Re: bind2nd, mem_fun, and references

From:

"Noah Roberts" <roberts.noah@gmail.com>

Newsgroups:

comp.lang.c++

Date:

14 Jul 2006 16:46:10 -0700

Message-ID:

<1152920770.393499.220010@h48g2000cwc.googlegroups.com>

Alf P. Steinbach wrote:

* Noah Roberts:

#include <vector>
#include <algorithm>
#include <functional>

class X
{
  int x;
public:
  X(int i) : x(i) {}
  bool eq(const X & other) const { return x == other.x; }
};

int main(int argc, char* argv[])
{
  std::vector<X> xes(10);

  X x(10);

  std::vector<X>::iterator it = std::find_if(xes.begin(), xes.end(),
    std::bind2nd(std::mem_fun(&X::eq), x));

  return 0;
}

Compilation result:

1>c:\program files\microsoft visual studio 8\vc\include\functional(312)
: error C2529: '_Right' : reference to reference is illegal

    binder2nd(const _Fn2& _Func,
        const typename _Fn2::second_argument_type& _Right)
        : op(_Func), value(_Right)
        { // construct from functor and right operand
        }

This would follow...

So, what is the correct and portable way to do what I want or is it
just not possible?

One way could be to use to Boost binders (don't know if that works, but
probably, else I would probably have remembered).

That's out until I can convince boss Boost good.

bool operator==(const X & other) const { return x == other.x; }

That would work except my real-world type is polymorphic.