Workstream 006's exact arithmetic: decimals, quantities, and the conservation audit,
decomposed into the 15-crate target design, with exact_arith as a deliberately thin
facade — a single block of pub use over the 14 leaf crates — plus one smoke lane.
This directory holds only the crates themselves. Each crate's purpose and the
real dependency graph are in
docs/guide/001_crate_family_overview.md
— not duplicated here. The original proposal's own dependency tree, and where
the real family deviates from it, is recorded in
docs/readme.md § Dependency Tree.
- Money, quantity, and price must stay non-interchangeable types
- Cross-scale operations must fail to compile, not resolve silently at runtime
- Values must be plain
Copybits, snapshot-safe, no heap - Needs a built-in zero-sum conservation audit
- Dust remainder and tick/lot snapping are first-class policy
- Bit-for-bit determinism required across every platform
- Hot match-loop operations (add, compare, ratio) must be cheap — no heap allocation
- No single existing crate bundles all of these
Full comparison against rust_decimal, bigdecimal, fixed, and others:
docs/research/001_exact_vs_open_source_alternatives.md.
| Directory | Responsibility |
|---|---|
exact_minor/ |
Tier 0 of the 15-crate target design — the raw subunit integer and its checked/saturating arithmetic |
exact_scale/ |
Tier 0 of the 15-crate target design — scale-factor math and the declared ceiling |
exact_round/ |
Tier 0 of the 15-crate target design — rounding modes and the family's default policy |
exact_sign/ |
Tier 1 of the 15-crate target design — sign classification and the negative-value admission policy |
exact_kind/ |
Tier 1 of the 15-crate target design — the conserved value type family: Money, Qty, Price |
exact_add/ |
Tier 2 of the 15-crate target design — checked and saturating add/sub per kind |
exact_ratio/ |
Tier 2 of the 15-crate target design — a rational multiplier and mode-driven division per kind |
exact_parse/ |
Tier 2 of the 15-crate target design — text parsing per kind |
exact_fmt/ |
Tier 2 of the 15-crate target design — formatting per kind and a buffer-writing primitive |
exact_bytes/ |
Tier 2 of the 15-crate target design — the wire encoding and its to/from conversions per kind |
exact_snap/ |
Tier 2 of the 15-crate target design — tick/lot grid snapping |
exact_cmp/ |
Tier 2 of the 15-crate target design — comparison, equality, and min/max per kind |
exact_dust/ |
Tier 3 of the 15-crate target design — equal-parts splitting with an explicit remainder destination |
exact_conserve/ |
Tier 3 of the 15-crate target design — conservation auditing, the plain-log verifier plus a typed per-kind layer |
exact_arith/ |
Tier 4 of the 15-crate target design — the facade over all 14 other crates, re-exports only |
smoke_exact_market_split/ |
Tier 5 of the 15-crate target design — this family's slice end to end through exact_arith alone |
docs/ |
Family-level material belonging to no single crate — two archived external conversations, plus the 15-crate target design corpus |
