Call function with part of variadic arguments

Question

Consider I have the following:

void bar(int a, int b)
{
}   

template
void foo(F function, Args... args>
{
    function(a         


        

Answer 1

First, we need a function to retrieve the number or arguments the function requires. This is done using function_traits:

template 
constexpr std::size_t nb_args() {
   return utils::function_traits::arity;
}

And with the help of std::index_sequence, we only dispatch the nb_args() first arguments:

template
void foo_impl(F && f, std::index_sequence, Tup && tup) {
    std::forward(f)( std::get(tup)... );
}

template
void foo(F && f, Args&&... args) {
    foo_impl(std::forward(f),
             std::make_index_sequence()>{},
             std::forward_as_tuple(args...) );
}

Demo