* Canonical add-hook idiom
@ 2003-11-15 5:35 Bob Nelson
2003-11-15 8:25 ` Oliver Scholz
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Bob Nelson @ 2003-11-15 5:35 UTC (permalink / raw)
What is the preferred approach given these examples:
1). (add-hook 'some-mode-hook (lambda () [...]
2). (add-hook 'some-mode-hook '(lambda () [...]
3). (add-hook 'some-mode-hook (function (lambda () [...]
4). None of the above -- please explain.
--
=============================================================================
Bob Nelson -- Dallas, Texas, USA (nelsonbe@earthlink.net)
http://www.oldradio.com/archives/nelson/open-computing.html
Good engineering is finding the right wrench to pound in the correct screw
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Canonical add-hook idiom
2003-11-15 5:35 Canonical add-hook idiom Bob Nelson
@ 2003-11-15 8:25 ` Oliver Scholz
2003-11-15 18:27 ` Henrik Enberg
2003-11-15 16:55 ` Jesper Harder
2003-11-16 23:26 ` Stefan Monnier
2 siblings, 1 reply; 5+ messages in thread
From: Oliver Scholz @ 2003-11-15 8:25 UTC (permalink / raw)
Bob Nelson <bnelson@nelsonbe.com> writes:
> What is the preferred approach given these examples:
>
> 1). (add-hook 'some-mode-hook (lambda () [...]
> 2). (add-hook 'some-mode-hook '(lambda () [...]
> 3). (add-hook 'some-mode-hook (function (lambda () [...]
> 4). None of the above -- please explain.
[...]
I definitely prefer (1).
Some would prefer #'(lambda () ...), which for the Lisp interpreter
is the same as (3). But AFAIK this is just a Common Lisp idiom and
it makes no difference in Emacs Lisp.
Oliver
--
25 Brumaire an 212 de la Révolution
Liberté, Egalité, Fraternité!
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Canonical add-hook idiom
2003-11-15 5:35 Canonical add-hook idiom Bob Nelson
2003-11-15 8:25 ` Oliver Scholz
@ 2003-11-15 16:55 ` Jesper Harder
2003-11-16 23:26 ` Stefan Monnier
2 siblings, 0 replies; 5+ messages in thread
From: Jesper Harder @ 2003-11-15 16:55 UTC (permalink / raw)
Bob Nelson <bnelson@nelsonbe.com> writes:
> What is the preferred approach given these examples:
>
> 1). (add-hook 'some-mode-hook (lambda () [...]
> 2). (add-hook 'some-mode-hook '(lambda () [...]
> 3). (add-hook 'some-mode-hook (function (lambda () [...]
> 4). None of the above -- please explain.
1) or 4).
It's sometimes better to avoid lambda and add a function instead.
This makes it easier to remove it from the hook again:
(add-hook 'foo-hook 'bar)
;; Oops, bar didn't work as expected:
(remove-hook 'foo-hook 'bar)
Removing isn't quite as easy for lambda's.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Canonical add-hook idiom
2003-11-15 8:25 ` Oliver Scholz
@ 2003-11-15 18:27 ` Henrik Enberg
0 siblings, 0 replies; 5+ messages in thread
From: Henrik Enberg @ 2003-11-15 18:27 UTC (permalink / raw)
Oliver Scholz <alkibiades@gmx.de> writes:
> Bob Nelson <bnelson@nelsonbe.com> writes:
>
>> What is the preferred approach given these examples:
>>
>> 1). (add-hook 'some-mode-hook (lambda () [...]
>
> I definitely prefer (1).
>
> Some would prefer #'(lambda () ...), which for the Lisp interpreter
> is the same as (3). But AFAIK this is just a Common Lisp idiom and
> it makes no difference in Emacs Lisp.
In addition using #'(lambda () ...) or '(lambda () ...) means the lambda
form won't be compiled if the file is.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Canonical add-hook idiom
2003-11-15 5:35 Canonical add-hook idiom Bob Nelson
2003-11-15 8:25 ` Oliver Scholz
2003-11-15 16:55 ` Jesper Harder
@ 2003-11-16 23:26 ` Stefan Monnier
2 siblings, 0 replies; 5+ messages in thread
From: Stefan Monnier @ 2003-11-16 23:26 UTC (permalink / raw)
> What is the preferred approach given these examples:
> 1). (add-hook 'some-mode-hook (lambda () [...]
> 2). (add-hook 'some-mode-hook '(lambda () [...]
> 3). (add-hook 'some-mode-hook (function (lambda () [...]
> 4). None of the above -- please explain.
The '(lambda form is to be avoided: the ' says "what follows
is pure data" whereas what follows is actually code, so it's
confusing (I expect humans won't get confused, but byte-compilers
do get confused).
`lambda' is a macro that expands to (function (lambda so the two are
pretty much interchangeable. As for #'(lambda, it is a shorthand
for (function (lambda.
I thus recommend (lambda since it's the shortest and ask people to stay away
from '(lambda since it poses problems to the byte-compiler (as well as to
other code-walkers such as some fancy CL macros (typically
`lexical-let')). But if you prefer #(lambda or (function (lambda,
that's OK: you won't burn in hell for it.
Stefan
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2003-11-15 5:35 Canonical add-hook idiom Bob Nelson
2003-11-15 8:25 ` Oliver Scholz
2003-11-15 18:27 ` Henrik Enberg
2003-11-15 16:55 ` Jesper Harder
2003-11-16 23:26 ` Stefan Monnier
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