Incorrect floatfract behaviour at negative values.

[MuthaX]

Abstract

The floatfract(Float:value); function is most likely implemented in backend (C) as

float floatfract(float value) {
return (value - floor(value));
}

Which is incorrect when value is negative. The proper way is (c):

float floatfract(float value) {
return (value - trunc(value));
}

or (Pawn):

Float:floatfract_odd(Float:value) {
return (value - floatround(value, floatround_tozero));
}

Proof/Issue reason

When you try this function at positive values - everything is ok, but at negative values you get:

floatfract(0.000000) = 0.000000; ok floatfract(-0.200000) = 0.800000; instead of -0.2 floatfract(-0.500000) = 0.500000; instead of -0.5 floatfract(-0.800000) = 0.199999; instead of -0.2 floatfract(-1.000000) = 0.000000; ok floatfract(-1.300000) = 0.699999; instead of -0.7 floatfract(-1.500000) = 0.500000; instead of -0.5 floatfract(-1.800000) = 0.199999; instead of -0.2 floatfract(-1.899999) = 0.100000; instead of -0.1 floatfract(-2.000000) = 0.000000; ok floatfract(-2.100000) = 0.899999; instead of -0.9

Note

By definition "whole_value = truncated_value +fractional_value". There is also reason in fact of inaccurate definition of floatfract (it is exist another 2 ways to get fractional part).

[Y-Less]

While I agree that those results look wrong, I'm not sure your versions are better. Surely the fractional part of -1.80 is -0.80 not 0.2 (current) or -0.2 (yours).

[Y-Less]

Though that does seem to match the code you posted, which is using floatround_tozero as I'd expect.