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Re: Finding out whether a class instantiates a template

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On Thursday, March 1, 2012 6:10:48 PM UTC-6, Ed Anson wrote:
> My problem involves template parameters (of class templates) -- not 
> function parameters. What I have looks something like this:
> 
> template <class T> class foo {};
> template <class U> class bar {};
> 
> where T is required to be an instantiation of bar<U>, such as
> 
> bar<foo<int> > A;
> 

I'm assuming you mean "U is required to be an instantiation of foo<>" since that's what your example is. I think it's standard practice to use a "trait" template for this:

template <typename T> struct is_foo { static const bool value = false; };
template <typename T> struct is_foo< foo<T> > { static const bool value = true; };

So T is an instation of foo iff is_foo<T>::value == true.

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Thread

Finding out whether a class instantiates a template Ed Anson <EdAnson@comcast.net> - 2012-02-29 19:50 -0500
  Re: Finding out whether a class instantiates a template Christian Gollwitzer <auriocus@gmx.de> - 2012-03-01 07:58 +0100
    Re: Finding out whether a class instantiates a template Ed Anson <EdAnson@comcast.net> - 2012-03-01 19:10 -0500
      Re: Finding out whether a class instantiates a template cartec69@gmail.com - 2012-03-22 07:49 -0700
        Re: Finding out whether a class instantiates a template Ed Anson <EdAnson@comcast.net> - 2012-03-22 22:30 -0400
          Re: Finding out whether a class instantiates a template Ed Anson <EdAnson@comcast.net> - 2012-03-23 18:31 -0400
            Re: Finding out whether a class instantiates a template Marc <marc.glisse@gmail.com> - 2012-03-24 23:08 +0000

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