95 lines
2.1 KiB
Zig
95 lines
2.1 KiB
Zig
// Special Cases:
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//
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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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const math = @import("index.zig");
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const assert = @import("../debug.zig").assert;
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pub const trunc = trunc_workaround;
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pub fn trunc_workaround(x: var) -> @typeOf(x) {
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const T = @typeOf(x);
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switch (T) {
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f32 => @inlineCall(trunc32, x),
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f64 => @inlineCall(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 = 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 = u32(@maxValue(u32)) >> u5(e);
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if (u & m == 0) {
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x
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} else {
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math.forceEval(x + 0x1p120);
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@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 = 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 = u64(@maxValue(u64)) >> u6(e);
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if (u & m == 0) {
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x
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} else {
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math.forceEval(x + 0x1p120);
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@bitCast(f64, u & ~m)
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}
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}
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test "math.trunc" {
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assert(trunc(f32(1.3)) == trunc32(1.3));
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assert(trunc(f64(1.3)) == trunc64(1.3));
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}
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test "math.trunc32" {
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assert(trunc32(1.3) == 1.0);
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assert(trunc32(-1.3) == -1.0);
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assert(trunc32(0.2) == 0.0);
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}
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test "math.trunc64" {
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assert(trunc64(1.3) == 1.0);
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assert(trunc64(-1.3) == -1.0);
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assert(trunc64(0.2) == 0.0);
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}
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test "math.trunc32.special" {
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assert(trunc32(0.0) == 0.0); // 0x3F800000
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assert(trunc32(-0.0) == -0.0);
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assert(math.isPositiveInf(trunc32(math.inf(f32))));
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assert(math.isNegativeInf(trunc32(-math.inf(f32))));
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assert(math.isNan(trunc32(math.nan(f32))));
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}
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test "math.trunc64.special" {
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assert(trunc64(0.0) == 0.0);
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assert(trunc64(-0.0) == -0.0);
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assert(math.isPositiveInf(trunc64(math.inf(f64))));
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assert(math.isNegativeInf(trunc64(-math.inf(f64))));
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assert(math.isNan(trunc64(math.nan(f64))));
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}
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