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Telos in Common Lisp. Copyright (C) Russell Bradford, August 1992, August 1993, rjb@maths.bath.ac.uk.
For educational use only.
An implementation of Telos as taken from the EuLisp document version 0.95, and from the “Balancing” paper by Harry Bretthauer et al.
There are some differences with the above descriptions, mostly due to the 2-valued nature of CL, some due to a passing attempt to integrate with the usual type hierarchy of CL, others due to laziness on my part.
Disclaimer: this code was written to help me to understand Telos and MOPs in general. Thus there are probably many features, naiveities, or even bugs. Plus the optimisations are somewhat simplistic. I am interested in hearing about bugs/improvements and so on, but won’t necessarily act upon them.
Developed on AKCL, has run on CMU, Clisp, HCL and WCL in its lifetime. Works best when compiled: otherwise somewhat slow! See the documentation strings for defclass, defgeneric, defmethod for more information.
Added attractions: describe tells you much about an object. defstructure is a simple implementation of structures. class-hierarchy gives the current subclass hierarchy. instance-hierarchy gives the current class instance hierarchy.
Version 2.0: First released version RJB 92/10/27
2.1: Fixed bug in sorting applicable methods that was revealed by MI
module RJB 92/10/29
2.2: Disambiguate find-key returning () to indicate key absent;
more checking in add-method and generic-prin RJB 93/01/11
2.3: Add remove-subclass and change defclass to aid debugging
RJB 93/01/18
2.4: Add method-lambda, call-method-function, apply-method-function;
change .method-list. to be a list of method-function-lambdas
RJB 93/01/20
2.5: Major renaming of parts, now classes are <classes>
RJB 93/01/29
2.6: Some tidying and rearrangement of redundant code: removed last
traces of support for unrestricted metaclasses
RJB 93/02/03
2.7: Added generic-lambda, and subsequent tidying; added
selective discrimination
RJB 93/03/18
2.8: Altered inheritance of initargs and initforms; added slot
initargs RJB 93/04/06
3.0: Class hierarchy rearranged and names changed to reflect latest
EuLisp definition; default slot accessors are now simple
functions; general other tidying RJB 93/12/01
3.1: Bug in lookup of methods on generics with non-discriminating
arguments fixed RJB 93/12/17
Thoughts for the day: Have add-method to call compute-discriminating-function et al, and do extra optimisation. Share method-functions amongst compatible methods. Lazy finalization of classes and gfs. trace-method