Avoiding abstract

[Oliver Ruebenkoenig]

Jarrett Billingsley Wrote:

> "Oliver Ruebenkoenig" <oliver.ruebenkoenig at web.de> wrote in message 
> news:f3kdri$ap4$1 at digitalmars.com...
> > Hi everyone,
> >
> > the following code does what i want. I was wondering if the same out put 
> > can be produced without having the abstract char [] rawSymName(); in the 
> > Expr class? Thanks for any hints and thoughts,
> >
> > Oliver
> 
> Why do you want to avoid abstract?

If i derive another class, say Integer i'd have to insert something like abstract int val(); for the value of the Integer. Now, I do not want specify an Integer for my Symbol and like wise i do not need a char []  in my Integer. How can i do this? The only thing the expressions share is their virtual head.

the following code does NOT work but shows the problem - i hope ;-)

thanks for the comments concerning the public: and private: 

Oliver

import std.stdio;

Expr mySymbol;
Expr myInteger;

public class Expr {
public:
    abstract char [] rawSymName();
    abstract int val();
    abstract Expr head();
}


class Symbol : public Expr {
public: 
    this( char [] name ) { this.itsName = name; }
    Expr head() { return mySymbol; }
    char [] rawSymName() { return this.itsName; }
private:
    char [] itsName;
}

class Integer : public Expr {
public: 
    this( int value ) { this.itsValue = value; }
    Expr head() { return myInteger; }
    int val() { return this.itsValue; }
private:
    int itsValue;
}


int main( char [][] arg ) { 

    Expr myString;
    Expr myInt;

    mySymbol = new Symbol("Symbol");
    myString = new Symbol("String");
    myInteger = new Symbol("Integer");
    anInt = new Integer(42);

    writefln(mySymbol.rawSymName() );
    writefln(mySymbol.head().rawSymName() );
    writefln(mySymbol.head().head().rawSymName() );

    writefln(myString.head().head().rawSymName() );
    writefln(myInteger.head().rawSymName() );

//    writefln(anInt.val() );

    return 0;
}