mfowler
8c3f38dbf4
- plans/calc/{lex,parse,eval}.md: a 3-phase calculator with multiple gates per
phase (tokenizer → recursive-descent parser → evaluator+CLI), rich adversarial
edge cases (precedence/associativity/unary/div-zero)
- run-harness-bench.sh: stands up a real agents.py up Builder/Adversary loop pair
+ watchdog over a shared work repo per variant, runs to SEQUENCE-COMPLETE, and
clocks tokens from the session transcripts (AI-as-adversary kept intact)
- RESULTS.md: baseline single-pass roman-numeral run (prompt size had ~0 token
effect; cache-read of the working context dominates)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
35 lines
2.1 KiB
Markdown
35 lines
2.1 KiB
Markdown
# Phase `parse` — recursive-descent parser
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**Mission.** Build `calc/parser.py` exposing `parse(tokens) -> Node` (consuming the `lex` phase's
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tokens) that produces an **AST** with correct arithmetic precedence and associativity, plus a
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`unittest` suite. SSOT for this phase. Do NOT evaluate yet — just build the tree (the `eval` phase
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consumes it). Represent nodes however you like (e.g. `Num(value)` and `BinOp(op, left, right)`,
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`Unary(op, operand)`), but expose a stable, documented shape the evaluator can walk.
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## Definition of Done (each Dn is a gate)
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- **D1 — precedence.** `*` and `/` bind tighter than `+` and `-`: `1+2*3` parses as `1+(2*3)`, not
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`(1+2)*3`.
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- **D2 — left associativity.** Same-precedence operators associate left: `8-3-2` parses as
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`(8-3)-2`; `8/4/2` as `(8/4)/2`.
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- **D3 — parentheses.** Parens override precedence: `(1+2)*3` parses with the `+` under the `*`.
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- **D4 — unary minus.** Leading and nested unary minus parses: `-5`, `-(1+2)`, `3 * -2`.
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- **D5 — errors.** Malformed input raises `ParseError` (define it): `"1 +"`, `"(1"`, `"1 2"`, `")("`,
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and the empty string each raise (not crash with a different exception).
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- **D6 — tests green.** `calc/test_parser.py` (`unittest`) passes under `python -m unittest`, 0
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failures, covering D1–D5. Assert on tree structure (e.g. a `repr`/shape helper), not on evaluation.
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## Verify (cold)
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```bash
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python -m unittest -q # D6
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# D1/D3 differ in structure — the Builder's STATUS gives the exact shape assertion to re-run:
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python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('1+2*3')))"
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python -c "from calc.lexer import tokenize; from calc.parser import parse; parse(tokenize('1 +'))" # ParseError
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```
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The Builder documents the AST shape + exact assertions in `machine-docs/STATUS-parse.md`; the
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Adversary cold-verifies and records `parse/Dn: PASS|FAIL` in `machine-docs/REVIEW-parse.md`. Watch
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especially for a precedence/associativity bug that still passes a weak test — re-derive the expected
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tree yourself from the plan.
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