q_rsqrt.jule

use "std/math"

// Fast inverse square root.
// See: https://en.wikipedia.org/wiki/Fast_inverse_square_root
fn QRsqrt(mut f: f64): f64 {
	const ThreeHalfs = 1.5
	const Magic = 0x5FE6EB50C7B537A9

	let n2 = f * 0.5
	let b = Magic - (math::F64Bits(f) >> 1)
	f = math::F64FromBits(b)
	f *= ThreeHalfs - (n2 * f * f)
	ret f
}