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vladiant/1_tuple_iter.cpp

Created November 4, 2025 19:15
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C++ tuple iteration 1
Raw
1_tuple_iter.cpp
#include <iostream>
#include <tuple>
template <typename T>
void printElem(const T& x) {
std::cout << x << ',';
};
template <typename TupleT, std::size_t... Is>
void printTupleManual(const TupleT& tp) {
(printElem(std::get<Is>(tp)), ...);
}
int main() {
std::tuple tp { 10, 20, "hello"};
printTupleManual<decltype(tp), 0, 1, 2>(tp);
}
Raw
2_index_sequence.cpp
#include <iostream>
#include <tuple>
template <typename T>
void printElem(const T& x) {
std::cout << x << ',';
};
template <typename TupleT, std::size_t... Is>
void printTupleManual(const TupleT& tp, std::index_sequence<Is...>) {
(printElem(std::get<Is>(tp)), ...);
}
template <typename TupleT, std::size_t TupSize = std::tuple_size_v<TupleT>>
void printTupleGetSize(const TupleT& tp) {
printTupleManual(tp, std::make_index_sequence<TupSize>{});
}
int main() {
std::tuple tp { 10, 20, "hello"};
printTupleGetSize(tp);
}
Raw
3_print_tuple.cpp
template <typename TupleT, std::size_t... Is>
void printTupleImp(const TupleT& tp, std::index_sequence<Is...>) {
size_t index = 0;
auto printElem = [&index](const auto& x) {
if (index++ > 0)
std::cout << ", ";
std::cout << x;
};
std::cout << "(";
(printElem(std::get<Is>(tp)), ...);
std::cout << ")";
}
template <typename TupleT, std::size_t TupSize = std::tuple_size_v<TupleT>>
void printTuple(const TupleT& tp) {
printTupleImp(tp, std::make_index_sequence<TupSize>{});
}
int main() {
std::tuple tp { 10, 20, "hello"};
printTuple(tp);
}
Raw
4_stream_operator.cpp
#include <iostream>
#include <ostream>
#include <tuple>
template <typename TupleT, std::size_t... Is>
std::ostream& printTupleImp(std::ostream& os, const TupleT& tp, std::index_sequence<Is...>) {
size_t index = 0;
auto printElem = [&index, &os](const auto& x) {
if (index++ > 0)
os << ", ";
os << x;
};
os << "(";
(printElem(std::get<Is>(tp)), ...);
os << ")";
return os;
}
template <typename TupleT, std::size_t TupSize = std::tuple_size_v<TupleT>>
std::ostream& printTuple(std::ostream& os, const TupleT& tp) {
return printTupleImp(os, tp, std::make_index_sequence<TupSize>{});
}
template <typename TupleT, std::size_t TupSize = std::tuple_size<TupleT>::value>
std::ostream& operator <<(std::ostream& os, const TupleT& tp) {
return printTupleImp(os, tp, std::make_index_sequence<TupSize>{});
}
int main() {
std::tuple tp { 10, 20, "hello"};
std::cout << tp << '\n';
}
Raw
5_add_index.cpp
#include <iostream>
#include <ostream>
#include <tuple>
template <typename TupleT, std::size_t... Is>
std::ostream& printTupleImp(std::ostream& os, const TupleT& tp, std::index_sequence<Is...>) {
auto printElem = [&os](const auto& x, size_t id) {
if (id > 0)
os << ", ";
os << id << ": " << x;
};
os << "(";
(printElem(std::get<Is>(tp), Is), ...);
os << ")";
return os;
}
template <typename TupleT, std::size_t TupSize = std::tuple_size<TupleT>::value>
std::ostream& operator <<(std::ostream& os, const TupleT& tp) {
return printTupleImp(os, tp, std::make_index_sequence<TupSize>{});
}
int main() {
std::tuple tp { 10, 20, "hello"};
std::cout << tp << '\n';
std::tuple vals { 1.1, 2.2, "hello", "world"};
std::cout << vals << '\n';
}
Raw
6_std_apply.cpp
#include <iostream>
#include <tuple>
int sum(int a, int b, int c) {
return a + b + c;
}
void print(std::string_view a, std::string_view b) {
std::cout << "(" << a << ", " << b << ")\n";
}
int main() {
std::tuple numbers {1, 2, 3};
std::cout << std::apply(sum, numbers) << '\n';
std::tuple strs {"Hello", "World"};
std::apply(print, strs);
}
Raw
7_std_apply_helper.cpp
#include <iostream>
#include <tuple>
template <typename... Args>
void printImpl(const Args&... tupleArgs) {
size_t index = 0;
auto printElem = [&index](const auto& x) {
if (index++ > 0)
std::cout << ", ";
std::cout << x;
};
(printElem(tupleArgs), ...);
}
template <typename... Args>
void printTupleApplyFn(const std::tuple<Args...>& tp) {
std::cout << "(";
std::apply(printImpl<Args...>, tp); // <<
std::cout << ")";
}
int main() {
std::tuple tp { 10, 20, 3.14, 42, "hello"};
printTupleApplyFn(tp);
}
Raw
8_std_apply_lambda.cpp
#include <iostream>
#include <tuple>
template <typename TupleT>
void printTupleApply(const TupleT& tp) {
std::cout << "(";
std::apply
(
[](const auto&... tupleArgs)
{
size_t index = 0;
auto printElem = [&index](const auto& x) {
if (index++ > 0)
std::cout << ", ";
std::cout << x;
};
(printElem(tupleArgs), ...);
}, tp
);
std::cout << ")";
}
int main() {
std::tuple tp { 10, 20, 3.14, 42, "hello"};
printTupleApply(tp);
}
Raw
9_std_apply_simple.cpp
#include <iostream>
#include <tuple>
template <typename TupleT>
void printTupleApply(const TupleT& tp) {
std::apply
(
[](const auto& first, const auto&... restArgs)
{
auto printElem = [](const auto& x) {
std::cout << ", " << x;
};
std::cout << "(" << first;
(printElem(restArgs), ...);
}, tp
);
std::cout << ")";
}
int main() {
std::tuple tp { 10, 20, 3.14, 42, "hello"};
printTupleApply(tp);
}
Raw
notes.txt
https://www.cppstories.com/2022/tuple-iteration-basics/
https://www.cppstories.com/2022/tuple-iteration-apply/
https://www.cppstories.com/2025/tuple-iteration-cpp26/
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