The crate provides the following types:
FixedI8is a signed eight-bit fixed-point number,
FixedI16is a signed 16-bit fixed-point number,
FixedI32is a signed 32-bit fixed-point number,
FixedI64is a signed 64-bit fixed-point number,
FixedI128is a signed 128-bit fixed-point number,
FixedU8is an unsigned eight-bit fixed-point number,
FixedU16is an unsigned 16-bit fixed-point number,
FixedU32is an unsigned 32-bit fixed-point number,
FixedU64is an unsigned 64-bit fixed-point number, and
FixedU128is an unsigned 128-bit fixed-point number.
All fixed-point numbers can have
Frac fractional bits, where
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
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
// 20 integer bits, 12 fractional bits use fixed::types::I20F12; // 19/3 = 6 1/3 let six_and_third = I20F12::from_int(19) / 3; // four decimal digits for 12 binary digits assert_eq!(six_and_third.to_string(), "6.3333"); // find the ceil and convert to i32 assert_eq!(six_and_third.ceil().to_int::<i32>(), 7); // we can also compare directly to integers assert_eq!(six_and_third.ceil(), 7);
I20F12 is a 32-bit fixed-point signed number with 20
integer bits and 12 fractional bits. It is an alias to
FixedI32<frac::U12>. The unsigned counterpart would be
U20F12. Aliases are provided for all combinations of integer and
fractional bits adding up to a total of eight, 16, 32, 64 or 128 bits.
// −8 ≤ I4F4 < 8 with steps of 1/16 (about 0.06) use fixed::types::I4F4; let a = I4F4::from_int(1); // multiplication and division by integers is possible let ans1 = a / 5 * 17; // 1 / 5 × 17 = 3 2/5 (3.4), but we get 3 3/16 (3.19) assert_eq!(ans1, I4F4::from_bits((3 << 4) + 3)); assert_eq!(ans1.to_string(), "3.19"); // −8 ≤ I4F12 < 8 with steps of 1/4096 (about 0.0002) use fixed::types::I4F12; let wider_a = I4F12::from(a); let wider_ans = wider_a / 5 * 17; let ans2 = I4F4::from_fixed(wider_ans); // now the answer is the much closer 3 6/16 (3.38) assert_eq!(ans2, I4F4::from_bits((3 << 4) + 6)); assert_eq!(ans2.to_string(), "3.38");
The second example shows some precision and conversion issues. The low
a means that
a / 5 is 3⁄16 instead of 1⁄5, leading to
an inaccurate result
ans1 = 3 3⁄16 (3.19). With a higher precision,
wider_a / 5 equal to 819⁄4096, leading to a more accurate
wider_ans = 3 1635⁄4096. When we convert back to
four fractional bits, we get
ans2 = 3 6⁄16 (3.38).
Note that we can convert from
the target type has the same number of integer bits and a larger
number of fractional bits. Converting from
From as we have less fractional bits, so we use
[dependencies] fixed = "0.3.2"
If you are using the 2015 Rust edition, 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.
The fixed crate has two optional feature:
f16, disabled by default. This provides conversion to/from
f16. This features requires the half crate.
serde, disabled by default. This provides serialization support for the fixed-point types. This feature requires the serde crate.
To enable features, you can add the dependency like this to Cargo.toml:
[dependencies.fixed] version = "0.3.2" features = ["f16", "serde"]
This crate is free software: you can redistribute it and/or modify it under the terms of either
at your option.
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.
This module reexports items from the typenum crate.
This module contains sealed traits.
This module provides type aliases for all supported fixed-point numbers.
An eight-bit fixed-point signed integer with
A 16-bit fixed-point signed integer with
A 32-bit fixed-point signed integer with
A 64-bit fixed-point signed integer with
A 128-bit fixed-point signed integer with
An eight-bit fixed-point unsigned integer with
A 16-bit fixed-point unsigned integer with
A 32-bit fixed-point unsigned integer with
A 64-bit fixed-point unsigned integer with
A 128-bit fixed-point unsigned integer with
Provides intentionally wrapped arithmetic on fixed-point numbers.