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use core::f64;
const TOINT: f64 = 1. / f64::EPSILON;
/// Floor (f64)
///
/// Finds the nearest integer less than or equal to `x`.
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn floor(x: f64) -> f64 {
// On wasm32 we know that LLVM's intrinsic will compile to an optimized
// `f64.floor` native instruction, so we can leverage this for both code size
// and speed.
llvm_intrinsically_optimized! {
#[cfg(target_arch = "wasm32")] {
return unsafe { ::core::intrinsics::floorf64(x) }
}
}
let ui = x.to_bits();
let e = ((ui >> 52) & 0x7ff) as i32;
if (e >= 0x3ff + 52) || (x == 0.) {
return x;
}
/* y = int(x) - x, where int(x) is an integer neighbor of x */
let y = if (ui >> 63) != 0 {
x - TOINT + TOINT - x
} else {
x + TOINT - TOINT - x
};
/* special case because of non-nearest rounding modes */
if e < 0x3ff {
force_eval!(y);
return if (ui >> 63) != 0 { -1. } else { 0. };
}
if y > 0. {
x + y - 1.
} else {
x + y
}
}
#[cfg(test)]
mod tests {
use super::*;
use core::f64::*;
#[test]
fn sanity_check() {
assert_eq!(floor(1.1), 1.0);
assert_eq!(floor(2.9), 2.0);
}
/// The spec: https://en.cppreference.com/w/cpp/numeric/math/floor
#[test]
fn spec_tests() {
// Not Asserted: that the current rounding mode has no effect.
assert!(floor(NAN).is_nan());
for f in [0.0, -0.0, INFINITY, NEG_INFINITY].iter().copied() {
assert_eq!(floor(f), f);
}
}
}
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