101 lines
2.4 KiB
Zig
101 lines
2.4 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/truncf.c
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// https://git.musl-libc.org/cgit/musl/tree/src/math/trunc.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 the integer value of x.
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///
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/// Special Cases:
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/// - trunc(+-0) = +-0
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/// - trunc(+-inf) = +-inf
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/// - trunc(nan) = nan
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pub fn trunc(x: var) @TypeOf(x) {
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const T = @TypeOf(x);
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return switch (T) {
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f32 => trunc32(x),
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f64 => trunc64(x),
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else => @compileError("trunc not implemented for " ++ @typeName(T)),
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};
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}
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fn trunc32(x: f32) f32 {
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const u = @bitCast(u32, x);
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var e = @intCast(i32, ((u >> 23) & 0xFF)) - 0x7F + 9;
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var m: u32 = undefined;
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if (e >= 23 + 9) {
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return x;
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}
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if (e < 9) {
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e = 1;
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}
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m = @as(u32, maxInt(u32)) >> @intCast(u5, e);
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if (u & m == 0) {
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return x;
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} else {
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math.forceEval(x + 0x1p120);
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return @bitCast(f32, u & ~m);
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}
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}
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fn trunc64(x: f64) f64 {
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const u = @bitCast(u64, x);
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var e = @intCast(i32, ((u >> 52) & 0x7FF)) - 0x3FF + 12;
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var m: u64 = undefined;
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if (e >= 52 + 12) {
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return x;
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}
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if (e < 12) {
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e = 1;
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}
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m = @as(u64, maxInt(u64)) >> @intCast(u6, e);
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if (u & m == 0) {
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return x;
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} else {
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math.forceEval(x + 0x1p120);
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return @bitCast(f64, u & ~m);
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}
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}
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test "math.trunc" {
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expect(trunc(@as(f32, 1.3)) == trunc32(1.3));
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expect(trunc(@as(f64, 1.3)) == trunc64(1.3));
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}
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test "math.trunc32" {
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expect(trunc32(1.3) == 1.0);
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expect(trunc32(-1.3) == -1.0);
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expect(trunc32(0.2) == 0.0);
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}
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test "math.trunc64" {
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expect(trunc64(1.3) == 1.0);
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expect(trunc64(-1.3) == -1.0);
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expect(trunc64(0.2) == 0.0);
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}
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test "math.trunc32.special" {
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expect(trunc32(0.0) == 0.0); // 0x3F800000
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expect(trunc32(-0.0) == -0.0);
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expect(math.isPositiveInf(trunc32(math.inf(f32))));
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expect(math.isNegativeInf(trunc32(-math.inf(f32))));
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expect(math.isNan(trunc32(math.nan(f32))));
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}
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test "math.trunc64.special" {
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expect(trunc64(0.0) == 0.0);
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expect(trunc64(-0.0) == -0.0);
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expect(math.isPositiveInf(trunc64(math.inf(f64))));
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expect(math.isNegativeInf(trunc64(-math.inf(f64))));
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expect(math.isNan(trunc64(math.nan(f64))));
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}
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