boost/iterator/generator_iterator.hpp

0001 // (C) Copyright Jens Maurer 2001.
0002 // Distributed under the Boost Software License, Version 1.0. (See
0003 // accompanying file LICENSE_1_0.txt or copy at
0004 // http://www.boost.org/LICENSE_1_0.txt)
0005 //
0006 // Revision History:
0007
0008 // 15 Nov 2001   Jens Maurer
0009 //      created.
0010
0011 //  See http://www.boost.org/libs/utility/iterator_adaptors.htm for documentation.
0012
0013 #ifndef BOOST_ITERATOR_GENERATOR_ITERATOR_HPP_INCLUDED_
0014 #define BOOST_ITERATOR_GENERATOR_ITERATOR_HPP_INCLUDED_
0015
0016 #include <memory>
0017 #include <type_traits>
0018
0019 #include <boost/iterator/iterator_facade.hpp>
0020 #include <boost/iterator/iterator_categories.hpp>
0021
0022 namespace boost {
0023 namespace iterators {
0024
0025 template< typename Generator >
0026 class generator_iterator :
0027     public iterator_facade<
0028         generator_iterator< Generator >,
0029         decltype(std::declval< Generator& >()()),
0030         single_pass_traversal_tag,
0031         decltype(std::declval< Generator& >()()) const&
0032     >
0033 {
0034     friend class iterator_core_access;
0035
0036 private:
0037     using super_t = iterator_facade<
0038         generator_iterator< Generator >,
0039         decltype(std::declval< Generator& >()()),
0040         single_pass_traversal_tag,
0041         decltype(std::declval< Generator& >()()) const&
0042     >;
0043
0044 public:
0045     generator_iterator() :
0046         m_g(nullptr),
0047         m_value()
0048     {}
0049
0050     generator_iterator(Generator* g) :
0051         m_g(g),
0052         m_value((*m_g)())
0053     {}
0054
0055 private:
0056     void increment()
0057     {
0058         m_value = (*m_g)();
0059     }
0060
0061     typename super_t::reference dereference() const
0062     {
0063         return m_value;
0064     }
0065
0066     bool equal(generator_iterator const& y) const
0067     {
0068         return m_g == y.m_g && m_value == y.m_value;
0069     }
0070
0071 private:
0072     Generator* m_g;
0073     typename Generator::result_type m_value;
0074 };
0075
0076 template< typename Generator >
0077 struct generator_iterator_generator
0078 {
0079     using type = generator_iterator< Generator >;
0080 };
0081
0082 template< typename Generator >
0083 inline generator_iterator< Generator > make_generator_iterator(Generator& gen)
0084 {
0085     return generator_iterator< Generator >(std::addressof(gen));
0086 }
0087
0088 } // namespace iterators
0089
0090 using iterators::generator_iterator;
0091 using iterators::generator_iterator_generator;
0092 using iterators::make_generator_iterator;
0093
0094 } // namespace boost
0095
0096 #endif // BOOST_ITERATOR_GENERATOR_ITERATOR_HPP_INCLUDED_