pointer to any member function of any class

Subject: pointer to any member function of any class.

The "C++ FAQ Lite" explains how to hand a pointer to a member function
to a signal handler etc, but only to a static function (33.2), to
a fixed class (33.2), any member of a fixed class (33.6), to a fixed
function of any object (functiods, 33.10).

What I wanted was to be able to hand any member function of any
created object to a signal hander etc.

The code below achieves this, using functiods and templates. The code
compiles cleanly with "g++ -Wall -pedantic" (g++ 4.0 & 4.1), haven't
tried other compilers.

#include <iostream>
using namespace std;

//The base-class of the functiod:
class callbase{
public:
  virtual ~callbase(){};
  virtual int operator() (int i)=0; //Change/add arguments to taste
};

template<class classtocall>
class calltemplate:public callbase{
  classtocall &object;
  int (classtocall::*methodtocall)(int);
public:
  calltemplate(classtocall &o,int (classtocall::*m)(int))
  : object(o){
    methodtocall=m;
  }
  int operator()(int i){ //Change/add arguments to taste
    return (object.*methodtocall)(i);
  }
};

//the signal handler, system call that starts a thread, etc:
class handler {
  callbase *m;
public:
  handler(callbase *b):m(b){};
  int h(int i){
    return (*m)(i); //Change/add arguments to taste
  }
};

// A class whose memebers we want to pass to a signal handler etc.
class worker {
  int i; //data member, just to show each instance is different
public:
  worker(int j):i(j){}
  int callme(int j){ //Change/add arguments to taste
    return j*i;
  }
  int pleasecall(int j){
    return j+i;
  }
};

//need a typedef for each class whose members we want to be called
typedef calltemplate<worker> call_worker;

int main (){
  worker w1(3);
  worker w2(7);
  handler h1(new call_worker(w1, &worker::pleasecall));
  handler h2(new call_worker(w2, &worker::callme));

  callbase *members[]={
    new call_worker(w1, &worker::callme),
    new call_worker(w2, &worker::pleasecall)};
  cout<<"h1 met arg 4="<<h1.h(4)<<endl;
  cout<<"h2 met arg 4="<<h2.h(4)<<endl;
  cout<<"arraymember: "<<(*members[0])(3)<<endl;;
  cout<<"arraymember: "<<(*members[1])(3)<<endl;;
}