Collegues:

I would like to point out some aspects of Fortran's tenative inheritence
model that were not made explicit in Van Snyder's current proposal

1. Like most object oriented languages, but unlike C++ and CLOS, it has a
single inheritence model. This simplifies the implementation at the cost of
some flexibility.

2. Like most object oriented languages, polymorphism is strongly tied to
the inheritence chain. This is in contrast to Java which separates
interface from implementation. This reduces the amount of new syntax at a
cost of some flexibility.

3. Its design facilitates single dispatch, which simplifies the
implementation. Combining single dispatch with multiple inheritence, a la
C++, has proved confusing and error prone, and true multimethods, a la
CLOS, are very difficult to implement efficiently and maintain separate
compilation.

4. To compensate for the potential loss of performance implied by tying
polymorphism to the inheritence chain, it is expected that the use of
polymorphic behavior needs to be explicitly invoked, but the detailed
syntax for that invocation has not been defined.



 William B. Clodius            Phone: (505) 665-9370
 Los Alamos Natl. Lab., NIS-2  FAX: (505) 667-3815
 PO Box 1663, MS-C323          Group Off.: 505/667-3422 or 667-5127
 Los Alamos, NM 87545          email: [log in to unmask]




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