Re: [Boost-users] [bind] How to dereference _1 in a boost::bind expression

2 Oct 2008

      On Thu, Oct 2, 2008 at 11:39 AM, Robert Jones <robertgbjones@gmail.com> wrote:
...
On Thu, Oct 2, 2008 at 11:12 AM, Peter Barker <newbarker@gmail.com> wrote:
...
Hello,
Here's an example of my problem:
#include <algorithm>
#include <vector>
#include <boost/bind.hpp>
class TheClass
{
};
void accept(TheClass& tc)
{
}
int main()
{
       std::vector<TheClass*> cont;
// Compile error - how to dereference _1 ???
       std::for_each(cont.begin(),cont.end(),boost::bind(&accept,_1));
}
How can I dereference _1 so I can use the accept function?
#include <algorithm>
#include <vector>
#include <boost/lambda/bind.hpp>
#include <boost/lambda/lambda.hpp>
class TheClass
{
};
void accept(TheClass& tc)
{
}
int main()
{
      using namespace boost;
      using namespace boost::lambda;
std::vector<TheClass*> cont;
// Compile error - how to dereference _1 ???
      std::for_each(cont.begin(),cont.end(),bind(accept,*_1));
}
Rob,

Thanks for the suggestion - my sample program was actually too
stripped down. TheClass is a base with pure virtual methods and your
suggestion gives me the "cannot instantiate abstract class" compiler
error. Here's a new sample program:

#include <algorithm>
#include <vector>

#include <boost/lambda/bind.hpp>
#include <boost/lambda/lambda.hpp>

class TheClass
{
public:
	virtual ~TheClass() {}
	virtual void pvm() = 0;
};

class DerivedClass : public TheClass
{
	void pvm() {}
};

void accept(TheClass& tc)
{
}

int main()
{
	std::vector<TheClass*> cont;

	using namespace boost::lambda;
	using boost::lambda::_1;

	// Compile error - cannot instantiate abstract class - how to
dereference _1 ???
	std::for_each(cont.begin(),cont.end(),bind(&accept,*_1));
}