std::input_iterator

The input_iterator concept is a refinement of input_or_output_iterator, adding the requirement that the referenced values can be read (via indirectly_readable

Iterator concept determination

Definition of this concept is specified via an exposition-only alias template /*ITER_CONCEPT*/.

In order to determine /*ITER_CONCEPT*/<I>, let ITER_TRAITS<I> denote I if the specialization std::iterator_traits<I> is generated from the primary template, or std::iterator_traits<I>

• If ITER_TRAITS<I>::iterator_concept is valid and names a type, /*ITER_CONCEPT*/<I>
• Otherwise, if ITER_TRAITS<I>::iterator_category is valid and names a type, /*ITER_CONCEPT*/<I>
• Otherwise, if std::iterator_traits<I> is generated from the primary template, /*ITER_CONCEPT*/<I> denotes std::random_access_iterator_tag
• Otherwise, /*ITER_CONCEPT*/<I>

Notes

Unlike the LegacyInputIterator requirements, the input_iterator concept does not require equality_comparable

Example

A minimum input iterator.

#include <cstddef>
#include <iterator>
 
struct SimpleInputIterator
{
    using difference_type = std::ptrdiff_t;
    using value_type = int;
 
    int operator*() const;
 
    SimpleInputIterator& operator++();
    void operator++(int) { ++*this; }
};
 
static_assert(std::input_iterator<SimpleInputIterator>);

See also