Re: Having friend templates in class templates

From:

n2xssvv g02gfr12930 <n2xssvv.g02gfr12930@ntlworld.com>

Newsgroups:

comp.lang.c++.moderated

Date:

29 Apr 2006 06:25:45 -0400

Message-ID:

<6Rh4g.31$k72.16@newsfe2-gui.ntli.net>

n2xssvv g02gfr12930 wrote:

jehugaleahsa@gmail.com wrote:

I am trying to create a friend function template that can access the
members of an outer class template and an inner class template. My
class template looks something like this:

template <typename T>
struct Outer
{

   // not sure how to define this function
   template <typename U>
   friend void doSomething(U const& value);

   template <typename U>
   struct Inner
   {
       static int num;
   };
};

template <typename T>
template <typename U>
int Outer<T>::Inner<U>::num = 0;

// END example

I have been reading a template book but have not been able to resolve
my issue. Does someone know the syntax to define function doSomething?

I'm not sure if I've understood your problem but maybe
this will help;

// declare template function prototype
template <typename T>
void SomeFunction(void);

template <typename T>
class Outter
{
    private:
      friend void SomeFunction<T>(void);
      int a;
      T b;
      template <typename U>
      class Inner
      {
        private:

              // CORRECTION

              friend void SomeFunction<T>(void);

              // CORRECTION

          //friend void SomeFunction<U>(void);
          U a;
      };
    public:
};

template <typename T>
void SomeFunction(void)
{
    // implement function here
    // Will have access to all members of both Outter<T> and
    // Outer<T>::Inner<float>
    Outter<T>::Inner<float> ITmp;
    Outter<T> OTmp;
    ITmp.a = 3.4f;
    OTmp.a = -7;
}

Well does it help?

Sorry for the mistake, but now corrected and will work.

JB

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