container_util

iterator_utils.hpp

#include <iterator>

namespace bbb {
	namespace detail {
		template <typename _>
		std::true_type make_true(_ = std::declval<_>());
	};
	
	template <typename checkee_type>
	struct is_iteratable {
		template <typename checkee>
		static auto check(checkee c)
			-> decltype(detail::make_true(std::begin(c)));
		static auto check(...)
			-> std::false_type;
			
		using type = decltype(check(std::declval<checkee_type>()));
		static constexpr bool value = type::value;
	};
	
	template <typename type>
	using is_iteratable_t = typename is_iteratable<type>::type;
	template <typename type>
	static constexpr bool is_iteratable_f() { return is_iteratable<type>::value; }
	
	template <typename checkee_type>
	struct has_value_type {
		template <typename checkee>
		static auto check(checkee)
			-> decltype(detail::make_true<typename checkee::value_type>());
		static auto check(...)
			-> std::false_type;
		
		using type = decltype(check(std::declval<checkee_type>()));
		static constexpr bool value = type::value;
	};
	
	template <typename type>
	using has_value_type_t = typename has_value_type<type>::type;
	template <typename type>
	static constexpr bool has_value_type_f() { return has_value_type<type>::value; }
};

test.cpp

#include "iterator_utils.hpp"

#include <iostream>
#include <array>
#include <vector>
#include <map>
#include <string>
#include <memory>

struct P {
private:
	P() {};
};

int main(int argc, char *argv[]) {
	std::cout << bbb::is_iteratable<int>::value << std::endl;
	std::cout << bbb::is_iteratable<std::vector<int>>::value << std::endl;
	std::cout << bbb::is_iteratable<std::array<int, 4>>::value << std::endl;
	std::cout << bbb::is_iteratable<std::map<int, int>>::value << std::endl;
	std::cout << bbb::is_iteratable<std::string>::value << std::endl;
	std::cout << bbb::is_iteratable<std::shared_ptr<int>>::value << std::endl;
	
	std::cout << std::endl;
	
	std::cout << bbb::has_value_type<int>::value << std::endl;
	std::cout << bbb::has_value_type<std::vector<P>>::value << std::endl;
	std::cout << bbb::has_value_type<std::array<int, 4>>::value << std::endl;
	std::cout << bbb::has_value_type<std::map<int, int>>::value << std::endl;
	std::cout << bbb::has_value_type<std::string>::value << std::endl;
	std::cout << bbb::has_value_type<std::shared_ptr<int>>::value << std::endl;
}