20 unstable releases (4 breaking)
✓ Uses Rust 2018 edition
|new 0.4.4||Aug 24, 2019|
|0.3.3||Jun 27, 2019|
|0.3.2||Feb 27, 2019|
|0.1.4||Nov 29, 2018|
#20 in Math
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Used in 1 crate
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
Various conversion methods are available:
- All lossless infallible conversions between fixed-point numbers
and numeric primitives are implemented. You can use
Intofor conversions that always work without losing any bits.
- For lossy infallible conversions between fixed-point numbers and
numeric primitives, where the source type may have more fractional
bits than the destination type, the
LossyIntotraits can be used. Excess fractional bits are truncated.
- Checked conversions are provided between fixed-point numbers and
numeric primitives using the
ToFixedtraits, or using the
to_nummethods and their checked versions.
- Fixed-point numbers can be parsed from decimal strings using
FromStr, or from binary, octal or hexadecimal using the
from_str_hexmethods. The result is rounded to the nearest, with ties rounded to even.
- Fixed-point numbers can be converted to strings using
UpperHex. The output is rounded to the nearest, with ties rounded to even.
- The fixed crate now requires rustc version 1.34.0 or later.
- The precision argument is no longer ignored when formatting fixed-point numbers; precision should now be handled the same as for primitive floating-point numbers in the standard library.
- Parsing strings now rounds to the nearest with ties rounded to even.
- Checked versions of string parsing methods are now available as
inherent methods to all fixed-point numbers, and as methods in the
Wrappingnow has methods for parsing with wrapping, including an implementation of
- The following methods are now
- The associated constants
- The reexports in the
fracmodule and the
LeEqU*traits were moved into the new
- The new methods
to_numtogether with their checked versions were added to all fixed-point numbers.
- The methods
to_float, and their checked versions, were deprecated.
- The new method
from_numwas added to the
- Bug fix: parsing of decimal fractions was fixed to give correctly rounded results for long decimal fraction strings, for example with four fractional bits, 0.96874999… (just below 31⁄32) and 0.96875 (31⁄32) are now parsed correctly as 0.9375 (15⁄16) and 1.0.
- All fixed-point types now implement
- The methods
- The fixed crate now requires rustc version 1.31.0 or later.
traitsmodule was added, with its traits
saturating_negmethod was added to all fixed-point numbers, and the
saturating_absmethod was added to signed fixed-point numbers.
constsmodule was added.
signummethod now wraps instead of panics in release mode.
- The sealed traits
Floatnow have no provided methods; the methods in the old implementation are new provided by
- Deprecated methods were removed.
Details on other releases can be found in RELEASES.md.
// 20 integer bits, 12 fractional bits use fixed::types::I20F12; // 19/3 = 6 1/3 let six_and_third = I20F12::from_num(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_num::<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
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 (~0.06) use fixed::types::I4F4; let a = I4F4::from_num(1); // multiplication and division by integers are possible let ans1 = a / 5 * 17; // 1 / 5 × 17 = 3 2/5 (3.4), but we get 3 3/16 (~3.2) assert_eq!(ans1, I4F4::from_bits((3 << 4) + 3)); assert_eq!(ans1.to_string(), "3.2"); // −8 ≤ I4F12 < 8 with steps of 1/4096 (~0.0002) use fixed::types::I4F12; let wider_a = I4F12::from(a); let wider_ans = wider_a / 5 * 17; let ans2 = I4F4::from_num(wider_ans); // now the answer is the much closer 3 6/16 (~3.4) assert_eq!(ans2, I4F4::from_bits((3 << 4) + 6)); assert_eq!(ans2.to_string(), "3.4");
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 (~3.2). 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 (~3.4).
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 = "0.4.3"
The fixed crate requires rustc version 1.34.0 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 = "0.4.3" 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.