zig/std/math/expo2.zig

29 lines
670 B
Zig

const math = @import("index.zig");
pub fn expo2(x: var) -> @typeOf(x) {
const T = @typeOf(x);
switch (T) {
f32 => expo2f(x),
f64 => expo2d(x),
else => @compileError("expo2 not implemented for " ++ @typeName(T)),
}
}
fn expo2f(x: f32) -> f32 {
const k: u32 = 235;
const kln2 = 0x1.45C778p+7;
const u = (0x7F + k / 2) << 23;
const scale = @bitCast(f32, u);
math.exp(x - kln2) * scale * scale
}
fn expo2d(x: f64) -> f64 {
const k: u32 = 2043;
const kln2 = 0x1.62066151ADD8BP+10;
const u = (0x3FF + k / 2) << 20;
const scale = @bitCast(f64, u64(u) << 32);
math.exp(x - kln2) * scale * scale
}