. . .
> I was hoping that the examples I requested would be examples of
> particular control constructs or extensions to the language's syntax
> and semantics. Though I admit that such things are possible in lisp,
> I suspect that their utility is minimal.
As to utility, quite the contrary, I think. Offhand I can think of the
screamer package for Common Lisp, which provides non-deterministic
mechanisms for use in backtracking applications. For a while in the
80's there was practically a cottage industry implementing various
flavors of Prolog and other Logic Programming languages in Lisp; one
notable example was LogLisp. I think many of the more advanced
constructs in CL were originally macro extensions to the earlier lisps;
e.g. structures, objects and classes, the LOOP macro, streams and
iterators, generalized setters and getters.
Actors, which was one of the ancestors of OOP, was first as a Lisp
extension. In the AI hayday of the mid-80's most of the expert system
shells, providing forward and backward chaining mechanisms, frames and
semantic nets, and object-centered and data-driven programming, were
originally implemented as packages integrated into Lisp.
All of these made non-trivial extensions to Lisp, and all were of
arguably great utility.
-- Bill Wood
[EMAIL PROTECTED]
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