#decimal #financial #fixed #precision

rust_decimal

A Decimal Implementation written in pure Rust suitable for financial calculations

50 releases (15 stable)

new 1.8.1 Sep 15, 2020
1.7.0 Jul 11, 2020
1.4.0 Mar 23, 2020
1.1.0 Dec 27, 2019
0.1.0 Nov 16, 2016

#1 in Science

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47,667 downloads per month
Used in 115 crates (46 directly)

MIT license

150KB
3K SLoC

Decimal   Build Status Latest Version

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

Usage

Decimal numbers can be created in a few distinct ways. The easiest and most optimal method of creating a Decimal is to use the procedural macro within the rust_decimal_macros crate:

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

let number = dec!(-1.23);

Alternatively you can also use one of the Decimal number convenience functions:

use rust_decimal::prelude::*;

// 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);

Features

db-postgres

This feature enables a PostgreSQL communication module. It allows for reading and writing the Decimal type by transparently serializing/deserializing into the NUMERIC data type within PostgreSQL.

db-tokio-postgres

Enables the tokio postgres module allowing for async communication with PostgreSQL.

db-diesel-postgres

Enable diesel PostgreSQL support.

serde-float

Enable this so that JSON serialization of Decimal types are sent as a float instead of a string (default).

e.g. with this turned on, JSON serialization would output:

{
  "value": 1.234
}

serde-bincode

Since bincode does not specify type information, we need to ensure that a type hint is provided in order to correctly be able to deserialize. Enabling this feature on it's own will force deserialization to use deserialize_str instead of deserialize_any.

If, for some reason, you also have serde-float enabled then this will use deserialize_f64 as a type hint. Because converting to f64 loses precision, it's highly recommended that you do NOT enable this feature when working with bincode. That being said, this will only use 8 bytes so is slightly more efficient in regards to storage size.

std

Enable std library support. This is enabled by default, however in the future will be opt in. For now, to support no_std libraries, this crate can be compiled with --no-default-features.

Dependencies

~0.3–2MB
~42K SLoC