Is there a way to pass auto as an argument in C++?

Question

Is there a way to pass auto as an argument to another function?

int function(auto data)
{
    //DOES something
}

Answer 1

Templates are the way you do this with normal functions:

template <typename T>
int function(T data)
{
    //DOES something
}

Alternatively, you could use a lambda:

auto function = [] (auto data) { /*DOES something*/ };

Answer 2

I dont know when it changed, but currently syntax from Question is possible with c++14:

https://coliru.stacked-crooked.com/a/93ab03e88f745b6c

There is only warning about it:

g++ -std=c++14 -Wall -pedantic -pthread main.cpp && ./a.out main.cpp:5:15: warning: use of 'auto' in parameter declaration only available with -fconcepts void function(auto data)

With c++11 there is an error:

main.cpp:5:15: error: use of 'auto' in parameter declaration only available with -std=c++14 or -std=gnu++14

Answer 3

If you want that to mean that you can pass any type to the function, make it a template:

template <typename T> int function(T data);

There's a proposal for C++17 to allow the syntax you used (as C++14 already does for generic lambdas), but it's not standard yet.