Cpp Tuple use get with a variable

Question

So, i was trying to use std::get with a variable to search a certain position of a tuple. But for my surprise i cannot access any position using a tuple. Do you guys know why and how to overcome this problem? I need a lot of a container that gives me different types.

I will put my code here:

#include <iostream> #include <tuple> struct MyStruct { std::tuple<int, float> t; int pos; } myStruct; int main() { MyStruct* var = new MyStruct(); var->t = std::make_tuple(1,2.33); var->pos = 1; std::get<1>(var->t); //this works std::get<var->pos>(var->t); //this doesn't work but i need to search "dynamically" }

best regards!

Are you sure that you want a tuple or perhaps a std::variant? — Timo
– Timo, Commented Jul 14, 2020 at 12:19
What can you do if you you can get a specific element from a tuple which has different type? Can you show any real world use case please! — Klaus
– Klaus, Commented Jul 14, 2020 at 12:50
A tuple that you can access with a variable is spelled std::array. — n. m. could be an AI
– n. m. could be an AI, Commented Jul 16, 2020 at 6:33

Stefan Scheller · Accepted Answer · 2020-07-14 12:48:28Z

Templates are resolved at compile time, so you cannot use a variable whose value is not known until runtime to access the tuple with get. If you are using C++17 an alternative could be to use something like std::vector<std::any> (suggested reading: std::any: How, when, and why).

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Cpp Tuple use get with a variable

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