easeInOutCubic is wrong

[Denis535]

I'm trying your easeInOutCubic:

double easeInOutCubic( double t ) {
   return t < 0.5 ? 4 * t * t * t : 1 + (--t) * (2 * (--t)) * (2 * t);
}

But it returns wrong result for case t >= 0.5.

[micuat]

I guess the correct implementation is

return t < 0.5 ? 4 * t * t * t : (t-1)*(2*t-2)*(2*t-2)+1

(from https://gist.github.com/gre/1650294)

--t is useful but sometimes get tricky to debug. In this case the second and third parentheses should be 2*t - 2 but in the repo it's 2*(t-2) which of course gives wrong results

[Olof-IL]

Using --t and t several times in an expression like this is unfortunately not useful at all, it's Undefined Behaviour. You can't rely on the order of evaluation without sequence points.