Re: Template-Meta: Finding out whether a template-definition exists

From:
Barry <dhb2000@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 03 Sep 2007 20:47:09 +0800
Message-ID:
<fbgvpg$5g4$1@aioe.org>
xtrigger303@gmail.com wrote:

On Sep 3, 2:13 pm, "Hendrik Schober" <SpamT...@gmx.de> wrote:

Hi,

suppose we have

  template< typename T >
  struct X;

and some specializations:

  template<>
  struct X<A> {};

  template<>
  struct X<B> {};

  template<>
  struct X<B> {};

Given a type 'U', is there a way to find out whether the
definition 'X<U>' exists? (The result should be a compile-
time constant, so that it can be used for specializing
other templates.)

Schobi

--
SpamT...@gmx.de is never read
I'm HSchober at gmx dot de
"A patched buffer overflow doesn't mean that there's one less way attackers
can get into your system; it means that your design process was so lousy
that it permitted buffer overflows, and there are probably thousands more
lurking in your code."
Bruce Schneier


IMHO

template< typename T >
struct X
{
    enum { kIsSpecialized = false };
};

template<>
struct X< A >
{
    enum { kIsSpecialized = true };
};

if you cannot touch the structs you might keep a manually updated


what do you mean by "you cannot touch the structs"?

typelist ( a la Alexandrescu ) of the specialized types anche check if
a type is in the typelist...


what will the typelist contains?

I can't think of any other way ( so probably there are a thousands
more ... )


--
Thanks
Barry

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