No relation to the sports channel.

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Joined 1 year ago
Cake day: June 9th, 2023
  • fubo@lemmy.worldtoProgrammer Humor@lemmy.ml•Oh boy what a beautiful regex. I'm sure it does something logical and easy to understand.
    12·
    25 days ago

    Regex is good for a few very specific things, and sysadmins used to use it for goddamn everything. If all your server logs are in lightly-structured text files on a small number of servers, being able to improvise regex is damn useful for tracking down server problems. Just write a shell loop that spawns an ssh logging into each server and running grep over the log files, to look for that weird error.

    These days, if you need to crunch production server logs you probably need to improvise in SQL and jq and protobufs or systemd assmonkery or something.

    But if you actually need a parser, for goodness sake use a parser combinator toolkit, don’t roll your own, especially not with regex. Describing your input language in plain Haskell is much nicer than kludging it.

    (This is the “totally serious software engineering advice” forum, right?)

  • fubo@lemmy.worldtoProgrammer Humor@lemmy.ml•Oh boy what a beautiful regex. I'm sure it does something logical and easy to understand.
    136·
    25 days ago

    The answer given in the spoiler tag is not quite correct!

    Test case

    According to the spoiler, this shouldn’t match “abab”, but it does.

    Corrected regex

    This will match what the spoiler says: ^.?$|^((.)\2+?)\1+$

    Full workup

    Any Perl-compatible regex can be parsed into a syntax tree using the Common Lisp package CL-PPCRE. So if you already know Common Lisp, you don’t need to learn regex syntax too!

    So let’s put the original regex into CL-PPCRE’s parser. (Note, we have to add a backslash to escape the backslash in the string.) The parser will turn the regex notation into a nice pretty S-expression.

    > (cl-ppcre:parse-string "^.?$|^(..+?)\\1+$")
(:ALTERNATION
 (:SEQUENCE :START-ANCHOR (:GREEDY-REPETITION 0 1 :EVERYTHING) :END-ANCHOR)
 (:SEQUENCE :START-ANCHOR
  (:REGISTER
   (:SEQUENCE :EVERYTHING (:NON-GREEDY-REPETITION 1 NIL :EVERYTHING)))
  (:GREEDY-REPETITION 1 NIL (:BACK-REFERENCE 1)) :END-ANCHOR))

    At which point we can tell it’s tricky because there’s a capturing register using a non-greedy repetition. (That’s the \1 and the +? in the original.)

    The top level is an alternation (the | in the original) and the first branch is pretty simple: it’s just zero or one of any character.

    The second branch is the fun one. It’s looking for two or more repetitions of the captured group, which is itself two or more characters. So, for instance, “aaaa”, or “abcabc”, or “abbaabba”, but not “aaaaa” or “abba”.

    So strings that this matches will be of non-prime length: zero, one, or a multiple of two numbers 2 or greater.

    But it is not true that it matches only “any character repeated a non-prime number of times” because it also matches composite-length sequences formed by repeating a string of different characters, like “abcabc”.

    If we actually want what the spoiler says — only non-prime repetitions of a single character — then we need to use a second capturing register inside the first. This gives us:

    ^.?$|^((.)\2+?)\1+$.

    Specifically, this replaces (..+?) with ((.)\2+?). The \2 matches the character captured by (.), so the whole regex now needs to see the same character throughout.

  • fubo@lemmy.worldtoAsklemmy@lemmy.ml•Attitude to Religion and its believers.
    453·
    5 months ago

    Imagine if that person did all the same things they do, but without the label of “religion” being attached.

    Charity? Awesome! Habitat for Humanity is an explicitly Christian organization and does great work. In my neighborhood, the local Lutheran and Quaker churches give out free food to the poor, and they don’t sneak any Lutheran or Quaker cooties into it. If you’re good to others because you think God wants you to be good to others, that still really does count as being good to others.

    Prayer? Okay, take “religion” off of it and they’re meditating, thinking, or talking to themselves. That’s good. Unless they’re thinking and talking about torturing their neighbors eternally, or something creepy like that. (But even then, better to keep those fantasies to yourself than to act them out in public.) Die Gedanken sind frei — thoughts are free.

    Going to worship services? Okay, they’ve got a weekly social event where they sing songs and listen to speeches. Sounds great, unless the songs are about “everyone outside this room is a terrible person and deserves to suffer forever” and the speeches are about hate politics. If they’re about how wonderful it is to be nice to each other, or being brave and standing up against oppression, or something else that would be positive even without the label of “religion” on it, great!

    Dietary rules? It’s okay to have preferences, distinct cultures, cuisines, and so forth. For that matter: my family isn’t Jewish, but when I was little, we ate kosher beef hot dogs, because my mom expected the rabbis would care about the meat being sanitary. (Unfortunately in retrospect, kosher slaughter is, shall we say, not clearly better than secular slaughter.)