🚀 go-pugleaf

| QUESTION 1:
| why doesn't c++ accept the template function
| has_property (const Property<Obj>&) as a specialization of
| has_property (const Obj&). (idem for set_property).

| QUESTION 2:
| According to c++ standard, is there a way to define global functions
| has_property and set_property that enable to write for any object:

       obj.has_property();

| that would enable to define these as Property's methods.

| this programming approch intents to design simple objects then
| add to these objects template properties (ex: color, sharability
| and so on). An object with some properties has the general
| functionalities of the base class and some additional
| functionalities associated with its properties.

#include <iostream.h>

enum boolean {false, true};

class MyObj {
    unsigned i_;
public:
    MyObj (unsigned i) : i_ (i) {}
};

template <class Obj> class Property : public Obj {
    unsigned	prop_;
public:
    Property (const Obj& o)			: Obj (o), prop_ (0) {}
    Property (const Obj& o, unsigned prop)	: Obj (o), prop_ (prop) {}
    void set_property (unsigned p) {prop_ = p;}
};

template <class Obj> boolean has_property (const Property<Obj>&) {return true;}
template <class Obj> boolean has_property (const Obj&) {return false;}
template <class Obj> void    set_property (Property<Obj>& o, int p) {o.set_property(p);}
template <class Obj> void    set_property (Obj&, int) {throw "don't have property";}

void main ()
{
    MyObj o1 (10);
    Property<MyObj> o2 (20);
    cout << has_property (o1) << "," << has_property(o2) << endl;
    set_property (o1,1);
    set_property (o2,1);
}

thank you to enlight me. regards.

jlm


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