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  1. #include <iterator>
  2. #include <stdexcept>
  3.  
  4. template <class Range> class MultiRangeIterator;
  5. template <class Iterator, class SubRange>
  6. struct MultiRange;
  7.  
  8. template <class E> struct EmptyRange 
  9. { 
  10.   typedef MultiRangeIterator<EmptyRange<E>> iterator;
  11.   iterator begin();
  12.   iterator end(); 
  13.  
  14.   template <class NewIter>
  15.   struct Append
  16.   {
  17.     typedef MultiRange<NewIter, EmptyRange<E>> type;
  18.   };
  19.  
  20.   template <class NewIter>
  21.   typename Append<NewIter>::type append(NewIter first, NewIter last) const;
  22. };
  23.  
  24. template <class Iterator, class SubRange = EmptyRange<typename Iterator::value_type>>
  25. struct MultiRange
  26. {
  27.   Iterator first;
  28.   Iterator last;
  29.   SubRange deeper;
  30.  
  31.   template <class NewIter>
  32.   struct Append {
  33.     typedef MultiRange<Iterator, typename SubRange::template Append<NewIter>::type> type;
  34.   };
  35.  
  36.   typedef MultiRangeIterator<MultiRange> iterator;
  37.   MultiRange(Iterator a, Iterator b, SubRange s = SubRange())
  38.     : first(a), last(b), deeper(s) {}
  39.  
  40.   iterator begin();
  41.   iterator end();
  42.  
  43.   template <class NewIter>
  44.   typename Append<NewIter>::type operator()(NewIter newFirst, NewIter newLast) const
  45.   { return this->append(newFirst, newLast); }
  46.  
  47.   template <class NewIter>
  48.   typename Append<NewIter>::type append(NewIter newFirst, NewIter newLast) const
  49.   { 
  50.     typedef typename Append<NewIter>::type NewMultiRange;
  51.     return NewMultiRange(first, last, deeper.append(newFirst, newLast));
  52.   }
  53. };
  54.  
  55. template <class E>
  56.   template <class NewIter>
  57. typename EmptyRange<E>::template Append<NewIter>::type EmptyRange<E>::append(NewIter first, NewIter last) const
  58. {
  59.   return MultiRange<NewIter,EmptyRange<E>>(first, last);
  60. }
  61.  
  62. template <class Iterator>
  63. MultiRange<Iterator> makeRange(Iterator first, Iterator last)
  64. { return MultiRange<Iterator> (first, last); }
  65.  
  66. template <class E>
  67. struct MultiRangeIterator<EmptyRange<E>>
  68. {
  69.   E& operator*() const { throw std::out_of_range("past the end!"); }
  70.   MultiRangeIterator& operator++() { return *this; }
  71. };
  72.  
  73. template <class Iterator, class SubRange>
  74. struct MultiRangeIterator<MultiRange<Iterator, SubRange>>
  75. {
  76.   MultiRange<Iterator, SubRange> const& myRange;
  77.   Iterator myIter;
  78.   MultiRangeIterator<SubRange> deeperIter;
  79.  
  80.   typedef typename std::iterator_traits<Iterator>::reference reference;
  81.  
  82.   MultiRangeIterator(MultiRange<Iterator, SubRange> const& r, Iterator it, MultiRangeIterator<SubRange> d )
  83.     : myRange(r), myIter(it), deeperIter(d) {}
  84.  
  85.   bool pastEndOfRange() const
  86.   { return myIter == myRange.last; }
  87.  
  88.   reference operator*() const 
  89.   { return pastEndOfRange() ? 
  90.       *deeperIter : 
  91.       *myIter; }
  92.  
  93.   MultiRangeIterator& operator++() 
  94.   { 
  95.     if (!pastEndOfRange())
  96.       ++myIter;
  97.     else
  98.       ++deeperIter;
  99.     return *this;
  100.   }
  101. }; 
  102.  
  103. namespace std {
  104.   template <class Iterator, class SubRange>
  105.   struct iterator_traits<MultiRangeIterator<MultiRange<Iterator, SubRange>>>
  106.     : std::iterator_traits<Iterator>
  107.   {};
  108. };
  109.  
  110. template <class Iterator, class SubRange>
  111. bool operator== (MultiRangeIterator<MultiRange<Iterator, SubRange>> const& lhs,
  112.   MultiRangeIterator<MultiRange<Iterator, SubRange>> const& rhs)
  113. { return lhs.myIter == rhs.myIter && lhs.deeperIter == rhs.deeperIter; }
  114.  
  115. template <class E>
  116. bool operator == (MultiRangeIterator<EmptyRange<E>> const& lhs,
  117.   MultiRangeIterator<EmptyRange<E>> const& rhs)
  118. { return true; }
  119.  
  120. template <class Range>
  121. bool operator != (MultiRangeIterator<Range> const& lhs, MultiRangeIterator<Range> const& rhs)
  122. { return !(lhs==rhs); }
  123.  
  124. template <class Iterator, class SubRange>
  125. typename MultiRange<Iterator, SubRange>::iterator
  126. MultiRange<Iterator, SubRange>::begin()
  127. { return iterator(*this, first, deeper.begin()); }
  128.  
  129. template <class Iterator, class SubRange>
  130. typename MultiRange<Iterator, SubRange>::iterator
  131. MultiRange<Iterator, SubRange>::end()
  132. { return iterator(*this, last, deeper.end()); }
  133.  
  134. template <class E>
  135. typename EmptyRange<E>::iterator
  136. EmptyRange<E>::begin()
  137. { return iterator(); } 
  138. template <class E>
  139. typename EmptyRange<E>::iterator
  140. EmptyRange<E>::end()
  141. { return iterator(); } 
  142.  
  143.  
  144. #include <vector>
  145. #include <list>
  146. #include <set>
  147. #include <iostream>
  148. #include <string>
  149. #include <sstream>
  150. #include <iterator>
  151.  
  152. /* nur zu Testzwecken...
  153. template <class E>
  154. char const* debug(MultiRangeIterator<EmptyRange<E>>) {return "()";}
  155.  
  156. template <class Iterator, class SubRange>
  157. std::string debug(MultiRangeIterator<MultiRange<Iterator, SubRange>> const& mri)
  158. { 
  159.   std::ostringstream out;
  160.   out << '(' << std::distance(mri.myRange.first, mri.myIter);
  161.   if (mri.pastEndOfRange()) out << "=end";
  162.   out << debug(mri.deeperIter) << ')';
  163.   return out.str();
  164. } */
  165.  
  166. using namespace std;
  167.  
  168. int main()
  169. {
  170.   vector<int> vi = {1,2,3,4};
  171.   list<int> li = {5,6,7,8};
  172.   list<int> li2 = {9,10};
  173.  
  174.   auto myRange = makeRange(vi.begin(), vi.end())
  175.        (li.begin(), li.end());
  176.  
  177.   auto newRange = myRange.append(myRange.begin(), myRange.end())
  178.        (li2.begin(), li2.end());
  179.  
  180.   for(auto it = newRange.begin(); it != newRange.end(); ++it)
  181.   { 
  182.     //    cout << debug(it) << ": "; 
  183.     cout << *it << ','; 
  184.   }
  185. }
  186.  
Success #stdin #stdout 0s 3020KB
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Standard input is empty
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1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,9,10,
https://ideone.com/Izr1P
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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