Explicitly use defaults for some parameters in class template instantiation

Question

A class template can have multiple parameters that all have defaults.

template

        

Answer 1

I came across this issue again and came up with a more general version of Sebastian Redl's solution.

//given an index to replace at, a type to replace with and a tuple to replace in
//return a tuple of the same type as given, with the type at ReplaceAt set to ReplaceWith
template 
auto replace_type (std::index_sequence, std::tuple)
    -> std::tuple...>;

//instantiates a template with the types held in a tuple
template