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From: mcconnel@zodiac.ads.com (Chris McConnell)
Newsgroups: comp.lang.lisp,comp.sys.mac.programmer
Subject: Re: Anyone using pcl (clos) under Allegro Common Lisp?
Message-ID: <3978@zodiac.UUCP>
Date: 19 May 88 17:43:22 GMT
References: <24158@ucbvax.BERKELEY.EDU>
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Reply-To: mcconnel@ads.com (Chris McConnell)
Organization: Advanced Decision Systems, Mt. View, CA (415) 960-7300
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The current version of PCL is implementing most of the Common Lisp
Object System (CLOS).  This will be the Object Oriented Programming
standard for Common Lisp.  I believe it will be officially approved
sometime in June.  

PCL is fairly portable.  I plan to bring it up in Allegro in the next
month.  If you accept the most generic implementation, it should
already run in Allegro.  (In fact, it may even have optimizations
already since Allegro is really Franz and it already runs in Franz.)
There are numerous ways to get it to run faster on a given
implementation, but modifying the PCL code requires a very good
knowledge of Lisp.  I have done a lot of it fixing bugs and adding
features, and I can tell you that it is no picnic.

I ran some benchmarks a while ago on a Symbolics and a Sun running
Lucid.  The speed was better than I thought it would be for an early
and portable implementation.  Creation is slow, but execution speed of
generic functions is very good.  (Some of this is due to the caching
mechanism that makes more recent methods faster.)  We developed an
image understanding environment using it, so the speed can't be too
slow! 

I have been working in CLOS for a year (> 25,000 lines), and I have to
say that even in its presently incomplete state that I love it.  I
have worked extensively in Flavors, an in house system called SOPE and
some in Smalltalk.  CLOS is far and away my favorite.  Multiple
specializers are great, especially on normal Lisp objects.  The spec
takes great pains to make all of the hooks that are needed available
and public while still allowing implementations to do all of the
things that are required to make things run fast.