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Bit-exact decimal arithmetic for Rust

decimal-scaled

Const-generic base-10 fixed-point decimals — thirteen widths from D9 to D1231 — with ≤ 0.5 ULP correctly-rounded integer-only transcendentals. Deterministic across every platform. no_std-friendly. Caller-chosen rounding mode at every lossy operation.

$ cargo add decimal-scaled

Get started Benchmarks GitHub

  • Getting started

    Install snippet, the first D38<2> value, and a tour of the per-width macros.

    getting-started.md

  • Usage guides

    Per-topic deep-dives: widths, scales, strict-vs-fast routing, rounding, macros, Cargo features.

    widths.md

  • Benchmarks

    Per-width speed tables plus the §5 like-for-like library comparison vs the top crates.io peers.

    benchmarks.md

  • API reference

    Rustdoc for every type, trait, method, and Cargo feature across every supported width.

    api/decimal_scaled/index.html

  • Algorithms

    Möller–Granlund magic-multiply, artanh-series transcendentals, Cody-Waite range reduction - the catalogue of techniques the crate uses and why.

    ALGORITHMS.md

  • Roadmap

    The wide-tier ÷ 10^SCALE, mul, and transcendental-throughput gaps and the planned algorithmic fix per item.

    ROADMAP.md

  • Changelog

    What changed in every release.

    CHANGELOG.md

Why decimal-scaled

You need… decimal-scaled gives you…
Decimal arithmetic that doesn't drift (0.1 + 0.2 == 0.3) Base-10 storage; exact + - %, correctly-rounded * /.
Bit-identical results across Linux / macOS / Windows / ARM / x86 *_strict transcendentals - integer-only, no platform libm.
Compile-time-fixed precision with zero per-value scale byte Const-generic D38<19>, D76<35> etc. - scale is in the type.
no_std (or no_std + alloc) Default features build under no_std; the strict tier needs no libm.
≤ 0.5 ULP correctly-rounded ln / exp / sin / cos / tan / sqrt / atan / sinh / cosh / tanh and friends — by default At every shipped width, HalfToEven by default, bit-identical across every platform. Switch rounding mode per call via *_with(mode) or crate-wide via the rounding-* features. See Benchmarks §5.

What it isn't

For runtime-variable scale, look at rust_decimal. For arbitrary precision at runtime, look at bigdecimal or dashu-float. For binary fixed-point (DSP, embedded radio), look at fixed. decimal-scaled is for the case where you want decimal, compile-time-fixed, and deterministic - all three.