Re: Is it legal code?

From:
Leigh Johnston <leigh@i42.co.uk>
Newsgroups:
comp.lang.c++
Date:
Tue, 01 Mar 2011 18:47:09 +0000
Message-ID:
<25KdnV4gcdKwovDQnZ2dnUVZ8oSdnZ2d@giganews.com>
On 01/03/2011 18:41, Paul wrote:

"Gerhard Fiedler" <gelists@gmail.com> wrote in message
news:7l4qxi2mntr9.dlg@gelists.gmail.com...

Paul wrote:

I think this proves the same point using standard C++ code:

#include <iostream>
class Animal{public:
virtual void eat(){std::cout<< "Animal Eating"<< std::endl;}
virtual int getID()=0;
static int count;
};
class Dog: public Animal{
public:
void eat(){std::cout<< "Dog Eating"<< std::endl;}
int getID(){return 1;}
};
class Cat: public Animal{
public:
void eat(){std::cout<< "Cat Eating"<< std::endl;}
int getID(){return 0;}
};
int Animal::count =10;

Dog* overwriteCat(Animal* ptr){
delete ptr;
Dog* p = reinterpret_cast<Dog*>(ptr);
p = new Dog;
return p;
}

Cat* overwriteDog(Animal* ptr){
delete ptr;
Cat* p = reinterpret_cast<Cat*>(ptr);
p = new Cat;
return p;
}

void ordinary_function(Animal* obj){
Animal::count--;
std::cout<<"Address of obj: " <<obj << " ";
obj->eat();
if(obj->getID()){overwriteDog(obj);}
else {overwriteCat(obj);}
if(Animal::count){
ordinary_function(obj);
}
}

int main()
{
Cat* p_cat = new Cat;
Animal* p_anim = p_cat;

ordinary_function(p_cat);
}


What point are you trying to prove with this code?


It proves a function can be recursed with a different object parameter
each recursion.

This cannot be done with a NSMF, thus it proves a significant difference
between an ordinary function an a NSMF.


struct foo
{
    ...
    void wibble()
    {
        ...
        foo differentObject;
        differentObject.wibble();
        ...
    }
    ...
};

/Leigh

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