range/adaptor/replaced_if.hpp

0001 // Boost.Range library
0002 //
0003 //  Copyright Neil Groves 2007. Use, modification and
0004 //  distribution is subject to the Boost Software License, Version
0005 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
0006 //  http://www.boost.org/LICENSE_1_0.txt)
0007 //
0008 // For more information, see http://www.boost.org/libs/range/
0009 //
0010
0011 #ifndef BOOST_RANGE_ADAPTOR_REPLACED_IF_IMPL_HPP_INCLUDED
0012 #define BOOST_RANGE_ADAPTOR_REPLACED_IF_IMPL_HPP_INCLUDED
0013
0014 #include <boost/config.hpp>
0015 #include <boost/range/adaptor/argument_fwd.hpp>
0016 #include <boost/range/iterator_range.hpp>
0017 #include <boost/range/begin.hpp>
0018 #include <boost/range/end.hpp>
0019 #include <boost/range/value_type.hpp>
0020 #include <boost/range/concepts.hpp>
0021 #include <boost/iterator/iterator_adaptor.hpp>
0022 #include <boost/iterator/transform_iterator.hpp>
0023 #include <boost/optional/optional.hpp>
0024
0025 namespace boost
0026 {
0027     namespace range_detail
0028     {
0029         template< class Pred, class Value >
0030         class replace_value_if
0031         {
0032         public:
0033             typedef const Value& result_type;
0034             typedef const Value& first_argument_type;
0035
0036             // Rationale:
0037             // required to allow the iterator to be default constructible.
0038             replace_value_if()
0039             {
0040             }
0041
0042             replace_value_if(const Pred& pred, const Value& to)
0043                 : m_impl(data(pred, to))
0044             {
0045             }
0046
0047             const Value& operator()(const Value& x) const
0048             {
0049                 return m_impl->m_pred(x) ? m_impl->m_to : x;
0050             }
0051
0052         private:
0053             struct data
0054             {
0055                 data(const Pred& p, const Value& t)
0056                     : m_pred(p), m_to(t)
0057                 {
0058                 }
0059
0060                 Pred  m_pred;
0061                 Value m_to;
0062             };
0063             boost::optional<data> m_impl;
0064         };
0065
0066         template< class Pred, class R >
0067         class replaced_if_range :
0068             public boost::iterator_range<
0069                 boost::transform_iterator<
0070                     replace_value_if< Pred, BOOST_DEDUCED_TYPENAME range_value<R>::type >,
0071                     BOOST_DEDUCED_TYPENAME range_iterator<R>::type > >
0072         {
0073         private:
0074             typedef replace_value_if< Pred, BOOST_DEDUCED_TYPENAME range_value<R>::type > Fn;
0075
0076             typedef boost::iterator_range<
0077                 boost::transform_iterator<
0078                     replace_value_if< Pred, BOOST_DEDUCED_TYPENAME range_value<R>::type >,
0079                     BOOST_DEDUCED_TYPENAME range_iterator<R>::type > > base_t;
0080
0081         public:
0082             typedef BOOST_DEDUCED_TYPENAME range_value<R>::type value_type;
0083
0084             replaced_if_range( R& r, const Pred& pred, value_type to )
0085                 : base_t( make_transform_iterator( boost::begin(r), Fn(pred, to) ),
0086                           make_transform_iterator( boost::end(r), Fn(pred, to) ) )
0087             { }
0088         };
0089
0090         template< class Pred, class T >
0091         class replace_if_holder
0092         {
0093         public:
0094             replace_if_holder( const Pred& pred, const T& to )
0095                 : m_pred(pred), m_to(to)
0096             { }
0097
0098             const Pred& pred() const { return m_pred; }
0099             const T& to() const { return m_to; }
0100
0101         private:
0102             Pred m_pred;
0103             T m_to;
0104         };
0105
0106         template< class Pred, class SinglePassRange, class Value >
0107         inline replaced_if_range<Pred, SinglePassRange>
0108         operator|(SinglePassRange& r, const replace_if_holder<Pred, Value>& f)
0109         {
0110             BOOST_RANGE_CONCEPT_ASSERT((
0111                 SinglePassRangeConcept<SinglePassRange>));
0112
0113             return replaced_if_range<Pred, SinglePassRange>(
0114                 r, f.pred(), f.to());
0115         }
0116
0117         template< class Pred, class SinglePassRange, class Value >
0118         inline replaced_if_range<Pred, const SinglePassRange>
0119         operator|(const SinglePassRange& r, const replace_if_holder<Pred, Value>& f)
0120         {
0121             BOOST_RANGE_CONCEPT_ASSERT((
0122                 SinglePassRangeConcept<const SinglePassRange>));
0123
0124             return replaced_if_range<Pred, const SinglePassRange>(
0125                 r, f.pred(), f.to());
0126         }
0127     } // 'range_detail'
0128
0129     using range_detail::replaced_if_range;
0130
0131     namespace adaptors
0132     {
0133         namespace
0134         {
0135             const range_detail::forwarder2TU<range_detail::replace_if_holder>
0136                 replaced_if =
0137                     range_detail::forwarder2TU<range_detail::replace_if_holder>();
0138         }
0139
0140         template< class Pred, class SinglePassRange, class Value >
0141         inline replaced_if_range<Pred, SinglePassRange>
0142         replace_if(SinglePassRange& rng, Pred pred, Value to)
0143         {
0144             BOOST_RANGE_CONCEPT_ASSERT((
0145                 SinglePassRangeConcept<SinglePassRange>));
0146
0147             return range_detail::replaced_if_range<Pred, SinglePassRange>(
0148                 rng, pred, to);
0149         }
0150
0151         template< class Pred, class SinglePassRange, class Value >
0152         inline replaced_if_range<Pred, const SinglePassRange>
0153         replace_if(const SinglePassRange& rng, Pred pred, Value to)
0154         {
0155             BOOST_RANGE_CONCEPT_ASSERT((
0156                 SinglePassRangeConcept<const SinglePassRange>));
0157
0158             return range_detail::replaced_if_range<Pred, const SinglePassRange>(
0159                 rng, pred, to);
0160         }
0161     } // 'adaptors'
0162
0163 } // 'boost'
0164
0165 #endif // include guard