zig/lib/std/math/isfinite.zig

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2019-03-02 13:46:04 -08:00
const std = @import("../std.zig");
const math = std.math;
const expect = std.testing.expect;
const maxInt = std.math.maxInt;
/// Returns whether x is a finite value.
pub fn isFinite(x: var) bool {
const T = @typeOf(x);
switch (T) {
f16 => {
const bits = @bitCast(u16, x);
return bits & 0x7FFF < 0x7C00;
},
f32 => {
const bits = @bitCast(u32, x);
return bits & 0x7FFFFFFF < 0x7F800000;
},
f64 => {
const bits = @bitCast(u64, x);
return bits & (maxInt(u64) >> 1) < (0x7FF << 52);
},
else => {
@compileError("isFinite not implemented for " ++ @typeName(T));
},
}
}
test "math.isFinite" {
expect(isFinite(f16(0.0)));
expect(isFinite(f16(-0.0)));
expect(isFinite(f32(0.0)));
expect(isFinite(f32(-0.0)));
expect(isFinite(f64(0.0)));
expect(isFinite(f64(-0.0)));
expect(!isFinite(math.inf(f16)));
expect(!isFinite(-math.inf(f16)));
expect(!isFinite(math.inf(f32)));
expect(!isFinite(-math.inf(f32)));
expect(!isFinite(math.inf(f64)));
expect(!isFinite(-math.inf(f64)));
}