what does iskeyword option do?

[FlashBurn]

I'm trying to understand the meaning of 'iskeyword' option but I can't figure out from the help what it does. Any help in finding out of the meaning of this option is greatly appreciated.

[Ben Fritz]

On Wednesday, February 25, 2015 at 10:02:46 AM UTC-6, FlashBurn wrote:
> I'm trying to understand the meaning of 'iskeyword' option but I can't figure out from the help what it does. Any help in finding out of the meaning of this option is greatly appreciated.

What's not clear? The help says: 'Keywords are used in searching and recognizing with many commands: "w", "*", "[i", etc. It is also used for "\k" in a |pattern|.'

So, it affects where the 'w' command (move to next word) stops. It affects what text the '*' command searches for. It affects what text the '[i' command searches for. It affects what other similar commands search for.

It also affects what text the '\k' character class matches when you are searching.

Search the help with ':helpgrep iskeyword' for other things it affects, for example, the CTRL-W command in insert and command-line mode, for deleting a word.

[Tim Chase]

'isk' contains a list of characters (or character-ranges) for those
characters that should be considered a "word". This comes into play
when using "\<", "\>", "\k" and "\K" in a regular expression; what
gets considered when you use "*" and "#" to search; what the "iw" and
"aw" text-objects select; what's considered a "w"ord motion; how
abbreviations are found; and plenty of other places.

For example, by default "-" isn't part of the 'isk' setting, but if
you wanted "vip" to highlight/select whole CSS selectors like
"background-color"

:set isk+=-

to add the dash. Now, if you do "viw" anywhere in the attribute,
it will highlight/select the entire "background-color" not just
"background" or "color".

It's a little tricky to add certain characters as they have special
meaning. The easiest way I've found is to make a range of length one
for "@":

:set isk+=@-@ " add an at-sign, good for email addresses
" and Python decorators

-tim

[FlashBurn]

I was trying to understand if it has a meaning in the highlight context. I'm going through an online book, Learn Vimscript the Hard Way and in the following chapter, http://learnvimscriptthehardway.stevelosh.com/chapters/46.html, it talks about the # symbol not being in iskeyword in the context of comments and highlighting and I can't figure out why this matters. I think I'm getting the meaning of this option, i.e. it defines what a word is, but why it matters in highlighting, that is not clear to me.

[Charles Campbell]

Syntax highlighting is based upon regular expressions (see :he regexp).
A commonly used thing to pick up on are: words. Most variables,
function names, and commands, for example, fit into the description of
"word". Hence, the scripts that specify syntax highlighting often use
the \k atom (see :help /character-classes); and the \k atom depends upon
the iskeyword setting. For example, syntax/latex.vim (by default)
removes the underscore from the iskeyword option because latex will
(usually) flag usage of it as an error.

Regards,
Chip Campbell

[FlashBurn]

Thanks a lot Chip. That cleared it up.

[Erik Christiansen]

On 25.02.15 10:32, Tim Chase wrote:
> On 2015-02-25 08:02, FlashBurn wrote:
> > I'm trying to understand the meaning of 'iskeyword' option but I
> > can't figure out from the help what it does. Any help in finding
> > out of the meaning of this option is greatly appreciated.
>
> 'isk' contains a list of characters (or character-ranges) for those
> characters that should be considered a "word". This comes into play
> when using "\<", "\>", "\k" and "\K" in a regular expression; what
> gets considered when you use "*" and "#" to search; what the "iw" and
> "aw" text-objects select; what's considered a "w"ord motion; how
> abbreviations are found; and plenty of other places.
>
> For example, by default "-" isn't part of the 'isk' setting, but if
> you wanted "vip" to highlight/select whole CSS selectors like
> "background-color"
>
> :set isk+=-
>
> to add the dash. Now, if you do "viw" anywhere in the attribute,
> it will highlight/select the entire "background-color" not just
> "background" or "color".

That all seems to confirm that "iskeyword" is a misnomer for what in
reality is "istoken", AFAICT. Not only is token boundary recognition the
process described above, but the process in no way resembles detection
of a member of a keyword set, like those use in 'C': "if", "switch",
"case", etc.

If it were "isword", rather than "iskeyword", then the name would also
be truthful, and more easily understood, I guess.

Erik

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[Ben Fritz]

On Thursday, February 26, 2015 at 4:57:34 AM UTC-6, Erik Christiansen wrote:
> That all seems to confirm that "iskeyword" is a misnomer for what in
> reality is "istoken", AFAICT. Not only is token boundary recognition the
> process described above, but the process in no way resembles detection
> of a member of a keyword set, like those use in 'C': "if", "switch",
> "case", etc.
>

Actually it has a great deal to do with keyword detection. One use of 'iskeyword' is in syntax definition files, when using "keyword" type matches. :help :syn-keyword.

Syntax highlighting in Vim predates my use of Vim by many years. But since keyword highlighting is the most basic sort, I'd guess it was the first introduced.