Re: template function within class template not not resolving?

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Sun, 28 Feb 2010 14:22:20 -0500

Message-ID:

<daniel_t-18CC9E.14222028022010@70-3-168-216.pools.spcsdns.net>

jrwats <jrwats@gmail.com> wrote:

I'm trying to write a templated function within a templated class, but
keep getting:
Test.h:31: error: no matching function for call to
?List<int>::Map(List<T>::blah() [with T = int]::Functor)?
Test.h:45: error: no matching function for call to ?List<int>::Map()?

1) The class definition "Functor" must be pulled out of the function.
2) The op() of Functor must be made public.
3) The op() of Functor must be a const function.
4) The line "return Map<Functor>();" requires an argument.

You end up with the following:

template <class T>
class List
{
public:
    // Function template
    template <class Functor>
    int Map(const Functor& func);

    // Returns NULL if not found.
    int blah();
    int blah2();
};

template <class T>
template <class Functor>
int List<T>::Map(const Functor& func)
{
    return func() ? 0 : 1;
}

struct Functor
{
   bool operator()() const
   {
      return true;
   }
};

template<class T>
int List<T>::blah()
{
   return Map(Functor());
}

template<class T>
int List<T>::blah2()
{
    return Map<Functor>(Functor());
}

void blah()
{
    List<int> list;
    list.blah();
    list.blah2();
}