Re: Borland Ada

[comar@cs.nyu.edu (Cyrille Comar)]

ncohen@watson.ibm.com (Norman H. Cohen) writes:
: The context here (a putative Borland Ada) is imaginary, but it's
: important to point out that the absence of multiple inheritance in Ada
: does not preclude importing objects defined by multiple inheritance.
: Tom Quiggle demonstrated this quite impressively by importing classes
: from a C++ class library using GNAT.

Although Tom didn't import any object coming from a Class with
multiple inheritance in its Tri-Ada Demo (I guess that is hat you are
refering to), it is true that we addressed this possibility in our
design for interfacing GNAT and C++. By the way the problem is not
importing objects but rather being able to dispatch to primitives from
the different ancestors: This is possible with our interface but not
completely trivial, you better know what you are doing (this is
definitely a low-level interface)

: Multiple inheritance and single inheritance are different ways of
: DEFINING a class.  Once the class is defined, an object of that class is
: like an object of any other class: It has a unique tag; zero or more data
                                        ^^^^^^^^^^^^^^^^^
This is unfortunately not true, an objects coming from a class that
multiple-inherits, contains more than one virtual table pointer (the
equivalent of a tag), this is what makes the interfacing not
completely trivial... 

By the way, I agree with the essence of your post, it is possible to
inherit from a C++ class  even if it uses multipe inheritance...

--
------------------------------------------------------------------------
Cyrille Comar,                                  E-mail: comar@cs.nyu.edu
Gnat Project                                    US phone: (212) 998-3489



-- 
------------------------------------------------------------------------
Cyrille Comar,                                  E-mail: comar@cs.nyu.edu
Gnat Project                                    US phone: (212) 998-3489