John Russo wrote:
> 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?
>
The correct syntax for getting a pointer to a member function is
&StraberryField::water. I don't know the where that's found in the
Standard but I know it's there :)
With that change it works (tested with gcc4.1.0 SuSE)
MSVC++7 accepted what you used BTW and not the correct syntax. This
changed with the 2005 version.
HTH, Peter
>
> Thanks for the help,
>
> John Russo
