# Decimal   [![Build Status]][actions] [![Latest Version]][crates.io]
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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](https://docs.rs/rust_decimal/)
## 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:
```rust
// 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:
```rust
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](#db-postgres)
* [db-tokio-postgres](#db-tokio-postgres)
* [db-diesel-postgres](#db-diesel-postgres)
* [legacy-ops](#legacy-ops)
* [serde-float](#serde-float)
* [serde-str](#serde-str)
* [std](#std)
## `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.
## `legacy-ops`
As of `1.10` the algorithms used to perform basic operations have changed which has benefits of significant speed improvements.
To maintain backwards compatibility this can be opted out of by enabling the `legacy-ops` feature.
## `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-str`
This is typically useful for `bincode` or `csv` like implementations.
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.
## `serde-arbitrary-precision`
This is used primarily with `serde_json` and consequently adds it as a "weak dependency". This supports the
`arbitrary_precision` feature inside `serde_json` when parsing decimals.
This is recommended when parsing "float" looking data as it will prevent data loss.
## `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`.