Early adopters of C ++ 14: Implementing LINQ in C ++

Early adopters of C ++ 14: Implementing LINQ in C ++

Implement LINQ in C ++

 

#include 
 
  #include 
  
   template
   
    struct from_range{typedef typename std::iterator_traits
    
     ::value_type value_type;TIterator current, upcoming, end;from_range(TIterator begin, TIterator end): current(begin), upcoming(begin), end(end) {}template
     
      decltype(auto) operator>>(TRangeBuilder builder) const { return builder.build(*this); }decltype(auto) front() const { return *current; }bool next() { return upcoming == end ? false : (current = upcoming++, true); }};template
      
       struct where_range{typedef typename TRange::value_type value_type;TRange range;TPredicate predicate;where_range(TRange range, TPredicate predicate): range(range), predicate(predicate) {}template
       
        decltype(auto) operator>>(TRangeBuilder builder) const { return builder.build(*this); }decltype(auto) front() const { return range.front(); }bool next(){while(range.next())if(predicate(range.front()))return true;return false;}};template
        
         struct where_builder{TPredicate predicate;where_builder(TPredicate predicate) : predicate(predicate) {}template
         
          auto build(TRange range){return where_range
          
           (range, predicate);}};struct to_vector_builder{template
           
            auto build(TRange range){std::vector
            
              result;while(range.next())result.push_back(range.front());return result;}};template
             
              auto from(TContainer const& container){return from_range
              
               (std::begin(container), std::end(container));}auto to_vector() { return to_vector_builder(); }template
               
                auto where(TPredicate predicate) { return where_builder
                
                 (predicate); }int main(){int a[] = {1, 2, 3, 4};auto v = from(a) >> where([](int n){return n % 2 == 0;}) >> to_vector();for(int i : v) std::cout << i << std::endl;}/*24*/