From: Alan Mackenzie <acm@muc.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Skeleton angle brackets '<' and '>'
Date: Wed, 6 Jan 2016 17:59:39 +0000 (UTC) [thread overview]
Message-ID: <n6jkmb$hmt$1@colin.muc.de> (raw)
In-Reply-To: mailman.1800.1452028390.843.help-gnu-emacs@gnu.org
B.V. Raghav <bvraghav@iitk.ac.in> wrote:
> Hi,
> There are smart tools for the purpose, but I prefer to stick to the old
> school for auto pairing.
> Electric Pair mode and Skeleton pair, like this:
> (electric-pair-mode t)
> (setq skeleton-pair t)
> While in the c++ mode, (hopefully true for all c-modes)
> I am able to successfully pair (), {}, and [], with a single key press,
> i.e. of the preceding character of the pair.
> I also want to pair the angle brackets, i.e. `<' and `>' characters.
Be careful what you want! Do you also want automatically to pair up
"less than" with "greater than"? It could get pretty tedious if, every
time you wanted to write "i < 10", you got "i <>", forcing you to delete
the ">" before writing in the "10".
This overloading of < and > with two meanings (actually, three when you
count "#include <stdio.h>", but that causes few problems) causes great
difficulties for C++ Mode. Only after extensive analysis can the mode
determine that a < and a > are a pair of template delimiters, and even
then, can't do it with 100% certainty.
For example, how many parameters are passed to foo in the following:
foo (a < b, c > d);
? It might be a function call with two relational expressions, it might
be a declaration with the single parameter d of templated type a <b , c>.
Such was the wisdom of C++'s designers.
When it is determined there is a pair of delimiters, they are marked as
such with syntax-table text properties, but this marking is always done
on both delimiters at once.
In short, there is little chance of ever being able to insert angle
brackets as a pair in C++ Mode. Sorry!
> The documentation for the variable sekeleton-pair-alist says,
> [...]
> Each alist element, which looks like (ELEMENT ...), is passed to
> `skeleton-insert' with no interactor. Variable `str' does nothing.
> Elements might be (?` ?` _ "''"), (?\( ? _ ")") or(?{ \n > _ \n ?} >).
> [...]
> I am sorry to say, I cant make a head or tail of this cryptic value
> suggested for the variable.
Sorry to say this, but neither can I. I don't know what an "interactor"
is, variable `str' is obscure, and it is totally unclear what the various
example elements might mean.
> Help solicited.
Can I suggest you submit a bug report for this dreadful doc string?
> Thanks,
> r
> --
> (B.V. Raghav)
--
Alan Mackenzie (Nuremberg, Germany).
next parent reply other threads:[~2016-01-06 17:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.1800.1452028390.843.help-gnu-emacs@gnu.org>
2016-01-06 17:59 ` Alan Mackenzie [this message]
2016-01-07 4:03 ` Skeleton angle brackets '<' and '>' B.V. Raghav
2016-01-07 9:07 ` Yuri Khan
2016-01-08 18:33 ` B.V. Raghav
2016-01-05 21:12 B.V. Raghav
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