Calling template function inside function C++

Question

I have similar case but more complex. I am trying to call a template function inside a normal function but I can't compile...

#include <iostream>

using namespace std;

template<class T>
void ioo(T& x) { std::cout << x << "\n"; }

template<class T, class ReadFunc>
void f(T&& param, ReadFunc func) {
    func(param);
}

int main() {
    int x = 1;
    std::string y = "something";
    f(x, &::ioo);
}

Ted Lyngmo · Accepted Answer · 2021-10-01 09:58:23Z

5

ioo is a function template, not a function, so you can't take its address.

This would however work since it instantiates the function void ioo<int>(int&):

f(x, &ioo<decltype(x)>);

and as noted by Jarod42 in the comments, you could make it into a lambda:

f(x, [](auto& arg){ioo(arg);});

edited Oct 1, 2021 at 9:58

answered Oct 1, 2021 at 9:54

Ted Lyngmo

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3 Comments

Ted Lyngmo Over a year ago

@Jarod42 Indeed - added that as an option. Thanks!

Ionut Alexandru Over a year ago

Thanks that second comment was helpful for me. I had multiple params but I use f(x, [](auto&&... arg){ioo(...arg);});

Ted Lyngmo Over a year ago

@IonutAlexandru You are welcome! You may want to take a look at std::forward too in order to do perfect forwarding.

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