# `decimal-scaled` - usage guides
**[Docs](https://mootable.github.io/decimal-scaled/)** • **[Benchmarks](https://mootable.github.io/decimal-scaled/benchmarks/)** • **[Algorithms](https://mootable.github.io/decimal-scaled/ALGORITHMS/)** • **[Roadmap](https://mootable.github.io/decimal-scaled/ROADMAP/)** • **[API reference](https://docs.rs/decimal-scaled)**
`decimal-scaled` provides const-generic, base-10 fixed-point decimal
types with deterministic, bit-exact arithmetic. A value is stored as an
integer `raw` such that the logical value is `raw × 10^(-SCALE)`, where
`SCALE` is a compile-time const generic.
These guides cover how to use the library in depth. For the high-level
pitch and the "why another numeric type" comparison, see the
[crate README](../README.md). For the full API, see the
[rustdoc](https://docs.rs/decimal-scaled/).
## Guides
| [Getting started](getting-started.md) | Installing, constructing values, basic arithmetic, formatting, parsing. |
| [The width family](widths.md) | Thirteen widths from `D9` to `D1232` — when to pick which, scale aliases, the `Decimal` trait. |
| [Conversions](conversions.md) | Integer / float conversions, cross-width widening and narrowing, `to_int`, the float bridge. |
| [Rounding](rounding.md) | `RoundingMode`, the `_with` method pairs, `rescale`, and the compile-time `rounding-*` feature flags. |
| [Strict mode](strict-mode.md) | Integer-only transcendentals (`ln`, `exp`, `sqrt`, trig, …) under `--features strict`. |
| [The `d*!` macros](macros.md) | Compile-time decimal literals with automatic scale inference, scientific notation, explicit scale, rounding, and inline expressions. |
| [Cargo features](features.md) | Every feature flag and what it enables, plus the `dyn` runtime-polymorphism surface. |
| [Comparisons](comparisons.md) | How `decimal-scaled` fits alongside `f64` / `f128` / `fixed` / `rust_decimal` / `bigdecimal`; hash and equality semantics; transcendental accuracy. |
| [Benchmarks](benchmarks.md) | Head-to-head timings against `bnum`, `ruint`, `rust_decimal`, `fastnum`, `dashu-float`, `bigdecimal`, and `fixed`; fast vs strict transcendentals; the 0.5 [ULP](https://en.wikipedia.org/wiki/Unit_in_the_last_place) guarantee. |
## A 30-second tour
```rust
use decimal_scaled::{D38s2, d38};
// Compile-time literal - scale inferred from the written digits.
let price = d38!(19.99); // D38s2, exactly 19.99
let qty = D38s2::from_int(3); // 3.00
let total = price * qty; // 59.97, exact - no binary rounding
assert_eq!(total, d38!(59.97));
// Deterministic: identical bit pattern on every platform.
assert_eq!(total.to_bits(), 5997);
```