C模板编程自定义创建元组（tuple）

　　一、各个模块
　　1、将数组转换为指针// decay_array to pointer template auto decay_array(T(&array)[N]) { 	return array; }
　　2、定义初始模板类型
　　1）元素类型为T
　　2）容器类型为T
　　3）是否为字符数组类型：否
　　4）数组大小：0// primary class template template struct container_element_st { 	using type = T; 	using element_type = T; 	static constexpr bool is_character_array = false; 	static constexpr size_t array_count = 0; };
　　3、定义字符数组类型
　　1）元素类型为char
　　2）容器类型为std::string
　　3）是否为字符数组类型：是
　　4）数组大小：Ntemplate struct container_element_st	 // non reference { 	using type = char; 	using element_type = std::string; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = N; };
　　4、定义字符指针类型
　　1）元素类型为char
　　2）容器类型为std::string
　　3）是否为字符数组类型：是
　　4）数组大小：0template<> struct container_element_st	 // non reference { 	using type = char; 	using element_type = std::string; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = 0; };
　　5、定义非字符类型数组
　　1）元素类型为T
　　2）容器类型为std::vector
　　3）是否为字符数组类型：否// array but not character array template struct container_element_st { 	using type = T; 	using element_type = std::vector; 	static constexpr bool is_character_array = false; };
　　6、定义初始化列表类型
　　1）元素类型为T
　　2）容器类型为std::vector
　　3）是否为字符数组类型：否// from initializer_list to vector conversion template struct container_element_st> { 	using type = T; 	using element_type = std::vector; 	static constexpr bool is_character_array = false; };
　　7、定义各种类型
　　1）是否为字符数组类型
　　2）获取字符数组的大小
　　3）获取字符数组的类型，char or wchar_t
　　4）获取容器类型// get whethere character array template constexpr auto is_character_array_v = container_element_st>::is_character_array;  // get array size template constexpr auto array_count_v = container_element_st< tft::remove_const_reference_t>::array_count;  // define element type template using element_flat_t = typename container_element_st< tft::remove_const_reference_t>::type;  // define container element type template using container_element_t = typename container_element_st< tft::remove_const_reference_t>::element_type;
　　8、创建自定义元组
　　创建元组的时候，元组的元素可以是元组，可以使vector，也可以是各种基础类型元素。template auto make_tuple(Type&& first, Types&&... args) { 	using container_t = std::tuple, container_element_t...>; 	 	return container_t{ element_to_container(std::forward(first)), 		element_to_container(std::forward(args))... }; }
　　9、获取自定义元组中的元素
　　分别可以获取一层元组的元素、两层元组的元素、三层元组的元素。template decltype(auto) get(CntrType& cntr) { 	return std::get(cntr); }  template decltype(auto) get(CntrType& cntr) { 	if constexpr (sizeof...(Indices) > 0) 		return get(get(cntr)); 	else 		return get(cntr); }  template decltype(auto) get(CntrType& cntr, IndexType index) { 	if constexpr (sizeof...(Indices) > 0) 		return get(get(cntr))[index]; 	else 		return get(cntr)[index]; }
　　二、整体代码#include ＂tft_type_lib.h＂ #include ＂tpf_type_util.h＂  auto stream = tpf::stream();			// stream auto nl = stream.get_console_out();	  // new line  // decay_array to pointer template auto decay_array(T(&array)[N]) { 	return array; }  // primary class template template struct container_element_st { 	using type = T; 	using element_type = T; 	static constexpr bool is_character_array = false; 	static constexpr size_t array_count = 0; };  template struct container_element_st	 // non reference { 	using type = char; 	using element_type = std::string; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = N; };  template<> struct container_element_st	 // non reference { 	using type = char; 	using element_type = std::string; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = 0; };  template struct container_element_st	 // non reference { 	using type = wchar_t; 	using element_type = std::wstring; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = N; };  template<> struct container_element_st	 // non reference { 	using type = wchar_t; 	using element_type = std::wstring; 	static constexpr bool is_character_array = true; 	static constexpr size_t array_count = 0; };  // array but not character array template struct container_element_st { 	using type = T; 	using element_type = std::vector; 	static constexpr bool is_character_array = false; };  template struct container_element_st { 	using type = T; 	using element_type = std::vector; 	static constexpr bool is_character_array = false; };  // from initializer_list to vector conversion template struct container_element_st> { 	using type = T; 	using element_type = std::vector; 	static constexpr bool is_character_array = false; };  // get whethere character array template constexpr auto is_character_array_v = container_element_st>::is_character_array;  // get array size template constexpr auto array_count_v = container_element_st< tft::remove_const_reference_t>::array_count;  // define element type template using element_flat_t = typename container_element_st< tft::remove_const_reference_t>::type;  // define container element type template using container_element_t = typename container_element_st< tft::remove_const_reference_t>::element_type;  // create a vector template auto make_vector(Type&& first, Types&&... args) { 	// determine whether type argument is an array 	if constexpr (std::is_array_v>) 	{ 		// this is to allow only character array 		static_assert(is_character_array_v, ＂should be character array＂);  		using element_t = container_element_t; 		using container_t = std::vector;  		size_t size = array_count_v; 		const auto& last_character = first[size - 1];  		// last character is NULL character 		if (element_flat_t{} == last_character) 			return container_t{ decay_array(first),decay_array(args)... }; 		else 		{ 			return	container_t{ element_t{std::cbegin(first),std::cend(first)}, 					element_t{std::cbegin(args),std::cend(args)}... }; 		} 	} 	else 	{ 		using element_t = tft::remove_const_reference_t; 		return std::vector{ std::forward(first), std::forward(args)... }; 	} }  // 创建一个容器 template< template class CntrType, typename Type, typename... Types> auto make_container(Type&& first, Types&&... args) { 	if constexpr (std::is_array_v>) 	{ 		// this is to allow only character only 		static_assert(is_character_array_v, ＂should be character array＂);  		using element_t = container_element_t; 		using container_t = CntrType;  		size_t size = array_count_v; 		const auto& last_character = first[size - 1];  		// last character is NULL character 		if (element_flat_t{} == last_character) 			return container_t{ decay_array(first),decay_array(args)... }; 		else 		{ 			return	container_t{ element_t{std::cbegin(first),std::cend(first)}, 					element_t{std::cbegin(args),std::cend(args)}... }; 		} 	} 	else 	{ 		using element_t = tft::remove_const_reference_t; 		return CntrType{ std::forward(first), std::forward(args)... }; 	} }  template void print_type(T&& arg) { 	stream << ＂Type of T:＂ << Tpf_GetTypeName(T) 		<< ＂, Type of arg: ＂ << Tpf_GetTypeCategory(decay_array(arg)) << nl; }  void simple_tip() { 	int a = 1; 	std::vector v1{ 1,2,3,4,5 }; 	auto v2 = make_vector(a, 2, 3, 4, 5, 6, 7, 8, 9, 10); 	stream << ＂v1 = ＂ << v1 << nl; 	stream << ＂v2 = ＂ << v2 << nl;  	auto v3 = make_vector(＂123＂, ＂tomas kim＂, ＂han＂, ＂saimei＂, ＂shuang＂); 	stream << ＂v3 = ＂ << v3 << nl; }  void simple_tip_advance() { 	int a = 1; 	std::vector v1{ 1,2,3,4,5 }; 	auto v2 = make_container(a, 2, 3, 4, 5, 6, 7, 8, 9, 10); 	stream << ＂v1 = ＂ << v1 << nl; 	stream << ＂v2 = ＂ << v2 << nl;  	auto v3 = make_container(＂123＂, ＂tomas kim＂, ＂han＂, ＂saimei＂, ＂shuang＂); 	stream << ＂v3 = ＂ << v3 << nl; }  /* 	we have to convert const char* to  std::string 	const wchar_t* to std::wstring 	convert array,int[] to std::vector 	std::initializer_list<> to std::vector<> */  template auto element_to_container(Type&& arg) { 	// array  such as char[N],int[N] ect. 	if constexpr (std::is_array_v>) 	{ 		if constexpr (is_character_array_v) 		{ 			// character array ,we convert  			// const char* to std::string 			// const wchar_t* to std::wstring 			// char[N] to std::string 			// wchar_t[N] to std::wstring 			using element_t = container_element_t; 			size_t size = array_count_v; 			const auto& last_character = arg[size - 1]; 			 			// element_flat_t returns either char or wchar_t 			// testing if zero terminated character 			if (element_flat_t{} == last_character) 				return element_t{ decay_array(arg) };// decay_array() convert char[] to char* 			else // not zero terminating character array 				return element_t{ std::cbegin(arg),std::cend(arg) }; 		} 		else 		{ 			// non character array 			using element_t = container_element_t; 			return element_t{ std::cbegin(arg),std::cend(arg) }; 		} 	} 	else 	{ 		// non array case 		using element_t = container_element_t; 		return element_t{ std::forward(arg) }; 	} }  // this belongs to non-deduced context template auto element_to_container(std::initializer_list& lst) { 	// decltype(lst),decltype()，get variable type 	// using element_t = container_element_t>; 	using element_t = container_element_t;  	// conversion from std::initializer_list to std::vector 	return element_t{ lst }; }  // this belongs to non-deduced context template auto element_to_container(std::initializer_list&& lst) { 	// decltype(lst),decltype()，get variable type 	// using element_t = container_element_t>; 	using element_t = container_element_t;  	// conversion from std::initializer_list to std::vector 	return element_t{ std::forward>(lst) }; }  template auto make_tuple(Type&& first, Types&&... args) { 	using container_t = std::tuple, container_element_t...>; 	 	return container_t{ element_to_container(std::forward(first)), 		element_to_container(std::forward(args))... }; }  template decltype(auto) get(CntrType& cntr) { 	return std::get(cntr); }  template decltype(auto) get(CntrType& cntr) { 	if constexpr (sizeof...(Indices) > 0) 		return get(get(cntr)); 	else 		return get(cntr); }  template decltype(auto) get(CntrType& cntr, IndexType index) { 	if constexpr (sizeof...(Indices) > 0) 		return get(get(cntr))[index]; 	else 		return get(cntr)[index]; }  void test_element_to_container() { 	using literal_string_t = const char*;  	auto str1 = element_to_container(＂This is literal string＂); 	stream << ＂str1 = ＂ << str1 << ＂ Type: ＂ 		<< Tpf_GetTypeCategory(str1) << nl;  	int array[]{ 1,2,3,4,5 }; 	auto vtr1 = element_to_container(array); 	stream << ＂vtr1 = ＂ << vtr1 << ＂ Type: ＂ 		<< Tpf_GetTypeCategory(vtr1) << nl;  	auto lst = element_to_container({ 3.1,5.0,6.0 }); 	stream << ＂lst = ＂ << lst << ＂ Type: ＂ 		<< Tpf_GetTypeCategory(lst) << nl;  }  void test_make_tuple() { 	const char* msg1 = ＂Literal string＂; 	const wchar_t* msg2 = L＂wide character string＂; 	auto t1 = make_tuple(msg1,＂han＂, ＂shuang＂, ＂shuang han＂, 20, ＂sia mie＂,msg2); 	stream << ＂t1 = ＂ << t1 << /*＂ Type: ＂ 		<< Tpf_GetTypeCategory(t1) <<*/ nl;  	using t1_0_th_t = std::tuple_element_t<0, decltype(t1)>; 	stream << ＂t1-0-th element: ＂ << std::get<0>(t1) << ＂  Type: ＂ 		<< Tpf_GetTypeName(t1_0_th_t) << nl;  	using t1_4_th_t = std::tuple_element_t<4, decltype(t1)>; 	stream << ＂t1-4-th element: ＂ << std::get<4>(t1) << ＂  Type: ＂ 		<< Tpf_GetTypeName(t1_4_th_t) << nl;  	using t1_6_th_t = std::tuple_element_t<6, decltype(t1)>; 	stream << ＂t1-6-th element: ＂ << std::get<6>(t1) << ＂  Type: ＂ 		<< Tpf_GetTypeName(t1_6_th_t) << nl; }  void test_advanced_make_tuple() { 	auto t1 = make_tuple( 		make_tuple(1, 3.14, ＂han＂), 		make_tuple(make_vector(1, 2, 3, 4, 5), make_vector(3.0, 5.0, 6.1), 			make_tuple(＂han＂, ＂s shuang＂, 40.2f)), 		make_vector(＂james＂, ＂seveten＂));  	stream << t1 << nl; 	stream << get<0>(t1) << nl; 	stream << get<1>(t1) << nl;  	stream << get<1, 0>(t1) << nl; 	stream << get<1, 1>(t1) << nl; 	stream << get<1, 2>(t1) << nl;  	stream << nl;  	//get<1, 0>(t1) is a vector 	for (const auto& e : get<1, 0>(t1)) 		stream << e << ＂ ＂; 	stream << nl; }  int main() { 	//test_element_to_container(); 	//test_make_tuple(); 	test_advanced_make_tuple(); 	return 0; }