CGFloat argument type incorrectly traces out with zero value...why?

Question

Hi Really puzzled why the following is happening and hope someone can help.

// here xPos correctly traces out, always changing

 //CODE EXCERPT
 CGFloat xPos=currentTouchPosition.x - lastTouch.x;

   NSLog(@"touchesMoved and xPos= %f", xPos);

    if (startTouchPosition.x < currentTouchPosition.x)
     [self adjustTimer:xPos];
    else

//here newInterval always traces as 0...why????

-(void) adjustTimer:(CGFloat)newInterval
{
 NSLog(@" adjustTimer and newInterval = %f",newInterval);

Answer 1

Ok resolved by changing the method argument type to 'double' from CGFloat, but confused as to why this works.