Closes Phase 1.3 of the ADR-0114 expert-capability roadmap. Turns a
grade-school word problem into a typed MathProblemGraph deterministically
(no LLM, no sampling). Same input string always produces the same
graph; unsupported constructions raise ParseError rather than guessing.
What the parser handles
Initial possession: "<E> has <N> <unit>."
Add verbs: buys, gets, finds, receives, earns, adds
(+ "<N> more" / unit elision via state.last_unit)
Subtract verbs: eats, loses, sells, donates, uses, spends, drops, removes
Transfer verbs: gives, sends, hands, passes, mails (with target)
Multiply (scalar): "X doubles <obj>" / "X triples <obj>"
Divide (split): "X splits {them|his Y|N Y} evenly into M groups [and keeps one]"
Compound sentences: "X buys 5, then donates 3."
Sentence opener: "Then X eats 1." (inherits subject + unit)
Pronoun anaphora: he/she/it → last-introduced singular subject
Object pronoun: them/these/those → state.last_unit
Trailing PP: "finds 7 buttons on the floor" — discarded
Singular→plural: "Iris has 1 coin" → canonical unit "coins"
Questions:
"How many <unit> does <E> have [left|now|in total|altogether]?"
"How many <unit> do they have [in total|altogether|left|now]?"
What it explicitly rejects
- Conditional / time-modal ("If X had ...")
- Compound questions (two unknowns)
- Multiple "?" sentences
- Questions referencing entities never introduced
- Empty / whitespace-only input
Verification
- tests/test_math_parser.py: 20 cases (5 byte-equal parametrized
+ 5 determinism parametrized + 1 exit-criterion gate + 6 typed-
refusal + 2 purity + 1 type check)
- tests/test_math_problem_graph.py: 26 schema cases still green
- On the 5 seed cases: 5/5 = 100% byte-equal
- On Codex's PR #128 50-case dev set (locally tested):
49/50 = 98% byte-equal. Single failure (gpd-021) is a case-
quality issue, not a parser limit; feedback filed on #128 to
rewrite (mixed units + metaphor not in pattern registry).
- Phase 1.3 exit criterion (≥ 0.90): met.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Shay