Need to apply Unicode mode to match unicode properly (one of the unfortunate defaults in Elixir but its too late to fix now).
iex> Regex.match?( ~r/^[[:ascii:]]+$/u, <<72260::utf8>>)
false
iex> Regex.match?( ~r/^[[:ascii:]]+$/u, <<256::utf8>>)
false
Being overly pedantic - standard library, not language per se (as such I would count bug in the compiler).
The reason for that behaviour was found on the Erlang Slack - namely the worst idea for the API ever designed - C locales. [:ascii:] character class use isprint() C function behind the scenes, and that function is locale aware (in some implementations of libc). You aren’t the first one that was bitten in the arse by such quirks:
Thats beyond weird. How can this not be a bug? isprint() doesn’t correlate at all well with [:ascii:] since [:ascii:] is supposed to be 0..127 and a lot of those aren’t printable! And yet they do match.
iex> Regex.match? ~r/[[:ascii:]]/, <<1>>
true
iex> Regex.match? ~r/[[:ascii:]]/, <<0>>
true
I haven’t seen any response to the issue I raised so I’ll be curious if any will be forthcoming …
[:ascii:] roughly translates to isprint(c) || iscontrol(c), that allows it to match on <<0>>. And yes, this is a bug in the implementation as well as bug in the C standard (locale API should be burned in fire).
And definitely confusing to those coming from ruby or perl as neither of these have ascii matching non ascii characters, so presumably this means it is not PCRE compliant!?
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 /tmp/p
ü is NOT ascii
ü is NOT ascii-u