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use core::u64;
/// Absolute value (magnitude) (f64)
/// Calculates the absolute value (magnitude) of the argument `x`,
/// by direct manipulation of the bit representation of `x`.
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn fabs(x: f64) -> f64 {
// On wasm32 we know that LLVM's intrinsic will compile to an optimized
// `f64.abs` native instruction, so we can leverage this for both code size
// and speed.
llvm_intrinsically_optimized! {
#[cfg(target_arch = "wasm32")] {
return unsafe { ::core::intrinsics::fabsf64(x) }
}
}
f64::from_bits(x.to_bits() & (u64::MAX / 2))
}
#[cfg(test)]
mod tests {
use super::*;
use core::f64::*;
#[test]
fn sanity_check() {
assert_eq!(fabs(-1.0), 1.0);
assert_eq!(fabs(2.8), 2.8);
}
/// The spec: https://en.cppreference.com/w/cpp/numeric/math/fabs
#[test]
fn spec_tests() {
assert!(fabs(NAN).is_nan());
for f in [0.0, -0.0].iter().copied() {
assert_eq!(fabs(f), 0.0);
}
for f in [INFINITY, NEG_INFINITY].iter().copied() {
assert_eq!(fabs(f), INFINITY);
}
}
}
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