Path: utzoo!attcan!uunet!crdgw1!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!caen!hellgate.utah.edu!cdr.utah.edu!moore
From: moore%cdr.utah.edu@cs.utah.edu (Tim Moore)
Newsgroups: comp.lang.lisp
Subject: Re: STRUCTUREP
Message-ID: <1990Oct10.130925.18317@hellgate.utah.edu>
Date: 10 Oct 90 19:09:24 GMT
References: <753@forsight.Jpl.Nasa.Gov> <1990Oct10.091722.4495@hellgate.utah.edu> <754@forsight.Jpl.Nasa.Gov>
Organization: University of Utah CS Dept
Lines: 47

In article <754@forsight.Jpl.Nasa.Gov> gat@robotics.Jpl.Nasa.Gov (Erann Gat) writes:
>You are right, of course.  However, there are a number of things that you
>can do in T which you can't do in Common Lisp.  Among these are:
>
>1.  Create callable objects (which allow you to do things like SETF a locative
>passed to a function as an argument)

I'm not sure what you mean by this. If you mean that T has locatives,
it's not hard to simulate locatives in Common Lisp (see Lisp Pointers,
vol. 2 no. 2); they're just closures that encapsulate the information
needed to store into the general variable (I think that's essentially
what they are in T; feel free to correct me).

I think that locatives a la Lisp Machine Lisp (essentially pointers)
are impractical without massive gc complexity or microcode support.

>2.  Tell if an object is a structure :-)

It's unclear why you want to do this. Only system code should really
need a structurep.

>Personally, I think that it's the "and much more" part that is Common
>Lisp's biggest problem.  It's getting to the point where it is very difficult
>to get a grip on the entire language.  Not only does this make CL hard to
>write, it encourages writing code that is nearly impossible to read without
>a copy of CLTL in hand (and sometimes even then).  (It also makes it harder
>to tell when some crtitical feature has been omitted from the language :->)

The "hard-to-write" argument is the one I hear most frequently,
especially around here (where we are close to finishing a CL
implementation). I think only a handful of people (Lisp implementors)
really care about this.

I don't think Common Lisp function names are cryptic. There are a few
macros whose syntax is unfortunate, mostly for hysterical raisons. 

I keep a copy of CLTL around when I write code, mostly to check that
what I'm about to write isn't already part of the language. It's easy
to write obscure code in any Lisp.

>
>Just my opinion.
>E.
That's what the net is for!
Tim Moore                    moore@cs.utah.edu {bellcore,hplabs}!utah-cs!moore
"Ah, youth. Ah, statute of limitations."
		-John Waters