[Boost-users] Re: boost::bind and member functions

22 Mar 2005


      Maybe not the best solution performance-wise, but you can try the following:

Replace
    typedef float (A::*pfn)(int, float);
with
    typedef boost::function3 pfn;

then
    v.push_back(&A::a);
    ...
with
    v.push_back(boost::mem_fn(&A::a));
    ...

and finally
    transform(
          v.begin()
        , v.end()
        , back_inserter(f)
        , bind(apply<float>(), _1, a, m, x)
    );

with

    transform(
          v.begin()
        , v.end()
        , back_inserter(f)
        , bind(apply<float>(), _1, &a, m, x)
    );

I'm not sure if its necessary to include the extra header files, because 
bind might include them already, but you'll probably need:
#include 
#include 

HTH


Pablo Aguilar


"David Morrison"  wrote in message 
news:42406A71.3030803@bnl.gov...
...
Hi,
I'm interested in using boost::bind and std::transform to iterate through 
a container of member functions and initialize another container with the 
results.  I've read through the documentation pretty carefully - in 
particular this bit from the bind documentation:
typedef void (*pf)(int);
std::vector<pf> v;
std::for_each(v.begin(), v.end(), bind(apply<void>(), _1, 5));
So I've been able to iterator through a set of *non* member functions and 
intialize another container with the results.  When I try the code below, 
I get the following error message:
boost/bind/apply.hpp:39: must use .* or ->* to call pointer-to-member 
function
   in `f (...)'
I have tried several variations involving mem_fn to try and create the 
appropriate functors, but so far, no joy.  Is there a known solution to 
accomplish what I want to do?
Dave
#include <vector>
#include <iostream>
#include <iterator>
#include "boost/bind.hpp"
#include "boost/bind/apply.hpp"
using namespace std;
using namespace boost;
struct A {
float a(int m, float x) { return m * x;}
float b(int m, float x) { return m + x;}
float c(int m, float x) { return m - x;}
float d(int m, float x) { return m / x;}
};
typedef float (A::*pfn)(int, float);
int
main()
{
  A a;
  int m = 2;
  float x = 3.0;
vector<pfn> v;
  vector<float> f;
v.push_back(&A::a);
  v.push_back(&A::b);
  v.push_back(&A::c);
  v.push_back(&A::d);
transform(v.begin(), v.end(), back_inserter(f),
    bind(apply<float>(), _1, a, m, x));
copy(f.begin(), f.end(), ostream_iterator<float>(cout, "\n"));
}