Re: Template specialization help

From:
Ian Collins <ian-news@hotmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 19 Feb 2011 15:29:23 +1300
Message-ID:
<8s8o86Foh5U2@mid.individual.net>
On 02/19/11 01:50 PM, Adrian wrote:

I am trying to write a specialized version of print that will
automagically work out that the container is a pointer of containers and
does a double ref on each iterator.

It feels possible but I cannot think of a way to do it. My initial
thoughts where to use the STL contains ::value_type and ::const_pointer
typedefs

Happy to modify template params to pass enough information

Anyone done this, or got any ideas on how


Um, I'm sure there's a cleaner way, but these work for ordered and
unordered containers:

template <typename T,
           template <typename E,
                     typename A = std::allocator<E> > class Container>
void print( const Container<T>& c )
{
   for( typename Container<T>::const_iterator i = c.begin(); i !=
c.end(); ++i )
      std::cout << *i << std::endl;
}

template <typename T,
           template <typename E,
                     typename L = std::less<E>,
                     typename A = std::allocator<E> > class Container>
void print( const Container<T>& c )
{
   for( typename Container<T>::const_iterator i = c.begin(); i !=
c.end(); ++i )
      std::cout << *i << std::endl;
}

template <typename T,
           template <typename E,
                     typename A = std::allocator<E> > class Container>
void print( const Container<T*>& c )
{
   for( typename Container<T*>::const_iterator i = c.begin(); i !=
c.end(); ++i )
      std::cout << **i << std::endl;
}

template <typename T,
           template <typename E,
                     typename L = std::less<E>,
                     typename A = std::allocator<E> > class Container>
void print( const Container<T*>& c )
{
   for( typename Container<T*>::const_iterator i = c.begin(); i !=
c.end(); ++i )
      std::cout << **i << std::endl;
}

The horrible template template syntax will be much cleaner in C++0x.

int main(int argc, char *argv[])
{
std::vector<int> intlist;
std::vector<int*> intptrlist;

for(int i=0; i<10; ++i)
{
intlist.push_back(i);
intptrlist.push_back(new int(i));
}

print(intlist.begin(), intlist.end());
print(intptrlist.begin(), intptrlist.end());

return 0;
}


--
Ian Collins

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