On Wed, Jul 25, 2012 at 5:13 AM, Nathan Ridge <zeratul976@hotmail.com>wrote:
Here's how you might do such a thing (untested):
Hi Nathan That may be untested, but basically worked as is! All I had to do was adjust the access on equal(), increment() & dereference() and it worked perfectly. Full code attached, built with Boost 1.47 and gcc-4.6.2, many thanks. Rob. #include <iostream> #include <boost/iterator/iterator_facade.hpp> #include <boost/range/iterator_range.hpp> #include <boost/range/algorithm/for_each.hpp> #include <boost/range/adaptor/filtered.hpp> struct Thing { Thing( char c ) : c( c ) { } char c; }; std::ostream & operator << ( std::ostream & ostrm, const Thing & thing ) { return ostrm << thing.c; } struct ThingFeed { ThingFeed( const char * thing_values ) : m_current_value( thing_values ) { } Thing * getNextThing( ) { return * m_current_value ? new Thing( * m_current_value ++ ) : 0; } private: const char * m_current_value; }; struct ThingIterator : public boost::iterator_facade<ThingIterator, Thing, boost::single_pass_traversal_tag> { ThingIterator(ThingFeed& feed, Thing* cur = NULL) : m_feed(feed), m_cur(cur) {} bool equal(const ThingIterator& other) const { return m_cur == other.m_cur; } void increment() { m_cur = m_feed.getNextThing(); } Thing& dereference() const { return *m_cur; } private: ThingFeed& m_feed; Thing* m_cur; }; class ThingRange : public boost::iterator_range<ThingIterator> { public: ThingRange(ThingFeed& feed) : boost::iterator_range<ThingIterator>( ThingIterator(feed, feed.getNextThing()), ThingIterator(feed)) {} }; void printThing( const Thing & thing ) { std::cout << thing << "\n"; } bool thingFilter( const Thing & thing ) { return thing.c != 'c'; } int main( ) { ThingFeed feed( "abcd" ); boost::for_each( ThingRange(feed) | boost::adaptors::filtered( thingFilter ), printThing ); }