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