El sáb, 30 ene 2021 a las 7:24, ToddAndMargo via perl6-users (< perl6-us...@perl.org>) escribió:
> Hi All, > > rakudo-pkg-2020.12-01.x86_64 > > Why does this work? > > > $x = "1.33.222.4"; > 1.33.222.4 > > $x ~~ m/ (<:N>+) [.] (<:N>+) [.] (<:N>+) [.] (<:N>+) /; > ｢1.33.222.4｣ > 0 => ｢1｣ > 1 => ｢33｣ > 2 => ｢222｣ > 3 => ｢4｣ > This works because you have the right amount of capturing groups (<:N>+) ( https://docs.raku.org/language/regexes#capturing )separated by the right amount of single characters (. matches a single character, check https://docs.raku.org/language/regexes#Wildcards) It also works because <:N> matches the unicode property number ( https://docs.raku.org/language/regexes#Unicode_properties), which includes all kinds of numbers. If you are not going to use Balinese or Roman numerals, it's probably OK if you use \d instead. Then, the string you're matching (shown above) matches precisely the 4 groups there are. So ti works. You probably want this instead: say "1.33.222.4" ~~ m/(\d+) "." (\d+) "." (\d+) "." (\d+) / ｢1.33.222.4｣ 0 => ｢1｣ 1 => ｢33｣ 2 => ｢222｣ 3 => ｢4｣ Or, even better, say "1.33.222.4" ~~ m/(\d+) ** 4 % "." / Which uses the modified quantifier ( https://docs.raku.org/language/regexes#Modified_quantifier:_%,_%%) together with a general quantifier https://docs.raku.org/language/regexes#General_quantifier:_**_min..max saying "I want this (\d+) exactly four times (** 4 ) separated by (%) a literal dot "."". > > > But this does not? > --> Why the wrong number in $2? > --> Why no Nil for $3? > > > $x = "1.33.222"; > 1.33.222 > > $x ~~ m/ (<:N>+) [.] (<:N>+) [.] (<:N>+) [.] (<:N>+) /; > Because [.] is "a non-grouping class of characters that includes any character". So <:N> is matching the first 2, then [.] is matching any character, so matching and dropping ( https://docs.raku.org/language/regexes#Non-capturing_grouping) the second one, and then the last group of <:N> is capturing the last one. It would fail if you had had 2 digits, instead of three. This works and matches both strings. say $_ ~~ /(\d+) ** {3..4} % "\."/ for <1.33.222.4 1.33.222> ｢1.33.222.4｣ 0 => ｢1｣ 0 => ｢33｣ 0 => ｢222｣ 0 => ｢4｣ ｢1.33.222｣ 0 => ｢1｣ 0 => ｢33｣ 0 => ｢222｣ Once again, the regex tutorial is your friend https://docs.raku.org/language/regexes, as well as the reference for Regex or any of the other operators. Cheers -- JJ
