4.5 KiB
Fixed-point numbers
The fixed crate provides fixed-point numbers. Currently it uses the typenum crate for the fractional bit count; it is planned to move to const generics when they are implemented by the Rust compiler.
The crate provides the following types:
FixedI8
is a signed eight-bit fixed-point number,FixedI16
is a signed 16-bit fixed-point number,FixedI32
is a signed 32-bit fixed-point number,FixedI64
is a signed 64-bit fixed-point number,FixedI128
is a signed 128-bit fixed-point number,FixedU8
is an unsigned eight-bit fixed-point number,FixedU16
is an unsigned 16-bit fixed-point number,FixedU32
is an unsigned 32-bit fixed-point number,FixedU64
is an unsigned 64-bit fixed-point number, andFixedU128
is an unsigned 128-bit fixed-point number.
All fixed-point numbers can have Frac
fractional bits, where Frac
can have any value from 0 up to and including the size of the number
in bits. When Frac
is 0, the fixed-point number behaves like an
integer. When Frac
is equal to the number of bits, the value of the
fixed-point number lies in the range −0.5 ≤ x < 0.5 for signed
fixed-point numbers, and in the range 0 ≤ x < 1 for unsigned
fixed-point numbers.
What’s new
Version 0.1.4 news (2018-11-29)
Other releases
Details on other releases can be found in RELEASES.md.
Quick example
use fixed::frac;
use fixed::FixedI32;
// 20 integer bits, 12 fractional bits
type I20F12 = FixedI32<frac::U12>;
// 19/3 = 6 1/3
let six_and_third = I20F12::from_int(19).unwrap() / 3;
// four decimal digits for 12 binary digits
assert_eq!(six_and_third.to_string(), "6.3333");
// convert to i32, taking the ceil
assert_eq!(six_and_third.to_int_ceil(), 7);
Using the fixed crate
The fixed crate is available on crates.io. To use it in your crate, add it as a dependency inside Cargo.toml:
[dependencies]
fixed = "0.1.4"
You also need to declare it by adding this to your crate root (usually lib.rs or main.rs):
extern crate fixed;
The fixed crate requires rustc version 1.28.0 or later.
Optional features
The fixed crate has one optional feature:
f16
, disabled by default. This provides conversion to/fromf16
. This features requires the half crate.
To enable the feature, you can add the dependency like this to Cargo.toml:
[dependencies.fixed]
version = "0.1.4"
features = ["f16"]
License
This crate is free software: you can redistribute it and/or modify it under the terms of either
- the Apache License, Version 2.0 or
- the MIT License
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache License, Version 2.0, shall be dual licensed as above, without any additional terms or conditions.