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>
2.1 KiB
Phase parse — recursive-descent parser
Mission. Build calc/parser.py exposing parse(tokens) -> Node (consuming the lex phase's
tokens) that produces an AST with correct arithmetic precedence and associativity, plus a
unittest suite. SSOT for this phase. Do NOT evaluate yet — just build the tree (the eval phase
consumes it). Represent nodes however you like (e.g. Num(value) and BinOp(op, left, right),
Unary(op, operand)), but expose a stable, documented shape the evaluator can walk.
Definition of Done (each Dn is a gate)
- D1 — precedence.
*and/bind tighter than+and-:1+2*3parses as1+(2*3), not(1+2)*3. - D2 — left associativity. Same-precedence operators associate left:
8-3-2parses as(8-3)-2;8/4/2as(8/4)/2. - D3 — parentheses. Parens override precedence:
(1+2)*3parses with the+under the*. - D4 — unary minus. Leading and nested unary minus parses:
-5,-(1+2),3 * -2. - D5 — errors. Malformed input raises
ParseError(define it):"1 +","(1","1 2",")(", and the empty string each raise (not crash with a different exception). - D6 — tests green.
calc/test_parser.py(unittest) passes underpython -m unittest, 0 failures, covering D1–D5. Assert on tree structure (e.g. arepr/shape helper), not on evaluation.
Verify (cold)
python -m unittest -q # D6
# D1/D3 differ in structure — the Builder's STATUS gives the exact shape assertion to re-run:
python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('1+2*3')))"
python -c "from calc.lexer import tokenize; from calc.parser import parse; parse(tokenize('1 +'))" # ParseError
The Builder documents the AST shape + exact assertions in machine-docs/STATUS-parse.md; the
Adversary cold-verifies and records parse/Dn: PASS|FAIL in machine-docs/REVIEW-parse.md. Watch
especially for a precedence/associativity bug that still passes a weak test — re-derive the expected
tree yourself from the plan.