Re: Difference between \\w and [:word:]?

[Eric Abrahamsen]

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>
>> Can someone explain to me what's happening here? What's the difference
>> between \\w and [:word:], inside and outside of a bracket construction?
>>
>> (setq case-fold-search nil)
>> (string-match-p "[:word:]" "P") => nil
>
> This is the same as (string-match-p "[wrdo:]" "P").  It's just a
> collection of characters to be matched.

Yeah, I did figure that out once I read the manual properly.

>> (string-match-p "[[:word:]]" "P") => 0
>
> This looks for a member of the character class [:word:] in the string.
> It finds it (case-insensitively) at position 0.  Technically, the
> current character class table determines what is a word-constituent.
>
>> (string-match-p "\\w" "P") => 0
>
> This does the same.
>
>> (string-match-p "[\\w]" "P") = nil
>
> And this is just a normal character class match looking for either a w
> or a \.
>
> I can never quite decide if it's good or bad that the named character
> classes use the same [...] syntax.  [:digit:] is just a plain character
> set with a duplicated : and i in it.  It only becomes a named class
> inside a character set.

It definitely felt a little weird writing something like
"\\w[[:word:]-']+", where we're required to use two different notations
for the same match.

Thanks,
Eric