    const std = @import("../std.zig");
    const math = std.math;
    const expect = std.testing.expect;

    /// Returns whether x is negative or negative 0.
    pub fn signbit(x: anytype) bool {
        const T = @TypeOf(x);
        const TBits = std.meta.Int(.unsigned, @typeInfo(T).Float.bits);
        return @bitCast(TBits, x) >> (@bitSizeOf(T) - 1) != 0;
    }

    test "math.signbit" {
        inline for ([_]type{ f16, f32, f64, f80, f128 }) |T| {
            try expect(!signbit(@as(T, 0.0)));
            try expect(!signbit(@as(T, 1.0)));
            try expect(signbit(@as(T, -2.0)));
            try expect(signbit(@as(T, -0.0)));
            try expect(!signbit(math.inf(T)));
            try expect(signbit(-math.inf(T)));
            try expect(!signbit(math.nan(T)));
            try expect(signbit(-math.nan(T)));
        }
    }