Polymorphism ..Anyone??

[madhosh]

Where can I find good material on how polymorphism is internally implemented in C++. ?
Thanks

 

[Cagliostro]

I think you can just look into disassembler code. If you want, I posted a code on OOP in C in C forum thread205-115970. Almost the same way is in C++ but is hidden. If you have some more questions, please ask, because I posted a very short sample. It can be made much more labile with some small adds, but in this case it will be much hard to understand. John Fill

ivfmd@mail.md

 

[greatkingrat]

I think it is simple, it is implemented by
internally performed compile-time C++ name mangling
rules and function pointer for virtual functions.
Hee S. Chung
heesc@netian.com

http://www.netian.com/~heesc

 

[Cagliostro]

yes, in C++ is much more simple. All theese details are hidden. John Fill

ivfmd@mail.md

 

[tekbond007]

hai everybody,

I feel polymarphism is used for very good user interaction. Simply what is polymarphism ? Object behaves differently in different situation based on the given input parameter.

Suppose if ur creating a userdefined class u for example a calculator class u have to write methods for adding two integers and another method which accepts two flotes like different combinations. Insted of giving different method names u are giving same name so that the end user need not remember different methods. a single method will satisfy all his needs by accepting different type of input paramethers. If u want program send me mail i will sent to u thru mail

Bye

 

[Cagliostro]

#include<iostream.h>
class computer
{
public:
virtual void start() = 0;//means pure virtual function
};//because of pure virtual the class is abstract and can't
//be instanciated directly
class pcublic computer
{
public:
virtual void start()
{cout<<&quot;start_the_pc();&quot;<<endl;}
};
calss makintosh
{
public:
virtual void start()
{cout<<&quot;start_the_makintosh();&quot;<<endl;}
};
void start_computer(computer* cmp)
{
cmp->start();
}
//using computer
int main()
{
computer* xx;
xx = new pc;
start_computer(xx);
delete xx;
xx = new makintosh;
start_computer(xx);
delete xx;
xx = GetCompInterfaceFromOtherPlace
(&quot;for example some CORBA interface if exists such one&quot;
start_computer(xx);
delete xx;
}
//as you see the interface is declared as computer, but it can be not implemented always in your program. It is a only a interface to a memory location where you don't know anything about it. John Fill

ivfmd@mail.md

 

[brudnakm]

All,

When C++ was first developed, it was in the form of a code generator which converted C++ code into C code. The user would then compile the generated C code using their normal C compiler. This program was developed by AT&T and was called cfront (I think).

If you could find this program, and generate a C file from a C++ file, then you can see exactly how the language implements polymorphism, inheritence, classes, etc!!

Of course, modern compilers do a direct compile, so this is currently not available.

Brudnakm