[iNils]

function factorial (a:Number):Number {
	if (a >= 0 && a < Number.MAX_VALUE && a != Number.MIN_VALUE && !isNaN (a)) {
		var factor:Number = 1;
		for (var i:Number = 1; i <= Math.round (a); i++) {
			factor *= i;
		}
		return factor;
	} else {
		return Number.NaN;
	}
}
var a = 5;
trace (factorial (a));
trace (factorial (Number.NaN));
trace (factorial (Number.MIN_VALUE));
trace (factorial (Number.MAX_VALUE));
trace (factorial (Number.NEGATIVE_INFINITY));
trace (factorial (Number.POSITIVE_INFINITY));