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From: andy@Shasta.STANFORD.EDU (Andy Freeman)
Newsgroups: net.lang.lisp
Subject: Re: Against the Tide of Common LISP
Message-ID: <654@Shasta.STANFORD.EDU>
Date: Wed, 2-Jul-86 22:40:51 EDT
Article-I.D.: Shasta.654
Posted: Wed Jul  2 22:40:51 1986
Date-Received: Fri, 4-Jul-86 08:38:02 EDT
References: <1311@well.UUCP> <3827@utah-cs.UUCP> <1316@well.UUCP> <3837@utah-c <1372@well.UUCP>
Reply-To: andy@Shasta.UUCP (Andy Freeman)
Organization: Stanford University
Lines: 22

(apply foo <args>) should be interpreted iff the function it is
in is interpreted or it is typed at top level (or appears at top
level in a file that is loaded).  The function being called will
be interpreted if it hasn't been compiled but what's strange about
that?  If the function was compiled, then compiled code will be run.
Any implementation that can't handle this is wrong.

It is possible to do lexical variable reference in interpreted code
as fast as deep-binding lookup of dynamic variables.  Deep-binding 
lookup in compiled code isn't much faster than it is in interpreted
code.  (The exception to this is when it can be shown equivalent to
lexical scope.  Unfortunately, broken compilers don't bother to
prove equivalence, they just change the semantics.)  Lexical variable
reference is much faster in compiled code than in interpreted code.

For those of you who are saying "but shallow-binding is much faster,
why would anyone use deep-binding", think about multi-processors, or
even multi-tasking.  Now name a lisp machine that uses shallow-binding.
Shallow-binding only works in a very restricted environment.  No
one wants to work in that kind of environment anymore.

-andy