How do I set parameter default values that rely on other parameters?

Question

The following code compiles and works as expected.

#include 

void function(std::vector vec, int size=1);

int main(){
    std::vect         


        

Answer 1

If you truly want a function with a size parameter, and want the size to default to the vector size (instead of just getting it as a local variable), then you could solve this with two functions. One taking just the vector, and one taking the vector and the size (without default). Then the one-argument function can just call the second.

So

void function(const std::vector<int>& vec, const size_t size)
{
   ...
}

void function(const std::vector<int>& vec)
{
   function(vec, vec.size());
}

Answer 2

Why do you need second parameter if it based on the first?

    void function(std::vector<int> vec ){
        size_t size = vec.size();
        //code..
        return;
    }

Isn't it easier?