code: function inc (value, step, mult) {
  	mult = mult || 0;
  
  	var isArr = isArray(value);
  	value = plainify(value);
  
  	if (isFn(step)) step = step(value + (mult > 0 ? + MIN_STEP : - MIN_STEP));
  
  	value += step * mult;
  
  	return isArr ? [value] : value;
  }
docs: Increment & decrement value by the step [N times]