A Decimal implementation written in pure Rust suitable for financial calculations that require significant integral and fractional digits with no round-off errors.

The binary representation consists of a 96 bit integer number, a scaling factor used to specify the decimal fraction and a 1 bit sign. Because of this representation, trailing zeros are preserved and may be exposed when in string form. These can be truncated using the normalize or round_dp functions.

Documentation

Decimal numbers can be created in a few distinct ways, depending on the rust compiler version you're targeting.

The stable version of rust requires you to create a Decimal number using one of it's convenience methods.

use rust_decimal::Decimal;

// Using an integer followed by the decimal points
let scaled = Decimal::new(202, 2); // 2.02

// From a string representation
let from_string = Decimal::from_str("2.02").unwrap(); // 2.02

// Using the `Into` trait
let my_int : Decimal = 3i32.into();

// Using the raw decimal representation
// 3.1415926535897932384626433832
let pi = Decimal::from_parts(1102470952, 185874565, 1703060790, false, 28);

With the nightly version of rust you can use a procedural macro using the rust_decimal_macros crate. The advantage of this method is that the decimal numbers are parsed at compile time.

// Procedural macros need importing directly
use rust_decimal_macros::*;

let number = dec!(-1.23);