help-gnu-emacs
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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 <address@hidden>,
 "Pascal J. Bourguignon" <address@hidden> wrote:

> Stefan Monnier <address@hidden> 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, address@hidden
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***


reply via email to

[Prev in Thread] Current Thread [Next in Thread]