code: function fact(x)
  {
  	if (x <= 0)
  	{
  		return 0
  	}
  	if (x > 100)
  	{
  		return 0
  	}
  
  	var i, result=1
  	for(i = 1; i<=x ; i++)
  	{
  		result = result * i
  	}
  	return result
  }
docs: /*
  
  e^x = lim(n->+infini)( (1+x/n)^n )