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Option A (text-faithful): RateProblem gains time_unit (the duration's ORIGINAL unit; time stays int; defaults to the rate denominator). The SOLVER converts via convert_time -> exact Fraction -> int-or-refuse(non_integer); Fraction never leaves the solver, no floats. The reader accepts a convertible (minute<->hour) duration mismatch (keeps original time_unit); a non-convertible one still refuses rate_unit_mismatch. Signature includes time_unit ('30 minutes' != '30 hours').
Gold: r3-09 flips reader_refuses -> SOLVED (60 mph for 30 min = 30 mile, exact 1/2 hour; distractor 1800 rejected); new r3-13 non-convertible (3 gallons) stays rate_unit_mismatch. R3 gold 13/13; reader 9/0/0 -> answers 7/0/6 (setup_correct 8->9). Failure-family: rate_unit_mismatch now non-convertible-only -> still unsupported_rate_duration proposal surface; router-hygiene invariant stays green; R1 7/0/3, R2 10/0/0 unchanged. 119-test smoke green incl. invariants. Off-serving, no float path.
48 lines
3 KiB
Markdown
48 lines
3 KiB
Markdown
# R3.2 — explicit time-unit conversion (single-rate)
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**As of:** R3.2, on `main` + `feat/r3-2-conversion`.
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R3.2 adds exactly one capability to the single-rate organ: a duration whose unit **converts** to the
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rate's denominator (`minute` ↔ `hour`) is now **solved** instead of refused. It closes the most
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common rate gap — `60 miles per hour for 30 minutes → 30 miles` — which the R3.1 loop surfaced as a
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proposal.
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## Lane state
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- R3 gold **13 / 13 valid** (7 solved / 2 solver_refuses / 4 reader_refuses)
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- R3 reader **9 setup_correct / 0 setup_wrong / 4 refused** → answers **7 / 0 / 6**
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- R1 **7/0/3** · R2 **10/0/0** · serving unchanged · router-hygiene invariant green · off-serving
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## Design — Option A (text-faithful model, Fraction in the solver)
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- **Model** (`RateProblem`) gains `time_unit` — the duration's **original** unit from the text; `time`
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stays the original `int`. `rate_unit.denominator` is the target unit for composition. The setup
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remembers what the text said ("30 minutes"), not a normalized internal.
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- **Conversion** (`conversion.py`): `convert_time(value, from, to) -> Fraction` — exact rational
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(`fractions.Fraction`), identity for the same unit (incl. non-time like `box`), `minute ↔ hour`
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otherwise, refuse else. **No floats.**
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- **Solver** confines `Fraction`: `rate × convert(time)` (or the inverses), then exact-int-or-refuse
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(`non_integer_solution`). A non-convertible duration raises `ConversionError` → `rate_unit_mismatch`.
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- **Reader** accepts a convertible mismatch (keeps the original `time_unit`; the solver converts);
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a non-convertible mismatch still refuses `rate_unit_mismatch`.
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- **Signature** includes `time_unit` — "30 minutes" and "30 hours" are different setups at the same rate.
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## Gold change
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- `r3-09` flips **reader_refuses → solved**: "60 mph for 30 minutes" → 30 minute = `Fraction(1,2)` hour
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→ `60 × 1/2 = 30` mile (the never-convert distractor `1800` is rejected).
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- New `r3-13` (non-convertible): "…per hour for 3 gallons" → `rate_unit_mismatch` (gallon is not a
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time unit). Stays a proposal surface.
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## Failure-family / hygiene (confirmed, no code change)
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- `rate_unit_mismatch` now fires **only for non-convertible** durations → still maps to the
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`unsupported_rate_duration` growth surface (propose adding *that* unit pair). Convertible mismatches
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now **solve** (no longer a failure). `temporal_state` / `not_rate_shaped` unchanged.
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- The **router-organ-hygiene invariant** stays green — R3 still refuses foreign R1/R2 text as
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`input_shape`, never a substantive boundary.
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## Acceptance (met)
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R3 `setup_correct` **8 → 9** · `answer_wrong = 0` · `r3-09` refused/proposal → solved ·
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non-convertible mismatch still refused/proposal · R1/R2 unchanged · **no float path** (Fraction →
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int-or-refuse).
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## Deferred (named for later)
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length (`mile ↔ km`), currency (`dollar ↔ cent`), compound conversions, combined/multi-rate,
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clock-time intervals. The dimensional substrate is now proven for exact rational time conversion.
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