[][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.