FPL Abs bug

[ZhangHuan0407]

PL16 value = FPL16.MinValue;
FPL16 absValue = value.Abs();
Console.WriteLine($"{value}, {absValue}"); // -140737488355328, -140737488355328
value = new FPL16(-1);
absValue = value.Abs();
Console.WriteLine($"{value}, {absValue}"); // -1, 1

long testValue = long.MinValue;
Console.WriteLine($"{long.MinValue}, {-testValue}"); // -9223372036854775808, -9223372036854775808
try
{
Math.Abs(testValue);
}
catch (Exception ex)
{
// System.OverflowException: Negating the minimum value of a twos complement number is invalid.
Console.WriteLine(ex.ToString());
}

[ZhangHuan0407]

I think the result of FPL16.Abs cannot be negative.
Version: Nuget 30.1.1

// Decompile the code
public FPL16 Abs()
{
return Prescaled((N >= 0) ? N : (-N));
}

// Modified
public FPI16 Abs()
{
Int32 valueN = N;
if (valueN == MinValue.N)
valueN = MaxValue.N;
return Prescaled(valueN >= 0 ? valueN : -valueN);
}

// dotnet source code
https://referencesource.microsoft.com/#mscorlib/system/random.cs,61
They changed MinValue to MaxValue where they didn't expect an error.

System.Math.Abs throw exception, if value equal long.MinValue.

Console.WriteLine(Math.Abs(float.MinValue)); // 3.4028235E+38

Are fixed point and decimal more similar?

[qwertie]

Hi, sorry for not replying to this.

I suggest adding an extension method for this. I definitely don't want to throw an exception like Math.Abs(int.MinValue) (it's very surprising behavior) so if I were to fix it, I'd have MinValue flip to MaxValue. But I don't even want the performance cost of checking for MinValue either.

[ZhangHuan0407]

I'm currently clone and modified the repository source code.
As described in the license, since I use esharp, I need to publish the modified ecsharp source code when I release the product.
(At least 3 months before the product will be released)

I also didn't test the performance...
I'm using Unity's IL2CPP, and I'm guessing that a simple comparison of values won't be able to test the performance difference.

	public FPL16 Abs()
	{
		Int64 valueN = N;
		if (valueN == MinValue.N)
			valueN = MaxValue.N;
		return Prescaled(valueN >= 0 ? valueN : -valueN);
	}