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Re: Lexical vs. dynamic: small examples?
From: |
tomas |
Subject: |
Re: Lexical vs. dynamic: small examples? |
Date: |
Sat, 14 Aug 2021 22:41:04 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sat, Aug 14, 2021 at 07:00:29PM +0000, Gregory Heytings wrote:
>
> >
> >I am trying to write a section on lexical vs. dynamic binding for
> >a tutorial on Emacs Lisp, and I am looking for very short demos
> >that show how things work differently in dynamic and in lexical
> >binding...
> >
>
> Suppose you write a function to remove unnecessary whitespaces at
> the end of lines:
>
> (defun delete-whitespace-at-eol ()
> (interactive)
> (save-excursion (replace-regexp " *$" "" nil (point-min) (point-max))))
This is a good example. There are other ones. Basically, whenever
you want some "dynamic state" to be in effect for the whole
"call tree" below you. Typically those are well-known things
with an agreed-upon purpose.
My favourite example is some kind of "debug setting" (a function,
a value, whatever).
There's a reason why the convention in CL is to have those
variable named with asterisks around, like *this*.
(I had many arguments whithin Perl. With the arrival of lexical
variables, there was a fraction which tried to convince people
to /never/ use dynamic variables, and I tried to explain that,
yes, use sparingly, but sometimes they can make code clearer.
Cheers
- t
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- Re: Lexical vs. dynamic: small examples?, (continued)
RE: [External] : Lexical vs. dynamic: small examples?, Drew Adams, 2021/08/14
Re: Lexical vs. dynamic: small examples?, Gregory Heytings, 2021/08/14
Re: Lexical vs. dynamic: small examples?,
tomas <=
RE: [External] : Re: Lexical vs. dynamic: small examples?, Drew Adams, 2021/08/14
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/14
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/14
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/14
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- RE: [External] : Re: Lexical vs. dynamic: small examples?, Drew Adams, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15