C++14 early adopters: Implementing LINQ in C + +

Implementing LINQ in C + +

#include <iostream> #include <vector>template<typename titerator>struct from_range{typedef TypeName Std::iterator_traits<titerator>::value_type Value_type; Titerator Current, upcoming, End;from_range (Titerator begin, Titerator end): current (begin), upcoming (begin), end (end) { }template<typename trangebuilder>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<typename Trange, TypeName tpredicate>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 <typename trangebuilder>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<typename tpredicate>struct where_builder{tpredicate predicate;where_builder (TPredicate predicate): predicate (predicate) {}template<typename Trange>auto build (Trange range) {return where_range<trange, Tpredicate> (range, predicate);}; struct To_vector_builder{template<typename Trange>auto build (Trange range) {Std::vector<trange::value_type > Result;while (Range.next ()) Result.push_back (Range.front ()); return result;}}; Template<typename Tcontainer>auto from (Tcontainer const& container) {return From_range<decltype (std:: Begin (Container)) > (Std::begin (Container), Std::end (Container));} Auto To_vector () {return To_vector_builder ();} Template<typename Tpredicate>auto WHERE (tpredicate predicate) {return where_builder<tpredicate> ( predicate); }int Main () {int a[] = {1, 2, 3, 4};auto v = from (a) >> where ([] (int n) {return n% 2 = = 0;}) >> to_vector (); (int i : v) std::cout << i << Std::endl;} /*24*/

C++14 early adopters: Implementing LINQ in C + +