What must iterators do

To see what iterators must do, consider a typical algorithm:

	template <class T>
	iterator find 
		(iterator first, iterator last, T & value)
	{
		while (first != last && *first != value) ++first;
		return first;
	}

Could be used to find values in an array, or in a list:

int data[100];
	...
int * where = find(data, data+100, 7);
list<int>::iterator where = find(aList.begin(), aList.end(), 7);