functors and callbacks

[John Russo <j dot russo at caspur dot it>]

Hello list,

I'm having some problems using functors to implement callbacks.

I tried to compile the following code with g++ version 4.0.1 and 3.3.6

class Functor
{
   public:
       virtual void operator()(double)=0;
};

template<class TClass>
class SpecFunct: public Functor
{
   public:
       SpecFunct(TClass* _ob,void 
(TClass::*_f)(double)):fpt(_f),object(_ob){}
       virtual void operator()(double num)
       {
           (*object.*fpt)(num);
       }
  
   private:
       void (TClass::*fpt)(double);
       TClass* object;
};

class TemperatureSensor {
              
       public:
           TemperatureSensor():temperature(10.){}
          
           void get_temperature(Functor* func)
           {
              
               if (temperature>5.)
                   (*func)(temperature);
           }
   private:
       double temperature;
};

class StrawberryField{
  
   public:
              
       StrawberryField(TemperatureSensor* pr):sensor(pr){}
      
      
       void water(double temp)
       {
           std::cout << "The temperature is " << temp <<" let's put 
some water " << std::endl;
       }
      
       void ask_sensor(Functor *func)
       {
           sensor->get_temperature(func);
       }
      
      
   private:
       TemperatureSensor *sensor;
  
};

int main()
{
  
   TemperatureSensor sensor;
  
   StrawberryField field(&sensor);
  
   SpecFunct<StrawberryField> functor(&field,StrawberryField::water);
  
   field.ask_sensor(&functor);
  
   return 0;
}



but I get the following error message:

bash-3.00$ g++ Fun_eng.cpp
Fun_eng.cpp: In function `int main()':
Fun_eng.cpp:69: error: no matching function for call to `
  SpecFunct<StrawberryField>::SpecFunct(StrawberryField*, <unknown type>)'
Fun_eng.cpp:11: error: candidates are:
  SpecFunct<StrawberryField>::SpecFunct(const SpecFunct<StrawberryField>&)
Fun_eng.cpp:13: error:                 SpecFunct<TClass>::SpecFunct(TClass*,
  void (TClass::*)(double)) [with TClass = StrawberryField]


I tried the same code with the Intel Compiler and it compiles and runs 
without problems. What's wrong?


Thanks for the help,

 John Russo