//
// 4.3.cpp
// c++1x tutorial
//
// created by changkun at changkun.de
//
// std::tuple åŠå…¶æ“作
#include
#include
#include
auto get_student(int id)
{
if (id == 0)
return std::make_tuple(3.8, 'A', "å¼ ä¸‰");
if (id == 1)
return std::make_tuple(2.9, 'C', "æŽå››");
if (id == 2)
return std::make_tuple(1.7, 'D', "王五");
// 返回类型被推æ–为 std::tuple
return std::make_tuple(0.0, 'D', "null");
}
template
boost::variant _tuple_index(size_t i, const std::tuple& tpl) {
if (i == n)
return std::get(tpl);
else if (n == sizeof...(T) - 1)
throw std::out_of_range("越界.");
else
return _tuple_index<(n < sizeof...(T)-1 ? n+1 : 0)>(i, tpl);
}
template
boost::variant tuple_index(size_t i, const std::tuple& tpl) {
return _tuple_index<0>(i, tpl);
}
template
auto tuple_len(T &tpl) {
return std::tuple_size::value;
}
int main()
{
auto student = get_student(0);
std::cout << "ID: 0, "
<< "GPA: " << std::get<0>(student) << ", "
<< "æˆç»©: " << std::get<1>(student) << ", "
<< "姓å: " << std::get<2>(student) << '\n';
double gpa;
char grade;
std::string name;
// 元组进行拆包
std::tie(gpa, grade, name) = get_student(1);
std::cout << "ID: 1, "
<< "GPA: " << gpa << ", "
<< "æˆç»©: " << grade << ", "
<< "姓å: " << name << '\n';
std::tuple<:string double int> t("123", 4.5, 6.7, 8);
std::cout << std::get<:string>(t) << std::endl;
// std::cout << std::get(t) << std::endl; // éžæ³•, 引å‘编译期错误
std::cout << std::get<3>(t) << std::endl;
// 拼接元组
auto new_tuple = std::tuple_cat(get_student(1), std::move(t));
// è¿ä»£
for(int i = 0; i != tuple_len(new_tuple); ++i)
// è¿è¡ŒæœŸç´¢å¼•
std::cout << tuple_index(i, new_tuple) << std::endl;
}