4.1-4.2

function say_hello(){
	 //alert(sum([1, 2, 3, 4]))
	//alert(count([1, 2, 3, 4]))
	//alert( max([1, 5, 10, 25, 16, 1]) );
	alert(quicksort([10, 5, 2, 3]));
}
function sum(arr){
     if(arr.length == 0)
		return 0;
	return arr[0] + sum(arr.slice(1));
}
function count(arr){
       if(arr.length == 0)
		return 0;
	return 1 + count(arr.slice(1));
}
function max(arr){
      if(arr.length == 2){
	  return arr[0] > arr[1] ? arr[0] : arr[1];
	}
	var subMax = max(arr.slice(1));
	return arr[0] > subMax ? arr[0] : subMax;
}
function quicksort(arr){
     if(arr.length < 2)
		  return arr;
	var pivot = arr[0];
	var less = arr.slice(1).filter(function(v){ return v <= pivot;});
	var greater = arr.slice(1).filter(function(v){ return v > pivot;});
	return quicksort(less).concat([pivot],quicksort(greater));
}