Experimental version of mul_add in core. See f64::mul_add for details.

Examples

#![feature(core_float_math)]

# // FIXME(#140515): mingw has an incorrect fma
# // https://sourceforge.net/p/mingw-w64/bugs/848/
# #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
use core::f64;

let m = 10.0_f64;
let x = 4.0_f64;
let b = 60.0_f64;

assert_eq!(f64::math::mul_add(m, x, b), 100.0);
assert_eq!(m * x + b, 100.0);

let one_plus_eps = 1.0_f64 + f64::EPSILON;
let one_minus_eps = 1.0_f64 - f64::EPSILON;
let minus_one = -1.0_f64;

// The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
assert_eq!(
    f64::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
    -f64::EPSILON * f64::EPSILON
);
// Different rounding with the non-fused multiply and add.
assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
# }

This standalone function is for testing only. It will be stabilized as an inherent method.