What's wrong with passing C++ iterator by reference?

Question

I\'ve written a few functions with a prototype like this:

template 
int parse_integer(input_iterator &begin, input_iterato         


        

Answer 1

In my opinion, if you want to do this the argument should be a pointer to the iterator you'll be changing. I'm not a big fan of non-const reference arguments because they hide the fact that the passed parameter might change. I know there's a lot of C++ users who disagree with my opinion on this - and that's fine.

However, in this case it's so common for iterators to be treated as value arguments that I think it's a particularly bad idea to pass iterators by non-const reference and modify the passed iterator. It just goes against the idiomatic way iterators are usually used.

Since there is a great way to do what you want that doesn't have this problem, I think you should use it:

template <typename input_iterator>
int parse_integer(input_iterator* begin, input_iterator end);

Now a caller would have to do:

int i = parse_integer(&p, end);

And it'll be obvious that the iterator can be changed.

By the way, I also like litb's suggestion of returning the new iterator and putting the parsed values into a location specified by an output iterator.