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Re: What does "lacks a prefix" mean?
From: |
Barry Margolin |
Subject: |
Re: What does "lacks a prefix" mean? |
Date: |
Fri, 10 Jul 2015 10:42:19 -0400 |
User-agent: |
MT-NewsWatcher/3.5.3b3 (Intel Mac OS X) |
In article <mailman.6643.1436488423.904.help-gnu-emacs@gnu.org>,
Drew Adams <drew.adams@oracle.com> wrote:
> > > And non-parallelizable theoretically :)
> >
> > Regular let isn't parallelizable. It specifies that the value
> > expressions are evaluated in order.
> >
> > The only difference between the two is the environment within which
> > later expressions are evaluated.
>
> FWIW, Common Lisp specifies that "let performs the bindings
> in parallel and let* does them sequentially."
It specifies that the bindings are done in parallel, but evaluation of
the initialization forms is sequential. From
http://www.lispworks.com/documentation/HyperSpec/Body/s_let_l.htm#let
"LET ... first evaluates the expressions init-form-1, init-form-2, and
so on, in that order, saving the resulting values. Then all of the
variables varj are bound to the corresponding values"
whereas
"LET* ... first evaluates the expression init-form-1, then binds the
variable var1 to that value; then it evaluates init-form-2 and binds
var2, and so on"
If the forms have no side effects, LET can indeed execute them in
parallel, since there's no way to tell the difference. LET* can also do
that for any initialization expressions that don't refer back to earlier
variables and have no side effects.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
- Re: What does "lacks a prefix" mean?, (continued)
- Re: What does "lacks a prefix" mean?, Filipp Gunbin, 2015/07/13
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/10
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/09
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/09
- Message not available
- Re: What does "lacks a prefix" mean?, Pascal J. Bourguignon, 2015/07/09
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/10
- Message not available
- Re: What does "lacks a prefix" mean?,
Barry Margolin <=
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/10
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/09
- Re: What does "lacks a prefix" mean?, Rusi, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/09
- Message not available
- Re: What does "lacks a prefix" mean?, Rusi, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/10
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/11
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/12
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/12