Re: Bizarre behavior of \w in a regular expression bracket construct

On 2021-Feb-23, Tom Lane wrote:

> * Create infrastructure to allow treating \w as a character class
> in its own right. (I did not expose [[:word:]] as a class name,
> though it would be a little more symmetric to do so; should we?)

Apparently [:word:] is a GNU extension (or at least a "bash-specific
character class"[1] but apparently Emacs also supports it?); all the
others are mandated by POSIX[2].

[1] https://en.wikibooks.org/wiki/Regular_Expressions/POSIX_Basic_Regular_Expressions
[2] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05

I think it'd be fine to expose [:word:] ...

> [1] https://www.regular-expressions.info/charclasssubtract.html

I had never heard of this subtraction thing. Nightmarish and confusing
syntax, but useful.

> + Also, the character class shorthands <literal>\D</literal>
> + and <literal>\W</literal> will match a newline regardless of this mode.
> + (Before <productname>PostgreSQL</productname> 14, they did not match
> + newlines in newline-sensitive mode.)

This seems an acceptable change to me, but then I only work here.

--
Álvaro Herrera 39°49'30"S 73°17'W