Hi Dean, Dean Michael Berris wrote on 23/06/2009 08:54:32:
Hi Guys,
I was wondering if a utility that allows the encapsulation (and merging) of two ranges is already part of RangeEx? I was thinking along the lines of:
vector<int> a, b; // populate a, populate b auto r = concat(a, b); // concatenates the ranges into a single range set<int> c(begin(r), end(r)); // r looks like a single forward range
I'm not sure if this is already supported in Boost.Range and it'd be nice to know if this is already in RangeEx.
I sketched up a trial solution (possibly naive and possibly inefficient) to this a while ago when I didn't find the capability in boost.range (though maybe I missed it). It works for two independent ranges whose value-types are convertible. Maybe such a utility could be included in boost.range after some validation/reviewing. I've copied the source below (I could attach to preserve line endings if requested -- just thought it would be easier to quick-scan if I included it in this post). Instead of providing a view on the concat'd range with concat(a,b) [which may be nicer] it allows you to get the begin and end iterators of it using multi_range_begin(a,b) and multi_range_end(a,b). It would be simple to create such a concat view though. Regards, Adam ///////////////////////////////////////////////////// ////////////// example ////////////////////////////// ///////////////////////////////////////////////////// #include <stdext/multi-range-iterator.h> #include <string> #include <iostream> #include <algorithm> #include <iterator> void addone( char& c ) { ++c; } int main() { // some ranges std::string a("First"); const char b[] = "Second"; char c[] = "Third"; // write the range [a,b] to stdout std::copy( stdext::multi_range_begin(a,b), stdext::multi_range_end(a,b), std::ostream_iterator<char>(std::cout) ); std::cout << std::endl; // add one to each char in the range [a,c] std::for_each( stdext::multi_range_begin(a,c), stdext::multi_range_end(a,c), &addone ); // add one to each char in the range [a,[c,a]]) std::for_each( stdext::multi_range_begin(a,boost::make_iterator_range(stdext::multi_range_begin(c,a),stdext::multi_range_end(c,a))), stdext::multi_range_end( a,boost::make_iterator_range(stdext::multi_range_begin(c,a),stdext::multi_range_end(c,a))), &addone ); // by now characters in 'a' have been incremented by 3 // and characters in 'c' have been incremented by 2. // write the range [a,b] to stdout std::copy( stdext::multi_range_begin(a,b), stdext::multi_range_end(a,b), std::ostream_iterator<char>(std::cout) ); std::cout << std::endl; // write the range [a,[b,c]] to stdout std::copy( stdext::multi_range_begin(a,boost::make_iterator_range(stdext::multi_range_begin(b,c),stdext::multi_range_end(b,c))), stdext::multi_range_end( a,boost::make_iterator_range(stdext::multi_range_begin(b,c),stdext::multi_range_end(b,c))), std::ostream_iterator<char>(std::cout) ); std::cout << std::endl; } ///////////////////////////////////////////////////// ////////////// utility ////////////////////////////// ///////////////////////////////////////////////////// #ifndef STDEXT_MULTI_RANGE_ITERATOR_H #define STDEXT_MULTI_RANGE_ITERATOR_H #include <boost/range.hpp> #include <boost/type_traits/is_convertible.hpp> #include <boost/mpl/if.hpp> #include <boost/mpl/or.hpp> namespace stdext { namespace multi_range_detail { struct mark_end {}; template <typename FirstIt, typename SecondIt> struct iterator_tools; } /** * An iterator that traverses the two ranges as if they were one range * ordered FirstRange, SecondRange. That is to say, the entire first * range is traversed, followed by the entire second range. Note that * this iterator itself wraps three iterators; begin and end of * FirstRange, and begin of SecondRange. Testing for end-of-range * should be made against end of SecondRange externally. */ template <typename FirstIt, typename SecondIt> struct multi_range_forward_iterator : private boost::is_convertible< typename boost::iterator_value<FirstIt>::type , typename boost::iterator_value<SecondIt>::type > { template <typename, typename> friend struct multi_range_detail::iterator_tools; typedef multi_range_detail::iterator_tools<FirstIt,SecondIt> iterator_tools; typedef std::forward_iterator_tag iterator_category; typedef typename boost::iterator_value<FirstIt>::type value_type; typedef typename boost::iterator_difference<FirstIt>::type difference_type; typedef typename iterator_tools::reference reference; typedef typename boost::iterator_pointer<FirstIt>::type pointer; multi_range_forward_iterator( FirstIt const& begin_of_first, FirstIt const& end_of_first, SecondIt const& begin_of_second ) : begin1(begin_of_first) , end1(end_of_first) , begin2(begin_of_second) { } multi_range_forward_iterator( FirstIt const& end_of_first, SecondIt const& end_of_second, multi_range_detail::mark_end ) : begin1(end_of_first) , end1(end_of_first) , begin2(end_of_second) { } template <typename Iterator> bool operator== ( Iterator const& it ) const { return iterator_tools::compare_equal( this, it ); } bool operator== ( multi_range_forward_iterator const& it ) const { return it.begin1 == begin1 && it.begin2 == begin2; } template <typename Iterator> bool operator!= ( Iterator const& it ) const { return !operator==(it); } multi_range_forward_iterator& operator++ () { if( begin1 != end1 ) ++begin1; else ++begin2; return *this; } multi_range_forward_iterator operator++ (int) const { multi_range_forward_iterator it(*this); ++it; return it; } reference operator* () { if( begin1 != end1 ) return *begin1; return *begin2; } private: FirstIt begin1, end1; SecondIt begin2; }; namespace multi_range_detail { using namespace boost::mpl; template <typename Ref1, typename Ref2, typename ValueType> struct common_reference { typedef typename boost::remove_reference<Ref1>::type without_ref1; typedef typename boost::remove_reference<Ref2>::type without_ref2; typedef typename if_< or_< boost::is_const<without_ref1>, boost::is_const<without_ref2> > , ValueType const& , ValueType& >::type type; }; template <typename FirstIt, typename SecondIt> struct iterator_tools { typedef multi_range_forward_iterator<FirstIt,SecondIt> owner_type; typedef typename multi_range_detail:: common_reference< typename boost::iterator_reference<FirstIt>::type , typename boost::iterator_reference<SecondIt>::type , typename boost::iterator_value<SecondIt>::type >::type reference; inline bool compare_equal( owner_type* owner, const FirstIt& it ) { return owner->begin1 == it; } static inline bool compare_equal( owner_type* owner, const SecondIt& it ) { return owner->begin2 == it; } }; template <typename CommonIt> struct iterator_tools<CommonIt,CommonIt> { typedef multi_range_forward_iterator<CommonIt,CommonIt> owner_type; typedef typename boost::iterator_reference<CommonIt>::type reference; static inline bool compare_equal( owner_type* owner, const CommonIt& it ) { return owner->begin1 == it || owner->begin2 == it; } }; } #define MULTI_RANGE_CONST const #define MULTI_RANGE_NONCONST #define DEFINE_MULTI_RANGE_BEGIN_END( const1, const2 ) \ \ template <typename FirstRange, typename SecondRange> \ multi_range_forward_iterator< typename boost::range_iterator<const1 FirstRange>::type, \ typename boost::range_iterator<const2 SecondRange>::type > \ multi_range_begin( const1 FirstRange& first, const2 SecondRange& second ) \ { \ typedef typename boost::range_iterator<const1 FirstRange>::type first_iterator; \ typedef typename boost::range_iterator<const2 SecondRange>::type second_iterator; \ return multi_range_forward_iterator<first_iterator,second_iterator>( boost::begin(first), boost::end(first), boost::begin(second) ); \ } \ \ template <typename FirstRange, typename SecondRange> \ multi_range_forward_iterator< typename boost::range_iterator<const1 FirstRange>::type, \ typename boost::range_iterator<const2 SecondRange>::type > \ multi_range_end( const1 FirstRange& first, const2 SecondRange& second ) \ { \ typedef typename boost::range_iterator<const1 FirstRange>::type first_iterator; \ typedef typename boost::range_iterator<const2 SecondRange>::type second_iterator; \ return multi_range_forward_iterator<first_iterator,second_iterator>( boost::end(first), boost::end(second), multi_range_detail::mark_end() ); \ } \ DEFINE_MULTI_RANGE_BEGIN_END( MULTI_RANGE_NONCONST, MULTI_RANGE_NONCONST ) DEFINE_MULTI_RANGE_BEGIN_END( MULTI_RANGE_NONCONST, MULTI_RANGE_CONST ) DEFINE_MULTI_RANGE_BEGIN_END( MULTI_RANGE_CONST, MULTI_RANGE_NONCONST ) DEFINE_MULTI_RANGE_BEGIN_END( MULTI_RANGE_CONST, MULTI_RANGE_CONST ) #undef DEFINE_MULTI_RANGE_BEGIN_END #undef MULTI_RANGE_NONCONST #undef MULTI_RANGE_CONST } // stdext #endif//STDEXT_MULTI_RANGE_ITERATOR_H ------------------------------------------------------------ This email and any attached files contains company confidential information which may be legally privileged. 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