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From: boning@boning.applicon.UUCP
Newsgroups: comp.lang.c++
Subject: Function Arguments
Message-ID: <31900002@boning>
Date: Tue, 26-May-87 14:58:00 EDT
Article-I.D.: boning.31900002
Posted: Tue May 26 14:58:00 1987
Date-Received: Sun, 31-May-87 20:48:52 EDT
Lines: 36
Nf-ID: #N:boning:31900002:000:1084
Nf-From: boning.applicon.UUCP!boning    May 26 14:58:00 1987



I'm new to C++ and I've come across a problem trying to use derived 
classes as argument types for base class functions.

Suppose I have a base class and another class derived from the base class.
I must declare the base class before the derived class. Then, if I try 
to use the derived class as an argument to a function in the base class 
the compiler signals an error since the derived class hasn't been defined 
yet.

Is there any way to use a derived class as an argument to a base class?
I don't want to use a void pointer and lose type checking.

The example I'm thinking of is a base class 'geometry' which has 
derived classes 'edges' and 'polygons'.  I want to have a function
'get_edges' under 'geometry' which will find the edges belonging to 
a piece of geometry, ie

  class geometry {
   public:
    void get_edges(edges *);
  };

  class edges: public geometry {
  ...
  };

Can I do this in C++? 

Thanks in advance,

				Peggy Boning.

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