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Path: utzoo!linus!security!genrad!decvax!duke!phs!smh@mit-eddie.UUCP (Steven M. Haflich)
From: smh@mit-eddie.UUCP
Newsgroups: net.lang
Subject: Re: Anti-CLU... Anti-Strong-Typing...
Message-ID: <957@mit-eddi.UUCP>
Date: Thu, 24-Nov-83 09:09:41 EST
Article-I.D.: mit-eddi.957
Posted: Thu Nov 24 09:09:41 1983
Date-Received: Sun, 27-Nov-83 03:42:08 EST
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Path:duke!decvax!genrad!mit-eddie!smh
Message-ID:<957@mit-eddie.UUCP>
Date:Thu, 24-Nov-83 09:09:41 EST
Organization:MIT, Cambridge, MA


	The actor languages perhaps have a nicer idea of types, since
	users can create their own types with somewhat less fuss than
	in languages like CLU etc.  Still, I have not used Smalltalk
	(eg) so I can't really say.

	Can someone who uses actor languages regularly join the fray,
	and say whether or not types work out well in them?

Just a reminder that active object programming is available in Lisp
as well as in smalltalk.  The active objects are called `flavors'
in keeping with the notion that new flavors may be created by mixing
of existing ones.  Lisp flavors are thought by some to be superior
to Smalltalk actors (with which I have no personal experience)
because Smalltalk method inheritance is strictly hierarchical.
(Is this still true?)  Lisp flavors have been extensively used,
even for tasks which might be considered `system programming.'
For instance, the window system for Lisp Machines is built upon the
flavor system.

Flavors are available on MIT Lisp Machines as well as those from
Symbolics and (I presume) LMI.  The MIT LM flavor code has been ported
into Franz, although licensing restrictions on the code may prevent
distribution.  (Or maybe not -- I'm not sure anyone has actually
checked.)  An independent but largely compatible implementation is
available from U-Maryland, as recently advertised in many of these same
newsgroups.  Finally, compatible flavors are an integral part of ylisp,
an experimental (i.e. non-production) Lisp available from Hebrew
University.  Somewhat different active objects are a feature of T Lisp,
available from Yale for Vaxex and 68000s.

A comment on the subject of strong typing and variable array bounds:
Even without flavors, many Lisps treat arrays as functional objects
which carry pointers to their accessor functions.  Thus even lowly
arrays are defined in terms of their response (when evaluated) instead
of in terms of their static storage and dimensions.  While this is
perhaps the `right' way to do things, almost all Lisps contain ugly
alternative kinds of array-like objects (e.g. hunks or vectors) which
avoid the extravagance in running time.

Steve Haflich, MIT Experimental Music Studio