Boost.Coroutine で itertoolsモドキ、その２

co_itertools.cpp

/*
* C++11 (VisualStudio 2013 Express Edition)
* boost 1.55.0
*/

#include <iostream>
#include <string>
#include <vector>
#include <boost/coroutine/all.hpp>

template<typename T>
class co_funcs{

	typedef typename boost::coroutines::coroutine<T>::push_type push_type;
	typedef typename boost::coroutines::coroutine<T>::pull_type pull_type;
	typedef typename boost::coroutines::pull_coroutine<T> pull_coroutine;

	co_funcs(){}

public:

	static pull_coroutine drop(const int n, pull_coroutine& gen){
		for (int i = 0; i < n; ++i) gen();
		return std::move(gen);
	}

	/*
	static pull_coroutine take(const int n, pull_coroutine& gen){
		return pull_type([n, gen](push_type& yield){
			for (int i = 0; i < n; ++i, g()) yield(gen.get());
		});
	}
	*/

	static pull_coroutine repeat(const T& value){
		return pull_type([value](push_type& yield){
			for (;;) yield(value);
		});
	}

	static pull_coroutine cycle(const std::vector<T>& values){
		return pull_type([values](push_type& yield){
			for (;;){
				for (auto& v : values) yield(v);
			}
		});
	}
};



int main(){
	
	typedef co_funcs<std::string> co;
	auto cycle = co::cycle;
	auto repeat = co::repeat;
	auto drop = co::drop;
	//auto take = co::take;

	int i;

	/*
	i = 0;
	for (auto& x : take(5, repeat("42"))){
		std::cout << i << " : " << x << std::endl;
	}
	*/

	i = 0;
	for (auto& x : drop(2, cycle({ "A", "B", "C", "X", "Y", "Z" }))){
		if (++i > 5) break;
		std::cout << i << " : " << x << std::endl;
	}


	return 0;
}