`mgl64.Round(0, 2)` returns `-0` about mathgl

[pwaller]

Nice find. Signed zero is a thing that floating point numbers have :)

https://en.wikipedia.org/wiki/Signed_zero

It looks like this is arising from the current definition of Round, which at a glance is doing 'tie breaks round towards nearest', with 'rounding towards zero'.

mathgl/mgl64/util.go

Lines 137 to 146 in 592312d

	// Round shortens a float32 value to a specified precision (number of digits after the decimal point)
	// with "round half up" tie-braking rule. Half-way values (23.5) are always rounded up (24).
	func Round(v float64, precision int) float64 {
	p := float64(precision)
	t := float64(v) * math.Pow(10, p)
	if t > 0 {
	return float64(math.Floor(t+0.5) / math.Pow(10, p))
	}
	return float64(math.Ceil(t-0.5) / math.Pow(10, p))
	}

The if t > 0 is false, so it's rounding as if 'zero is negative'. The sign is appearing from math.Ceil(-0.5): https://go.dev/play/p/RtDbZu9JNlF

I think the fix is to change the condition to if t >= 0 because negative zero was neglected. Patches welcome? :)