🚀 go-pugleaf

  Hello. I am a new user of Z and I have a question about handling
derived types in Z.  Suppose there is a class A, and also, class B and
C derived from A (the below example is written in C++).

  class A {          class B : public A {       class C : public A {
    ..                 ..                         ..
    some_op();       };                         };
  };       

  A::some_op can process objects of either class B or C, but accesses
only the components of A, leaving other components of B or C unchanged.

  My question is that how I can write the specification of operations
  like some_op(). 

--
Yasushi Saito
  Access Co. Ltd.  Tokyo, Japan.