Auto convert const char[] to const char * in template function

You could use a metafunction to transform the types passed as argument to your templates. Any array of chars would be transformed into a char*:

template< typename T > struct transform
{
    typedef T type;
};

template< std::size_t N > struct transform< char[N] >
{
    typedef char* type;
};
template< std::size_t N > struct transform< const char[N] >
{
    typedef const char* type;
};

Then, instead of using Tn directly you would use typename transform< Tn >::type.

Update: If you are working in C++11, then std::decay already does what you want.