Iterators Overview

Philosophy

Iterators are the glue between containers and algorithms. PrototypeSTL provides lightweight iterator types and utilities compatible with the standard iterator categories.

Iterator Categories

Category	Operations	Examples
InputIterator	++, *, ==, !=	Stream reading
OutputIterator	++, * (write)	Stream writing
ForwardIterator	Input + multi-pass	forward_list::iterator
BidirectionalIterator	Forward + --	list::iterator
RandomAccessIterator	Bidirectional + [], +, -, <	vector::iterator, raw pointers

Provided Types

reverse_iterator

Wraps any BidirectionalIterator to traverse in reverse.

prototype::reverse_iterator<It> rbegin(container);
prototype::reverse_iterator<It> rend(container);

move_iterator

Wraps any iterator so that dereferencing produces an rvalue reference, enabling move semantics during copy algorithms.

prototype::move_iterator<It> make_move_iterator(It it);

Iterator Operations

// Advance iterator by n positions
prototype::advance(it, n);

// Distance between two iterators
size_t d = prototype::distance(first, last);

// Next/prev (C++11 style)
auto next_it = prototype::next(it);
auto prev_it = prototype::prev(it);

iterator_traits

Type introspection for iterators:

template <typename It>
struct iterator_traits {
    using value_type = ...;
    using difference_type = ...;
    using pointer = ...;
    using reference = ...;
    using iterator_category = ...;
};

Specialized for raw pointers automatically.

Example

#include <prototype/iterators/reverse_iterator.hpp>
#include <prototype/iterators/operations.hpp>
#include <prototype/containers/vector.hpp>

prototype::vector<int> v = {1, 2, 3, 4, 5};

// Reverse iteration
for (auto it = prototype::reverse_iterator<int*>(v.end());
     it != prototype::reverse_iterator<int*>(v.begin()); ++it) {
    process(*it);  // 5, 4, 3, 2, 1
}

// Distance
auto d = prototype::distance(v.begin(), v.end());  // 5