Re: template template classes

From:
Barry <dhb2000@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 03 Sep 2007 18:50:36 +0800
Message-ID:
<fbgov3$hhp$1@aioe.org>
Anonymous wrote:

Could someone please explain template template classes, showing:

1). Why they are needed / i.e what problem do they solve ?


template <class T, class Container>
class Stack1;

template <class T, template <class> class Container>
class Stack2

with Stack1, the template parameter Container needs container class
with Stack2, Container is a template template parameter, it need a class
with *one* template parameter.

see the usage:

class Vector1; // holds int

template <class T>
class Vector2;

Stack1<int, Vector1> s1;
Stack1<int, Vector2<int> > s2;

Stack2<int, Vector1> s3; // compile time error
Stack2<int, Vector2<int> > s4;

so template template parameter restrict the parameter you pass into the
template class.
Any other use, I don't know.

Anyway it's not mandatory, in STL, as far as I know, there's no template
template parameter usage.

2). A simple example

I have read various articles etc, but it still dosen't seem to make
sense to me


--
Thanks
Barry

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