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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. |
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| ab5tract | glad my pain could bring some smiles into the world ;) | 16:44 | |
| timemelon | I'm getting some behaviour from regexes that I don't understand | 22:30 | |
| I'm used to * and + from PCREs | |||
| echo 'words: 12345' | grep -oP '\d+' and echo 'words: 12345' | grep -oP '\d*' both return 12345 | 22:31 | ||
| when I try echo 'words: 12345' | raku -e 'slurp.match(/\d+/).Str.say' I get 12345 just the same | 22:32 | ||
| but echo 'words: 12345' | raku -e 'slurp.match(/\d*/).Str.say' gives me an empty match | |||
| how come \d* doesn't match 12345? | 22:33 | ||
| (also: is this the most idiomatic way to use raku as a drop in grep/sed/etc) | 22:36 | ||
| ab5tract | it matches '0 or more', so when it hits that first 'w' from words, it has successfully matched 0 times | 22:47 | |
| definitely a bit of a gotcha, though, I agree | 22:48 | ||
| m: "words: 12345" ~~ /\D+(\d*)/ ==> say() | 22:50 | ||
| camelia | ｢words: 12345｣ 0 => ｢12345｣ |
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| ab5tract | or to drive the '0 or more' rule home: | 22:51 | |
| m: "words: 12345" ~~ /\D*(\d*)/ ==> say() | |||
| camelia | ｢words: 12345｣ 0 => ｢12345｣ |
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| timemelon | ahh that makes sense thank you | 22:53 | |
| I guess the difference between the grep example and that is that grep is finding the longest match while raku is finding the first match | |||
| ab5tract | yeah, we tend to refer to it as the "greediness" of the regex expression | 22:54 | |
| * is very gregarious, not greedy at all :) | 22:55 | ||
| As to the idiom, I might me more likely to use `$*IN.slurp ~~ /regex/` but it's really a matter of taste | 22:58 | ||
| There's also `-n` which allows: `echo "words: 12345" | raku -ne '$_ ~~ /\D*(\d*)/ ==> say()'`\ | 23:01 | ||
| timemelon | oh I didn't know about -n, that's nice ty | 23:25 | |
| is there a reason you prefer the explicit $*IN over a bare slurp? | 23:27 | ||