From: "A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
To: DJGPP AT SUN DOT SOE DOT CLARKSON DOT EDU
Date: Wed, 26 Jul 1995 11:46:50 BST
Subject: Function members of classes: 2 queries

  (1) How can I (say) declare a class of 8 bytes, the first 4 bytes are a
long, the other 4 bytes are a function entry address? If I write:-
    class qaz{long code; double fn(double); ......};
    qaz Sin, Cos, Exp, *q; double x;
    Sin.code=1; Cos.code=2; Exp.code=3;
    Sin.fn=sin; Cos.fn=cos; Exp.fn=exp;
    q->fn(x);
  I of course go hopelessly astray.

  (2) If I declare:-
    class qwerty{public: int q,w,e,r,t,y; ...........};
    class qwertyuiop : public qwerty{int u,i,o,p; .............};
    qwertyuiop Q; qwerty*W;
  how can I set `W' to point to the `qwerty' value which is within the
`qwertyuiop' value `Q'?

  (3) If I write e.g. `double (fn*)(double);', then `fn' can contain the entry
address of sin() or cos() or exp() or any other function of that argument and
result pattern which is not a class member. If I then declare:-
    class zoo{public: ...........
      double    yak(double x){................};
      double    gnu(double x){................};
      double   gaur(double x){................};
      double duiker(double x){................};
      double  eland(double x){................};......};
  how can I declare a pointer variable that can point to any one of the five
above-declared functions?
    double (ruminant*)(double);
  looks a likely starting point, but I likely need to insert `zoo.' or `zoo->'
or `zoo::' somewhere in it. Or would this work?:-
    double (ruminant*)(zoo&,double);
  Once I have done that, would this work?:-
    ruminant = zoo::yak;