Question

I’m writing a .hpp file for a class that should receive a function as one of it’s parameters and store it in a member variable, so far my code looks like this:

template<typename Function> class myClass
{
  public:
           myClass(Function function) : pvFunction( function ) {}

           //Functor operator
           double operator() (double x) const{
             return pvFunction(x+4);
           }
  private:
           Function pvFunction
}

The program looks pointless because it is, the values it returns are not important for now. I’m simply trying to figure out how to pass a function to this class and use its functor operator. The only problems are:

1) I don’t know if this class definition is correct, meaning is this the proper way of accepting any type of function to be passed as a parameter to an object of this class.

2) how do I create an instance of this class in my program? how do I pass the function to the new object and then call it?

Been at this for quite some time and can’t seem to figure it out

EDIT:

in my program file, main.cpp, this code receives an error:

double function(double);

int main()
{
   myClass<double> myClassObject((function));
   return 0;
}

double function(double x)
{
   return (x+3.0);
}

Answer 1

1) Yes it is.

2) The Type of myClassObject from your example should be

 myClass<double(*)(double)> myClassObject(function);

since function is of type double(*)(double). The best way to construct objects of such a template, is to use a function template like this:

template<typename Function>
myClass<Function> MakeMyClass(Function f)
{
    return myClass<Function>(f);
}


int main()
{
   auto withFuncPtr= MakeMyClass(function);
   auto withLambda= MakeMyClass([] (double v) {return v*2;});

   Foo foo;
   auto withStdFunction = MakeMyClass(
       std::bind(&Foo::Method, &foo, std::placeholders::_1));
   return 0;
}