libm/math/
copysign.rs

1/// Sign of Y, magnitude of X (f64)
2///
3/// Constructs a number with the magnitude (absolute value) of its
4/// first argument, `x`, and the sign of its second argument, `y`.
5#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
6pub fn copysign(x: f64, y: f64) -> f64 {
7    let mut ux = x.to_bits();
8    let uy = y.to_bits();
9    ux &= (!0) >> 1;
10    ux |= uy & (1 << 63);
11    f64::from_bits(ux)
12}