zig/std/math/signbit.zig
2018-06-30 01:58:17 +02:00

50 lines
1.0 KiB
Zig

const std = @import("../index.zig");
const math = std.math;
const assert = std.debug.assert;
pub fn signbit(x: var) bool {
const T = @typeOf(x);
return switch (T) {
f16 => signbit16(x),
f32 => signbit32(x),
f64 => signbit64(x),
else => @compileError("signbit not implemented for " ++ @typeName(T)),
};
}
fn signbit16(x: f16) bool {
const bits = @bitCast(u16, x);
return bits >> 15 != 0;
}
fn signbit32(x: f32) bool {
const bits = @bitCast(u32, x);
return bits >> 31 != 0;
}
fn signbit64(x: f64) bool {
const bits = @bitCast(u64, x);
return bits >> 63 != 0;
}
test "math.signbit" {
assert(signbit(f16(4.0)) == signbit16(4.0));
assert(signbit(f32(4.0)) == signbit32(4.0));
assert(signbit(f64(4.0)) == signbit64(4.0));
}
test "math.signbit16" {
assert(!signbit16(4.0));
assert(signbit16(-3.0));
}
test "math.signbit32" {
assert(!signbit32(4.0));
assert(signbit32(-3.0));
}
test "math.signbit64" {
assert(!signbit64(4.0));
assert(signbit64(-3.0));
}