function absoluteDifference( x, y ) {
	if ( isnan( x ) || isnan( y ) ) {
		return NaN;
	}
	if ( isInfinite( x ) || isInfinite( y ) ) {
		if ( x === y ) {
			return NaN;
		}
		return PINF;
	}
	return abs( x - y );
}
Computes the absolute difference.

@param {number} x - first number
@param {number} y - second number
@returns {number} absolute difference

@example
var d = absoluteDifference( 2.0, 5.0 );
// returns 3.0

@example
var d = absoluteDifference( -1.0, 3.14 );
// returns ~4.14

@example
var d = absoluteDifference( 10.1, -2.05 );
// returns ~12.15

@example
var d = absoluteDifference( -0.0, 0.0 );
// returns +0.0

@example
var d = absoluteDifference( NaN, 5.0 );
// returns NaN

@example
var d = absoluteDifference( Infinity, -Infinity  );
// returns Infinity

@example
var d = absoluteDifference( Infinity, Infinity  );
// returns NaN