cmpf2

pub inline fn cmpf2(comptime T: type, comptime RT: type, a: T, b: T) RT

File

Code

pub inline fn cmpf2(comptime T: type, comptime RT: type, a: T, b: T) RT {
    const bits = @typeInfo(T).float.bits;
    const srep_t = @Int(.signed, bits);
    const rep_t = @Int(.unsigned, bits);

    const significandBits = std.math.floatMantissaBits(T);
    const exponentBits = std.math.floatExponentBits(T);
    const signBit = (@as(rep_t, 1) << (significandBits + exponentBits));
    const absMask = signBit - 1;
    const infT = comptime std.math.inf(T);
    const infRep = @as(rep_t, @bitCast(infT));

    const aInt = @as(srep_t, @bitCast(a));
    const bInt = @as(srep_t, @bitCast(b));
    const aAbs = @as(rep_t, @bitCast(aInt)) & absMask;
    const bAbs = @as(rep_t, @bitCast(bInt)) & absMask;

    // If either a or b is NaN, they are unordered.
    if (aAbs > infRep or bAbs > infRep) return RT.Unordered;

    // If a and b are both zeros, they are equal.
    if ((aAbs | bAbs) == 0) return .Equal;

    // If at least one of a and b is positive, we get the same result comparing
    // a and b as signed integers as we would with a floating-point compare.
    if ((aInt & bInt) >= 0) {
        if (aInt < bInt) {
            return .Less;
        } else if (aInt == bInt) {
            return .Equal;
        } else return .Greater;
    } else {
        // Otherwise, both are negative, so we need to flip the sense of the
        // comparison to get the correct result.  (This assumes a twos- or ones-
        // complement integer representation; if integers are represented in a
        // sign-magnitude representation, then this flip is incorrect).
        if (aInt > bInt) {
            return .Less;
        } else if (aInt == bInt) {
            return .Equal;
        } else return .Greater;
    }
}