special-character> [
 
 after <handle-special-key> [
   {
-    move-to-end-of-line?:boolean <- equal *k, 65520/end
+    move-to-end-of-line?:boolean <- equal k, 65520/end
     break-unless move-to-end-of-line?
     <move-cursor-begin>
     move-to-end-of-line editor
@@ -1642,7 +1642,7 @@ scenario editor-deletes-to-start-of-line-with-ctrl-u [
 
 after <handle-special-character> [
   {
-    delete-to-start-of-line?:boolean <- equal *c, 21/ctrl-u
+    delete-to-start-of-line?:boolean <- equal c, 21/ctrl-u
     break-unless delete-to-start-of-line?
     <delete-to-start-of-line-begin>
     deleted-cells:address:shared:duplex-list:character <- delete-to-start-of-line editor
@@ -1776,7 +1776,7 @@ scenario editor-deletes-to-end-of-line-with-ctrl-k [
 
 after <handle-special-character> [
   {
-    delete-to-end-of-line?:boolean <- equal *c, 11/ctrl-k
+    delete-to-end-of-line?:boolean <- equal c, 11/ctrl-k
     break-unless delete-to-end-of-line?
     <delete-to-end-of-line-begin>
     deleted-cells:address:shared:duplex-list:character <- delete-to-end-of-line editor
@@ -2718,7 +2718,7 @@ d]
 
 after <handle-special-character> [
   {
-    page-down?:boolean <- equal *c, 6/ctrl-f
+    page-down?:boolean <- equal c, 6/ctrl-f
     break-unless page-down?
     old-top:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
     <move-cursor-begin>
@@ -2734,7 +2734,7 @@ after <handle-special-character> [
 
 after <handle-special-key> [
   {
-    page-down?:boolean <- equal *k, 65518/page-down
+    page-down?:boolean <- equal k, 65518/page-down
     break-unless page-down?
     old-top:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
     <move-cursor-begin>
@@ -2912,7 +2912,7 @@ d]
 
 after <handle-special-character> [
   {
-    page-up?:boolean <- equal *c, 2/ctrl-b
+    page-up?:boolean <- equal c, 2/ctrl-b
     break-unless page-up?
     old-top:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
     <move-cursor-begin>
@@ -2928,7 +2928,7 @@ after <handle-special-character> [
 
 after <handle-special-key> [
   {
-    page-up?:boolean <- equal *k, 65519/page-up
+    page-up?:boolean <- equal k, 65519/page-up
     break-unless page-up?
     old-top:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
     <move-cursor-begin>
diff --git a/sandbox/004-programming-environment.mu b/sandbox/004-programming-environment.mu
index a329c8c1..22fe6745 100644
--- a/sandbox/004-programming-environment.mu
+++ b/sandbox/004-programming-environment.mu
@@ -56,35 +56,35 @@ def event-loop screen:address:shared:screen, console:address:shared:console, env
     <handle-event>
     # check for global events that will trigger regardless of which editor has focus
     {
-      k:address:number <- maybe-convert e:event, keycode:variant
-      break-unless k
+      k:number, is-keycode?:boolean <- maybe-convert e:event, keycode:variant
+      break-unless is-keycode?
       <global-keypress>
     }
     {
-      c:address:character <- maybe-convert e:event, text:variant
-      break-unless c
+      c:character, is-unicode?:boolean <- maybe-convert e:event, text:variant
+      break-unless is-unicode?
       <global-type>
     }
     # 'touch' event
     {
-      t:address:touch-event <- maybe-convert e:event, touch:variant
-      break-unless t
+      t:touch-event, is-touch?:boolean <- maybe-convert e:event, touch:variant
+      break-unless is-touch?
       # ignore all but 'left-click' events for now
       # todo: test this
-      touch-type:number <- get *t, type:offset
+      touch-type:number <- get t, type:offset
       is-left-click?:boolean <- equal touch-type, 65513/mouse-left
       loop-unless is-left-click?, +next-event:label
       # later exceptions for non-editor touches will go here
       <global-touch>
-      move-cursor-in-editor screen, current-sandbox, *t
+      move-cursor-in-editor screen, current-sandbox, t
       screen <- update-cursor screen, current-sandbox, env
       loop +next-event:label
     }
     # 'resize' event - redraw editor
     # todo: test this after supporting resize in assume-console
     {
-      r:address:resize-event <- maybe-convert e:event, resize:variant
-      break-unless r
+      r:resize-event, is-resize?:boolean <- maybe-convert e:event, resize:variant
+      break-unless is-resize?
       # if more events, we're still resizing; wait until we stop
       more-events?:boolean <- has-more-events? console
       {
@@ -327,7 +327,7 @@ def render-code screen:address:shared:screen, s:address:shared:array:character,
 
 after <global-type> [
   {
-    redraw-screen?:boolean <- equal *c, 12/ctrl-l
+    redraw-screen?:boolean <- equal c, 12/ctrl-l
     break-unless redraw-screen?
     screen <- render-all screen, env:address:shared:programming-environment-data
     sync-screen screen
diff --git a/sandbox/005-sandbox.mu b/sandbox/005-sandbox.mu
index 0b6bd79c..7297c768 100644
--- a/sandbox/005-sandbox.mu
+++ b/sandbox/005-sandbox.mu
@@ -109,7 +109,7 @@ scenario run-and-show-results [
 after <global-keypress> [
   # F4? load all code and run all sandboxes.
   {
-    do-run?:boolean <- equal *k, 65532/F4
+    do-run?:boolean <- equal k, 65532/F4
     break-unless do-run?
     screen <- update-status screen, [running...       ], 245/grey
     test-recipes:address:shared:array:character, _/optional <- next-ingredient
@@ -606,7 +606,7 @@ scenario scrolling-down-past-bottom-of-sandbox-editor [
 # down on sandbox side updates render-from when sandbox editor has cursor at bottom
 after <global-keypress> [
   {
-    down?:boolean <- equal *k, 65516/down-arrow
+    down?:boolean <- equal k, 65516/down-arrow
     break-unless down?
     sandbox-bottom:number <- get *current-sandbox, bottom:offset
     sandbox-cursor:number <- get *current-sandbox, cursor-row:offset
@@ -646,7 +646,7 @@ after <update-cursor-special-cases> [
 # 'up' on sandbox side is like 'down': updates first-sandbox-to-render when necessary
 after <global-keypress> [
   {
-    up?:boolean <- equal *k, 65517/up-arrow
+    up?:boolean <- equal k, 65517/up-arrow
     break-unless up?
     render-from:number <- get *env, render-from:offset
     at-beginning?:boolean <- equal render-from, -1
diff --git a/sandbox/006-sandbox-edit.mu b/sandbox/006-sandbox-edit.mu
index c863efe1..91c632ed 100644
--- a/sandbox/006-sandbox-edit.mu
+++ b/sandbox/006-sandbox-edit.mu
@@ -67,13 +67,13 @@ after <global-touch> [
   # below editor? pop appropriate sandbox contents back into sandbox editor provided it's empty
   {
     sandbox-left-margin:number <- get *current-sandbox, left:offset
-    click-column:number <- get *t, column:offset
+    click-column:number <- get t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
     first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
-    click-row:number <- get *t, row:offset
+    click-row:number <- get t, row:offset
     below-sandbox-editor?:boolean <- greater-or-equal click-row, first-sandbox-begins
     break-unless below-sandbox-editor?
     empty-sandbox-editor?:boolean <- empty-editor? current-sandbox
diff --git a/sandbox/007-sandbox-delete.mu b/sandbox/007-sandbox-delete.mu
index f99012b6..2fed31cd 100644
--- a/sandbox/007-sandbox-delete.mu
+++ b/sandbox/007-sandbox-delete.mu
@@ -66,7 +66,7 @@ scenario deleting-sandboxes [
 after <global-touch> [
   # on a sandbox delete icon? process delete
   {
-    was-delete?:boolean <- delete-sandbox *t, env
+    was-delete?:boolean <- delete-sandbox t, env
     break-unless was-delete?
     hide-screen screen
     screen <- render-sandbox-side screen, env
diff --git a/sandbox/008-sandbox-test.mu b/sandbox/008-sandbox-test.mu
index acd4c04d..04a83ac6 100644
--- a/sandbox/008-sandbox-test.mu
+++ b/sandbox/008-sandbox-test.mu
@@ -106,13 +106,13 @@ after <global-touch> [
   # check if it's inside the output of any sandbox
   {
     sandbox-left-margin:number <- get *current-sandbox, left:offset
-    click-column:number <- get *t, column:offset
+    click-column:number <- get t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
     first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
-    click-row:number <- get *t, row:offset
+    click-row:number <- get t, row:offset
     below-sandbox-editor?:boolean <- greater-or-equal click-row, first-sandbox-begins
     break-unless below-sandbox-editor?
     # identify the sandbox whose output is being clicked on
diff --git a/sandbox/009-sandbox-trace.mu b/sandbox/009-sandbox-trace.mu
index a85a1920..c5f96726 100644
--- a/sandbox/009-sandbox-trace.mu
+++ b/sandbox/009-sandbox-trace.mu
@@ -134,13 +134,13 @@ after <global-touch> [
   # check if it's inside the code of any sandbox
   {
     sandbox-left-margin:number <- get *current-sandbox, left:offset
-    click-column:number <- get *t, column:offset
+    click-column:number <- get t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
     first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
-    click-row:number <- get *t, row:offset
+    click-row:number <- get t, row:offset
     below-sandbox-editor?:boolean <- greater-or-equal click-row, first-sandbox-begins
     break-unless below-sandbox-editor?
     # identify the sandbox whose code is being clicked on
diff --git a/sandbox/011-editor-undo.mu b/sandbox/011-editor-undo.mu
index 07ecb14f..94135346 100644
--- a/sandbox/011-editor-undo.mu
+++ b/sandbox/011-editor-undo.mu
@@ -63,7 +63,7 @@ container editor-data [
 # ctrl-z - undo operation
 after <handle-special-character> [
   {
-    undo?:boolean <- equal *c, 26/ctrl-z
+    undo?:boolean <- equal c, 26/ctrl-z
     break-unless undo?
     undo:address:shared:list:address:shared:operation <- get *editor, undo:offset
     break-unless undo
@@ -81,7 +81,7 @@ after <handle-special-character> [
 # ctrl-y - redo operation
 after <handle-special-character> [
   {
-    redo?:boolean <- equal *c, 25/ctrl-y
+    redo?:boolean <- equal c, 25/ctrl-y
     break-unless redo?
     redo:address:shared:list:address:shared:operation <- get *editor, redo:offset
     break-unless redo
@@ -151,16 +151,17 @@ before <insert-character-end> [
     # if previous operation was an insert, coalesce this operation with it
     break-unless undo
     op:address:shared:operation <- first undo
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
-    break-unless typing
-    previous-coalesce-tag:number <- get *typing, tag:offset
+    typing:insert-operation, is-insert?:boolean <- maybe-convert *op, typing:variant
+    break-unless is-insert?
+    previous-coalesce-tag:number <- get typing, tag:offset
     break-unless previous-coalesce-tag
     before-cursor:address:shared:duplex-list:character <- get *editor, before-cursor:offset
     insert-until:address:shared:duplex-list:character <- next before-cursor
-    *typing <- put *typing, insert-until:offset, insert-until
-    *typing <- put *typing, after-row:offset, cursor-row
-    *typing <- put *typing, after-column:offset, cursor-column
-    *typing <- put *typing, after-top-of-screen:offset, top-after
+    typing <- put typing, insert-until:offset, insert-until
+    typing <- put typing, after-row:offset, cursor-row
+    typing <- put typing, after-column:offset, cursor-column
+    typing <- put typing, after-top-of-screen:offset, top-after
+    *op <- merge 0/insert-operation, typing
     break +done-adding-insert-operation:label
   }
   # if not, create a new operation
@@ -210,19 +211,19 @@ def add-operation editor:address:shared:editor-data, op:address:shared:operation
 
 after <handle-undo> [
   {
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
-    break-unless typing
-    start:address:shared:duplex-list:character <- get *typing, insert-from:offset
-    end:address:shared:duplex-list:character <- get *typing, insert-until:offset
+    typing:insert-operation, is-insert?:boolean <- maybe-convert *op, typing:variant
+    break-unless is-insert?
+    start:address:shared:duplex-list:character <- get typing, insert-from:offset
+    end:address:shared:duplex-list:character <- get typing, insert-until:offset
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     before-cursor:address:shared:duplex-list:character <- prev start
     *editor <- put *editor, before-cursor:offset, before-cursor
     remove-between before-cursor, end
-    cursor-row <- get *typing, before-row:offset
+    cursor-row <- get typing, before-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *typing, before-column:offset
+    cursor-column <- get typing, before-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *typing, before-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get typing, before-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
@@ -410,18 +411,18 @@ scenario editor-redo-typing [
 
 after <handle-redo> [
   {
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
-    break-unless typing
+    typing:insert-operation, is-insert?:boolean <- maybe-convert *op, typing:variant
+    break-unless is-insert?
     before-cursor <- get *editor, before-cursor:offset
-    insert-from:address:shared:duplex-list:character <- get *typing, insert-from:offset  # ignore insert-to because it's already been spliced away
+    insert-from:address:shared:duplex-list:character <- get typing, insert-from:offset  # ignore insert-to because it's already been spliced away
     # assert insert-to matches next(before-cursor)
     insert-range before-cursor, insert-from
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
-    cursor-row <- get *typing, after-row:offset
+    cursor-row <- get typing, after-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *typing, after-column:offset
+    cursor-column <- get typing, after-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *typing, after-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get typing, after-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
@@ -730,14 +731,15 @@ before <move-cursor-end> [
     undo:address:shared:list:address:shared:operation <- get *editor, undo:offset
     break-unless undo
     op:address:shared:operation <- first undo
-    move:address:move-operation <- maybe-convert *op, move:variant
-    break-unless move
-    previous-coalesce-tag:number <- get *move, tag:offset
+    move:move-operation, is-move?:boolean <- maybe-convert *op, move:variant
+    break-unless is-move?
+    previous-coalesce-tag:number <- get move, tag:offset
     coalesce?:boolean <- equal undo-coalesce-tag, previous-coalesce-tag
     break-unless coalesce?
-    *move <- put *move, after-row:offset, cursor-row
-    *move <- put *move, after-column:offset, cursor-column
-    *move <- put *move, after-top-of-screen:offset, top-after
+    move <- put move, after-row:offset, cursor-row
+    move <- put move, after-column:offset, cursor-column
+    move <- put move, after-top-of-screen:offset, top-after
+    *op <- merge 1/move-operation, move
     break +done-adding-move-operation:label
   }
   op:address:shared:operation <- new operation:type
@@ -748,14 +750,14 @@ before <move-cursor-end> [
 
 after <handle-undo> [
   {
-    move:address:move-operation <- maybe-convert *op, move:variant
-    break-unless move
+    move:move-operation, is-move?:boolean <- maybe-convert *op, move:variant
+    break-unless is-move?
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
-    cursor-row <- get *move, before-row:offset
+    cursor-row <- get move, before-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *move, before-column:offset
+    cursor-column <- get move, before-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *move, before-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get move, before-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
@@ -1378,14 +1380,14 @@ ghi]
 
 after <handle-redo> [
   {
-    move:address:move-operation <- maybe-convert *op, move:variant
-    break-unless move
+    move:move-operation, is-move?:boolean <- maybe-convert *op, move:variant
+    break-unless is-move?
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
-    cursor-row <- get *move, after-row:offset
+    cursor-row <- get move, after-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *move, after-column:offset
+    cursor-column <- get move, after-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *move, after-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get move, after-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
@@ -1620,18 +1622,19 @@ before <backspace-character-end> [
       # if previous operation was an insert, coalesce this operation with it
       break-unless *undo
       op:address:shared:operation <- first undo
-      deletion:address:delete-operation <- maybe-convert *op, delete:variant
-      break-unless deletion
-      previous-coalesce-tag:number <- get *deletion, tag:offset
+      deletion:delete-operation, is-delete?:boolean <- maybe-convert *op, delete:variant
+      break-unless is-delete?
+      previous-coalesce-tag:number <- get deletion, tag:offset
       coalesce?:boolean <- equal previous-coalesce-tag, 1/coalesce-backspace
       break-unless coalesce?
-      *deletion <- put *deletion, delete-from:offset, before-cursor
-      backspaced-so-far:address:shared:duplex-list:character <- get *deletion, deleted-text:offset
+      deletion <- put deletion, delete-from:offset, before-cursor
+      backspaced-so-far:address:shared:duplex-list:character <- get deletion, deleted-text:offset
       insert-range backspaced-cell, backspaced-so-far
-      *deletion <- put *deletion, deleted-text:offset, backspaced-cell
-      *deletion <- put *deletion, after-row:offset, cursor-row
-      *deletion <- put *deletion, after-column:offset, cursor-column
-      *deletion <- put *deletion, after-top-of-screen:offset, top-after
+      deletion <- put deletion, deleted-text:offset, backspaced-cell
+      deletion <- put deletion, after-row:offset, cursor-row
+      deletion <- put deletion, after-column:offset, cursor-column
+      deletion <- put deletion, after-top-of-screen:offset, top-after
+      *op <- merge 2/delete-operation, deletion
       break +done-adding-backspace-operation:label
     }
     # if not, create a new operation
@@ -1645,38 +1648,38 @@ before <backspace-character-end> [
 
 after <handle-undo> [
   {
-    deletion:address:delete-operation <- maybe-convert *op, delete:variant
-    break-unless deletion
-    anchor:address:shared:duplex-list:character <- get *deletion, delete-from:offset
+    deletion:delete-operation, is-delete?:boolean <- maybe-convert *op, delete:variant
+    break-unless is-delete?
+    anchor:address:shared:duplex-list:character <- get deletion, delete-from:offset
     break-unless anchor
-    deleted:address:shared:duplex-list:character <- get *deletion, deleted-text:offset
+    deleted:address:shared:duplex-list:character <- get deletion, deleted-text:offset
     old-cursor:address:shared:duplex-list:character <- last deleted
     insert-range anchor, deleted
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     before-cursor <- copy old-cursor
-    cursor-row <- get *deletion, before-row:offset
+    cursor-row <- get deletion, before-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *deletion, before-column:offset
+    cursor-column <- get deletion, before-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *deletion, before-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get deletion, before-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
 
 after <handle-redo> [
   {
-    deletion:address:delete-operation <- maybe-convert *op, delete:variant
-    break-unless deletion
-    start:address:shared:duplex-list:character <- get *deletion, delete-from:offset
-    end:address:shared:duplex-list:character <- get *deletion, delete-until:offset
+    deletion:delete-operation, is-delete?:boolean <- maybe-convert *op, delete:variant
+    break-unless is-delete?
+    start:address:shared:duplex-list:character <- get deletion, delete-from:offset
+    end:address:shared:duplex-list:character <- get deletion, delete-until:offset
     data:address:shared:duplex-list:character <- get *editor, data:offset
     remove-between start, end
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
-    cursor-row <- get *deletion, after-row:offset
+    cursor-row <- get deletion, after-row:offset
     *editor <- put *editor, cursor-row:offset, cursor-row
-    cursor-column <- get *deletion, after-column:offset
+    cursor-column <- get deletion, after-column:offset
     *editor <- put *editor, cursor-column:offset, cursor-column
-    top:address:shared:duplex-list:character <- get *deletion, before-top-of-screen:offset
+    top:address:shared:duplex-list:character <- get deletion, before-top-of-screen:offset
     *editor <- put *editor, top-of-screen:offset, top
   }
 ]
@@ -1845,19 +1848,20 @@ before <delete-character-end> [
       # if previous operation was an insert, coalesce this operation with it
       break-unless undo
       op:address:shared:operation <- first undo
-      deletion:address:delete-operation <- maybe-convert *op, delete:variant
-      break-unless deletion
-      previous-coalesce-tag:number <- get *deletion, tag:offset
+      deletion:delete-operation, is-delete?:boolean <- maybe-convert *op, delete:variant
+      break-unless is-delete?
+      previous-coalesce-tag:number <- get deletion, tag:offset
       coalesce?:boolean <- equal previous-coalesce-tag, 2/coalesce-delete
       break-unless coalesce?
       delete-until:address:shared:duplex-list:character <- next before-cursor
-      *deletion <- put *deletion, delete-until:offset, delete-until
-      deleted-so-far:address:shared:duplex-list:character <- get *deletion, deleted-text:offset
+      deletion <- put deletion, delete-until:offset, delete-until
+      deleted-so-far:address:shared:duplex-list:character <- get deletion, deleted-text:offset
       deleted-so-far <- append deleted-so-far, deleted-cell
-      *deletion <- put *deletion, deleted-text:offset, deleted-so-far
-      *deletion <- put *deletion, after-row:offset, cursor-row
-      *deletion <- put *deletion, after-column:offset, cursor-column
-      *deletion <- put *deletion, after-top-of-screen:offset, top-after
+      deletion <- put deletion, deleted-text:offset, deleted-so-far
+      deletion <- put deletion, after-row:offset, cursor-row
+      deletion <- put deletion, after-column:offset, cursor-column
+      deletion <- put deletion, after-top-of-screen:offset, top-after
+      *op <- merge 2/delete-operation, deletion
       break +done-adding-delete-operation:label
     }
     # if not, create a new operation