Re: Templates and private data

From:

Alberto Ganesh Barbati <AlbertoBarbati@libero.it>

Newsgroups:

comp.lang.c++.moderated

Date:

28 Nov 2006 16:11:28 -0500

Message-ID:

<gX0bh.60043$uv5.445259@twister1.libero.it>

Matthias Kluwe ha scritto:

template<int n>
class Foo {
     int i;
public:
     Foo( int i ): i( i ) {};
     template<int p>
     Foo( const Foo<p> &f ): i( f.i ) {};
     int getint() const { return i; };
};

Why do you put semicolons after the braces? They are not needed.

does not work because of 'i' being private. That came surprising for me.
An easy way to get around this would be changing 'f.i' to 'f.getint()',
but the 'real' class interface I have in mind does not allow for such a
method.

What is happening is that you want class Foo<N> to access to the private
members of class Foo<M>. The problem is that if N != M those are two
completely different classes and neither has privileged access the other.

Just add a friend declaration as you would do for a non-template class:

     template <int p>
     friend class Foo;

HTH,

Ganesh

--
      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]