This channel is intended for people just starting with the Raku Programming Language (raku.org). Logs are available at irclogs.raku.org/raku-beginner/live.html
Set by lizmat on 8 June 2022.
01:47 MasterDuke joined 06:25 kjp left 06:26 kjp joined 06:27 kjp left 06:28 kjp joined
nahita3882 hi, sorry for the late response. You are right!: m/.../; automatically matches against $_; m { ... } is actually the same as m/.../ only using a different separator for regex: {} pairs instead of || -- this is for convenience, e.g., if your regex to contain a lot of forward slashes, you would need to escape it to not confuse with the ending delimeter (or you must quote it). 08:58
rx { ... } on the other hand performs no match but makes a Regex object
a12l @nahita3882 Thanks! 09:03
I want to write a regex that match against any character that isn't A, C, G, or T. My current attempt is / <-[A | C | G | T]> /, but doesn't work. It does work if I only specify two letters. 09:06
09:07 jaguart joined
kjp a12l: / <-[ACGT]> / works for me 09:20
nahita3882 yeah the | is treated literally in there (in the character class), not as an "or" switch 09:35
jaguart what does this signature mean? ``multi MAIN(:h(:$help)!)`` 11:32
lizmat m: sub a(:h(:$help) { dd $help ); a :h; a :help 11:58
camelia ===SORRY!=== Error while compiling <tmp>
Missing block
at <tmp>:1
------> sub a(:h(:$help) ⏏{ dd $help ); a :h; a :help
lizmat m: sub a(:h(:$help) { dd $help }; a :h; a :help
camelia ===SORRY!=== Error while compiling <tmp>
Missing block
at <tmp>:1
------> sub a(:h(:$help) ⏏{ dd $help }; a :h; a :help
lizmat m: sub a(:h(:$help)) { dd $help }; a :h; a :help
camelia Bool::True
Bool::True
lizmat heh
basically, it allows both --h and --help 11:59
if such a signature is used on MAIN
nahita3882 docs.raku.org/language/signatures#...nt_aliases 12:05
to link the documentation 12:06
12:32 habere-et-disper joined
a12l kjp, @nahita3882: Thought that the pattern would match against the first substring "ACGT" 13:20
If I would like to match against the substring ACGT, should I have quoted the letters? 13:29
Or even against several different substrings? E.g. "abc", "def", "ghi"? How do I OR them? 13:32
nahita3882 <[ACGT]> actually forms a character class -- it means "match any of the characters I put in there" 13:38
<-[ACGT]> is the negation of that (fun fact: we can actually do <+[ACGT]> but + is redundant) 13:39
> If I would like to match against the substring ACGT, should I have quoted the letters? yeah you need to write it without the <[...]> stuff. Since neither of those characters are special, you can write it directly, but writing it in quotes will do the same thing 13:40
and for consistency, i think it's better to do in quotes and never think about special characters' escaping 13:41
> Or even against several different substrings? E.g. "abc", "def", "ghi"? How do I OR them? ORing is with ||
examples:
raku # With a character class -- any of the characters A, C, G, T In [1]: "A" ~~ / <[ACGT]> / ｢A｣ # Match literally the four-char sequence ACGT In [2]: "A" ~~ / ACGT / Nil # Same as above, quoting not necessary since no special characters (like "-") but safe, consistent In [3]: "A" ~~ / "ACGT" / Nil # Character class again -- only A part is matched In [4]: "ACGT was here" ~~ / <[ACGT]> / ｢A｣ # 13:47
Literal -- full sequence is matched In [5]: "ACGT was here" ~~ / ACGT / ｢ACGT｣ # Same as above but in quotes (safer, cooler) In [6]: "ACGT was here" ~~ / "ACGT" / ｢ACGT｣ # Matching against alternatives: either literally ACGT *or* TTGA In [7]: "TTGA was here" ~~ / "ACGT" || "TTGA" / ｢TTGA｣
as a "corollary", / <[ACGT]> / is the same as / A || C || G || T / or with quotes / 'A' || 'C' || 'G' || 'T' / if that makes sense 13:49
a12l Thanks for the examples @nahita3882 ! 14:07
Btw, when is it necessary to group the characters in a subexpression? 14:08
nahita3882 hmm, not sure I understood but for precedence, we might want to use grouping like: perl > "text-end" ~~ / "text" || "no" "-end" / ｢text｣ > "text-end" ~~ / ["text" || "no"] "-end" / ｢text-end｣ 14:13
in the first one, alternatives are "text" OR "no-end", and so it matches "text"
but what's wanted is "text-end" OR "no-end"; of course we can write "text-end" || "no-end", but to "factor out" and not repeat -end again, we made the first attempt 14:14
but the precedence kicked in and didn't reach the desired result; for that, we use non-capturing grouper [ ] and it's all set 14:15
in the second one, it's "either "text" OR "no", followed by "-end""
14:19 habere-et-disper left
a12l I'm thinking of why raku > "abcd" ~~ / <[abc]> / ｢a｣ > "abcd" ~~ / <abc> / No such method 'abc' for invocant of type 'Match'. Did you mean 'abs'? in block <unit> at <unknown file> line 1 in any <main> at /nix/store/g1bz1z20yh9n8dg7913r68grnkgg3584-rakudo-2024.01/share/perl6/runtime/perl6.moarvm line 1 in any <entry> at 17:33
/nix/store/g1bz1z20yh9n8dg7913r68grnkgg3584-rakudo-2024.01/share/perl6/runtime/perl6.moarvm line 1
I'm thinking of why raku > "abcd" ~~ / <[abc]> / ｢a｣ > "abcd" ~~ / <abc> / No such method 'abc' for invocant of type 'Match'. Did you mean 'abs'? in block <unit> at <unknown file> line 1 in any <main> at /nix/store/g1bz1z20yh9n8dg7913r68grnkgg3584-rakudo-2024.01/share/perl6/runtime/perl6.moarvm line 1 in any <entry> at 17:34
/nix/store/g1bz1z20yh9n8dg7913r68grnkgg3584-rakudo-2024.01/share/perl6/runtime/perl6.moarvm line 1
What I understand, grouping is only necessary you want to group characters in another order than is specified by the default precedence rules. 17:35
My (obvious wrong) understanding is that abc is the same as [abc] when enclosed in angle brackets. But that mental model is obviously wrong. What have I misunderstood? 17:36
librasteve m: say "abcd" ~~ / abc / 17:44
Raku eval ｢abc｣
librasteve @a12l - no need for angle brackets unless you are using a regex (aka sub-expression), doing interpolation or (with <[...]> angle-square combo) need a char class 17:46
<abc> is neither a predefined regex (aka a predefined char class like <alpha>) nor is it one you defined like my regex abc { \w } 17:48
/ abc / will match a then b then c, / <[abc]>{3} / will match a or b or c 3 times 17:50
a12l What I'm wondering is why grouping a regex inside angle brackets automatically create a char class 18:01
librasteve it doesn't - there is just some syntax for regex <...> and some other syntax for char classes <[...]> - they just look similar 18:02
a12l Wait, so < ... > (named subexpression), [ ... ] (grouping), and <[ ... ]> (create a char class) are totally different things? 18:09
librasteve yep 18:10
a12l And do I understand char classes correctly that they are "anonymous subexpressions", compared to named sub expressions (my regex foo { ... })? 18:12
librasteve I ... don't think so ... feels like you are over analysing this 18:13
a12l I'm just trying to figure out the relation between the different constructs. 18:15
librasteve they just look a bit similar - otherwise there is no relation
a12l There so much syntactic overlap in Raku, but the docs don't (I think) make they difference clear when they talking about different stuff. 18:16
librasteve well, by definition, there is no syntactic overlap (since the syntax leads to determined results), but I agree that raku is very syntactically dense - it is surely not python 18:19
a12l Thanks your patience @librasteve ! 18:21
librasteve you are looking at regex also which, with the need to have character level syntax that maps closely to the char patterns in the input string, is very syntactically dense, raku is less extreme in other areas (eg OO, concurrency, file IO and so on)
np
I learn (or relearn) aspects of raku every time I try to answer a question! 18:22

Powered by Cro and the Raku® Programming Language.

Please report any issues / comments / feature requests as an issue on App::Raku::Log.

Thank you!