Module libm

Floating-point math functions for no_std.

• Crate ::libm.
• docs.rs
• crates.io
• GitHub

libm is a pure-Rust port of the C library's math routines, maintained by the Rust project alongside compiler-builtins.

The interesting math operations on f32 and f64 — sin, exp, pow, sqrt, and friends — are inherent methods in std only. They are absent from core because the standard library implements them by calling the platform's C libm, which a no_std target may not have. Code written against core therefore needs this crate instead. Its other use is reproducibility: libm computes the same results on every platform, while the system libm may not.

Examples

Math on f64 and f32 without std:

// `core` has no `f64::sqrt`, so call the free function.
let x = libm::sqrt(2.0);
assert!((x - 1.414213562373095).abs() < 1e-15);

// The `f32` variants carry an `f` suffix, as in C.
let y = libm::sqrtf(2.0);
assert!((y - 1.4142135_f32).abs() < 1e-6);

Dispatching by float width with Libm:

use libm::Libm;

// `Libm<T>` selects the suffixed function matching `T`.
assert_eq!(Libm::<f64>::sqrt(4.0), libm::sqrt(4.0));
assert_eq!(Libm::<f32>::sqrt(4.0), libm::sqrtf(4.0));