Re: Understanding Word Boundaries

[address@hidden]

Am 16.06.2010 12:44, schrieb Paul Drummond:
> I have been an Emacs users for a few years now so definitely still a
> newbie!  While initially I struggled to control its power, I eventually came
> round.  Every issue I've had so far I've been able to fix by a quick search
> in EmacsWiki, except for one frustrating and re-occurring problem that has
> plagued me for years - word boundaries.
>
> Before Emacs I used Vim exclusively and the word boundary behaviour in Vim
> *just worked* - I didn't even have to think about it.  No matter what
> language I used I could navigate and manipulate words without thinking about
> it.  The way word boundaries work in Vim is elegant and I have spent a lot
> of time trying to find some elisp to replicate the behaviour in Emacs but to
> no avail.
>
> I could write some elisp myself but I am still very new to it so it will
> take a while - it's something I would like to do but I don't have time at
> the moment.  Regardless, an elisp solution to the problem is not the point
> of this post.  I want to understand why word boundaries behave the way they
> do in Vanilla Emacs and I would greatly appropriate some views on this from
> some Emacs Gurus!
>
> Every time I notice the word boundary behaviour when hacking in Emacs I
> wonder to myself - "I must be missing something here.  Surely, experienced
> Emacs users don't just *put up* with this!  Yet every forum response, blog
> post, mailing-list post I have read suggests they do.  This is atypical of
> the Emacs community in my experience.  Usually when something behaves wrong
> in Emacs, it's easy to find some elisp that just fixes the problem full
> stop.  Yet with word-boundaries all I can find is suggestions that fix a
> particular gripe but nothing that provides a general solution.
>
> I have loads of examples but I will mentioned just a few here to hopefully
> kick-start further discussion.
>
> ** Example 1
>
> I use org-mode for my journal and today I hit the word-boundary problem
> while entering my morning journal entry - here's a contrived example of what
> I entered:
>
> ** [10:27] Understanding Word Boundaries in Emacs
>                                     ^
> With point at the end of the word "Understanding" I hit C-w (which I bind to
> backward-kill-word) and the word "Understanding" is killed as expected.  But
> when I hit C-w again, the point kills to the colon.  Why?  Why is colon a
> word-boundary but the closing square bracket isn't?
>
> ** Example 2
>
> When editing C++ files I often need to delete the "ClassName::" part when
> declaring functions in the header:
>
> void ClassName::function();
>         ^
>
> With point at the start of ClassName I want to press M-d twice to delete
> ClassName and :: but "::" isn't recognised as a word.  In Vim I just type
> "dw" twice and it *just works*.

Hi,


seems not a question of word-boundaries, but a feature:

as you describe, Vim says: when word-chars are under cursor, kill them.
When non-word chars are there, kill until next word.

Interesting.


> ** Example 3
>
> I have loads of problems when deleting and navigating words over multiple
> lines.  In the following C++ code for instance:
>
>      Page *page = new _Page(this);
>      page.load();
>             ^
>
> When point is after "page", before the dot on the second line and I hit M-b
> (backward-word) point ends up at the first opening bracket of "Page(" !!!
>
> Again, vim does the right thing here - pressing 'b' takes the point to the
> closing bracket of Page(this) so it doesn't recognise the semi-colon as a
> bracket which is intuitive and what I would expect.  This is really the
> point I am trying to make.  I have never taken the time to understand the
> behaviour of word boundaries in Vim because *it just works*.  In Emacs I am
> forced to think about word boundaries because Emacs keeps surprising me with
> its weird behaviour!


Forward-moves stop after the object, backward-moves before.
When a mode defines '()' as word-characters, M-x backward-word will stop 
at the semi-colon at your example.


Andreas

> Note: My examples happen to be C++ but I use lots of other languages too
> including elisp, Clojure, JavaScript, Python and Java and the
> word-boundaries seem to be wrong for all of them.
>
> I have tried several different elisp solutions but each one has at least one
> feature that isn't quite right.  Here are some links I kept, I've tried many
> other solutions but don't have the links to hand:
>
> http://stackoverflow.com/questions/2078855/about-the-forward-and-backward-a-word-behaviour-in-emacs
> http://stackoverflow.com/questions/1771102/changing-emacs-forward-word-behaviour/1772365#1772365
>
> So to wrap up, the point of this post is to kick-start a discussion about
> why the word boundaries in Vanilla Emacs (specifically GNU Emacs 23.1.50.1
> in my case) seem to be so awkward and unintuitive.
>
> Regards,
> Paul Drummond