From: Andy Wingo <wingo@pobox.com>
To: Michael Lucy <MichaelGLucy@Gmail.com>
Cc: Ken Raeburn <raeburn@raeburn.org>, guile-devel@gnu.org
Subject: Re: expression
Date: Thu, 24 Jun 2010 15:05:38 +0200 [thread overview]
Message-ID: <m3hbks7f8d.fsf@pobox.com> (raw)
In-Reply-To: <AANLkTimNBbhJWnSWewhL6n1Rs7E1iSKeK5nkwLXJDGeg@mail.gmail.com> (Michael Lucy's message of "Thu, 24 Jun 2010 02:52:26 -0500")
Hi,
On Thu 24 Jun 2010 09:52, Michael Lucy <MichaelGLucy@Gmail.com> writes:
> scheme@(guile-user)> ,c (begin a b 1)
> Disassembly of #<objcode d123d28>:
>
> 0 (assert-nargs-ee/locals 0)
> 2 (load-symbol "a") ;; a
> 7 (link-now)
> 8 (variable-ref)
> 9 (drop)
> 10 (load-symbol "b") ;; b
> 15 (link-now)
> 16 (variable-ref)
> 17 (drop)
> 18 (make-int8:1) ;; 1
> 19 (return)
>
> Out of curiosity, why are variables left in? Are there situations
> where evaluating a variable will have side-effects?
Global variable references can cause side effects (exceptions, module
autoloads, binders, duplicates handlers, etc) so they are not optimized
out. Lexical references cannot cause side effects, so they are optimized
out.
Andy
--
http://wingolog.org/
next prev parent reply other threads:[~2010-06-24 13:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-23 21:09 expression Michael Lucy
2010-06-23 23:14 ` expression No Itisnt
2010-06-23 23:23 ` expression Michael Lucy
2010-06-24 13:01 ` expression Andy Wingo
2010-06-24 6:55 ` expression Ken Raeburn
2010-06-24 7:27 ` expression Thien-Thi Nguyen
2010-06-24 7:52 ` expression Michael Lucy
2010-06-24 13:05 ` Andy Wingo [this message]
2010-06-24 13:03 ` expression Andy Wingo
2010-06-24 14:40 ` expression Ken Raeburn
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