iskeyword for latex

Question

Context

Currently, when I set ft=tex, my set isk? reads

iskeyword=@,48-57,_,192-255

that is, the default for vim.

My "issue"

Currently, in a LaTeX string such as

$\abcde_\fgh$

the w jump would take me from the start to

1. a
2. \
3. f
4. $

Thus, the above setting does not feel very natural, nor optimal.

Indeed, it would probably be more reasonable to jump to

1. \
2. _
3. \
4. $

My attempt

I'm thinking of something more like set iskeyword=\,192-255 so as to have words consist of characters that would fit in

• natural language words
• or LaTeX commands.

Questions

1. Is it supposed to be so ? yes, since it is the default
2. What are better settings ?
3. How to properly set this variable for this filetype ?

Cheers,

Answer 1

You can't get all LaTeX strings right using iskeyword, that is because the iskeyword works on characters and some characters may have different meanings in different contexts. A better way than b and w to test iskeyword is viw which should visually select all characters from the cursors in both directions until it hits a character that is not in iskeyword.

On example of where this is useful are quoted strings, for example:

"abc"

Here viw will select abc and not the double quotes. But LaTeX can be ambiguous, how about this:

"Bj\{"o}rn"

Therefore a way to finding all possible LaTeX commands that can be inside a natural language word would require you to set iskeyword to everything but non-printables (space, tab, and special characters).

But Vim already does that for you!

If instead of using viw, b and w, you use viW, B and W you are selecting Vim WORDs (not words). Vim makes a distinction between WORDs and words. See :h WORD:

A WORD consists of a sequence of non-blank characters, separated with white space. An empty line is also considered to be a WORD.

(...)

---

Therefore:

1. Is it supposed to be so? yes, since it is the default

And moreover since the tex.vim ftplugin did not overwrite it.

2. What are better settings?

You probably should not play with iskeyword, different file types will have different ones but most use the defaults. Messing with iskeyword in vimrc may become a burden when you overwrite it for a filetype that needs it (you could write your own ftplugin for TeX but there is no real need here). Instead use WORDs where you need them.

3. How to properly set this variable for this filetype?

See above.

---

_{P.S. I wrote my entire dissertation in LaTeX, and all in Vim. I have been before where you are now :).}

Answer 2

I think what I want is too complicated for iskeyword.

This is because iskeyword does not use regex.

But, in what I want, a backslash could only appear as the start of a word.

For now, I think the following lines in my ~/.vim/after/ftplugin/tex.vim may improve my quality of life when editing tex files :

set isk-=_
nmap w /\\\\|\\\@<!\<\k\\|\(\>\\|\s\)\@<=\S<CR>:noh<CR>
nmap b ?\\\\|\\\@<!\<\k\\|\(\>\\|\s\)\@<=\S<CR>:noh<CR>

It enables to jump to next / previous

• backslash
• or word not starting with a backslash
• or non-blank character preceded by the end of a word or some whitespace

Basically, I use

/\<\k<CR>:noh<CR>

as an approximation for w and patch from there.

The obvious drawback is that it fills the search history with junk !

Cheers,