❯❯❯❯ locale ~/Temp
LANG="de_DE.UTF-8"
LC_COLLATE="de_DE.UTF-8"
LC_CTYPE="de_DE.UTF-8"
LC_MESSAGES="de_DE.UTF-8"
LC_MONETARY="de_DE.UTF-8"
LC_NUMERIC="de_DE.UTF-8"
LC_TIME="de_DE.UTF-8"
LC_ALL=
❯❯❯❯ cat p ~/Temp
my $s = "ü";
if ($s =~ /^[[:ascii:]]+$/ ) {
print "$s is ascii\n";
} else {
print "$s is NOT ascii\n";
}
if ( $s =~ /^[[:ascii:]]+$/u ) {
print "$s is ascii-u\n";
} else {
print "$s is NOT ascii-u\n";
}%
❯❯❯❯ perl p ~/Temp
ü is NOT ascii
ü is NOT ascii-u
❯❯❯❯ iex ~/Temp
Erlang/OTP 23 [erts-11.1.4] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [hipe]
Interactive Elixir (1.11.2) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> Regex.match?( ~r/^[[:ascii:]]+$/, "ü")
true
LostKobrakai
1
hauleth
I cannot force Perl to run in Latin-1 mode, but grep shows exactly the same quirk:
$ printf "\303\274" | LC_ALL=sv_SE.iso88591 grep -P "[[:ascii:]]"
��
Remember that for compatibility reasons Erlang will always use sv_SE.iso88591 encoding when running the re module. So it is “consistent” with that behaviour.
Answering questions:
- is this confusing? YES
- is this stupid? YES
- should that ever happened in the first place? NO
- why does this happen? Because C committee don’t want to state that locales API is a mistake and should be removed.
- can we do anything about it? Not really, at least not without breaking backward compatibility. However we could issue warning if there is
[:ascii:]character class used in precompiled regexes
2
kip
ex_cldr Core Team
…and the documentation can be updated to NOT say 0..127. I guess I can try for my first Erlang PR. If I’m feeling brave.
5
kip
ex_cldr Core Team
jhogberg
Erlang Core Team
I’ve merged a documentation fix to master now, thanks for looking into and reporting this. 
8
Nicd
I think we will need an explainer to Elixir docs as well, or a link to read the notes from Erlang docs. Otherwise many people will make the same mistake (or worse, don’t know that they’ve made the same mistake).
0
hauleth
Elixir documentation do not have regex syntax description AFAIK, it points to Erlang docs. However I think that we could parse static regexes during compilation and warn about these. It shouldn’t be hard to implement that via compiler tracers.
1
Sebb