Variadic Functions in C++

Variadic functions can be called with any number of trailing arguments. For example, `fmt.Println` is a common variadic function.

Here's a function that will take an arbitrary number of `int`s as arguments.

```cpp
#include <iostream>
#include <vector>

void sum(std::initializer_list<int> nums) {
    for (auto num : nums) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    int total = 0;
    for (auto num : nums) {
        total += num;
    }
    std::cout << total << std::endl;
}

int main() {
    sum({1, 2});
    sum({1, 2, 3});
    
    std::vector<int> numbers = {1, 2, 3, 4};
    sum({numbers.begin(), numbers.end()});

    return 0;
}

Within the function, the type of nums is equivalent to std::vector<int>. We can call nums.size(), iterate over it with a range-based for loop, etc.

Variadic functions can be called in the usual way with individual arguments.

sum({1, 2});
sum({1, 2, 3});

If you already have multiple args in a slice, apply them to a variadic function using a braced-init-list like this.

std::vector<int> nums = {1, 2, 3, 4};
sum({nums.begin(), nums.end()});

To run the program, put the code in a file named variadic_functions.cpp and use the following commands to compile and run it:

$ g++ variadic_functions.cpp -o variadic_functions
$ ./variadic_functions
[1 2] 3
[1 2 3] 6
[1 2 3 4] 10

Another key aspect of functions in C++ is their ability to form closures, which we’ll look at next.

Multiple Return Values in C++

Closures in C++

Learn X By Example

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Variadic Functions in C++