Ambiguous Function Calls to C++ base classes

Question

I\'m trying to create a variadic templated class which provides a method for each class in the typelist. An example is shown below which creates a print method for

Answer 1

To resolve the ambiguity, it is possible to do

template 
struct Printer : PrintHelper...
{
    template 
    void print (const U& t)
    {
        PrintHelper::print (t);
    }
};

(see an example )

but this is not quite as robust as one would hope. In particular, you cannot print an object which is convertible to one of the types from the type list.

With some template metaprogramming, it is possible to dispatch to the correct printer however. To do this you have to select a type from Ts... to which U is convertible, and call the right PrintHelper, ie.

PrintHelper::type>::print (t);

where find_convertible is defined by

template 
struct find_convertible
{};

template 
struct find_convertible :
    std::conditional<
        std::is_convertible::value, 
        std::common_type, // Aka identity
        find_convertible
    >::type
{};

(see example)