Math.scale should work for "negative" output scales too

[schnepe2]

The current (as of 2016-09-29) implementation of Math.scale does not work if the output scale is "negative"

Math.scale(0.6, 0,1, 0,10);  // <= should return  6 [0...1] => [0...10]
Math.scale(0.6, 0,1, 10,0);  // <= should return  4 [0...1] => [10...0]
Math.scale(0.6, 0,1, 0,-10); // <= should return -6 [0...1] => [0...-10]

I also think this "flipping of scales" should maybe mentioned specifically in the reference / manual

A working polyfill seems to be this:

defineMath("scale", function scale(value, inMin, inMax, outMin, outMax)
{
  if ( arguments.length === 0 || Number.isNaN(value) ||
       Number.isNaN(inMin) || Number.isNaN(inMax) ||
       Number.isNaN(outMin) || Number.isNaN(outMax) )
  {
    return NaN;
  }

  if ( value === Infinity || value === -Infinity || (inMin == outMin && inMax == outMax) )
  {
    return value;
  }

  return outMin + ((value - inMin) / (inMax - inMin)) * (outMax - outMin);
});