75 lines
2.1 KiB
Zig
75 lines
2.1 KiB
Zig
// Ported from musl, which is licensed under the MIT license:
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// https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
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//
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// https://git.musl-libc.org/cgit/musl/tree/src/math/copysignf.c
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// https://git.musl-libc.org/cgit/musl/tree/src/math/copysign.c
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const std = @import("../std.zig");
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const math = std.math;
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const expect = std.testing.expect;
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const maxInt = std.math.maxInt;
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/// Returns a value with the magnitude of x and the sign of y.
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pub fn copysign(comptime T: type, x: T, y: T) T {
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return switch (T) {
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f16 => copysign16(x, y),
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f32 => copysign32(x, y),
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f64 => copysign64(x, y),
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else => @compileError("copysign not implemented for " ++ @typeName(T)),
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};
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}
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fn copysign16(x: f16, y: f16) f16 {
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const ux = @bitCast(u16, x);
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const uy = @bitCast(u16, y);
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const h1 = ux & (maxInt(u16) / 2);
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const h2 = uy & (u16(1) << 15);
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return @bitCast(f16, h1 | h2);
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}
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fn copysign32(x: f32, y: f32) f32 {
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const ux = @bitCast(u32, x);
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const uy = @bitCast(u32, y);
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const h1 = ux & (maxInt(u32) / 2);
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const h2 = uy & (u32(1) << 31);
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return @bitCast(f32, h1 | h2);
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}
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fn copysign64(x: f64, y: f64) f64 {
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const ux = @bitCast(u64, x);
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const uy = @bitCast(u64, y);
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const h1 = ux & (maxInt(u64) / 2);
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const h2 = uy & (u64(1) << 63);
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return @bitCast(f64, h1 | h2);
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}
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test "math.copysign" {
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expect(copysign(f16, 1.0, 1.0) == copysign16(1.0, 1.0));
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expect(copysign(f32, 1.0, 1.0) == copysign32(1.0, 1.0));
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expect(copysign(f64, 1.0, 1.0) == copysign64(1.0, 1.0));
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}
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test "math.copysign16" {
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expect(copysign16(5.0, 1.0) == 5.0);
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expect(copysign16(5.0, -1.0) == -5.0);
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expect(copysign16(-5.0, -1.0) == -5.0);
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expect(copysign16(-5.0, 1.0) == 5.0);
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}
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test "math.copysign32" {
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expect(copysign32(5.0, 1.0) == 5.0);
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expect(copysign32(5.0, -1.0) == -5.0);
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expect(copysign32(-5.0, -1.0) == -5.0);
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expect(copysign32(-5.0, 1.0) == 5.0);
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}
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test "math.copysign64" {
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expect(copysign64(5.0, 1.0) == 5.0);
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expect(copysign64(5.0, -1.0) == -5.0);
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expect(copysign64(-5.0, -1.0) == -5.0);
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expect(copysign64(-5.0, 1.0) == 5.0);
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}
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