C++ High Performance

Iterator traits

As mentioned, STL differentiates iterators by which categories they fulfill. This is achieved by defining the following five specific types in the iterator class:

• iterator_category, the category the iterator fulfills
• difference_type, the type used to store the distance between two iterators
• value_type, the value the iterator returns when dereferenced
• reference, the type used for referencing the value_type
• pointer, the type of pointer used for pointing to the value_type

For the IntIterator, the following types would be defined:

class IntIterator {public:  ...  using difference_type = int;  using value_type = int;  using reference = int&;  using pointer = int*;  using iterator_category = std::forward_iterator_tag;  ...}

It might ...