Regexp matching (was: HowTo: directory-files and friends and case-insensitive match)

[Stefan Monnier]

> To make any variation on .jpeg:

>     (directory-files DIR t "\\.[Jj][Pp][Ee]?[Gg]\\'")

> You could write a helper function to "case insensitize" regexps, if one
> doesn't already exist somewhere.

FWIW:

- We need to update/replace/rewrite our C-level regexp matching code.
- Most likely, along the way we may be able to add
  "compiled-regexp" objects.  Currently the regexp-compilation is done
  transparently, with a cache to avoid obvious performance issues;
  this works well in most cases, but offering access to compiled-regexps
  could open up a few more options.
- I'd love it if the new code could provide something like
  `make-regexp-case-insensitive'; either applied to the string-regexp or
  to the compiled-regexp, or maybe as an option to `regexp-compile'.


        Stefan