Re: Problems mixing boost::lambda::bind and boost::shared_ptr..

From:
boaz_sade@yahoo.com
Newsgroups:
comp.lang.c++
Date:
1 Jun 2006 13:24:47 -0700
Message-ID:
<1149193487.140545.307300@i39g2000cwa.googlegroups.com>
Toby Bradshaw wrote:

Hi,

Consider the following:

class A
{
public:
   virtual bool foo() = 0;
};

class B : public A
{
public:
   virtual bool foo() { return false; }
};

void fn()
{
   std::list< A * > aList(10);
   std::list< boost::shared_ptr<A> > aSharedList(10);

   // This works fine..
   std::count_if(
     aList.begin(),
     aList.end(),
     boost::lambda::bind(A::foo, boost::lambda::_1)
   );

   // This doesn't compile..
   std::count_if(
     aSharedList.begin(),
     aSharedList.end(),
     boost::lambda::bind(A::foo, boost::lambda::_1)
   );
}

--

Why doesn't the second case compile ? The only difference is that I'm
making the call through a shared_ptr instead of a naked one. If
shared_ptr semantics are (essentially) identical to the naked pointer
ones then this should surely work ? Is there some extra syntax required
in the shared_ptr case or does this simply not work ?

Thanks in advance,

--
t o b e
Rawflow,
London, UK.

With g++ the error is this (sorry that is very very long lines)
no matching function for call to `boost::lambda::function_adaptor<bool
(A::*)() const>::apply(bool (A::*const&)() const,
boost::shared_ptr<A>&)'
canidate are:
static Result boost::lambda::function_adaptor<Result (Object::*)()
const>::apply(Result (Object::*)() const, const Object&) [with RET =
bool, Object = A, Result = bool]

As you can see it trys to match pointer to member function with
reference to member function - with boost::lambda don't have - why
shared_ptr is passing this? I'm not sure (its gatting late :) )
Hope you can continue from here..
good luck

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