The user wants me to look at GitHub issue #72, specifically the most recent comment. Let me fetch that information.
author: associate-1 association: member edited: false status: none -- Analysis complete — see the detailed findings in [this comment on PR #71](https://github.com/codeassociates/occam2go/pull/71#issuecomment-3945869818). Seven unsupported features were identified and filed as individual issues: #73, #74, #75, #76, #77, #78, #79. -- author: dboreham association: member edited: false status: none -- I've been doing some manual testing of this. The life example now compiles and runs. In addition a recent fix to the transpiler golang preamble has made individual keystrokes on the keyboard channel work correctly. However, when I run the life program I'm not sure it is working. I see it display "Idle". If I hit the "e" key it seems to pause updating the screen, perhaps indicating that has indeed entered edit mode. But when I hit the A, B, C, D keys for direction and asterisk to activate a cell, I don't see anything on the screen. If I hit the q key it looks like it exits edit mode. So at least something is working but I haven't been able to get it to fully work with live cells and running the game. --
{
"subagent_type": "Explore",
"prompt": "Find all files related to the \"life\" or \"Game of Life\" example in this repository. Look for .occ source files, any related test files, and any documentation about this example. Search broadly - check examples/, kroc/, and any other directories. I need to understand what source files make up the life example and how it's built/run."
}[
{
"type": "text",
"text": "Perfect! Now let me compile the comprehensive report of all files related to the life example:\n\n## Summary of Life/Game of Life Example Files\n\nBased on my comprehensive search, here are all the files related to the \"life\" or \"Game of Life\" example in this repository:\n\n### Primary Source File\n- **`/home/david/projects/code-associates/occam2go/historical-examples/life.occ`** (453 lines)\n - The main Conway's Game of Life implementation in occam\n - Adapted from \"Programming in occam®2\" by Geraint Jones and Michael Goldsmith (1988, 2001)\n - Originally adapted for occam2go by replacing book library functions with inline definitions\n - Contains full implementation of cellular automaton including:\n - Helper procedures (`write.string`, `write.small.int`)\n - Configuration constants (20x20 board, radius 1)\n - Protocol definitions (STATE, COMMAND, RESPONSE)\n - Cell processes (broadcast, calculate next state)\n - Terminal I/O routines (ANSI escape sequences for screen control)\n - Display routines (initialization, state display, activity display)\n - Interactive editor (keyboard-based cell manipulation)\n - Game controller (manages editing vs. running modes)\n - Main entry point `PROC life (CHAN BYTE keyboard?, screen!, error!)`\n\n### Git History & Related Commits\nThe life example has been the subject of several important development efforts:\n\n1. **Initial Addition** (PR #71, commit 8acee6e / 9588006):\n - \"Add Conway Life example program from Programming in occam2 for study of transpiler compatibility\"\n - Added the original life.occ file\n\n2. **Game of Life Compilation Fix** (PR #72, commit 126b182):\n - \"Fix Game of Life example compilation (#72)\"\n - Fixed three transpiler bugs:\n - VAL [n]TYPE abbreviations generated wrong Go type\n - ALT guard channels hardcoded to chan int\n - Added chanElemTypes tracking for channel element types\n - Adapted life.occ to remove dependencies on book library functions\n - Added inline helper PROCs and rewrote ANSI escape output\n\n3. **Issues Resolution** (PR #80, commit 34f69ff):\n - \"Merge pull request #80 from codeassociates/fix/life-occ-issues-73-75-78-79\"\n - Addressed issues #73, #75, #78, #79\n\n4. **Entry Point PROC Pattern** (PR #89, commit 5ab69cb):\n - \"Use entry point PROC pattern for life.occ terminal I/O (#90)\"\n - Wrapped main body in `PROC life (CHAN BYTE keyboard?, screen!, error!)`\n - Added channel direction annotations to all PROCs\n - Fixed ALT guard variables to use `<-chan` (receive-only)\n\n5. **Raw Terminal Keyboard Support** (PR #91, commit 6272c72):\n - \"Merge pull request #91 from codeassociates/feat/raw-terminal-keyboard-90\"\n - Latest enhancement for terminal I/O\n\n### Related Git Branches\n- `fix/life-occ-compilation-72` — Fix for compilation issues\n- `fix/life-occ-issues-73-75-78-79` — Additional issue fixes\n- `dboreham/add-life-example` — Original feature branch\n\n### Related Image Assets\n- `/home/david/projects/code-associates/occam2go/kroc/modules/occade/examples/images/lifeno.png`\n- `/home/david/projects/code-associates/occam2go/kroc/modules/occade/examples/images/lifeyes.png`\n - These appear to be documentation images for an occade-based (graphical) version of life\n\n### Build/Run Instructions\nBased on the code structure, the life example can be built and run as follows:\n\n```bash\n./occam2go -o life.go historical-examples/life.occ\ngo run life.go\n```\n\nThe transpiler will automatically generate the `main()` function with stdin/stdout/stderr harness since the entry point is defined as `PROC life (CHAN BYTE keyboard?, screen!, error!)`.\n\n### Key Features Demonstrated by Life Example\nThe life.occ file serves as a comprehensive real-world test case demonstrating:\n- Multi-dimensional channel arrays (`[][][]CHAN OF STATE link`)\n- Protocol definitions (STATE, COMMAND with variants, RESPONSE)\n- PAR (parallel) blocks with replicators\n- CASE statements (multi-branch conditionals)\n- PRI ALT (prioritized alternation) with guards\n- Channel send/receive operations\n- WHILE loops with complex state management\n- Nested PROCs with parameter passing\n- Array slicing and indexing\n- Type conversions (INT to BYTE, BOOL operations)\n- Bitwise modulo operations (`\\`)\n\nThis example has been crucial in driving transpiler development, particularly for fixing issues with ALT guards, channel element type tracking, and array abbreviation handling."
},
{
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"text": "agentId: a8963fa7291c1a9d0 (for resuming to continue this agent's work if needed)\n<usage>total_tokens: 35065\ntool_uses: 21\nduration_ms: 32121</usage>"
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]{"body":"A code example from the book \"Programming in Occam2\" has been added to this repo here: ./historical-examples/life.occ\n\nPlease analyze this program to determine why it doesn't parse and run with the current version of the transpiler.\n\n","title":"Investigate transpiler compatibility with example program from the Occam2 book"}The user wants me to look at the most recent comment on issue #72, which is from dboreham describing manual testing of the life example. The life program compiles and runs, but there seem to be functional issues:
So the program is partially working but the edit mode doesn't seem to be functioning correctly.
Now I need to examine the life.occ source code to understand how the editor is supposed to work and identify where the issue might be.
{
"file_path": "/home/david/projects/code-associates/occam2go/historical-examples/life.occ"
} 1→-- Code copied from Programming in occam®2
2→-- © Geraint Jones, Michael Goldsmith 1988, 2001.
3→-- Permission is granted to copy this material for private study; for other uses please contact occam-book@comlab.ox.ac.uk
4→--
5→-- The program in this chapter plays Life on a terminal screen.
6→--
7→-- Adapted for occam2go: replaced book-library functions
8→-- (write.string, write.formatted, DATA.ITEM) with inline
9→-- definitions; added terminal.keyboard/terminal.screen declarations.
10→--
11→
12→--
13→-- helper procedures (replaces book standard library)
14→--
15→
16→PROC write.string(CHAN OF BYTE out!, VAL []BYTE s)
17→ SEQ i = 0 FOR SIZE s
18→ out ! s[i]
19→:
20→
21→PROC write.small.int(CHAN OF BYTE out!, VAL INT n)
22→ -- outputs a small non-negative integer (0..999) as decimal digits
23→ IF
24→ n >= 100
25→ SEQ
26→ out ! BYTE ((n / 100) + (INT '0'))
27→ out ! BYTE (((n / 10) \ 10) + (INT '0'))
28→ out ! BYTE ((n \ 10) + (INT '0'))
29→ n >= 10
30→ SEQ
31→ out ! BYTE ((n / 10) + (INT '0'))
32→ out ! BYTE ((n \ 10) + (INT '0'))
33→ TRUE
34→ out ! BYTE (n + (INT '0'))
35→:
36→
37→--
38→-- configuration constants
39→--
40→
41→VAL INT array.width IS 20 : -- number of cells across the board
42→VAL INT array.height IS 20 : -- number of cells down the board
43→
44→VAL INT radius IS 1 : -- of the `sphere of influence'
45→VAL INT diameter IS (2 * radius) + 1 :
46→VAL INT neighbours IS (diameter * diameter) - 1 :
47→
48→VAL INT number.of.cells IS array.height * array.width :
49→VAL INT number.of.links IS neighbours * number.of.cells :
50→
51→--
52→-- protocols
53→--
54→
55→PROTOCOL STATE IS BOOL :
56→
57→VAL BOOL alive IS TRUE :
58→VAL BOOL dead IS NOT alive :
59→
60→PROTOCOL COMMAND
61→ CASE
62→ set.state; BOOL
63→ evolve
64→ terminate
65→:
66→
67→PROTOCOL RESPONSE IS BOOL; BOOL :
68→--
69→-- cell processes
70→--
71→
72→PROC broadcast.present.state([][][]CHAN OF STATE link,
73→ VAL INT x, y, VAL BOOL state )
74→ PAR d = 0 FOR neighbours
75→ link[x][y][d] ! state
76→:
77→
78→PROC calculate.next.state([][][]CHAN OF STATE link,
79→ VAL []INT nx, ny,
80→ VAL BOOL state, BOOL next.state )
81→ INT count : -- number of living neighbours
82→ SEQ
83→ [neighbours]BOOL state.of.neighbour :
84→ SEQ
85→ PAR d = 0 FOR neighbours
86→ link[nx[d]][ny[d]][d] ? state.of.neighbour[d]
87→ count := 0
88→ SEQ d = 0 FOR neighbours
89→ IF
90→ state.of.neighbour[d] = alive
91→ count := count + 1
92→ state.of.neighbour[d] = dead
93→ SKIP
94→ IF
95→ count < 2 -- death from isolation
96→ next.state := dead
97→ count = 2 -- this cell is stable
98→ next.state := state
99→ count = 3 -- stable if alive, a birth if dead
100→ next.state := alive
101→ count > 3 -- death from overcrowding
102→ next.state := dead
103→:
104→
105→
106→
107→
108→
109→
110→
111→
112→
113→
114→
115→
116→
117→
118→
119→PROC cell([][][]CHAN OF STATE link,
120→ VAL INT x, y, VAL []INT nx, ny,
121→ CHAN OF COMMAND control,
122→ CHAN OF RESPONSE sense )
123→ BOOL state, not.finished :
124→ SEQ
125→ state := dead -- the whole board starts off dead
126→ not.finished := TRUE
127→ WHILE not.finished
128→ control ? CASE
129→
130→ set.state; state
131→ SKIP -- state has been set to the new value
132→
133→ evolve
134→ BOOL next.state :
135→ SEQ
136→ PAR
137→ broadcast.present.state(link, x, y, state)
138→ SEQ
139→ calculate.next.state(link, nx, ny,
140→ state, next.state )
141→ sense ! (state <> next.state); next.state
142→ state := next.state
143→
144→ terminate
145→ not.finished := FALSE
146→:
147→
148→--
149→-- terminal-dependent output routines
150→--
151→
152→PROC clear.screen(CHAN OF BYTE terminal!)
153→ -- clear screen sequence for an ANSI terminal: ESC [ 2 J
154→ SEQ
155→ terminal ! BYTE #1B
156→ terminal ! '['
157→ terminal ! '2'
158→ terminal ! 'J'
159→:
160→
161→PROC move.cursor(CHAN OF BYTE terminal!, VAL INT x, y)
162→ -- left-handed co-ordinates, origin 0,0 at top left
163→ -- outputs ANSI escape sequence: ESC [ row ; col H
164→ SEQ
165→ terminal ! BYTE #1B
166→ terminal ! '['
167→ write.small.int(terminal, y + 1)
168→ terminal ! ';'
169→ write.small.int(terminal, x + 1)
170→ terminal ! 'H'
171→:
172→
173→
174→
175→
176→--
177→-- display routines
178→--
179→
180→PROC initialize.display(CHAN OF BYTE screen!)
181→ -- display an entirely dead board
182→ clear.screen(screen)
183→:
184→
185→PROC clean.up.display(CHAN OF BYTE screen!)
186→ move.cursor(screen, 0, array.height)
187→:
188→
189→PROC display.state(CHAN OF BYTE screen!, VAL INT x, y, VAL BOOL state)
190→ SEQ
191→ move.cursor(screen, x, y)
192→ IF
193→ state = alive
194→ screen ! '**'
195→ state = dead
196→ screen ! '*s'
197→:
198→
199→--
200→-- controller states
201→--
202→
203→VAL INT idle IS 0 : -- controller activity values
204→VAL INT editing IS 1 :
205→VAL INT single.step IS 2 :
206→VAL INT free.running IS 3 :
207→VAL INT terminated IS 4 :
208→
209→
210→INT FUNCTION new.activity(VAL BYTE char)
211→ INT activity :
212→ VALOF
213→ CASE char -- typed on the keyboard ...
214→ 'q', 'Q' -- ... Q to finish program
215→ activity := terminated
216→ 's', 'S' -- ... S to halt evolution
217→ activity := idle
218→ 'e', 'E' -- ... E to start editing
219→ activity := editing
220→ 'r', 'R' -- ... R to start evolution
221→ activity := free.running
222→ ELSE -- ... or anything else for one generation
223→ activity := single.step
224→ RESULT activity
225→:
226→
227→PROC display.activity(CHAN OF BYTE screen!, VAL INT activity)
228→ SEQ
229→ move.cursor(screen, array.width+1, array.height/2)
230→ CASE activity
231→ idle
232→ write.string(screen, "Idle")
233→ editing
234→ write.string(screen, "Edit")
235→ single.step
236→ write.string(screen, "Step")
237→ free.running
238→ write.string(screen, "Busy")
239→ terminated
240→ write.string(screen, "Done")
241→:
242→
243→--
244→-- generation
245→--
246→
247→PROC generation(CHAN OF BYTE screen!,
248→ [][]CHAN OF COMMAND control,
249→ [][]CHAN OF RESPONSE sense,
250→ BOOL active )
251→ SEQ
252→ PAR x = 0 FOR array.width
253→ PAR y = 0 FOR array.height
254→ control[x][y] ! evolve
255→ active := FALSE
256→ SEQ x = 0 FOR array.width
257→ SEQ y = 0 FOR array.height
258→ BOOL changed, next.state :
259→ SEQ
260→ sense[x][y] ? changed; next.state
261→ IF
262→ changed
263→ SEQ
264→ display.state(screen, x, y, next.state)
265→ active := TRUE
266→ NOT changed
267→ SKIP
268→:
269→
270→
271→
272→
273→
274→
275→
276→
277→
278→--
279→-- editor
280→--
281→
282→INT FUNCTION min(VAL INT a, b)
283→ INT min :
284→ VALOF
285→ IF
286→ a <= b
287→ min := a
288→ b <= a
289→ min := b
290→ RESULT min
291→:
292→
293→INT FUNCTION max(VAL INT a, b)
294→ INT max :
295→ VALOF
296→ IF
297→ a >= b
298→ max := a
299→ b >= a
300→ max := b
301→ RESULT max
302→:
303→
304→
305→
306→
307→
308→
309→
310→
311→
312→
313→
314→
315→
316→
317→
318→
319→
320→
321→
322→
323→
324→
325→
326→
327→
328→
329→PROC editor(CHAN OF BYTE keyboard?, screen!,
330→ [][]CHAN OF COMMAND control )
331→ INT x, y :
332→ BOOL editing :
333→ SEQ
334→ -- initialize co-ordinates to centre of board
335→ x, y := array.width / 2, array.height / 2
336→ editing := TRUE
337→ WHILE editing
338→ BYTE char :
339→ SEQ
340→ move.cursor(screen, x, y)
341→ keyboard ? char
342→ CASE char
343→ 'A' -- move up, if possible
344→ y := max(y - 1, 0)
345→ 'B' -- move down, if possible
346→ y := min(y + 1, array.height - 1)
347→ 'C' -- move right, if possible
348→ x := min(x + 1, array.width - 1)
349→ 'D' -- move left, if possible
350→ x := max(x - 1, 0)
351→ '*s', '**'
352→ VAL BOOL state IS (char = '**') = alive :
353→ PAR
354→ control[x][y] ! set.state; state
355→ display.state(screen, x, y, state)
356→ 'q', 'Q'
357→ editing := FALSE
358→ ELSE
359→ SKIP -- ignore anything else
360→:
361→
362→
363→
364→
365→
366→
367→
368→
369→
370→
371→
372→
373→
374→
375→
376→
377→
378→
379→
380→--
381→-- controller
382→--
383→
384→PROC controller(CHAN OF BYTE keyboard?, screen!,
385→ [][]CHAN OF COMMAND control,
386→ [][]CHAN OF RESPONSE sense )
387→ INT activity :
388→ SEQ
389→ activity := idle
390→ initialize.display(screen)
391→ WHILE activity <> terminated
392→ SEQ
393→ display.activity(screen, activity)
394→ BYTE char :
395→ PRI ALT
396→ (activity <> editing) & keyboard ? char
397→ activity := new.activity(char)
398→ (activity <> idle) & SKIP
399→ CASE activity
400→ editing
401→ SEQ
402→ editor(keyboard, screen, control)
403→ activity := idle
404→ free.running, single.step
405→ BOOL changing :
406→ SEQ
407→ generation(screen, control, sense, changing)
408→ IF
409→ (activity = single.step) OR (NOT changing)
410→ activity := idle
411→ (activity = free.running) AND changing
412→ SKIP
413→ display.activity(screen, activity)
414→ PAR x = 0 FOR array.width
415→ PAR y = 0 FOR array.height
416→ control[x][y] ! terminate
417→ clean.up.display(screen)
418→:
419→
420→
421→
422→
423→
424→
425→
426→
427→
428→
429→
430→
431→--
432→-- structure of the program
433→--
434→
435→PROC life (CHAN BYTE keyboard?, screen!, error!)
436→ [array.width][array.height][neighbours]CHAN OF STATE link :
437→ [array.width][array.height]CHAN OF COMMAND control :
438→ [array.width][array.height]CHAN OF RESPONSE sense :
439→ PAR
440→ controller(keyboard, screen, control, sense)
441→ PAR x = 0 FOR array.width
442→ PAR y = 0 FOR array.height
443→ VAL INT left IS ((x - 1) + array.width) \ array.width :
444→ VAL INT right IS (x + 1) \ array.width :
445→ VAL INT up IS (y + 1) \ array.height :
446→ VAL INT down IS ((y - 1) + array.height) \ array.height :
447→ VAL [neighbours]INT nx IS
448→ [ right, x, left, left, left, x, right, right ] :
449→ VAL [neighbours]INT ny IS
450→ [ down, down, down, y, up, up, up, y ] :
451→ cell(link, x, y, nx, ny, control[x][y], sense[x][y])
452→:
453→
454→Now I understand the life program. Let me look at the editor more carefully.
The editor at line 329-360 handles keyboard input. In edit mode: - 'A' = move up - 'B' = move down - 'C' = move right - 'D' = move left - 's' (space) or '*' (asterisk) = set cell state - 'q'/'Q' = exit edit mode
Wait - these are the raw characters 'A', 'B', 'C', 'D'. In a terminal, when you press arrow keys, the terminal sends escape sequences like ESC [ A, ESC [ B, ESC [ C, ESC [ D. The original occam program on a transputer probably had different key mappings, or the keyboard channel delivered processed keys.
But I'm realizing there's a mismatch here - the program expects uppercase 'A', 'B', 'C', 'D', yet in raw terminal mode pressing the 'a' key sends lowercase 'a', not uppercase 'A'. You'd need Shift+A to generate the uppercase character. So either the user needs to hold Shift while using these keys, or there's something else going on with how the input is being processed.
Looking at this from the original transputer context, arrow keys on a VT100 terminal send escape sequences like ESC [ A for up, ESC [ B for down, and so on - the final character is what matches the program's expectations. The original occam code might have had some preprocessing to extract just that final character from the escape sequence, or it simply expected users to type the uppercase letters directly.
When the transpiler reads from stdin in raw mode, it gets those three bytes one at a time. The first two bytes (ESC and [) don't match any case in the switch statement, so they get skipped, and only when the third byte arrives does it match 'A' and trigger the up movement. So arrow keys should technically work, just with a slight delay as those prefix bytes are consumed. But the user is reporting nothing appears on screen at all, which suggests something else is wrong with the display or input handling. I should actually transpile the code and examine the generated Go output to identify where the issue might be occurring, rather than just speculating about potential problems.
Let me transpile the life example and examine the generated Go code to investigate the issue.
go build -o occam2go . && ./occam2go -o /tmp/life.go historical-examples/life.occ 2>&1
1→package main
2→
3→import (
4→ "bufio"
5→ "os"
6→ "os/signal"
7→ "sync"
8→ "syscall"
9→
10→ "golang.org/x/term"
11→)
12→
13→type _proto_STATE = bool
14→
15→type _proto_COMMAND interface {
16→ _is_COMMAND()
17→}
18→
19→type _proto_COMMAND_set_state struct {
20→ _0 bool
21→}
22→func (_proto_COMMAND_set_state) _is_COMMAND() {}
23→
24→type _proto_COMMAND_evolve struct{}
25→func (_proto_COMMAND_evolve) _is_COMMAND() {}
26→
27→type _proto_COMMAND_terminate struct{}
28→func (_proto_COMMAND_terminate) _is_COMMAND() {}
29→
30→type _proto_RESPONSE struct {
31→ _0 bool
32→ _1 bool
33→}
34→
35→var array_width int = 20
36→var array_height int = 20
37→var radius int = 1
38→var diameter int = ((2 * radius) + 1)
39→var neighbours int = ((diameter * diameter) - 1)
40→var number_of_cells int = (array_height * array_width)
41→var number_of_links int = (neighbours * number_of_cells)
42→var alive bool = true
43→var dead bool = !alive
44→var idle int = 0
45→var editing int = 1
46→var single_step int = 2
47→var free_running int = 3
48→var terminated int = 4
49→
50→func write_string(out chan<- byte, s []byte) {
51→ for i := 0; i < 0 + len(s); i++ {
52→ out <- s[i]
53→ }
54→}
55→
56→func write_small_int(out chan<- byte, n int) {
57→ if (n >= 100) {
58→ out <- byte(((n / 100) + int(byte(48))))
59→ out <- byte((((n / 10) % 10) + int(byte(48))))
60→ out <- byte(((n % 10) + int(byte(48))))
61→ } else if (n >= 10) {
62→ out <- byte(((n / 10) + int(byte(48))))
63→ out <- byte(((n % 10) + int(byte(48))))
64→ } else if true {
65→ out <- byte((n + int(byte(48))))
66→ }
67→}
68→
69→func broadcast_present_state(link [][][]chan _proto_STATE, x int, y int, state bool) {
70→ var wg sync.WaitGroup
71→ wg.Add(int(neighbours))
72→ for d := 0; d < 0 + neighbours; d++ {
73→ d := d
74→ go func() {
75→ defer wg.Done()
76→ link[x][y][d] <- state
77→ }()
78→ }
79→ wg.Wait()
80→}
81→
82→func calculate_next_state(link [][][]chan _proto_STATE, nx []int, ny []int, state bool, next_state *bool) {
83→ var count int
84→ _ = count
85→ state_of_neighbour := make([]bool, neighbours)
86→ var wg sync.WaitGroup
87→ wg.Add(int(neighbours))
88→ for d := 0; d < 0 + neighbours; d++ {
89→ d := d
90→ go func() {
91→ defer wg.Done()
92→ state_of_neighbour[d] = <-link[nx[d]][ny[d]][d]
93→ }()
94→ }
95→ wg.Wait()
96→ count = 0
97→ for d := 0; d < 0 + neighbours; d++ {
98→ if (state_of_neighbour[d] == alive) {
99→ count = (count + 1)
100→ } else if (state_of_neighbour[d] == dead) {
101→ // SKIP
102→ }
103→ }
104→ if (count < 2) {
105→ *next_state = dead
106→ } else if (count == 2) {
107→ *next_state = state
108→ } else if (count == 3) {
109→ *next_state = alive
110→ } else if (count > 3) {
111→ *next_state = dead
112→ }
113→}
114→
115→func cell(link [][][]chan _proto_STATE, x int, y int, nx []int, ny []int, control chan _proto_COMMAND, sense chan _proto_RESPONSE) {
116→ var state, not_finished bool
117→ _ = state
118→ _ = not_finished
119→ state = dead
120→ not_finished = true
121→ for not_finished {
122→ switch _v := (<-control).(type) {
123→ case _proto_COMMAND_set_state:
124→ state = _v._0
125→ // SKIP
126→ case _proto_COMMAND_evolve:
127→ var next_state bool
128→ _ = next_state
129→ var wg sync.WaitGroup
130→ wg.Add(2)
131→ go func() {
132→ defer wg.Done()
133→ broadcast_present_state(link, x, y, state)
134→ }()
135→ go func() {
136→ defer wg.Done()
137→ calculate_next_state(link, nx, ny, state, &next_state)
138→ sense <- _proto_RESPONSE{(state != next_state), next_state}
139→ }()
140→ wg.Wait()
141→ state = next_state
142→ case _proto_COMMAND_terminate:
143→ not_finished = false
144→ }
145→ }
146→}
147→
148→func clear_screen(terminal chan<- byte) {
149→ terminal <- byte(27)
150→ terminal <- byte(91)
151→ terminal <- byte(50)
152→ terminal <- byte(74)
153→}
154→
155→func move_cursor(terminal chan<- byte, x int, y int) {
156→ terminal <- byte(27)
157→ terminal <- byte(91)
158→ write_small_int(terminal, (y + 1))
159→ terminal <- byte(59)
160→ write_small_int(terminal, (x + 1))
161→ terminal <- byte(72)
162→}
163→
164→func initialize_display(screen chan<- byte) {
165→ clear_screen(screen)
166→}
167→
168→func clean_up_display(screen chan<- byte) {
169→ move_cursor(screen, 0, array_height)
170→}
171→
172→func display_state(screen chan<- byte, x int, y int, state bool) {
173→ move_cursor(screen, x, y)
174→ if (state == alive) {
175→ screen <- byte(42)
176→ } else if (state == dead) {
177→ screen <- byte(32)
178→ }
179→}
180→
181→func new_activity(char byte) int {
182→ var activity int
183→ _ = activity
184→ switch char {
185→ case byte(113), byte(81):
186→ activity = terminated
187→ case byte(115), byte(83):
188→ activity = idle
189→ case byte(101), byte(69):
190→ activity = editing
191→ case byte(114), byte(82):
192→ activity = free_running
193→ default:
194→ activity = single_step
195→ }
196→ return activity
197→}
198→
199→func display_activity(screen chan<- byte, activity int) {
200→ move_cursor(screen, (array_width + 1), (array_height / 2))
201→ switch activity {
202→ case idle:
203→ write_string(screen, []byte("Idle"))
204→ case editing:
205→ write_string(screen, []byte("Edit"))
206→ case single_step:
207→ write_string(screen, []byte("Step"))
208→ case free_running:
209→ write_string(screen, []byte("Busy"))
210→ case terminated:
211→ write_string(screen, []byte("Done"))
212→ }
213→}
214→
215→func generation(screen chan<- byte, control [][]chan _proto_COMMAND, sense [][]chan _proto_RESPONSE, active *bool) {
216→ var wg sync.WaitGroup
217→ wg.Add(int(array_width))
218→ for x := 0; x < 0 + array_width; x++ {
219→ x := x
220→ go func() {
221→ defer wg.Done()
222→ var wg sync.WaitGroup
223→ wg.Add(int(array_height))
224→ for y := 0; y < 0 + array_height; y++ {
225→ y := y
226→ go func() {
227→ defer wg.Done()
228→ control[x][y] <- _proto_COMMAND_evolve{}
229→ }()
230→ }
231→ wg.Wait()
232→ }()
233→ }
234→ wg.Wait()
235→ *active = false
236→ for x := 0; x < 0 + array_width; x++ {
237→ for y := 0; y < 0 + array_height; y++ {
238→ var changed, next_state bool
239→ _ = changed
240→ _ = next_state
241→ _tmp0 := <-sense[x][y]
242→ changed = _tmp0._0
243→ next_state = _tmp0._1
244→ if changed {
245→ display_state(screen, x, y, next_state)
246→ *active = true
247→ } else if !changed {
248→ // SKIP
249→ }
250→ }
251→ }
252→}
253→
254→func min(a int, b int) int {
255→ var min int
256→ _ = min
257→ if (a <= b) {
258→ min = a
259→ } else if (b <= a) {
260→ min = b
261→ }
262→ return min
263→}
264→
265→func max(a int, b int) int {
266→ var max int
267→ _ = max
268→ if (a >= b) {
269→ max = a
270→ } else if (b >= a) {
271→ max = b
272→ }
273→ return max
274→}
275→
276→func editor(keyboard <-chan byte, screen chan<- byte, control [][]chan _proto_COMMAND) {
277→ var x, y int
278→ _ = x
279→ _ = y
280→ var editing bool
281→ _ = editing
282→ x, y = (array_width / 2), (array_height / 2)
283→ editing = true
284→ for editing {
285→ var char byte
286→ _ = char
287→ move_cursor(screen, x, y)
288→ char = <-keyboard
289→ switch char {
290→ case byte(65):
291→ y = max((y - 1), 0)
292→ case byte(66):
293→ y = min((y + 1), (array_height - 1))
294→ case byte(67):
295→ x = min((x + 1), (array_width - 1))
296→ case byte(68):
297→ x = max((x - 1), 0)
298→ case byte(32), byte(42):
299→ var state bool = ((char == byte(42)) == alive)
300→ _ = state
301→ var wg sync.WaitGroup
302→ wg.Add(2)
303→ go func() {
304→ defer wg.Done()
305→ control[x][y] <- _proto_COMMAND_set_state{state}
306→ }()
307→ go func() {
308→ defer wg.Done()
309→ display_state(screen, x, y, state)
310→ }()
311→ wg.Wait()
312→ case byte(113), byte(81):
313→ editing = false
314→ default:
315→ // SKIP
316→ }
317→ }
318→}
319→
320→func controller(keyboard <-chan byte, screen chan<- byte, control [][]chan _proto_COMMAND, sense [][]chan _proto_RESPONSE) {
321→ var activity int
322→ _ = activity
323→ activity = idle
324→ initialize_display(screen)
325→ for (activity != terminated) {
326→ display_activity(screen, activity)
327→ var char byte
328→ _ = char
329→ var _alt0 <-chan byte = nil
330→ if (activity != editing) { _alt0 = keyboard }
331→ select {
332→ case char = <-_alt0:
333→ activity = new_activity(char)
334→ default:
335→ if (activity != idle) {
336→ switch activity {
337→ case editing:
338→ editor(keyboard, screen, control)
339→ activity = idle
340→ case free_running, single_step:
341→ var changing bool
342→ _ = changing
343→ generation(screen, control, sense, &changing)
344→ if ((activity == single_step) || !changing) {
345→ activity = idle
346→ } else if ((activity == free_running) && changing) {
347→ // SKIP
348→ }
349→ }
350→ }
351→ }
352→ }
353→ display_activity(screen, activity)
354→ var wg sync.WaitGroup
355→ wg.Add(int(array_width))
356→ for x := 0; x < 0 + array_width; x++ {
357→ x := x
358→ go func() {
359→ defer wg.Done()
360→ var wg sync.WaitGroup
361→ wg.Add(int(array_height))
362→ for y := 0; y < 0 + array_height; y++ {
363→ y := y
364→ go func() {
365→ defer wg.Done()
366→ control[x][y] <- _proto_COMMAND_terminate{}
367→ }()
368→ }
369→ wg.Wait()
370→ }()
371→ }
372→ wg.Wait()
373→ clean_up_display(screen)
374→}
375→
376→func life(keyboard <-chan byte, screen chan<- byte, _error chan<- byte) {
377→ link := make([][][]chan _proto_STATE, array_width)
378→ for _i0 := range link {
379→ link[_i0] = make([][]chan _proto_STATE, array_height)
380→ for _i1 := range link[_i0] {
381→ link[_i0][_i1] = make([]chan _proto_STATE, neighbours)
382→ for _i2 := range link[_i0][_i1] { link[_i0][_i1][_i2] = make(chan _proto_STATE) }
383→ }
384→ }
385→ control := make([][]chan _proto_COMMAND, array_width)
386→ for _i0 := range control {
387→ control[_i0] = make([]chan _proto_COMMAND, array_height)
388→ for _i1 := range control[_i0] { control[_i0][_i1] = make(chan _proto_COMMAND) }
389→ }
390→ sense := make([][]chan _proto_RESPONSE, array_width)
391→ for _i0 := range sense {
392→ sense[_i0] = make([]chan _proto_RESPONSE, array_height)
393→ for _i1 := range sense[_i0] { sense[_i0][_i1] = make(chan _proto_RESPONSE) }
394→ }
395→ var wg sync.WaitGroup
396→ wg.Add(2)
397→ go func() {
398→ defer wg.Done()
399→ controller(keyboard, screen, control, sense)
400→ }()
401→ go func() {
402→ defer wg.Done()
403→ var wg sync.WaitGroup
404→ wg.Add(int(array_width))
405→ for x := 0; x < 0 + array_width; x++ {
406→ x := x
407→ go func() {
408→ defer wg.Done()
409→ var wg sync.WaitGroup
410→ wg.Add(int(array_height))
411→ for y := 0; y < 0 + array_height; y++ {
412→ y := y
413→ go func() {
414→ defer wg.Done()
415→ var left int = (((x - 1) + array_width) % array_width)
416→ _ = left
417→ var right int = ((x + 1) % array_width)
418→ _ = right
419→ var up int = ((y + 1) % array_height)
420→ _ = up
421→ var down int = (((y - 1) + array_height) % array_height)
422→ _ = down
423→ var nx []int = []int{right, x, left, left, left, x, right, right}
424→ _ = nx
425→ var ny []int = []int{down, down, down, y, up, up, up, y}
426→ _ = ny
427→ cell(link, x, y, nx, ny, control[x][y], sense[x][y])
428→ }()
429→ }
430→ wg.Wait()
431→ }()
432→ }
433→ wg.Wait()
434→ }()
435→ wg.Wait()
436→}
437→
438→func main() {
439→ keyboard := make(chan byte, 256)
440→ screen := make(chan byte, 256)
441→ _error := make(chan byte, 256)
442→
443→ // Raw terminal mode — gives character-at-a-time keyboard input
444→ var rawMode bool
445→ var oldState *term.State
446→ fd := int(os.Stdin.Fd())
447→ if term.IsTerminal(fd) {
448→ var err error
449→ oldState, err = term.MakeRaw(fd)
450→ if err == nil {
451→ rawMode = true
452→ defer term.Restore(fd, oldState)
453→ // Restore terminal on external signals
454→ sigCh := make(chan os.Signal, 1)
455→ signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
456→ go func() {
457→ <-sigCh
458→ term.Restore(fd, oldState)
459→ os.Exit(1)
460→ }()
461→ }
462→ }
463→
464→ var wg sync.WaitGroup
465→ wg.Add(2)
466→
467→ go func() {
468→ defer wg.Done()
469→ w := bufio.NewWriter(os.Stdout)
470→ for b := range screen {
471→ if b == 255 {
472→ w.Flush()
473→ } else {
474→ if rawMode && b == '\n' {
475→ w.WriteByte('\r')
476→ }
477→ w.WriteByte(b)
478→ }
479→ }
480→ w.Flush()
481→ }()
482→
483→ go func() {
484→ defer wg.Done()
485→ w := bufio.NewWriter(os.Stderr)
486→ for b := range _error {
487→ if b == 255 {
488→ w.Flush()
489→ } else {
490→ if rawMode && b == '\n' {
491→ w.WriteByte('\r')
492→ }
493→ w.WriteByte(b)
494→ }
495→ }
496→ w.Flush()
497→ }()
498→
499→ go func() {
500→ if rawMode {
501→ buf := make([]byte, 1)
502→ for {
503→ n, err := os.Stdin.Read(buf)
504→ if err != nil || n == 0 {
505→ close(keyboard)
506→ return
507→ }
508→ if buf[0] == 3 { // Ctrl+C
509→ term.Restore(fd, oldState)
510→ os.Exit(1)
511→ }
512→ keyboard <- buf[0]
513→ }
514→ } else {
515→ r := bufio.NewReader(os.Stdin)
516→ for {
517→ b, err := r.ReadByte()
518→ if err != nil {
519→ close(keyboard)
520→ return
521→ }
522→ keyboard <- b
523→ }
524→ }
525→ }()
526→
527→ life(keyboard, screen, _error)
528→
529→ close(screen)
530→ close(_error)
531→ wg.Wait()
532→}
533→Now I can see the issue. Let me analyze the transpiled code carefully, focusing on the editor and controller.
The main issue I can see is in the controller function, specifically the PRI ALT translation at lines 329-351.
The original occam code is:
PRI ALT
(activity <> editing) & keyboard ? char
activity := new.activity(char)
(activity <> idle) & SKIP
CASE activity
editing
SEQ
editor(keyboard, screen, control)
activity := idle
free.running, single.step
BOOL changing :
SEQ
generation(screen, control, sense, changing)
IF
(activity = single.step) OR (NOT changing)
activity := idle
(activity = free.running) AND changing
SKIP
The transpiled Go is:
select {
case char = <-_alt0:
activity = new_activity(char)
default:
if (activity != idle) {
switch activity {
case editing:
editor(keyboard, screen, control)
activity = idle
...
}
}
}
Wait, this is a PRI ALT with a keyboard input guard and a default branch that handles the generation and state transitions. The issue is that the transpiler is not properly handling the conditional logic for the free.running and single.step cases where it needs to check the changing variable to determine whether to continue or idle. two alternatives:
1. A channel input with a boolean guard (activity <> editing) & keyboard ? char
2. A SKIP guard with a boolean guard (activity <> idle) & SKIP
In occam, PRI ALT gives priority to earlier alternatives. The SKIP guard means "if the boolean guard is true, this alternative is immediately ready."
The translation to Go select with default seems correct at first glance - the default case handles the SKIP alternative. But there's a problem:
The Go select with default is non-blocking. If _alt0 is nil (activity == editing), the select goes directly to default. The default checks activity != idle, and if activity is editing, it runs the editor. This seems correct for the editing case.
But the real issue is that PRI ALT in occam enforces priority - it tries the keyboard channel first and only falls through to SKIP if the keyboard has no data. Go's select with default is non-blocking, so it immediately takes the default if no channel is ready, which breaks the priority semantics. When activity = free_running, this works fine - the game loops through generations while checking for keyboard input. But when activity = idle, the select tries the keyboard, finds nothing ready, takes the default, and then does nothing because the idle guard fails - creating a busy loop that wastes CPU cycles. I see the real issue now—the Go translation adds a default case to the select statement, which means it never actually blocks waiting for keyboard input when idle like the original occam code does. The PRI ALT in occam would disable the SKIP guard when idle and block on the keyboard channel, but Go's select with a default case will spin through immediately instead of waiting.
When the user presses 'e', the activity changes to editing and the editor function should be called, but the busy-wait loop is consuming CPU the whole time because the select keeps hitting that default case instead of blocking.
Looking at the editor's input handling, I think I found the actual bug—the editor is checking for uppercase ASCII values like 65 for 'A', but if the user is pressing lowercase keys, they'd be sending 97 for 'a', which wouldn't match any of the cases.
But wait, the user mentioned "A, B, C, D keys for direction," which in the context of a VT100 terminal would be arrow key escape sequences. When you press an arrow key, it sends multiple bytes: ESC followed by '[' followed by the direction character. The editor reads one byte at a time, so it would see ESC first (which doesn't match anything), then '[' (which also doesn't match), and never actually process the direction character properly.
Actually, I realize there's a bigger problem here with the buffering. The move_cursor function sends bytes through the screen channel, but the screen output goroutine uses buffered I/O that only flushes when it receives byte 255. Since the editor never sends byte 255, the cursor movement commands are probably stuck in the buffer and never actually reaching the terminal. I see the buffer is 4096 bytes by default, but the initial output—clear screen plus cursor movements and text—only amounts to around 20 bytes, so it shouldn't fill the buffer. Yet the user can see output on screen, which suggests the buffer is being flushed somehow, possibly due to timing or another mechanism I'm missing.
In the idle state, the busy-wait loop continuously calls display_activity, gradually accumulating bytes in the buffer until it eventually flushes and "Idle" appears. But in edit mode, the editor blocks waiting for keyboard input, so between key presses there's no output being sent. When cursor movements or state updates do occur, they only send 8-15 bytes each—not enough to trigger a buffer flush. The user is pressing keys and the program processes them, but the output remains stuck in the buffer.
So the core issue is that screen output gets buffered during editor mode and never flushes to the terminal. The original occam program had unbuffered I/O where each byte appeared immediately, but the Go version uses a buffered writer that only flushes when byte 255 is sent (which never happens) or when the 4096-byte buffer fills up. Though wait—the screen channel itself has a capacity of 256, so let me think through how the buffering actually works here.
The screen goroutine reads from the channel and writes to a bufio.Writer, but those bytes just accumulate in the buffer without flushing. The bufio.Writer's default 4096-byte buffer only auto-flushes when full. When the controller is idle and repeatedly calls the display function, it sends about 12-15 bytes per iteration, so after roughly 273 iterations the buffer would finally fill and flush—which might explain why the user sees "Idle" at all.
In edit mode though, the editor blocks waiting for keyboard input between actions, so each action only generates a few bytes. The buffer never accumulates enough to trigger a flush, which is why the display doesn't update. The idle loop's continuous writes eventually fill the buffer and flush, but the edit mode's sparse writes don't.
When the user presses 'e', the activity changes to editing and "Edit" gets written—maybe 12-15 bytes. But that's still nowhere near the 4096-byte threshold, so it might not appear immediately either. The timing probably depends on whether the idle loop had already accumulated close to that limit before the keypress.
Actually, thinking about what the user described—the screen "pausing" when they enter edit mode—it makes sense now. In free-running mode, the game constantly generates output: cursor movements and state updates for every changed cell. That's enough to regularly fill and flush the buffer. But once they switch to edit mode, those frequent updates stop, so the buffer never fills up enough to trigger a flush. The user sees the screen go silent.
The real issue is the buffered output. The fix is straightforward: either flush explicitly after each operation, flush periodically in a separate goroutine, or stop using buffered I/O altogether.
But the deeper problem is that the occam program was designed for unbuffered I/O—each byte sent to the screen channel should appear immediately. The Go transpiler's buffered output violates that assumption. The simplest solution would be to flush after each complete escape sequence or batch of related output, though that requires understanding the protocol. Alternatively, I could just have the transpiler use unbuffered writes directly to stdout.
Actually, the cleanest approach is to flush the screen goroutine whenever the channel empties out—after writing each byte, check if there are more bytes waiting, and if not, flush immediately. This way output gets flushed after each burst of writes rather than waiting for the buffer to fill.
Implementing the flush logic...
There's a potential race condition though—the channel might appear empty momentarily between sends from the occam program, even though more bytes are coming. But since the screen channel is buffered and bytes are sent sequentially, occasional premature flushes are fine. Flushing too often is better than not flushing, and any visual flickering would be minimal since terminal emulators handle their own rendering batching anyway.
Now I need to reconsider whether this is actually the root issue and what the proper fix should be. Let me look more carefully at how the PRI ALT is being translated to Go, particularly around the guard conditions and what happens when activity is idle.
The problem is that the Go translation uses a default case to handle the SKIP alternative, but this makes the select non-blocking—when no channel is ready, it immediately takes the default instead of blocking on the keyboard input. This causes a busy-wait loop spinning at 100% CPU when idle, whereas the original occam program would block waiting for keyboard input. The default case gets taken regardless of whether the SKIP guard's boolean condition is actually true, so the translation doesn't correctly implement the guarded alternatives. I need to restructure this so that when idle, only the keyboard channel is available to select on, and when editing, the select proceeds immediately without blocking. I see the core issue now—I need conditional select behavior depending on whether the SKIP guard is active, using a blocking receive when SKIP is disabled and a non-blocking one when it's enabled. But stepping back, the user's immediate concern is about the editor not displaying results, so I should focus on diagnosing that first rather than getting caught up in the guard logic complexity.
Looking at what the user reported: they can enter and exit edit mode, but cursor movement and cell activation don't show anything on screen. This points to a display flushing problem—the editor is processing input correctly but the terminal output isn't being rendered until they exit edit mode and the idle loop starts writing "Idle" repeatedly, which forces a flush.
There's also the separate performance issue of the busy-wait loop when idle. And I should verify whether the channel select logic with the PRI ALT guard is preventing the editor from receiving keyboard input properly—specifically checking if the activity switch is actually routing to the editor function as expected.
Looking at the keyboard input flow during cursor movement, the editor reads individual bytes from the keyboard channel sequentially, and each cursor position update gets written to the screen buffer. The real problem isn't input handling—it's that these screen writes aren't being flushed, so the user doesn't see the updates in real time.
With a 4096-byte buffer and each arrow key press generating about 24 bytes of output, it would take roughly 170 key presses before the buffer fills and anything appears on screen. The solution is to flush the output more aggressively. I'm considering a few approaches: flushing whenever the channel empties out to balance responsiveness with batching efficiency, using a timer-based flush every 16 milliseconds for consistent 60fps updates, or potentially removing buffering entirely.
Option 1 seems most practical. But I'm realizing I should double-check my understanding of the channel dynamics—the screen channel has a 256-byte buffer, and when the editor sends cursor movement bytes one at a time, the goroutine reading from it should drain them quickly since it's just doing a WriteByte operation. So after each byte, the channel should be empty and ready to trigger a flush.
That's actually fine—calling Flush() after every byte is inefficient but works correctly, and bufio.Writer.Flush() is pretty cheap with just one byte anyway. I could implement a smarter batching approach with a timeout, but the simple len(screen) == 0 check should be sufficient.
So the changes I need to make are fixing the screen output flushing in the preamble generation, and potentially addressing the PRI ALT busy-wait issue separately since that's a codegen problem rather than a preamble issue. The first fix goes into wherever the main() function preamble is generated to add auto-flushing to the screen output goroutine.
The second issue is trickier—when a PRI ALT has both channel guards and SKIP guards, Go's select statement can't properly handle the case where the SKIP guard's condition is false. The select needs to block on the channel in that scenario, but the default case prevents blocking. I need to think through the logic more carefully: when both guards' conditions are true, I want non-blocking behavior, but when only the channel guard is active, the select should actually wait for the channel.
The solution is to conditionally include the default case based on whether the SKIP guard's boolean condition is true, wrapping the select in an if statement that checks that condition.
This approach is getting unwieldy for the general case and would require substantial changes to the ALT code generation. I should prioritize fixing the screen flushing bug first since it has more immediate impact, then circle back to the PRI ALT issue as a follow-up. Let me track down where the main function preamble gets generated in the codegen.
I can see two issues in the transpiled code. Let me find where the preamble is generated in codegen.
{
"pattern": "len\\(screen\\) == 0|bufio\\.NewWriter|for b := range screen|flush",
"path": "/home/david/projects/code-associates/occam2go/codegen",
"output_mode": "content",
"-i": true
}codegen/codegen.go:483: g.writeLine("w := bufio.NewWriter(os.Stdout)")
codegen/codegen.go:484: g.writeLine("for b := range screen {")
codegen/codegen.go:488: g.writeLine("w.Flush()")
codegen/codegen.go:500: g.writeLine("w.Flush()")
codegen/codegen.go:509: g.writeLine("w := bufio.NewWriter(os.Stderr)")
codegen/codegen.go:514: g.writeLine("w.Flush()")
codegen/codegen.go:526: g.writeLine("w.Flush()"){
"pattern": "SKIP guard|default:|select \\{",
"path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"output_mode": "content",
"-n": true
}209: default:
1136: g.writeLine("select {}")
1737: default:
1762: default:
1984: g.writeLine("select {")
1988: g.write("default:\n")
2302: default:
2697: g.writeLine("default:")
2872: default:{
"file_path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"offset": 475,
"limit": 60
} 475→ g.writeLine("var wg sync.WaitGroup")
476→ g.writeLine("wg.Add(2)")
477→ g.writeLine("")
478→
479→ // Screen writer goroutine — in raw mode, insert CR before LF
480→ g.writeLine("go func() {")
481→ g.indent++
482→ g.writeLine("defer wg.Done()")
483→ g.writeLine("w := bufio.NewWriter(os.Stdout)")
484→ g.writeLine("for b := range screen {")
485→ g.indent++
486→ g.writeLine("if b == 255 {")
487→ g.indent++
488→ g.writeLine("w.Flush()")
489→ g.indent--
490→ g.writeLine("} else {")
491→ g.indent++
492→ g.writeLine(`if rawMode && b == '\n' {`)
493→ g.writeLine(`w.WriteByte('\r')`)
494→ g.writeLine("}")
495→ g.writeLine("w.WriteByte(b)")
496→ g.indent--
497→ g.writeLine("}")
498→ g.indent--
499→ g.writeLine("}")
500→ g.writeLine("w.Flush()")
501→ g.indent--
502→ g.writeLine("}()")
503→ g.writeLine("")
504→
505→ // Error writer goroutine — same CR/LF handling
506→ g.writeLine("go func() {")
507→ g.indent++
508→ g.writeLine("defer wg.Done()")
509→ g.writeLine("w := bufio.NewWriter(os.Stderr)")
510→ g.writeLine("for b := range _error {")
511→ g.indent++
512→ g.writeLine("if b == 255 {")
513→ g.indent++
514→ g.writeLine("w.Flush()")
515→ g.indent--
516→ g.writeLine("} else {")
517→ g.indent++
518→ g.writeLine(`if rawMode && b == '\n' {`)
519→ g.writeLine(`w.WriteByte('\r')`)
520→ g.writeLine("}")
521→ g.writeLine("w.WriteByte(b)")
522→ g.indent--
523→ g.writeLine("}")
524→ g.indent--
525→ g.writeLine("}")
526→ g.writeLine("w.Flush()")
527→ g.indent--
528→ g.writeLine("}()")
529→ g.writeLine("")
530→
531→ // Keyboard reader goroutine
532→ g.writeLine("go func() {")
533→ g.indent++
534→ g.writeLine("if rawMode {")Now I understand both issues:
Screen output buffering: The screen goroutine uses bufio.NewWriter with a 4096-byte default buffer. It only flushes on byte 255 (special marker) or when the channel closes. During edit mode, cursor movements and cell state changes produce only a few bytes, never reaching the 4096-byte threshold. The output sits in the buffer invisible to the user.
PRI ALT busy-wait: The PRI ALT with a SKIP guard translates to select { case ... : ... ; default: ... }. When the SKIP guard's boolean condition is false (e.g., activity != idle is false when idle), the default branch should not be taken, but Go always takes default when no channel is ready, causing a busy-wait spin.
I should present these findings to the user and let them decide how to proceed with fixes. occ) or the buffer fills up
- In edit mode, each key press generates ~8-24 bytes of cursor movement output
- This never reaches the 4096-byte threshold, so nothing appears on screen
- "Idle" is visible because the busy-wait loop writes it thousands of times, eventually filling the buffer
- Fix: Auto-flush the buffer when the channel is drained (i.e., len(screen) == 0)
Issue 2: PRI ALT busy-wait when idle (secondary issue)
- When activity = idle, the SKIP guard's boolean is false (activity != idle = false)
- The occam PRI ALT should block waiting for keyboard input
- But Go's select with default is always non-blocking, causing a tight CPU spin loop
- Fix: Conditionally include default in the select based on the SKIP guard's condition, so the select blocks properly when idle instead of spinning.
I've found two bugs in the transpiled code. Here's my analysis:
The screen output goroutine at /tmp/life.go:469-481 uses a bufio.NewWriter with the default 4096-byte buffer. Output only flushes when:
- Byte 255 is received (a special flush marker) — never sent by life.occ
- The buffer fills up to 4096 bytes
In edit mode, each cursor movement writes only ~8-24 bytes to the screen channel. This never reaches 4096 bytes, so nothing appears on the terminal. The editor is actually processing keys correctly — the cursor coordinates are updating — but the output is stuck in the buffer.
The reason "Idle" is visible: when idle, the busy-wait loop (see issue 2) calls display_activity thousands of times per second, quickly filling the 4096-byte buffer and triggering a flush.
Fix: Auto-flush the buffer when the channel is drained. After w.WriteByte(b), add:
if len(screen) == 0 {
w.Flush()
}
This flushes after each burst of output while still batching rapid sequential writes.
The controller's PRI ALT at life.occ:395-412:
PRI ALT
(activity <> editing) & keyboard ? char -- guard 1
...
(activity <> idle) & SKIP -- guard 2
...
Translates to a Go select with default (/tmp/life.go:331-351). The problem: Go's default fires unconditionally when no channel is ready, ignoring the SKIP guard's boolean condition (activity <> idle).
When activity = idle: the SKIP guard should be disabled and the ALT should block on the keyboard channel. Instead, the default branch fires, checks activity != idle → false, does nothing, and loops — spinning the CPU at 100%.
This is a codegen bug: when the only non-channel alternative is a guarded SKIP, the default case should be conditional on the boolean guard.
Want me to fix these? Issue 1 is a simple preamble change. Issue 2 is a more involved ALT codegen change.
{
"pattern": "generateAlt|SKIP guard|func.*Alt",
"path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"output_mode": "content",
"-n": true
}1131: g.generateAltBlock(s)
1947:func (g *Generator) generateAltBlock(alt *ast.AltBlock) {
2035:func (g *Generator) generateReplicatedAlt(alt *ast.AltBlock) {
3030:func (g *Generator) containsAltReplicator(stmt ast.Statement) bool {{
"file_path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"offset": 1947,
"limit": 100
} 1947→func (g *Generator) generateAltBlock(alt *ast.AltBlock) {
1948→ if alt.Replicator != nil {
1949→ g.generateReplicatedAlt(alt)
1950→ return
1951→ }
1952→
1953→ // ALT becomes Go select statement
1954→ // For guards, we use a pattern with nil channels
1955→
1956→ // Check if any cases have guards
1957→ hasGuards := false
1958→ for _, c := range alt.Cases {
1959→ if c.Guard != nil {
1960→ hasGuards = true
1961→ break
1962→ }
1963→ }
1964→
1965→ if hasGuards {
1966→ // Generate channel variables for guarded cases
1967→ for i, c := range alt.Cases {
1968→ if c.Guard != nil && !c.IsSkip {
1969→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1970→ // Look up the channel's element type
1971→ elemType := "int" // default fallback
1972→ if t, ok := g.chanElemTypes[c.Channel]; ok {
1973→ elemType = t
1974→ }
1975→ g.write(fmt.Sprintf("var _alt%d <-chan %s = nil\n", i, elemType))
1976→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1977→ g.write(fmt.Sprintf("if "))
1978→ g.generateExpression(c.Guard)
1979→ g.write(fmt.Sprintf(" { _alt%d = %s }\n", i, goIdent(c.Channel)))
1980→ }
1981→ }
1982→ }
1983→
1984→ g.writeLine("select {")
1985→ for i, c := range alt.Cases {
1986→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1987→ if c.IsSkip {
1988→ g.write("default:\n")
1989→ } else if c.IsTimer {
1990→ g.write("case <-time.After(time.Duration(")
1991→ g.generateExpression(c.Deadline)
1992→ g.write(" - int(time.Now().UnixMicro())) * time.Microsecond):\n")
1993→ } else if c.Guard != nil {
1994→ varRef := goIdent(c.Variable)
1995→ if len(c.VariableIndices) > 0 {
1996→ varRef += g.generateIndicesStr(c.VariableIndices)
1997→ }
1998→ g.write(fmt.Sprintf("case %s = <-_alt%d:\n", varRef, i))
1999→ } else if len(c.ChannelIndices) > 0 {
2000→ varRef := goIdent(c.Variable)
2001→ if len(c.VariableIndices) > 0 {
2002→ varRef += g.generateIndicesStr(c.VariableIndices)
2003→ }
2004→ g.write(fmt.Sprintf("case %s = <-%s", varRef, goIdent(c.Channel)))
2005→ g.generateIndices(c.ChannelIndices)
2006→ g.write(":\n")
2007→ } else {
2008→ varRef := goIdent(c.Variable)
2009→ if len(c.VariableIndices) > 0 {
2010→ varRef += g.generateIndicesStr(c.VariableIndices)
2011→ }
2012→ g.write(fmt.Sprintf("case %s = <-%s:\n", varRef, goIdent(c.Channel)))
2013→ }
2014→ g.indent++
2015→ guardedSkip := c.IsSkip && c.Guard != nil
2016→ if guardedSkip {
2017→ g.builder.WriteString(strings.Repeat("\t", g.indent))
2018→ g.write("if ")
2019→ g.generateExpression(c.Guard)
2020→ g.write(" {\n")
2021→ g.indent++
2022→ }
2023→ for _, s := range c.Body {
2024→ g.generateStatement(s)
2025→ }
2026→ if guardedSkip {
2027→ g.indent--
2028→ g.writeLine("}")
2029→ }
2030→ g.indent--
2031→ }
2032→ g.writeLine("}")
2033→}
2034→
2035→func (g *Generator) generateReplicatedAlt(alt *ast.AltBlock) {
2036→ // Replicated ALT: ALT i = start FOR count
2037→ // Uses reflect.Select for runtime-variable case count
2038→ if len(alt.Cases) == 0 {
2039→ return
2040→ }
2041→ c := alt.Cases[0]
2042→ rep := alt.Replicator
2043→ v := goIdent(rep.Variable)
2044→
2045→ // Determine receive type from scoped declarations
2046→ recvType := "int" // defaultNow I understand the current ALT codegen. Let me also look at the AST to understand the AltCase structure.
{
"pattern": "type AltCase|type AltBlock|IsSkip|Guard",
"path": "/home/david/projects/code-associates/occam2go/ast/ast.go",
"output_mode": "content",
"-n": true
}388:type AltBlock struct {
399:type AltCase struct {
400: Guard Expression // optional guard condition (nil if no guard)
407: IsSkip bool // true if this is a guarded SKIP case (guard & SKIP){
"file_path": "/home/david/projects/code-associates/occam2go/ast/ast.go",
"offset": 388,
"limit": 30
} 388→type AltBlock struct {
389→ Token lexer.Token // the ALT token
390→ Cases []AltCase
391→ Replicator *Replicator // optional replicator
392→ Priority bool // true for PRI ALT
393→}
394→
395→func (a *AltBlock) statementNode() {}
396→func (a *AltBlock) TokenLiteral() string { return a.Token.Literal }
397→
398→// AltCase represents a single case in an ALT block
399→type AltCase struct {
400→ Guard Expression // optional guard condition (nil if no guard)
401→ Channel string // channel name
402→ ChannelIndices []Expression // non-empty for cs[i] ? x or cs[i][j] ? x in ALT
403→ Variable string // variable to receive into
404→ VariableIndices []Expression // non-empty for c ? flags[0] or c ? grid[i][j]
405→ Body []Statement // the body to execute
406→ IsTimer bool // true if this is a timer AFTER case
407→ IsSkip bool // true if this is a guarded SKIP case (guard & SKIP)
408→ Timer string // timer name (when IsTimer)
409→ Deadline Expression // AFTER deadline expression (when IsTimer)
410→ Declarations []Statement // scoped declarations before channel input (e.g., BYTE ch:)
411→}
412→
413→// TimerDecl represents a timer declaration: TIMER tim:
414→type TimerDecl struct {
415→ Token lexer.Token // the TIMER token
416→ Names []string // timer variable names
417→}Now let me look at existing tests for ALT with SKIP guards to understand what's being tested.
{
"pattern": "SKIP.*ALT|ALT.*SKIP|IsSkip|guarded.*skip|skip.*guard",
"path": "/home/david/projects/code-associates/occam2go/codegen",
"output_mode": "content",
"-n": true,
"-i": true
}codegen/codegen.go:1968: if c.Guard != nil && !c.IsSkip {
codegen/codegen.go:1987: if c.IsSkip {
codegen/codegen.go:2015: guardedSkip := c.IsSkip && c.Guard != nil
codegen/codegen.go:2016: if guardedSkip {
codegen/codegen.go:2026: if guardedSkip {
codegen/e2e_misc_test.go:212:func TestE2E_AltGuardedSkip(t *testing.T) {
codegen/e2e_misc_test.go:213: // Issue #78: guard & SKIP in ALT (always-ready alternative)
codegen/e2e_misc_test.go:236:func TestE2E_AltGuardedSkipTrue(t *testing.T) {
codegen/e2e_misc_test.go:237: // Issue #77: ALT with channel case and guarded SKIP where guard is TRUE
codegen/e2e_misc_test.go:263:func TestE2E_AltGuardedSkipFalse(t *testing.T) {
codegen/e2e_misc_test.go:264: // Issue #77: ALT with channel case and guarded SKIP where guard is FALSE
codegen/e2e_misc_test.go:265: // The SKIP guard is false, so the channel case fires{
"file_path": "/home/david/projects/code-associates/occam2go/codegen/e2e_misc_test.go",
"offset": 212,
"limit": 90
} 212→func TestE2E_AltGuardedSkip(t *testing.T) {
213→ // Issue #78: guard & SKIP in ALT (always-ready alternative)
214→ occam := `SEQ
215→ CHAN OF INT c:
216→ INT result:
217→ BOOL ready:
218→ ready := TRUE
219→ result := 0
220→ PAR
221→ SEQ
222→ ALT
223→ ready & SKIP
224→ SKIP
225→ c ! 42
226→ c ? result
227→ print.int(result)
228→`
229→ output := transpileCompileRun(t, occam)
230→ expected := "42\n"
231→ if output != expected {
232→ t.Errorf("expected %q, got %q", expected, output)
233→ }
234→}
235→
236→func TestE2E_AltGuardedSkipTrue(t *testing.T) {
237→ // Issue #77: ALT with channel case and guarded SKIP where guard is TRUE
238→ // The SKIP fires immediately, then the channel send proceeds
239→ occam := `SEQ
240→ CHAN OF INT c:
241→ INT result:
242→ BOOL ready:
243→ ready := TRUE
244→ result := 0
245→ PAR
246→ SEQ
247→ ALT
248→ ready & SKIP
249→ result := 99
250→ c ? result
251→ SKIP
252→ c ! 42
253→ c ? result
254→ print.int(result)
255→`
256→ output := transpileCompileRun(t, occam)
257→ expected := "42\n"
258→ if output != expected {
259→ t.Errorf("expected %q, got %q", expected, output)
260→ }
261→}
262→
263→func TestE2E_AltGuardedSkipFalse(t *testing.T) {
264→ // Issue #77: ALT with channel case and guarded SKIP where guard is FALSE
265→ // The SKIP guard is false, so the channel case fires
266→ occam := `SEQ
267→ CHAN OF INT c:
268→ INT result:
269→ BOOL ready:
270→ ready := FALSE
271→ result := 0
272→ PAR
273→ SEQ
274→ ALT
275→ ready & SKIP
276→ result := 99
277→ c ? result
278→ SKIP
279→ c ! 77
280→ print.int(result)
281→`
282→ output := transpileCompileRun(t, occam)
283→ expected := "77\n"
284→ if output != expected {
285→ t.Errorf("expected %q, got %q", expected, output)
286→ }
287→}
288→
289→func TestE2E_MultiLineAbbreviation(t *testing.T) {
290→ // Issue #79: IS at end of line as continuation
291→ occam := `SEQ
292→ VAL INT x IS
293→ 42 :
294→ print.int(x)
295→`
296→ output := transpileCompileRun(t, occam)
297→ expected := "42\n"
298→ if output != expected {
299→ t.Errorf("expected %q, got %q", expected, output)
300→ }
301→}Now I understand the current behavior. Let me look at how the existing TestE2E_AltGuardedSkipFalse test generates code to understand how the current codegen handles the false guard case.
Let me trace through the codegen for the false guard case:
The ALT has:
- Case 0: ready & SKIP (IsSkip=true, Guard=ready)
- Case 1: c ? result (IsSkip=false, Guard=nil)
Current codegen:
1. For guarded cases that are not SKIP (case 1 has no guard), no _alt variable is generated
ready = false, the default case executes but the guard prevents the SKIP assignment, so the loop continues waiting for the actual channel receiveLet me trace through what actually happens: if goroutine 2 sends 77 on the channel before goroutine 1 even enters the ALT, then the channel has data waiting. When goroutine 1 enters the ALT, the c ? result branch becomes available to read, so it should take that path instead of the default. But the test is checking that result stays 99, which means the default branch must be firing... unless the scheduling is such that goroutine 1 always hits the ALT first while the channel is still empty, causing the guard to fire and skip the read entirely, leaving goroutine 2 blocked on the send.
Actually, I need to look at the actual codegen to understand what's being generated here.
Generating select statement code... So the test passes despite what looks like a deadlock scenario. The key is that Go's select statement picks randomly when multiple cases are ready—both the default and the channel receive could be available depending on timing. If goroutine 2 sends before goroutine 1 executes the select, the receive case becomes ready and gets chosen instead of the default, avoiding the deadlock. channel case (correct) and sometimes it picks default (incorrect - leads to deadlock).
But the test passes... maybe Go's scheduler consistently runs the goroutines in a specific order? Or maybe there's a race. Let me check by actually running the test multiple times.
Actually, looking at it more carefully: in Go, select with both a ready channel and default is not guaranteed to pick either one. But in practice, when a channel has data, Go may favor the channel case. Or... well, the Go spec says "If one or more of the communications can proceed, a single one that can proceed is chosen via a uniform pseudo-random selection."
So if the sender goroutine starts first and is blocked waiting on c, then when goroutine 1 reaches the select, both the channel case AND the default can proceed. Go will randomly pick one. The test is racy.
But maybe I'm overthinking this. The test might just happen to work consistently because of Go's goroutine scheduling behavior. In any case, the current behavior is wrong for the PRI ALT case in life.occ.
Now I need to figure out the fixes. For screen flushing, I should flush the writer after each byte when the screen buffer is empty. For the guarded SKIP case in ALT, the issue is that I'm unconditionally emitting a default case, but when there's a guarded SKIP, I need to conditionally include that default behavior instead.
I'm considering two approaches: either generate two separate select blocks (one with default, one without) based on the guard condition, or use a clever timeout trick with a closed channel. The first approach duplicates code but is straightforward. The second is more elegant but harder to read.
Actually, I think the cleanest solution is to initialize a nil channel variable and only close it if the guard is true—a nil channel never fires in a select, while a closed one always does, which perfectly models the guarded SKIP behavior without any code duplication.
But now I'm realizing there's a complication with PRI ALT semantics, since Go's select chooses randomly among ready cases rather than respecting priority order. So the current approach with select and default actually handles PRI ALT correctly when SKIP is the lower-priority alternative—the channel case fires if data's available, otherwise default fires. The real problem emerges with non-PRI ALT where SKIP is always-ready; Go's select will always pick default immediately instead of fairly choosing between ready alternatives, though that's less critical to fix right now. The actual issue I need to address is what happens when the guard condition on the SKIP case evaluates to false—the SKIP alternative should be disabled entirely so the ALT blocks waiting on channel cases. My solution uses a nil channel for the SKIP case when the guard is false, which prevents it from ever firing, while a closed channel makes it always-ready when the guard is true. This elegantly handles both PRI and non-PRI ALT scenarios without needing strict priority enforcement between the channel and SKIP alternatives.
Now I'm realizing there's a key distinction: default in a select only fires when no channels are ready, giving channels priority, but a closed channel case fires randomly alongside other ready channels. For PRI ALT where channels should have strict priority over SKIP, default was actually the right choice—the guard issue was the real bug. For fair ALT semantics where SKIP competes equally, the closed channel approach works better.
The fix needs to handle both cases: for PRI ALT with a guard, I'll use default when the guard is true and omit it when false, duplicating the channel cases to keep the logic clean.
For plain ALT with a guard, I'll create a closed channel that's only included in the select when the guard is true, letting it compete fairly with the other cases.
The duplication approach for PRI ALT gets messy with many channels, so I'm exploring an alternative using a non-blocking channel write instead.
Actually, a buffered channel with one element ready to read behaves the same as a closed channel—it doesn't give me the priority semantics I need. The cleanest solution is the dual-select approach: when the guard is true, I use a select with a default case to prioritize the channel, and when it's false, I use a regular select without the default.
But looking back at the actual code generation, I realize the guard is already being checked properly on lines 2015-2029—the code wraps the default case in a conditional based on whether it's a guarded skip. So the current implementation might actually be correct for PRI semantics.
The real issue is that when the guard is false, the default case fires but the body doesn't execute, leaving the ALT to terminate without blocking on the channel. For a cleaner solution, I could use a loop with select and retry logic instead of the dual-select approach, though I need to weigh that against code duplication concerns. Looking at typical ALTs like the one in life.occ with just 2 alternatives, the duplication would be minimal.
Actually, I'm realizing the dual-select approach is the most straightforward path forward despite the code duplication.
Let me reconsider using a closed-channel trick for the guarded SKIP case instead of a default clause. I could create a channel that's either closed when the guard is true or nil when it's false, then use that in the select statement...
Setting up a channel... I see the issue with the priority semantics—when both the keyboard input and the SKIP are ready, Go's select will pick randomly instead of preferring the keyboard, which breaks the PRI ALT guarantee. I'm considering using a helper function that returns a closed channel when the guard is true (making SKIP immediately ready) and nil otherwise (blocking it), but that approach feels clunky. Let me think through a cleaner way to handle the guard condition without the inline function overhead. I'm settling on conditional logic based on the guard value: when the guard is true, I use default for PRI ALT to respect priority ordering, but for plain ALT I need the closed-channel approach to avoid giving channels unintended priority over SKIP. The pragmatic question is whether the existing implementation already handles this correctly or if I need to refactor it.
Now I'm looking at how the current codegen structures the ALT generation...
Examining the generator function...
I need to detect when there's a guarded SKIP case and handle it specially by generating conditional channel variables before the select statement, then using those variables in the select cases instead of trying to use the guard directly in the case condition.
For the actual implementation, I'm thinking about the cleanest way to structure this without duplicating the select generation logic. I could generate the channel cases into a separate helper method that both the guarded and non-guarded paths can call, or I could use a flag to control whether the default case gets included. The key insight is that I need to separate the concern of "which cases to include" from "how to generate each case."
Actually, I'm going to accept some code duplication here—the generated output doesn't need to be perfectly DRY as long as it's correct and readable.
My approach is to generate a guard variable first, then use it to conditionally structure the select statement: if the guard is true, I'll generate a select with a default case that handles the skip, otherwise I'll generate a select with only the channel cases. This way each branch gets its own complete select statement without needing to share logic between them. Writing the dual-select pattern...
I'm realizing I need to avoid duplicating the channel case generation across both branches. Rather than trying to save and restore builder state, I should extract the channel case generation into a helper method that I can call from both the guarded and unguarded branches. Generating the dual-select pattern... Still writing the select logic...
Actually, I'm realizing the closed-channel approach has a fundamental problem with PRI ALT semantics—when the SKIP guard is true and no channel data is ready, a closed channel case would fire immediately instead of respecting the priority order, which breaks the intended behavior even more than the random selection issue.
The dual-select approach is the right call here to maintain proper priority semantics. I'll implement a helper method to generate the channel cases and avoid duplicating the logic.
My plan is to add a method that extracts the channel case generation, then modify the main block handler to detect guarded SKIP cases and wrap them in an if/else with two separate selects. This way I can handle the different channel case types (guarded, indexed, simple) and their bodies in one place.
Writing the helper method... Extracting the case generation logic... Writing the select statement logic... Still writing the select statement... Finishing the fixed implementation...
The refactored approach splits the select statement based on whether we're idle or not. When idle, we block on the keyboard channel waiting for input. When actively doing something, we use a non-blocking select with a default case so the editor or other activity can continue running while still checking for keyboard interrupts. This ensures the editor gets control flow when needed while preventing the system from getting stuck when idle.
Now I need to extract a helper method for generating individual ALT channels to keep the code clean.
Then I'll modify the main ALT block generator to detect when a guard is a SKIP and apply the dual-select pattern instead.
I also need to add the screen flush fix during preamble code generation and write tests to verify the behavior.
For naming, I should use unique variable names like _skipGuard0 indexed by the ALT case to avoid conflicts if there are multiple ALTs at the same scope level, since the variable is declared outside the select statement. a unique suffix. Actually, looking at the existing code, _alt0, _alt1 etc. are used for channel guard variables. I could use _altSkipGuard to avoid conflicts.
Hmm, actually, looking at the codegen more carefully, each ALT case is in its own statement, and statements in Go are scoped to their containing block. So _skipGuard declared in one ALT won't conflict with _skipGuard in another ALT, as long as they're not in the same block at the same level.
But actually they could be. If two ALTs are sequential statements in the same block, I'd get a redeclaration error. I could wrap each one in its own block to isolate the scope, or just use unique variable names like the existing code does with indexed channel guards. Since there's at most one SKIP case per ALT, I can just use a simple suffix like _altSkipReady to keep it clean. I should check whether each ALT block is in its own scope—if they are, the var _alt0 redeclaration won't actually be a problem. For the life.occ code there's only one ALT anyway, so I'll keep it simple. I need to handle the edge case where SKIP has no guard and should still use default:, and I'll assume multiple SKIP cases aren't valid occam. The SKIP body just contains regular statements that get generated normally, so I can proceed with modifying generateAltBlock.
Now I'm planning the actual fixes: for screen flushing, I'll add a flush call after writing bytes when the buffer is empty, and for guarded SKIP in ALT, I'll detect that pattern and generate a dual-select structure instead of trying to extract separate methods for case labels.
Writing the helper function... Finishing the case statement generation for simple channel receives, then iterating through the body statements with proper indentation. After that, I'm detecting whether there's a guarded skip case in the alternatives so I can handle it specially...
Now I'm evaluating the skip guard condition and generating code that branches into a select statement with a default case when the guard is true, executing the skip body statements when that default is triggered. Still writing select statement logic... Refining the guard logic structure...
The guard variable generation happens upfront and is shared between both paths. In the new dual-select path for guarded SKIPs, the guard check is already handled by the outer conditional, so the SKIP body doesn't need an inner guard wrapper. But in the existing path where there's no guarded SKIP, that inner guard check logic stays intact since guardedSkip will always be false there.
For multiple guarded SKIP cases, I'm just handling the first one for now since that's what the current use case needs. And for unguarded SKIPs...
Handling unguarded SKIP cases...
Now I need to implement both the guarded SKIP fix and the screen flush fix, and I should apply the same approach to the error channel writer as well.
Entered plan mode. You should now focus on exploring the codebase and designing an implementation approach. In plan mode, you should: 1. Thoroughly explore the codebase to understand existing patterns 2. Identify similar features and architectural approaches 3. Consider multiple approaches and their trade-offs 4. Use AskUserQuestion if you need to clarify the approach 5. Design a concrete implementation strategy 6. When ready, use ExitPlanMode to present your plan for approval Remember: DO NOT write or edit any files yet. This is a read-only exploration and planning phase.
I've already done extensive exploration and analysis. I understand both issues well. Let me now write the plan file and exit plan mode.
Let me first verify a few things by looking at the relevant codegen code to make sure my plan is solid.
I've already done extensive exploration. Let me verify a few remaining details and then write the plan.
{
"file_path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"offset": 1947,
"limit": 90
} 1947→func (g *Generator) generateAltBlock(alt *ast.AltBlock) {
1948→ if alt.Replicator != nil {
1949→ g.generateReplicatedAlt(alt)
1950→ return
1951→ }
1952→
1953→ // ALT becomes Go select statement
1954→ // For guards, we use a pattern with nil channels
1955→
1956→ // Check if any cases have guards
1957→ hasGuards := false
1958→ for _, c := range alt.Cases {
1959→ if c.Guard != nil {
1960→ hasGuards = true
1961→ break
1962→ }
1963→ }
1964→
1965→ if hasGuards {
1966→ // Generate channel variables for guarded cases
1967→ for i, c := range alt.Cases {
1968→ if c.Guard != nil && !c.IsSkip {
1969→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1970→ // Look up the channel's element type
1971→ elemType := "int" // default fallback
1972→ if t, ok := g.chanElemTypes[c.Channel]; ok {
1973→ elemType = t
1974→ }
1975→ g.write(fmt.Sprintf("var _alt%d <-chan %s = nil\n", i, elemType))
1976→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1977→ g.write(fmt.Sprintf("if "))
1978→ g.generateExpression(c.Guard)
1979→ g.write(fmt.Sprintf(" { _alt%d = %s }\n", i, goIdent(c.Channel)))
1980→ }
1981→ }
1982→ }
1983→
1984→ g.writeLine("select {")
1985→ for i, c := range alt.Cases {
1986→ g.builder.WriteString(strings.Repeat("\t", g.indent))
1987→ if c.IsSkip {
1988→ g.write("default:\n")
1989→ } else if c.IsTimer {
1990→ g.write("case <-time.After(time.Duration(")
1991→ g.generateExpression(c.Deadline)
1992→ g.write(" - int(time.Now().UnixMicro())) * time.Microsecond):\n")
1993→ } else if c.Guard != nil {
1994→ varRef := goIdent(c.Variable)
1995→ if len(c.VariableIndices) > 0 {
1996→ varRef += g.generateIndicesStr(c.VariableIndices)
1997→ }
1998→ g.write(fmt.Sprintf("case %s = <-_alt%d:\n", varRef, i))
1999→ } else if len(c.ChannelIndices) > 0 {
2000→ varRef := goIdent(c.Variable)
2001→ if len(c.VariableIndices) > 0 {
2002→ varRef += g.generateIndicesStr(c.VariableIndices)
2003→ }
2004→ g.write(fmt.Sprintf("case %s = <-%s", varRef, goIdent(c.Channel)))
2005→ g.generateIndices(c.ChannelIndices)
2006→ g.write(":\n")
2007→ } else {
2008→ varRef := goIdent(c.Variable)
2009→ if len(c.VariableIndices) > 0 {
2010→ varRef += g.generateIndicesStr(c.VariableIndices)
2011→ }
2012→ g.write(fmt.Sprintf("case %s = <-%s:\n", varRef, goIdent(c.Channel)))
2013→ }
2014→ g.indent++
2015→ guardedSkip := c.IsSkip && c.Guard != nil
2016→ if guardedSkip {
2017→ g.builder.WriteString(strings.Repeat("\t", g.indent))
2018→ g.write("if ")
2019→ g.generateExpression(c.Guard)
2020→ g.write(" {\n")
2021→ g.indent++
2022→ }
2023→ for _, s := range c.Body {
2024→ g.generateStatement(s)
2025→ }
2026→ if guardedSkip {
2027→ g.indent--
2028→ g.writeLine("}")
2029→ }
2030→ g.indent--
2031→ }
2032→ g.writeLine("}")
2033→}
2034→
2035→func (g *Generator) generateReplicatedAlt(alt *ast.AltBlock) {
2036→ // Replicated ALT: ALT i = start FOR count{
"pattern": "generateIndicesStr",
"path": "/home/david/projects/code-associates/occam2go/codegen/codegen.go",
"output_mode": "content",
"-n": true
}1362:// generateIndicesStr generates indices into a buffer and returns the string.
1363:func (g *Generator) generateIndicesStr(indices []ast.Expression) string {
1423: chanRef += g.generateIndicesStr(recv.ChannelIndices)
1433: varRef += g.generateIndicesStr(recv.VariableIndices)
1448: varRef += g.generateIndicesStr(recv.VariableIndices)
1508: chanRef += g.generateIndicesStr(vr.ChannelIndices)
1996: varRef += g.generateIndicesStr(c.VariableIndices)
2002: varRef += g.generateIndicesStr(c.VariableIndices)
2010: varRef += g.generateIndicesStr(c.VariableIndices)
2145: varRef += g.generateIndicesStr(c.VariableIndices)# Fix life.occ display buffering and PRI ALT busy-wait
## Context
The Game of Life example (`historical-examples/life.occ`) compiles and runs, but the editor mode doesn't visibly work (issue #72, latest comment). Two bugs:
1. **Screen output never flushes in editor mode**: The screen goroutine uses `bufio.NewWriter` (4096-byte buffer) and only flushes on byte 255 (never sent) or buffer full. In edit mode, cursor movements produce ~8-24 bytes per keypress — far too few to trigger a flush. "Idle" is visible only because the busy-wait loop writes it thousands of times.
2. **PRI ALT guarded SKIP causes busy-wait**: The controller's `PRI ALT` has `(activity <> idle) & SKIP`. When idle, this guard is false, so the ALT should block on the keyboard channel. But the Go translation uses unconditional `default:` in `select`, which always fires — creating a 100% CPU spin loop.
## Fix 1: Auto-flush screen output when channel drains
**File**: `codegen/codegen.go` (lines 483-502, screen writer goroutine)
After `w.WriteByte(b)` (line 495), add:
```go
if len(screen) == 0 {
w.Flush()
}
```
Apply the same fix to the error writer goroutine (line 521, after the error WriteByte).
This flushes after each burst of output while still batching rapid sequential writes.
## Fix 2: Guarded SKIP in ALT — conditional blocking
**File**: `codegen/codegen.go`, `generateAltBlock()` (lines 1947-2033)
### Approach: Dual-select pattern
When an ALT has a guarded SKIP case (`c.IsSkip && c.Guard != nil`), generate two `select` blocks instead of one:
```go
_altSkipReady := <guard expression>
if _altSkipReady {
select {
case x = <-_alt0:
...channel body...
default:
...skip body...
}
} else {
select {
case x = <-_alt0:
...channel body...
}
}
```
When guard is true: `default` fires if no channel ready (correct PRI ALT semantics).
When guard is false: no `default`, select blocks on channels (correct blocking).
### Implementation steps
1. Extract helper method `generateAltChannelCase(i int, c ast.AltCase)` — generates a single channel case label + body (the code currently at lines 1989-2013 + 2014-2030, minus the SKIP handling). This avoids duplicating the channel case generation code across both select blocks.
2. In `generateAltBlock()`, detect guarded SKIP:
```go
guardedSkipIdx := -1
for i, c := range alt.Cases {
if c.IsSkip && c.Guard != nil {
guardedSkipIdx = i
break
}
}
```
3. If `guardedSkipIdx >= 0`: generate `_altSkipReady` variable, then the if/else with two selects (using helper for channel cases). The SKIP body no longer needs the inner `if guard { }` wrapper since the guard is checked in the outer if.
4. If `guardedSkipIdx < 0`: existing codegen unchanged (unguarded SKIP → `default:`, no SKIP → no default).
## Tests
### E2E test for guarded SKIP with false guard (blocking behavior)
Add `TestE2E_AltGuardedSkipFalseBlocking` in `codegen/e2e_misc_test.go` — verify that when SKIP guard is false, the ALT blocks on the channel case and correctly receives.
### Fix existing flaky test
`TestE2E_AltGuardedSkipFalse` (line 263) is currently racy — it passes by luck because Go's scheduler runs the sender goroutine before the receiver reaches the select. With the fix, the blocking select correctly waits for channel data.
## Verification
```bash
go test ./... # all tests pass
go test ./codegen -run TestE2E_Alt # ALT-specific tests
./occam2go -o /tmp/life.go historical-examples/life.occ
go vet /tmp/life.go # compiles cleanly
go run /tmp/life.go # manual test: e→arrows→*→q→r works
```
{
"allowedPrompts": [
{
"tool": "Bash",
"prompt": "run tests"
},
{
"tool": "Bash",
"prompt": "build transpiler"
},
{
"tool": "Bash",
"prompt": "transpile occam files"
},
{
"tool": "Bash",
"prompt": "run go vet"
}
],
"plan": "# Fix life.occ display buffering and PRI ALT busy-wait\n\n## Context\n\nThe Game of Life example (`historical-examples/life.occ`) compiles and runs, but the editor mode doesn't visibly work (issue #72, latest comment). Two bugs:\n\n1. **Screen output never flushes in editor mode**: The screen goroutine uses `bufio.NewWriter` (4096-byte buffer) and only flushes on byte 255 (never sent) or buffer full. In edit mode, cursor movements produce ~8-24 bytes per keypress — far too few to trigger a flush. \"Idle\" is visible only because the busy-wait loop writes it thousands of times.\n\n2. **PRI ALT guarded SKIP causes busy-wait**: The controller's `PRI ALT` has `(activity <> idle) & SKIP`. When idle, this guard is false, so the ALT should block on the keyboard channel. But the Go translation uses unconditional `default:` in `select`, which always fires — creating a 100% CPU spin loop.\n\n## Fix 1: Auto-flush screen output when channel drains\n\n**File**: `codegen/codegen.go` (lines 483-502, screen writer goroutine)\n\nAfter `w.WriteByte(b)` (line 495), add:\n```go\nif len(screen) == 0 {\n w.Flush()\n}\n```\n\nApply the same fix to the error writer goroutine (line 521, after the error WriteByte).\n\nThis flushes after each burst of output while still batching rapid sequential writes.\n\n## Fix 2: Guarded SKIP in ALT — conditional blocking\n\n**File**: `codegen/codegen.go`, `generateAltBlock()` (lines 1947-2033)\n\n### Approach: Dual-select pattern\n\nWhen an ALT has a guarded SKIP case (`c.IsSkip && c.Guard != nil`), generate two `select` blocks instead of one:\n\n```go\n_altSkipReady := <guard expression>\nif _altSkipReady {\n select {\n case x = <-_alt0:\n ...channel body...\n default:\n ...skip body...\n }\n} else {\n select {\n case x = <-_alt0:\n ...channel body...\n }\n}\n```\n\nWhen guard is true: `default` fires if no channel ready (correct PRI ALT semantics).\nWhen guard is false: no `default`, select blocks on channels (correct blocking).\n\n### Implementation steps\n\n1. Extract helper method `generateAltChannelCase(i int, c ast.AltCase)` — generates a single channel case label + body (the code currently at lines 1989-2013 + 2014-2030, minus the SKIP handling). This avoids duplicating the channel case generation code across both select blocks.\n\n2. In `generateAltBlock()`, detect guarded SKIP:\n ```go\n guardedSkipIdx := -1\n for i, c := range alt.Cases {\n if c.IsSkip && c.Guard != nil {\n guardedSkipIdx = i\n break\n }\n }\n ```\n\n3. If `guardedSkipIdx >= 0`: generate `_altSkipReady` variable, then the if/else with two selects (using helper for channel cases). The SKIP body no longer needs the inner `if guard { }` wrapper since the guard is checked in the outer if.\n\n4. If `guardedSkipIdx < 0`: existing codegen unchanged (unguarded SKIP → `default:`, no SKIP → no default).\n\n## Tests\n\n### E2E test for guarded SKIP with false guard (blocking behavior)\nAdd `TestE2E_AltGuardedSkipFalseBlocking` in `codegen/e2e_misc_test.go` — verify that when SKIP guard is false, the ALT blocks on the channel case and correctly receives.\n\n### Fix existing flaky test\n`TestE2E_AltGuardedSkipFalse` (line 263) is currently racy — it passes by luck because Go's scheduler runs the sender goroutine before the receiver reaches the select. With the fix, the blocking select correctly waits for channel data.\n\n## Verification\n\n```bash\ngo test ./... # all tests pass\ngo test ./codegen -run TestE2E_Alt # ALT-specific tests\n./occam2go -o /tmp/life.go historical-examples/life.occ\ngo vet /tmp/life.go # compiles cleanly\ngo run /tmp/life.go # manual test: e→arrows→*→q→r works\n```\n"
}The user doesn't want to proceed with this tool use. The tool use was rejected (eg. if it was a file edit, the new_string was NOT written to the file). STOP what you are doing and wait for the user to tell you how to proceed.