[−][src]Crate fraction

Fraction is designed to be a precise lossless drop-in replacement for floating types (f32, f64).

It comes with a number of predefined type aliases covering the most common use cases such as Fraction, Decimal, BigFraction, DynaDecimal and so on (see prelude module for more examples).

The public API provides you with the generic types that you may use straightforwardly to build your own types, suiting your needs best (see prelude module for the examples).

Library features

Drop in replacement for floats with the exception for NaN == NaN so that it's hashable
It's hashable, so may be used as values in Sets and keys in dictionaries and hash maps
Display implementation for fractions and decimals
Fraction type, representing fractions
Decimal type, based on Fraction type represents floats as lossless decimals
DynaInt implements dinamically growing integer type that perfarms checked math and avoids stack overflows
PostgreSQL binary protocol integration for both fractions and decimals
Juniper support for both fractions and decimals
Generic integer conversions, such as i8 -> u8, usize -> u8 and so on
Lossless division with no allocations and infinite precision

Disclaimer

Even though we do our best to keep it well covered with tests, there may be bugs out there. The library API is still in flux. When it gets stable we will release the version 1.0.0. You may find more info about Semantic Versioning on https://semver.org/. Bug reports and contributions are appreciated.

Crate features

with-bigint (default) integration with num::BigInt and num::BigUint data types
with-decimal (default) Decimal type implemented upon GenericFraction
with-dynaint (default) dynamically growing integer avoiding stack overflows
with-juniper-support Juniper integration
with-postgres-support PostgreSQL integration; Numeric/Decimal type
with-serde-support Serde traits implementation

Implementation

Basic math implemented upon the num crate (in particular the num::rational module). The utilised traits from the num crate are re-exported, so you don't have to explicitly depend on that crate however, you may import them from either of crates if necessary.

Usage

To start using the library look no further than Prelude module.

Examples

Simple Fraction use:

type F = fraction::Fraction;

let result = F::from(0.7) / F::from(0.4);
assert_eq!(format!("{}", result), "7/4");
assert_eq!(format!("{:.2}", result), "1.75");
assert_eq!(format!("{:#.3}", result), "1.750");

Simple Decimal use:

type D = fraction::Decimal;

let result = D::from(0.5) / D::from(0.3);
assert_eq!(format!("{:.4}", result), "1.6666");

Generic integer conversion

use fraction::{Sign, GenericFraction};

type F = GenericFraction<u32>;

let fra = F::new_generic(Sign::Plus, 1i8, 42usize).unwrap();
assert_eq!(fra, F::new(1u32, 42u32));

Postgres usage

Postgres uses i16 for its binary protocol, so you'll have to use at least u16 as the base type for fractions/decimals. Otherwise you may workaround with DynaInt<u8, something_more_than_u8>. The safest way to go with would be DynaInt based types such as DynaFraction or DynaDecimal as they would prevent stack overflows for high values.

Beware bad numbers such as 1/3, 1/7. Fraction keeps the highest achievable precision (up to 16383 digits after floating point). Decimal uses its own precision. So, if you may end up with bad numbers, it may be preferable to go with Decimals over Fractions.

Both types (fractions and decimals) should work transparently in accordance with Postgres crate documentation

Re-exports

pub use self::prelude::*;

Modules

convert	Optimistic type conversion
display	Implementation of fmt::Display for GenericFraction and Sign structures
division	Lossless integer division
dynaint	Dynamic unsigned integer type selection
error	Crate error types
generic	Integer generic traits and operations
juniper_support	Juniper values conversion for GenericFraction The format is case sensitive text representation of the sign and numbers. Those are:
postgres_support
prelude	Predefines some types for the most common use cases

Structs

BigInt	A big signed integer type.
BigUint	A big unsigned integer type.
ParseRatioError
Ratio	Represents the ratio between two numbers.

Enums

GenericFraction	Generic implementation of the fraction type
Sign	Sign representation

Traits

Bounded	Numbers which have upper and lower bounds
CheckedAdd	Performs addition that returns `None` instead of wrapping around on overflow.
CheckedDiv	Performs division that returns `None` instead of panicking on division by zero and instead of wrapping around on underflow and overflow.
CheckedMul	Performs multiplication that returns `None` instead of wrapping around on underflow or overflow.
CheckedSub	Performs subtraction that returns `None` instead of wrapping around on underflow.
FromPrimitive	A generic trait for converting a number to a value.
Integer
Num	The base trait for numeric types, covering `0` and `1` values, comparisons, basic numeric operations, and string conversion.
One	Defines a multiplicative identity element for `Self`.
Signed	Useful functions for signed numbers (i.e. numbers that can be negative).
ToPrimitive	A generic trait for converting a value to a number.
Zero	Defines an additive identity element for `Self`.