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Re: Why are there two dolist?
From: |
Harald Hanche-Olsen |
Subject: |
Re: Why are there two dolist? |
Date: |
Tue, 11 Aug 2009 19:30:25 -0400 (EDT) |
+ Lennart Borgman <address@hidden>:
> On Wed, Aug 12, 2009 at 12:51 AM, Miles Bader<address@hidden> wrote:
> > I haven't looked at the code (recently), but because elisp doesn't
> > natively support lexical blocks, I suspect the cl-macs version either
> > (1) adds unnecessary runtime overhead, or (2) drags in lots of big and
> > crufty compile-time analysis code (cl.el has lots of this) to optimize
> > away the block when not used.
Actually, the cl-macs version looks pretty simple to me.
> Maybe the CL version should go away instead? It creates a lexically
> scoped block with a name nil. The explanation in (defmacro block ...)
> does however not say what is lexically scoped so I have no clue.
AFAICT, the only thing lexically scoped is the name of the block.
In other words, (return-from NAME) will return from the innermost
block named NAME that lexically contains the return-from form. I think
this is pretty well explained in the block docstring?
> (And I do not know if return-from mentioned there can work with a
> nil name.)
(return-from nil) is perfectly good CL, so it ought to work.
> However if if means that one dolist version makes VAR lexically scoped
> and the other does not, then the difference is big.
But it doesn't mean that, as a simple experiment bears out. I think
the only difference between the two is the block, and that will not
affect any elisp code that is unaware of block and return-from.
- Harald
- Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Miles Bader, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Miles Bader, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?,
Harald Hanche-Olsen <=
- Re: Why are there two dolist?, Miles Bader, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Miles Bader, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Harald Hanche-Olsen, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Miles Bader, 2009/08/11
- Re: Why are there two dolist?, Lennart Borgman, 2009/08/11
- Re: Why are there two dolist?, Harald Hanche-Olsen, 2009/08/11