Lisp Syntax #| ???
Jim Cheng
I am a new comer to lisp.
Is #| ... #1 used for annotation in Lisp?
for example, the contents between #| and #| are just annotations ?
#|(defstruct node
(x0) ;; after rotation
(y0)
(x1)
(y1)
(line)
) #|
Thanks!
Jim
Barry Margolin
>Is #| ... #1 used for annotation in Lisp?
>
>for example, the contents between #| and #| are just annotations ?
Yes. The term most computer programmers use (at least in the US) is
"comments".
However, the end is marked with |#, not #|. This is similar to many other
languages that have paired-up comment markers, e.g. /* ... */ in PL/I and
C.
--
Barry Margolin, bar...@genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
Christophe Rhodes
> In article <3988AB66...@yahoo.com>, Jim Cheng <jim...@yahoo.com> wrote:
> >Is #| ... #1 used for annotation in Lisp?
> >
> >for example, the contents between #| and #| are just annotations ?
>
> Yes. The term most computer programmers use (at least in the US) is
> "comments".
>
> However, the end is marked with |#, not #|. This is similar to many
> other languages that have paired-up comment markers, e.g. /* ... */
> in PL/I and C.
Although the lisp ones (#| ... |#) have the advantage that they nest
properly -- cf. /* /* ... */ */, which is a great advantage when
commenting out large chunks of code -- you don't need to worry about
whether you've got embedded comments.
Christophe
Robert Monfera
> for example, the contents between #| and #| are just annotations ?
This is how to remember #| ... |# :
# is the strong wall structure that stops the heap of comments from
breaking out of its barriers
| is the inner waterproofing
Robert
Martin Cracauer
>Hi,
> I am a new comer to lisp.
>Is #| ... #1 used for annotation in Lisp?
>for example, the contents between #| and #| are just annotations ?
The real comments in Lisp are to-end-of-liners with ';'
#|...|# is an example of a reader macro in action, using it to
implement multiline comments.
>#|(defstruct node
> (x0) ;; after rotation
> (y0)
> (x1)
> (y1)
> (line)
> ) #|
Temporarily disabling code like this is usually done with a different
reader macro instead:
#+nil
(defstruct
...
(line))
This is usually preferrable to #|...|# since the editor's indentiation
support still knows how to format the disabled code.
Martin
--
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Martin Cracauer <crac...@bik-gmbh.de> http://www.bik-gmbh.de/~cracauer/
FreeBSD - where you want to go. Today. http://www.freebsd.org/
Erik Naggum
| The real comments in Lisp are to-end-of-liners with ';'
|
| #|...|# is an example of a reader macro in action, using it to
| implement multiline comments.
You may be surprised, but ; is just a reader macro, too. I fail to
see how you can support "real" in any way. What's unreal about #||#?
| Temporarily disabling code like this is usually done with a
| different reader macro instead:
Some prefer it this way, but I haven't found any statistics that
support the "usually". Where did you find yours?
| This is usually preferrable to #|...|# since the editor's
| indentiation support still knows how to format the disabled code.
See above for "usually". _Your_ preferences are noted, but some
indentation support packages will indent commented code correctly,
in the understanding that you don't comment out text with #| ... |#.
For those cases, use several ;'s at the beginning of the line.
#:Erik
--
If this is not what you expected, please alter your expectations.
Kent M Pitman
> * Martin Cracauer
> | The real comments in Lisp are to-end-of-liners with ';'
> |
> | #|...|# is an example of a reader macro in action, using it to
> | implement multiline comments.
>
> You may be surprised, but ; is just a reader macro, too. I fail to
> see how you can support "real" in any way. What's unreal about #||#?
I didn't see the original context, but maybe this was partly about the use
of comments to annotate code vs to turn off code. I bet the statistical
norm is to use ";" more for the former and "#|...|#" more for the latter,
though I have no data. Personally, I use ";" for annotation and
"#||...||#" for commenting out code, mostly because double vertical bars
makes Emacs motion commands happier.
> | Temporarily disabling code like this is usually done with a
> | different reader macro instead:
>
> Some prefer it this way, but I haven't found any statistics that
> support the "usually". Where did you find yours?
We could take an informal poll here. I certainly never use #|...|# for
running comments, nor does anyone whose code I've ever read other than
in the occasional isolated situation where they are trying to quickly
annex a .text file until they've had time to process it.
And, of course, the ANSI spec contains non-normative advice that encourages
at least the semicolon comment behavior. The advice about #|...|# is less
direct, but does note the option to nest such comments, hence at least a
possible bias in usage toward using this for code. (Though one could always
use the feature to nest textual comments instead. ;-)
> | This is usually preferrable to #|...|# since the editor's
> | indentiation support still knows how to format the disabled code.
>
> See above for "usually". _Your_ preferences are noted, but some
> indentation support packages will indent commented code correctly,
> in the understanding that you don't comment out text with #| ... |#.
> For those cases, use several ;'s at the beginning of the line.
I find that in general the editor has poor support for formatting #|...|#
owing to numerous editors thinking that # is just an adornment and |...|
is a "stringer" (i.e., syntax like |foo| or "foo") that cannot be nested.
That's why I use #||...||#, so that it will think there are two "stringers",
each ||, and that the code between is not "strung".
Robert Monfera
> We could take an informal poll here. I certainly never use #|...|# for
> running comments, nor does anyone whose code I've ever read other than
> in the occasional isolated situation where they are trying to quickly
> annex a .text file until they've had time to process it.
Sometimes it's useful to embed short, tokenized comment this way:
(defmethod foo ((x bar) (y baz))
...)
(defmethod foo #|speed|# ((x specialized-bar) (y baz))
{faster, specialized functions while logic is the same})
(defmethod foo :around #|validation|# (x y)
(assert ...)
...)
(defmethod zot #|interface|# (x &optional y)
(foo x y))
(OK, these should eventually be GF and method attributes implemented
with MOP)
Robert
Martin Cracauer
>* Martin Cracauer
>| The real comments in Lisp are to-end-of-liners with ';'
>|
>| #|...|# is an example of a reader macro in action, using it to
>| implement multiline comments.
> You may be surprised, but ; is just a reader macro, too. I fail to
> see how you can support "real" in any way. What's unreal about #||#?
We're arguing words here, my intention was to point out that Common
Lisp as a language is powerful enough to even implement multiline
comments, without cluttering up the lowest level of syntax.
>| Temporarily disabling code like this is usually done with a
>| different reader macro instead:
> Some prefer it this way, but I haven't found any statistics that
> support the "usually". Where did you find yours?
No idea. I don't comment my code and don't need comments to
understand other people's code :-)
Seriously, I could review the sources I read in the past, but I think
it's better to agree with you that this is my preference and not
neccecarily everybody else'.
>| This is usually preferrable to #|...|# since the editor's
>| indentiation support still knows how to format the disabled code.
> See above for "usually". _Your_ preferences are noted, but some
> indentation support packages will indent commented code correctly,
> in the understanding that you don't comment out text with #| ... |#.
> For those cases, use several ;'s at the beginning of the line.
Sure. The problem here is that the editor's indentation may only
support you when you decide to use #|...|# either for disabling code
*or* for free-text comments, but not both (of course, you may stiil
use the other one after committing to one, but then you'll have to
indent on your own).
Since there is a seperate item #-... that I can use for code, I
reserve #|...|# for text.
The whole thing is a little nitpicky. ;;;... looks much nicer for
text comments, so I usually just use that.