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    Developing generic regex sequences

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    • PeterJonesP
      PeterJones @Alan Kilborn
      last edited by

      @Alan-Kilborn said in Developing generic regex sequences:

      I’m disturbed that some of your aaa in the first code block appears in italics – how does this happen in a code block?

      It appears NodeBB isn’t treating all code blocks the same. But while it was italicizing, it fortunately wasn’t taking any characters away, so those were the expressions I meant to convey.

      Giving the explicit txt filetype for the block:

      OR      (?=.*aaa|.*bbb)
      AND     (?=.*aaa)(?=.*bbb)
      XOR     (?=.*aaa)(?!.*bbb)|(?!.*aaa)(?=.*bbb)
      NOR     (?!.*aaa)(?!.*bbb)
      NOR     (?!.*(aaa|bbb))
      NAND    (?!(?=.*aaa)(?=.*bbb))
      
      PeterJonesP 1 Reply Last reply Reply Quote 1
      • PeterJonesP
        PeterJones @PeterJones
        last edited by

        Updating with n-term rather than just two-term:

        logic two-term expression n-term expression notes
        OR (?=.*aaa|.*bbb) (?=.*aaa|.*bbb|...|.*nnn) must match at least one
        AND (?=.*aaa)(?=.*bbb) (?=.*aaa)(?=.*bbb)...(?=.*nnn) must match all
        XOR (?=.*aaa)(?!.*bbb)|(?!.*aaa)(?=.*bbb) too complicated match one or the other, but not both
        NOR (?!.*aaa)(?!.*bbb) (?!.*aaa)(?!.*bbb)...(?!.*nnn) matches neither one nor the other
        NOR (?!.*(aaa|bbb)) (?!.*(aaa|bbb|...|nnn)) second syntax for the same concept
        NAND (?!(?=.*aaa)(?=.*bbb)) (?!(?=.*aaa)(?=.*bbb)...(?=.*nnn)) may match zero or one of the terms, but not both
        Alan KilbornA 1 Reply Last reply Reply Quote 4
        • guy038G
          guy038
          last edited by

          Hi @peterjones, @alan-kilborn and All,

          I gave a similar answer to @vijay-s ( refer here ), but Peter BRILLIANTLY beat me at it and gives us a complete panel of the look-aheads to use in order to simulate the main logical combinations !


          Now, Peter, I think it would be worth, in the general case, to add a ^ anchor, right in front of all these formulas !

          Best Regards,

          guy038

          PeterJonesP 1 Reply Last reply Reply Quote 1
          • PeterJonesP
            PeterJones @guy038
            last edited by

            @guy038 said in Developing generic regex sequences:

            Now, Peter, I think it would be worth, in the general case, to add a ^ anchor, right in front of all these formulas !

            The logic itself is independent of what you anchor it in. My two usage examples in my first post about “Logic Gates for Regular Expressions” show that you can use these standalone generic anchored either per-line or per-file depending on what you wrap around them. With generic, you could even stick these after some other match on the line, saying “after some prefix, match aaa or bbb” or similar. Hence, I didn’t want to specify the anchors in my generic expressions.

            1 Reply Last reply Reply Quote 2
            • Alan KilbornA
              Alan Kilborn @PeterJones
              last edited by

              @PeterJones said in Developing generic regex sequences:

              Updating with n-term rather than just two-term:

              Nice use of a table in a posting here, as well. :-)
              Seriously, valuable information here. Kudos.

              1 Reply Last reply Reply Quote 0
              • Alan KilbornA
                Alan Kilborn
                last edited by Alan Kilborn

                So as I often do, I dug in a bit deeper to what Peter presented.
                My conclusion is that pointing novices at regular expressions here and expecting them to solve their own related problems may not be super-successful.
                It isn’t that all the needed info isn’t here – it is – it just may require some base knowledge to be applicable, without readers saying “Huh?”.

                So maybe some really concrete examples help. In that light, my contribution will be how to match entire lines meeting the logic criteria that Peter brought to the table.

                Say you want to match some particular combination of Bob and Ted on a line – here’s information on doing that:

                Logic Expression to use Match entire line when…
                OR (?-s)(?:(?=.*Bob|.*Ted))^.*(?:\R|\z) Bob or Ted (or both) is present, in either order
                AND (?-s)(?:(?=.*Bob)(?=.*Ted))^.*(?:\R|\z) both Bob and Ted are present, in either order
                XOR (?-s)(?:(?=.*Bob)(?!.*Ted)|(?!.*Bob)(?=.*Ted))^.*(?:\R|\z) Bob or Ted is present, but not when both are present
                NOR-1 (?-s)(?:(?!.*Bob)(?!.*Ted))^.*(?:\R|\z) neither Bob/Ted are present (form 1)
                NOR-2 (?-s)(?:(?!.*(Bob|Ted)))^.*(?:\R|\z) neither Bob/Ted are present (form 2)
                NAND (?-s)(?:(?!(?=.*Bob)(?=.*Ted)))^.*(?:\R|\z) neither are present or one is present, but not when both are present

                I took a little liberty with Peter’s original “notes” table column; changed it up a bit. Also, obviously I only did a “two term” example.

                Maybe I’m off-base and this doesn’t provide additional insight on exactly how to use Peter’s info, but hopefully it does.

                PeterJonesP 1 Reply Last reply Reply Quote 3
                • PeterJonesP
                  PeterJones @Alan Kilborn
                  last edited by

                  @Alan-Kilborn said in Developing generic regex sequences:

                  My conclusion is that pointing novices at regular expressions here and expecting them to solve their own related problems may not be super-successful.

                  That’s why I posted here, rather than separately. This thread is for “developing” the generic expressions, with lots of back and forth. The “final version” will be published to its own separate thread. (I probably shouldn’t’ve posted a link back to here from the inspiration thread, because this one wasn’t ready yet)

                  I think your table is a good practical example of how to use it.

                  PeterJonesP 1 Reply Last reply Reply Quote 2
                  • Alan KilbornA
                    Alan Kilborn
                    last edited by Alan Kilborn

                    So a note on “practicality” here…
                    Recently I had cause to implement some “OR” searches as described above.
                    I pulled up this thread for the “formula”, put my specific use-case data in, and pressed Find All in Current Document, and, well, …, waited, a loooong time for results to come back.
                    It turns out that the regexes specified above are fine for “small” data, but are rather inefficient for “bigger” data, or at least the size/type of data I had.

                    Here’s an example:
                    The original “match entire line OR regex” above is (?-s)(?:(?=.*Bob|.*Ted))^.*(?:\R|\z)
                    For my data, that one took between one and two minutes to run.
                    If I change the regex to (?-s)^(?=.*?(?:Bob|Ted)).+, that one runs so quickly that it is hard to time, except to say maybe it takes a second or so.

                    Probably all of the regexes I presented in my table above could be better optimized. :-(

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                    • PeterJonesP
                      PeterJones @PeterJones
                      last edited by

                      A year later, I finally got around to making the “table of contents” post in the FAQ: “FAQ Desk: Generic Regular Expresion (regex) Formulas”

                      For now, it’s linking to the in-thread versions of these generic expressions… but I highly encourage the developers of the expression to spin off a new blog post for each generic regex.

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                      • C BaccaC
                        C Bacca
                        last edited by

                        Hi all,
                        I’m wondering if this needs to be added to the Regex FAQ or another thread. @PeterJones @guy038

                        There are some good regex tester sites out there. Here’s one and a search for others. It really helps in debugging regular expressions. Generally you add in test data and the regex, and the site will highlight the strings it matches.

                        Build and test regular expressions regex. Make a free account here to save your regexes. https://regex101.com/
                        Search for more: https://search.brave.com/search?q=free+account+test+regular+expression&source=web

                        I hope this is helpful!

                        C BaccaC PeterJonesP Alan KilbornA 3 Replies Last reply Reply Quote 0
                        • C BaccaC
                          C Bacca @C Bacca
                          last edited by

                          @c-bacca Ok this search is case sensitive.

                          Also, here’s an example with example data. https://regex101.com/r/Hfly86/1

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                          • PeterJonesP
                            PeterJones @C Bacca
                            last edited by

                            @c-bacca said in Developing generic regex sequences:

                            I’m wondering if this needs to be added to the Regex FAQ or another thread.

                            Why would it need to be added where it already exists?

                            Or were you not aware that we have two different regex FAQ entries?

                            The second was the one discussed in this original topic: a table of contents of “generic” regex at https://community.notepad-plus-plus.org/topic/22673/faq-desk-generic-regular-expression-regex-formulas

                            But the much earlier regex FAQ explains where to get regex help, including links to the Notepad++ regex documentation, plus links to a lot more “regex tester” sites than you mentioned: https://community.notepad-plus-plus.org/topic/15765/faq-desk-where-to-find-regular-expressions-regex-documentation

                            1 Reply Last reply Reply Quote 1
                            • Alan KilbornA
                              Alan Kilborn @C Bacca
                              last edited by

                              @c-bacca said in Developing generic regex sequences:

                              There are some good regex tester sites out there. Here’s one and a search for others. It really helps in debugging regular expressions. Generally you add in test data and the regex, and the site will highlight the strings it matches.
                              Build and test regular expressions regex. Make a free account here to save your regexes. https://regex101.com/

                              I suppose, but I don’t believe it uses the same regular expression engine as Notepad++, so it is of limited usefulness if you are going to use Notepad++ to do your regular expression searches and replacements.

                              Lycan ThropeL 1 Reply Last reply Reply Quote 1
                              • Lycan ThropeL
                                Lycan Thrope @Alan Kilborn
                                last edited by Lycan Thrope

                                @alan-kilborn ,
                                It actually let’s you use different regex flavors, (PCRE pre 7.3 and 7.3 plus, ECMAScript, Python, Golang, Java8, and .NET(C#), but the benefit of regex101.com, is that you can interactively see how your regex construction is going to work on the text you supply, either just Search or both Search and Replace. It’s actually educational to see what happens as you experiment with different regex constructions. You have to construct and then execute NPP to see results, and you’re not sure what you did wrong unless there’s a mode in NPP that does the same interactive result. I use it all the time to construct the regex I’ve been building, to be able to quickly see how the regex I’m constructing works on their supplied text. It’s just another tool, and it is recommended as Peter points out in the FAQ, which is where I learned about it. So I can see why someone might want to use that tool, Alan. :)

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                                • PeterJonesP
                                  PeterJones @PeterJones
                                  last edited by PeterJones

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