Hello,
Ricardo Wurmus <rek...@elephly.net> writes:
> Ludovic Courtès <l...@gnu.org> writes:
>
>> Using the “lower” regexp class instead of “[a-z]” works:
>>
>> --8<---------------cut here---------------start------------->8---
>> scheme@(guile-user)> (string-match "[[:lower:]]" "w")
>> $12 = #("w" (0 . 1))
>> --8<---------------cut here---------------end--------------->8---
>>
>> However, it’s not clear to me whether the “lower” class is supposed to
>> be the same for all locales or if we’re just lucky:
>>
>> http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html
>>
>> Thoughts?
>
> The lower class is much larger than [a-z]. If we only wanted to work
> around this particular problem we could explicitly spell out the range,
> which would be the same in all locales. (Obviously, that wouldn’t be
> pretty.)
I think that explicitly spelling out the range is the right thing to do
here. The POSIX spec says that character ranges work in the POSIX
locale, but “in other locales, a range expression has unspecified
behavior.”
> But can’t URI parts contain more than those characters?
A quick reading of RFC 3986 suggests that the host part of a URI can be
an IP address (version 4 or 6) or a registered name. It gives the
following rules for registered names:
reg-name = *( unreserved / pct-encoded / sub-delims )
unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
pct-encoded = "%" HEXDIG HEXDIG
sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
/ "*" / "+" / "," / ";" / "="
Here, “ALPHA”, “DIGIT”, and “HEXDIG” are specified in RFC 2234, and are
just the ASCII ranges you might expect (except for that “HEXDIG” only
allows uppercase letters).
It looks like Guile is currently a little stricter than this, but pretty
close (if you take the character ranges to mean ASCII ranges).
> To circumvent
> the question whether the lower class is locale dependent we could
> generate an explicit range from a charset.
I think this is the right approach. Using “[:lower:]” would allow
things outside of the RFC, like ‘é’. Adding support for
internationalized domain names using Punycode would be cool, but well
outside the scope of this bug. :)
-- Tim
