How can I cleanly specify which arguments I am passing and which remain default?

Question

Asked because of this: Default argument in c++

Say I have a function such as this: void f(int p1=1, int p2=2, int p3=3, int p4=4);

And

Answer 1

Have a look at the Boost.Parameter library.

It implements named paramaters in C++. Example:

#include 
#include 
#include 

//Define
BOOST_PARAMETER_NAME(p1)    
BOOST_PARAMETER_NAME(p2)
BOOST_PARAMETER_NAME(p3)
BOOST_PARAMETER_NAME(p4)

BOOST_PARAMETER_FUNCTION(
                         (void),
                         f,
                         tag,
                         (optional            
                          (p1, *, 1)
                          (p2, *, 2)
                          (p3, *, 3)
                          (p4, *, 4)))
{
    std::cout << "p1: " << p1 
            << ", p2: " << p2
            << ", p3: " << p3
            << ", p4: " << p4 << "\n";
}
//Use
int main()
{
    //Prints "p1: 1, p2: 5, p3: 3, p4: 4"
    f(_p2=5);
}