A Decimal number 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.
Using cargo-edit
:
$ cargo add rust_decimal
In addition, if you would like to use the optimized macro for convenient creation of decimals:
$ cargo add rust_decimal_macros
Alternatively, you can edit your Cargo.toml
directly and run cargo update
:
[dependencies]
rust_decimal = "1.31"
rust_decimal_macros = "1.31"
Decimal numbers can be created in a few distinct ways. The easiest and most efficient 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::dec;
let number = dec!(-1.23) + dec!(3.45);
assert_eq!(number, dec!(2.22));
assert_eq!(number.to_string(), "2.22");
Alternatively you can also use one of the Decimal number convenience functions (see the docs for more details):
// Using the prelude can help importing trait based functions (e.g. core::str::FromStr).
use rust_decimal::prelude::*;
// Using an integer followed by the decimal points
let scaled = Decimal::new(202, 2);
assert_eq!("2.02", scaled.to_string());
// From a 128 bit integer
let balance = Decimal::from_i128_with_scale(5_897_932_384_626_433_832, 2);
assert_eq!("58979323846264338.32", balance.to_string());
// From a string representation
let from_string = Decimal::from_str("2.02").unwrap();
assert_eq!("2.02", from_string.to_string());
// From a string representation in a different base
let from_string_base16 = Decimal::from_str_radix("ffff", 16).unwrap();
assert_eq!("65535", from_string_base16.to_string());
// From scientific notation
let sci = Decimal::from_scientific("9.7e-7").unwrap();
assert_eq!("0.00000097", sci.to_string());
// Using the `Into` trait
let my_int: Decimal = 3_i32.into();
assert_eq!("3", my_int.to_string());
// Using the raw decimal representation
let pi = Decimal::from_parts(1_102_470_952, 185_874_565, 1_703_060_790, false, 28);
assert_eq!("3.1415926535897932384626433832", pi.to_string());
Once you have instantiated your Decimal
number you can perform calculations with it just like any other number:
use rust_decimal::prelude::*;
use rust_decimal_macros::dec;
let amount = dec!(25.12);
let tax_percentage = dec!(0.085);
let total = amount + (amount * tax_percentage).round_dp(2);
assert_eq!(total, dec!(27.26));
Behavior / Functionality
Database
Serde
- serde-float
- serde-str
- serde-arbitrary-precision
- serde-with-float
- serde-with-str
- serde-with-arbitrary-precision
Enables Borsh serialization for Decimal
.
Forces Decimal
to use [repr(C)]
. The corresponding target layout is 128 bit aligned.
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.
Enables the tokio postgres module allowing for async communication with PostgreSQL.
Enable diesel
PostgreSQL support. By default, this enables version 1.4
of diesel
. If you wish to use the 2.0
version of diesel
then you can do so by using the feature db-diesel2-postgres
. Please note, if both features are
enabled then version 2 will supersede version 1.
Enable diesel
MySQL support. By default, this enables version 1.4
of diesel
. If you wish to use the 2.0
version of diesel
then you can do so by using the feature db-diesel2-mysql
. Please note, if both features are
enabled then version 2 will supersede version 1.
Warning: This is deprecated and will be removed from a future versions.
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.
The maths
feature enables additional complex mathematical functions such as pow
, ln
, enf
, exp
etc.
Documentation detailing the additional functions can be found on the
MathematicalOps
trait.
Please note that ln
and log10
will panic on invalid input with checked_ln
and checked_log10
the preferred functions
to curb against this. When the maths
feature was first developed the library would instead return 0
on invalid input. To re-enable this
non-panicking behavior, please use the feature: maths-nopanic
.
Enables arithmetic operations using ndarray
on arrays of Decimal
.
Enables a proptest
strategy to generate values for Rust Decimal.
Implements rand::distributions::Distribution<Decimal>
to allow the creation of random instances.
Note: When using rand::Rng
trait to generate a decimal between a range of two other decimals, the scale of the randomly-generated
decimal will be the same as the scale of the input decimals (or, if the inputs have different scales, the higher of the two).
Enables rkyv serialization for Decimal
.
Supports rkyv's safe API when the rkyv-safe
feature is enabled as well.
Enable support for Rocket forms by implementing the FromFormField
trait.
Enable rust-fuzz
support by implementing the Arbitrary
trait.
Note: it is recommended to use the serde-with-*
features for greater control. This allows configurability at the data
level.
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
}
Note: it is recommended to use the serde-with-*
features for greater control. This allows configurability at the data
level.
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 its 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 terms of storage size.
Note: it is recommended to use the serde-with-*
features for greater control. This allows configurability at the data
level.
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.
Enable this to access the module for serializing Decimal
types to a float. This can be use in struct
definitions like so:
#[derive(Serialize, Deserialize)]
pub struct FloatExample {
#[serde(with = "rust_decimal::serde::float")]
value: Decimal,
}
#[derive(Serialize, Deserialize)]
pub struct OptionFloatExample {
#[serde(with = "rust_decimal::serde::float_option")]
value: Option<Decimal>,
}
Enable this to access the module for serializing Decimal
types to a String
. This can be use in struct
definitions like so:
#[derive(Serialize, Deserialize)]
pub struct StrExample {
#[serde(with = "rust_decimal::serde::str")]
value: Decimal,
}
#[derive(Serialize, Deserialize)]
pub struct OptionStrExample {
#[serde(with = "rust_decimal::serde::str_option")]
value: Option<Decimal>,
}
Enable this to access the module for serializing Decimal
types to a String
. This can be use in struct
definitions like so:
#[derive(Serialize, Deserialize)]
pub struct ArbitraryExample {
#[serde(with = "rust_decimal::serde::arbitrary_precision")]
value: Decimal,
}
#[derive(Serialize, Deserialize)]
pub struct OptionArbitraryExample {
#[serde(with = "rust_decimal::serde::arbitrary_precision_option")]
value: Option<Decimal>,
}
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
.
Please refer to the Build document for more information on building and testing Rust Decimal.
The current minimum compiler version is 1.60.0
which was released on 2022-04-07
.
This library maintains support for rust compiler versions that are 4 minor versions away from the current stable rust compiler version.
For example, if the current stable compiler version is 1.50.0
then we will guarantee support up to and including 1.46.0
.
Of note, we will only update the minimum supported version if and when required.