Exact number of elements in std::array in function call

Question

I have a function that takes an std::array of given size N

void func(std::array<int,3> x) {
  // do something
}

int main() {
  func({4,4,4}) // works
  func({4}) // works as well
}

I understand why the second call works as well, my question is: is there a way to check at compile time how many arguments I've actually passed?

The background: I don't want to second call to be allowed, I want the user to pass exactly N arguments.

Answer 1

You can make the function more restrictive like this :

#include <type_traits>
    
// let sfinae disable mismatches
template<std::size_t N>
auto func(const int (&v)[N]) -> std::enable_if_t<N==3,void>
{
  // do something
}
        
int main() 
{
    func({4,4,4}); // works
    func({4}); // no longer compiles
}

Demo : https://onlinegdb.com/FHlRINqCZ

Answer 2

Alternatively, you might add a deleted overload:

void func(std::array<int, 3>) {
  // do something
}

template <std::size_t N>
requires (N != 3)
void func(const int(&)[N]) = delete;

Demo