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## Struct template iterator

boost::type_erasure::iterator

## Synopsis

    // In header: <boost/type_erasure/iterator.hpp>

    template<typename Traversal, typename T = _self,
             typename Reference = boost::use_default,
             typename DifferenceType = std::ptrdiff_t>
    struct iterator {
      // types
      typedef unspecified    value_type;
      typedef Reference      reference;
      typedef DifferenceType difference_type;
    };

## Description

The iterator concept can be used for any iterator category.

The value_type of the iterator is deduced. To force it to be a specific type, use the same_type concept.

Example:

    mpl::vector<
      iterator<boost::forward_traversal_tag>,
      same_type<iterator<boost::forward_traversal_tag>::value_type, int> > int_it;

### Template Parameters

1.     typename Traversal

   must be one of `boost::incrementable_traversal_tag`, `boost::single_pass_traversal_tag`, `boost::forward_traversal_tag`, `boost::bidirectional_traversal_tag`, and `boost::random_access_traversal_tag`.

2.     typename T = _self

   The placeholder representing the iterator.

3.     typename Reference = boost::use_default

   The reference type. If it is boost::use_default, then reference will be value_type&.

4.     typename DifferenceType = std::ptrdiff_t

   The iterator's difference type.