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Re: Always using let*
From: |
Barry Margolin |
Subject: |
Re: Always using let* |
Date: |
Mon, 15 Sep 2014 09:14:46 -0400 |
User-agent: |
MT-NewsWatcher/3.5.3b3 (Intel Mac OS X) |
In article <87mwa1lhb1.fsf@kuiper.lan.informatimago.com>,
"Pascal J. Bourguignon" <pjb@informatimago.com> wrote:
> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
> >> Lisps such as Common Lisp were specifically designed with this
> >> parallel evaluation in mind. The spec (and CLTL(2)) specifically
> >> emphasizes the inherent parallelism (independence) here that
> >> implies the *possibility* of parallel evaluation.
> >
> > I simply claim that this is bogus. Only the var-binding is "parallel", not
> > the computation of each value. So it's a "parallel binding" semantics,
> > but it has nothing to do with efficient execution on multiple
> > execution units.
>
> The claim is not bogus. It's just that in general, in presence of side
> effects, since the expressions must be evaluated from left to right,
> indeed, only the assignments can be performed in parallel.
If the LET can be done in parallel, so could LET*. Remember, we're
talking about compiled code. The inner and outer variables are not the
same memory location, even if they have the same name. The difference
between LET and LET* just has to do with which scope the compiler looks
up the name in.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
- RE: Always using let*, (continued)
- Message not available
- Re: Always using let*, Stefan Monnier, 2014/09/14
- Re: Always using let*, Pascal J. Bourguignon, 2014/09/14
- Re: Always using let*, Stefan Monnier, 2014/09/15
- RE: Always using let*, Drew Adams, 2014/09/15
- Re: Always using let*, Stefan Monnier, 2014/09/15
- Message not available
- Re: Always using let*, Emanuel Berg, 2014/09/15
- Re: Always using let*, Pascal J. Bourguignon, 2014/09/15
- Re: Always using let*,
Barry Margolin <=