What is wrong here? It looks fine to me

From:
Neil Morgenstern <dotfield2007@googlemail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 21 Aug 2009 05:12:24 -0700 (PDT)
Message-ID:
<b96a7f5a-d90c-456e-a5e6-4e9b22e8b505@k19g2000yqn.googlegroups.com>
Reproduced sample of the kind of thing I am trying to do. This fails
with VC2008, I'm not sure if it's an error in the code or in the
VC2008 library. I tried Comeau tryitout and it didn't recognise the
tr1 parts even though I am including all of the relevant headers so no
help there, unfortunately.

#include <memory>
#include <algorithm>
#include <functional>
#include <vector>
#include <iostream>
#include <sstream>

class Abstract1
{
public:
    virtual ~Abstract1()
    {
    }

    virtual std::string gimme() const = 0;
};

class Derived1 : public Abstract1
{
    std::string gimme() const
    {
        return "Take It\n";
    }
};

class Abstract2
{
public:
    virtual ~Abstract2()
    {
    }

    virtual void getme( const Abstract1 & abs1, std::ostream & ostr ) =
0;
};

class Derived2 : public Abstract2
{
public:
    void getme( const Abstract1 & abs1, std::ostream & ostr )
    {
         ostr << abs1.gimme();
    }
};

using std::tr1::shared_ptr;
using std::tr1::bind;
using std::tr1::placeholders::_1;
using std::tr1::ref;
using std::tr1::cref;

int main()
{
    shared_ptr< Abstract1 > ptr1( new Derived1 );

    typedef shared_ptr< Abstract2 > Ptr2;

    std::vector< Ptr2 > ptr2Vec;

    ptr2Vec.push_back( Ptr2( new Derived2 ) );
    std::ostringstream oss;

    std::for_each( ptr2Vec.begin(), ptr2Vec.end(),
        bind( &Abstract2::getme, _1, cref( *ptr1 ), ref( oss ) ) );

    std::cout << oss.str();
}

The error messages I am getting relate to Abstract1 being abstract (it
doesn't have a problem with Abstract2) even though I am clearly
passing the 3rd parameter in bind with the cref() modifier so it
should be passing through just a const reference.

In my real code I have had to workaround with a home-made functor.
Took me a few seconds to write that, but I'd rather use bind than have
to write functors.

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