giles
0f67021aa3
Five new guest-language plans mirroring the js-on-sx / hs-loop pattern, each with a phased roadmap (Progress log + Blockers), a self-contained agent briefing for respawning a long-lived loop, and a shared restore-all.sh that snapshots state across all seven language loops. Briefings bake in the lessons from today's stall debugging: never call sx_build (600s watchdog), only touch lib/<lang>/** + own plan file, commit every feature, update Progress log on each commit, route shared-file issues to Blockers rather than fixing them. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
98 lines
4.8 KiB
Markdown
98 lines
4.8 KiB
Markdown
# Prolog-on-SX: mini-Prolog interpreter on delimited continuations
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Horn clauses + unification + cut + arithmetic, implemented as an **interpreter** (clauses live as SX data, a SX-implemented solver walks them). Backtracking is powered by the delimited-continuations machinery in `lib/callcc.sx` + `spec/evaluator.sx` Step 5 — this is the reason Prolog fits SX well.
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End-state goal: **200+ tests passing** (classic programs + Hirst's ISO conformance subset + Hyperscript integration suite). Long-lived background agent driving the scoreboard up.
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## Ground rules
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- **Scope:** only touch `lib/prolog/**` and `plans/prolog-on-sx.md`. Do **not** edit `spec/`, `hosts/`, `shared/`, `lib/js/**`, `lib/hyperscript/**`, `lib/lua/**`, `lib/stdlib.sx`, or anything in `lib/` root. Prolog primitives go in `lib/prolog/runtime.sx`.
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- **Shared-file issues** go under "Blockers" below with a minimal repro; do not fix from this loop.
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- **SX files:** use `sx-tree` MCP tools only.
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- **Architecture:** Prolog source → term AST → clause DB. Solver is SX code walking the DB; backtracking via delimited continuations, not a separate trail machine.
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- **Commits:** one feature per commit. Keep `## Progress log` updated and tick boxes.
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## Architecture sketch
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```
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Prolog source text
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│
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▼
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lib/prolog/tokenizer.sx — atoms, vars, numbers, punct, comments
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│
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▼
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lib/prolog/parser.sx — term AST; phase 1: f(a,b) syntax only, no operator table
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│
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▼
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lib/prolog/runtime.sx — clause DB, unify!, trail, solver (DFS + delimited-cont backtracking)
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│ built-ins: =/2, \=/2, !/0, is/2, call/1, findall/3, …
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▼
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solutions / side-effects
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```
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Representation choices (finalise in phase 1, document here):
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- **Term:** nested SX list. Compound `(functor arg1 arg2)`. Atom = symbol. Number = number. Variable = `{:var "X" :binding <ref>}` with mutable binding slot.
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- **List:** cons-cell compound `(. H T)` or similar. `[1,2,3]` sugar desugared at parse.
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- **Clause:** `{:head <term> :body <term>}` where body is the conjunction goal.
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- **Clause DB:** dict `"functor/arity" → list of clauses`.
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## Roadmap
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### Phase 1 — tokenizer + term parser (no operator table)
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- [ ] Tokenizer: atoms (lowercase/quoted), variables (uppercase/`_`), numbers, strings, punct `( ) , . [ ] | ! :-`, comments (`%`, `/* */`)
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- [ ] Parser: clauses `head :- body.` and facts `head.`; terms `atom | Var | number | compound(args) | [list,sugar]`
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- [ ] **Skip for phase 1:** operator table. `X is Y + 1` must be written `is(X, '+'(Y, 1))`; `=` written `=(X, Y)`. Operators land in phase 4.
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- [ ] Unit tests in `lib/prolog/tests/parse.sx`
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### Phase 2 — unification + trail
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- [ ] `make-var`, `walk` (follow binding chain), `prolog-unify!` (terms + trail → bool), `trail-undo-to!`
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- [ ] Occurs-check off by default, exposed as flag
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- [ ] 30+ unification tests in `lib/prolog/tests/unify.sx`: atoms, vars, compounds, lists, cyclic (no-occurs-check), mutual occurs
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### Phase 3 — clause DB + DFS solver + cut + first classic programs
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- [ ] Clause DB: `"functor/arity" → list-of-clauses`, loader inserts
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- [ ] Solver: DFS with choice points backed by delimited continuations (`lib/callcc.sx`). On goal entry, capture; per matching clause, unify head + recurse body; on failure, undo trail, try next
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- [ ] Cut (`!`): cut barrier at current choice-point frame; collapse all up to barrier
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- [ ] Built-ins: `=/2`, `\\=/2`, `true/0`, `fail/0`, `!/0`, `,/2`, `;/2`, `->/2` inside `;`, `call/1`, `write/1`, `nl/0`
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- [ ] Arithmetic `is/2` with `+ - * / mod abs`
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- [ ] Classic programs in `lib/prolog/tests/programs/`:
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- [ ] `append.pl` — list append (with backtracking)
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- [ ] `reverse.pl` — naive reverse
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- [ ] `member.pl` — generate all solutions via backtracking
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- [ ] `nqueens.pl` — 8-queens
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- [ ] `family.pl` — facts + rules (parent/ancestor)
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- [ ] `lib/prolog/conformance.sh` + runner, `scoreboard.json` + `scoreboard.md`
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- [ ] Target: all 5 classic programs passing
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### Phase 4 — operator table + more built-ins (next run)
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- [ ] Operator table parsing (prefix/infix/postfix, precedence, assoc)
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- [ ] `assert/1`, `asserta/1`, `assertz/1`, `retract/1`
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- [ ] `findall/3`, `bagof/3`, `setof/3`
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- [ ] `copy_term/2`, `functor/3`, `arg/3`, `=../2`
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- [ ] String/atom predicates
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### Phase 5 — Hyperscript integration
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- [ ] `prolog-query` primitive callable from SX/Hyperscript
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- [ ] Hyperscript DSL: `when allowed(user, :edit) then …`
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- [ ] Integration suite
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### Phase 6 — ISO conformance
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- [ ] Vendor Hirst's conformance tests
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- [ ] Drive scoreboard to 200+
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### Phase 7 — compiler (later, optional)
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- [ ] Compile clauses to SX continuations for speed
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- [ ] Keep interpreter as the reference
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## Progress log
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_Newest first. Agent appends on every commit._
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- _(awaiting phase 1)_
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## Blockers
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_Shared-file issues that need someone else to fix. Minimal repro only._
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- _(none yet)_
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