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Re: trouble with pattern, character collections

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  • Christian Brabandt
    Hi Marc! ... I think, you are seeing some kind of inconsistency here. The problem is, that [^ n] does match newlines. This is allowed so that in a text which
    Message 1 of 28 , Feb 17, 2013
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      Hi Marc!

      On So, 17 Feb 2013, Marc Weber wrote:

      > I expect the following to output 1 (be equal), but its not. I don't understand why
      >
      > echo substitute("-D abc\nfoo/bar\n-L x", "-[DL][ ]*[^\n]*",'','g')
      > \ == substitute("-D abc\nfoo/bar\n-L x", '-[DL][ ]*[^\n]*','','g')
      >
      > Why do I expect so ? because "[\n]" should be the same as '[\n]' - however
      > '[\n]' should be replaced by chr(10) by the pattern interpreter according to help:
      >
      > according to :h pattern.txt /A collection. This is a sequence of characters enclosed in brackets
      > - The following translations are accepted when the 'l' flag is not
      > included in 'cpoptions' {not in Vi}:
      > [..]
      > \n line break, see above |/[\n]|
      >
      > Which piece am I missunderstanding?

      I think, you are seeing some kind of inconsistency here. The problem is,
      that '[^\n]' does match newlines. This is allowed so that in a text
      which is shown by vim as "A^@A" or "A^MA" the '.' also matches those
      control chars carrige return / line feed.

      Thus the '[^\n]*' matches everything and so everything is replaced.

      I thought about changing it, but that would be an incompatible change
      (and in fact already fails some tests). I have briefly mentioned this
      here:
      https://groups.google.com/d/topic/vim_dev/DzJ7ZzYlzQI/discussion

      regards,
      Christian

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    • Marc Weber
      ... This doesn t make sense. If I ask to not match n I don t want n to be matched. Its about following the principle of least surprise. The burden to learn
      Message 2 of 28 , Feb 17, 2013
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        > This is allowed so that in a text
        > which is shown by vim as "A^@A" or "A^MA" the '.' also matches those
        > control chars carrige return / line feed.
        This doesn't make sense. If I ask to not match \n I don't want \n to be
        matched. Its about following the principle of least surprise.
        The burden to learn vim specific regex is already high enough for most
        users.

        Also try to make me understand why "[^\n]" is supposed to do what it
        says, but '[^\n]' is not. In which way is either one related to .?

        > https://groups.google.com/d/topic/vim_dev/DzJ7ZzYlzQI/discussion
        In any case it should be documented.

        Also let me know if you think that I missunderstood the docs which I
        referenced.

        So this is either an implementation or a documentation bug.
        I'd like to this to be treated as a implementation bug.

        Vim should also follow the principle of "least suprprise" - and [^\n] is
        supposed to not match \n.

        There is more future than past - so its ok to break compatiblity in such
        an obvious case IMHO.

        Marc Weber

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      • Christian Brabandt
        Hi Marc! ... It depends. Within a text file those control chars can occur and you usually want them to be matched by . (or [^ n] which is the same). ... I
        Message 3 of 28 , Feb 17, 2013
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          Hi Marc!

          On So, 17 Feb 2013, Marc Weber wrote:

          > > This is allowed so that in a text
          > > which is shown by vim as "A^@A" or "A^MA" the '.' also matches those
          > > control chars carrige return / line feed.
          > This doesn't make sense. If I ask to not match \n I don't want \n to be
          > matched. Its about following the principle of least surprise.

          It depends. Within a text file those control chars can occur and you
          usually want them to be matched by '.' (or [^\n] which is the same).

          > The burden to learn vim specific regex is already high enough for most
          > users.

          I don't see a burden here. In fact I like the vim specific regex, as I
          see it as an enhanced version of BRE (but if you don't like it, use the
          \v modifier).

          > Also try to make me understand why "[^\n]" is supposed to do what it
          > says, but '[^\n]' is not. In which way is either one related to .?

          Because "\n" evals certain special backslash escaped chars within the
          string (:h expr-string) and by definition '.' is the same as [^\n] at
          least since one of the latest patches.

          >
          > > https://groups.google.com/d/topic/vim_dev/DzJ7ZzYlzQI/discussion
          > In any case it should be documented.
          >
          > Also let me know if you think that I missunderstood the docs which I
          > referenced.
          >
          > So this is either an implementation or a documentation bug.
          > I'd like to this to be treated as a implementation bug.
          >
          > Vim should also follow the principle of "least suprprise" - and [^\n] is
          > supposed to not match \n.

          I don't want to change the RE engine so that certain control chars are
          not matched anymore by '.' or [^\n]. This is at least backwards
          incompatible (which I wouldn't have a problem with) and unexpected
          (which I do have a problem with). But in the end, Bram decides.

          Mit freundlichen Grüßen
          Christian
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        • Erik Christiansen
          ... +1 ... And too much for some. The failure to employ posix EREs is Vim s only true failing, IME. (OK, by prefixing v to every regex, we get reasonably
          Message 4 of 28 , Feb 17, 2013
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            On 17.02.13 14:03, Marc Weber wrote:
            > This doesn't make sense. If I ask to not match \n I don't want \n to be
            > matched. Its about following the principle of least surprise.

            +1

            > The burden to learn vim specific regex is already high enough for most
            > users.

            And too much for some. The failure to employ posix EREs is Vim's only
            true failing, IME. (OK, by prefixing \v to every regex, we get
            reasonably close.)

            ...

            > Vim should also follow the principle of "least suprprise" - and [^\n] is
            > supposed to not match \n.
            >
            > There is more future than past - so its ok to break compatiblity in such
            > an obvious case IMHO.

            It is a compelling case - ya gotta admit.

            Erik

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          • Marc Weber
            ... Thanks for explaining it to me. So we ve hit the true question: Should . behave the same way as [^ n] ? Who is going to write [^ n] if you can use . ?
            Message 5 of 28 , Feb 17, 2013
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              > It depends. Within a text file those control chars can occur and you
              > usually want them to be matched by '.' (or [^\n] which is the same).
              Thanks for explaining it to me.

              So we've hit the true question:

              Should '.' behave the same way as [^\n] ?

              Who is going to write [^\n] if you can use '.' ?

              From my point of view there is no use of [^\n] other than causing
              surprise.

              New arguments for keeping surprising [^\n] behaviour?

              Let's ask in a different way: Is there a use case for [^\n] like
              patterns at all (except that '.' which can be expressed as '.')?

              Marc Weber

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            • Ben Fritz
              ... I thought 7.3.796 fixed this so [^ n] is the same as . ? Isn t that the case? -- -- You received this message from the vim_use maillist. Do not
              Message 6 of 28 , Feb 18, 2013
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                On Sunday, February 17, 2013 6:40:04 AM UTC-6, Christian Brabandt wrote:
                >
                > I think, you are seeing some kind of inconsistency here. The problem is,
                >
                > that '[^\n]' does match newlines.

                I thought 7.3.796 fixed this so [^\n] is the same as '.'? Isn't that the case?

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              • Marc Weber
                ... Rererad my message. My point is that [^ n] should *not* be the same as . following the principle of least surprise. Or tell me why there should be two
                Message 7 of 28 , Feb 18, 2013
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                  > I thought 7.3.796 fixed this so [^\n] is the same as '.'? Isn't that the case?
                  Rererad my message. My point is that [^\n] should *not* be the same as
                  '.' following the principle of least surprise.

                  Or tell me why there should be two ways to express the same - but no
                  sane way to express [^\n].

                  If its not possible to make [^\n] behave the way you expect there should
                  be an error instead.

                  Marc Weber

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                • Tim Chase
                  ... I seem to recall a similar thread a while back on similar topics of newlines inside negated character classes. [digging] yup:
                  Message 8 of 28 , Feb 18, 2013
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                    On 2013-02-18 20:28, Marc Weber wrote:
                    > > I thought 7.3.796 fixed this so [^\n] is the same as '.'? Isn't
                    > > that the case?
                    > Rererad my message. My point is that [^\n] should *not* be the same
                    > as '.' following the principle of least surprise.
                    >
                    > Or tell me why there should be two ways to express the same - but no
                    > sane way to express [^\n].
                    >
                    > If its not possible to make [^\n] behave the way you expect there
                    > should be an error instead.

                    I seem to recall a similar thread a while back on similar topics of
                    newlines inside negated character classes. [digging] yup:

                    http://permalink.gmane.org/gmane.editors.vim/107071

                    I don't know if my testing proves useful, or if the continuation of
                    the thread offers you anything valuable, but at least it's not the
                    first time this has been bumped against.

                    -tim


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                  • Marc Weber
                    I don t think that additional threads are going to help There is an issue, and we should find a way to fix (IMHO). Let me summarize again - and tell me if you
                    Message 9 of 28 , Feb 18, 2013
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                      I don't think that additional threads are going to help
                      There is an issue, and we should find a way to fix (IMHO).
                      Let me summarize again - and tell me if you feel differently.

                      Test cases:
                      [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                      [2] echo len(matchstr("\n","\\zs[^\n]\\ze"))

                      I expect both do the same, the difference is that the second as chr(10) in [^],
                      while the first has \n (which should be translated to chr(10).

                      However I obsorve that [2] returns 0 as expected , but [1] does return
                      1, thus it matches \n even though I told Vim that I do not want to match
                      it. People told me this was because '.' is equal to [^\n].


                      Current situation: at least to be fixed
                      1:
                      No matter whether '.' should behave like [^\n]
                      [1] and [2] should behave the same, right?
                      2:
                      This should be documented.
                      (Do you all at least agree these two statments?)

                      If so which is the best way to fix this - and which should be the way to
                      express [^\n] meaning do not match \n rather than behave like '.' then ?

                      Marc Weber

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                    • Christian Brabandt
                      Hi Ben! ... It is. The problem is, that there is a difference between the evaluated string [^ n] which means match anything but linefeed and [^ n] which
                      Message 10 of 28 , Feb 18, 2013
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                        Hi Ben!

                        On Mo, 18 Feb 2013, Ben Fritz wrote:

                        > I thought 7.3.796 fixed this so [^\n] is the same as '.'? Isn't that the case?

                        It is. The problem is, that there is a difference between the evaluated
                        string "[^\n]" which means match anything but linefeed and '[^\n]' which
                        means anything but "a line seperator". This is, so that the linefeed
                        control char whithin a text can be matched by '.' or [^\n]

                        regards,
                        Christian
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                      • Christian Brabandt
                        Hi Tim! ... That problem should have been solved by patch 7.3.796. regards, Christian -- Wie man sein Kind nicht nennen sollte: Bill Jard -- -- You received
                        Message 11 of 28 , Feb 18, 2013
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                          Hi Tim!

                          On Mo, 18 Feb 2013, Tim Chase wrote:

                          > I seem to recall a similar thread a while back on similar topics of
                          > newlines inside negated character classes. [digging] yup:
                          >
                          > http://permalink.gmane.org/gmane.editors.vim/107071
                          >
                          > I don't know if my testing proves useful, or if the continuation of
                          > the thread offers you anything valuable, but at least it's not the
                          > first time this has been bumped against.

                          That problem should have been solved by patch 7.3.796.

                          regards,
                          Christian
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                          Bill Jard

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                        • Christian Brabandt
                          Hi Marc! ... No, it is because n is evaluated to a true line feed, so [^ n] matches anything but ASCII NUL and ASCII 10, while [^ n] matches anything
                          Message 12 of 28 , Feb 18, 2013
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                            Hi Marc!

                            On Mo, 18 Feb 2013, Marc Weber wrote:

                            > I don't think that additional threads are going to help
                            > There is an issue, and we should find a way to fix (IMHO).
                            > Let me summarize again - and tell me if you feel differently.
                            >
                            > Test cases:
                            > [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                            > [2] echo len(matchstr("\n","\\zs[^\n]\\ze"))
                            >
                            > I expect both do the same, the difference is that the second as chr(10) in [^],
                            > while the first has \n (which should be translated to chr(10).
                            >
                            > However I obsorve that [2] returns 0 as expected , but [1] does return
                            > 1, thus it matches \n even though I told Vim that I do not want to match
                            > it. People told me this was because '.' is equal to [^\n].

                            No, it is because "\n" is evaluated to a true line feed, so "[^\n]"
                            matches anything but ASCII NUL and ASCII 10, while '[^\n]' matches
                            anything but ASCII NUL (which is used internally by Vim to distinguish
                            lines from each other (e.g. a line seperator), so that a . matches
                            anyhing in the buffer but the line seperator)

                            > If so which is the best way to fix this - and which should be the way to
                            > express [^\n] meaning do not match \n rather than behave like '.' then ?

                            [^\n] should always behave like '.'

                            Mit freundlichen Grüßen
                            Christian
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                          • Marc Weber
                            ... Christian: Once and for all - I don t want anybody to explain me that [^ n] behaves in a wired way because . should behave the way it does. I m *not*
                            Message 13 of 28 , Feb 18, 2013
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                              > No, it is because "\n" is evaluated to a true line feed, so "[^\n]"
                              > matches anything but ASCII NUL and ASCII 10, while '[^\n]' matches
                              > anything but ASCII NUL (which is used internally by Vim to distinguish
                              > lines from each other (e.g. a line seperator), so that a . matches
                              > anyhing in the buffer but the line seperator)

                              Christian: Once and for all - I don't want anybody to explain me that
                              [^\n] behaves in a wired way because '.' should behave the way it does.

                              I'm *not* talking about internals. I'm talking the user interface you
                              and me and new users are faced with every day. So help me think about
                              whether there is a way to improve the situation.

                              So why should anybody write [^\n] if you can use '.'? So why make [^\n]
                              behave the same way? Why not make it raise an error such as:

                              E99999: For odd reasons you should try "[\n]" instead of '[^\n]' and be
                              done. True reason see long reply by Christian on ml ..

                              Trouble solved within 2 min. No debugging why vim does not behave the
                              way you expect. This guard would be trival to implement. if []
                              collections are negated and contain \n show the message.
                              And it would not break backward compatibility. Which is the use case for
                              allowing '[^\n]' at all?

                              I'm not saying it solves the issue, but it would cause less pain,
                              do you agree on this?

                              I wrote vim-addon-manager to improve usage experience for users - and
                              this is another case just driving me crazy which I think needs to
                              improved - the issue is in which way.

                              Marc Weber

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                            • Erik Christiansen
                              ... Vim already uses $ for EOL, documented at :h $ , which even seems to offer the synonym . Vim already has . to mean . , so does not need
                              Message 14 of 28 , Feb 18, 2013
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                                On 18.02.13 23:06, Christian Brabandt wrote:
                                > No, it is because "\n" is evaluated to a true line feed, so "[^\n]"
                                > matches anything but ASCII NUL and ASCII 10, while '[^\n]' matches
                                > anything but ASCII NUL (which is used internally by Vim to distinguish
                                > lines from each other (e.g. a line seperator), so that a . matches
                                > anyhing in the buffer but the line seperator)
                                >
                                > > If so which is the best way to fix this - and which should be the way to
                                > > express [^\n] meaning do not match \n rather than behave like '.' then ?

                                Vim already uses '$' for EOL, documented at ":h $", which even seems to
                                offer the synonym "<End>". Vim already has '.' to mean '.', so does not
                                need <elephant> for the same. So why do it???

                                > [^\n] should always behave like '.'

                                No, sorry, only in a line devoid of newlines. By definition.
                                In regex terms, i.e the user view, [^\n] may match anything other than a
                                newline, while '.' may match any single character. Only if newlines have
                                been stripped in the internal line representation, and e.g. replaced
                                with NUL, can '.' legitimately fail to match \n. Otherwise, we can only
                                reasonably say the [^\n] should NOT always behave like '.'

                                In contrast, "[^\n]" _is_ identical to '[^\n]' in regex syntax, so must
                                be identical in behaviour, devoid of even subtle differences, in any
                                context.

                                On 18.02.13 23:38, Marc Weber wrote:
                                > I'm *not* talking about internals. I'm talking the user interface you
                                > and me and new users are faced with every day. So help me think about
                                > whether there is a way to improve the situation.
                                >
                                > So why should anybody write [^\n] if you can use '.'? So why make [^\n]
                                > behave the same way? Why not make it raise an error such as:
                                >
                                > E99999: For odd reasons you should try "[\n]" instead of '[^\n]' and be
                                > done. True reason see long reply by Christian on ml ..

                                Or E99999: Unsupported syntax. Vim fails to give rational syntax-relevant
                                effect to this regex. Try <whatever> instead.

                                Sorry, [^\n] can never match \n ; not even in pink. That is broken
                                behaviour.

                                Erik

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                                and totally illogical, with just a little bit more effort?"
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                              • Christian Brabandt
                                Hi Erik! ... Well, if you think about it, $ matches something different. You can t say, /n$n can you? ... Because the . is a perfect valid alias to [^ n]
                                Message 15 of 28 , Feb 19, 2013
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                                  Hi Erik!

                                  On Di, 19 Feb 2013, Erik Christiansen wrote:

                                  > On 18.02.13 23:06, Christian Brabandt wrote:
                                  > > No, it is because "\n" is evaluated to a true line feed, so "[^\n]"
                                  > > matches anything but ASCII NUL and ASCII 10, while '[^\n]' matches
                                  > > anything but ASCII NUL (which is used internally by Vim to distinguish
                                  > > lines from each other (e.g. a line seperator), so that a . matches
                                  > > anyhing in the buffer but the line seperator)
                                  > >
                                  > > > If so which is the best way to fix this - and which should be the way to
                                  > > > express [^\n] meaning do not match \n rather than behave like '.' then ?
                                  >
                                  > Vim already uses '$' for EOL, documented at ":h $", which even seems to
                                  > offer the synonym "<End>".


                                  Well, if you think about it, $ matches something different. You can't
                                  say, "/n$n" can you?

                                  > Vim already has '.' to mean '.', so does not
                                  > need <elephant> for the same. So why do it???

                                  Because the '.' is a perfect valid alias to [^\n] in most regexes
                                  anyway? Why cripple it?

                                  > > [^\n] should always behave like '.'
                                  >
                                  > No, sorry, only in a line devoid of newlines. By definition.
                                  > In regex terms, i.e the user view, [^\n] may match anything other than a
                                  > newline, while '.' may match any single character. Only if newlines have
                                  > been stripped in the internal line representation, and e.g. replaced
                                  > with NUL, can '.' legitimately fail to match \n. Otherwise, we can only
                                  > reasonably say the [^\n] should NOT always behave like '.'

                                  In all regexp engines that I know of, the '.' by default doesn't match a
                                  newline, so it is perfectly valid to have [^\n] match the same as '.'

                                  > In contrast, "[^\n]" _is_ identical to '[^\n]' in regex syntax, so must
                                  > be identical in behaviour, devoid of even subtle differences, in any
                                  > context.

                                  Please read again the article to which you replied. I already said, why
                                  this is different. This comes from the string-evaluation of the "[..]"
                                  expression. You can read about it at :h expr-string.

                                  > Sorry, [^\n] can never match \n ; not even in pink. That is broken
                                  > behaviour.

                                  Please come back with some arguments. I told you why this happens. If
                                  you don't want that, Vim already provides a setting to fix this.

                                  :set cpo+=l


                                  Mit freundlichen Grüßen
                                  Christian
                                  --
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                                • Christian Brabandt
                                  Hi Marc! ... Bram, here is a patch, making [^ n] not match NL within the text and that also documents, that . matches CR and LF within the text. This makes
                                  Message 16 of 28 , Feb 19, 2013
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                                    Hi Marc!

                                    On Mo, 18 Feb 2013, Marc Weber wrote:

                                    > I don't think that additional threads are going to help
                                    > There is an issue, and we should find a way to fix (IMHO).
                                    > Let me summarize again - and tell me if you feel differently.
                                    >
                                    > Test cases:
                                    > [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                                    > [2] echo len(matchstr("\n","\\zs[^\n]\\ze"))
                                    >
                                    > I expect both do the same, the difference is that the second as chr(10) in [^],
                                    > while the first has \n (which should be translated to chr(10).
                                    >
                                    > However I obsorve that [2] returns 0 as expected , but [1] does return
                                    > 1, thus it matches \n even though I told Vim that I do not want to match
                                    > it. People told me this was because '.' is equal to [^\n].
                                    >
                                    >
                                    > Current situation: at least to be fixed
                                    > 1:
                                    > No matter whether '.' should behave like [^\n]
                                    > [1] and [2] should behave the same, right?
                                    > 2:
                                    > This should be documented.
                                    > (Do you all at least agree these two statments?)

                                    Bram, here is a patch, making [^\n] not match NL within the text and
                                    that also documents, that '.' matches CR and LF within the text.

                                    This makes both [1] and [2] behave the same and seems to better match
                                    the users expectations.

                                    regards,
                                    Christian
                                    --
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                                    Menge stolz sein - die Genies können auf die Genies es sein.
                                    -- Jean Paul

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                                  • Christian Brabandt
                                    Hi Marc! ... Because [^ n] is perfectly valid? ... If you don t want that, use :set cpo+=l ... It is a perfect valid regular expression. What is the reason to
                                    Message 17 of 28 , Feb 19, 2013
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                                      Hi Marc!

                                      On Mo, 18 Feb 2013, Marc Weber wrote:

                                      > > No, it is because "\n" is evaluated to a true line feed, so "[^\n]"
                                      > > matches anything but ASCII NUL and ASCII 10, while '[^\n]' matches
                                      > > anything but ASCII NUL (which is used internally by Vim to distinguish
                                      > > lines from each other (e.g. a line seperator), so that a . matches
                                      > > anyhing in the buffer but the line seperator)
                                      >
                                      > Christian: Once and for all - I don't want anybody to explain me that
                                      > [^\n] behaves in a wired way because '.' should behave the way it does.
                                      >
                                      > I'm *not* talking about internals. I'm talking the user interface you
                                      > and me and new users are faced with every day. So help me think about
                                      > whether there is a way to improve the situation.
                                      >
                                      > So why should anybody write [^\n] if you can use '.'? So why make [^\n]
                                      > behave the same way? Why not make it raise an error such as:

                                      Because [^\n] is perfectly valid?

                                      >
                                      > E99999: For odd reasons you should try "[\n]" instead of '[^\n]' and be
                                      > done. True reason see long reply by Christian on ml ..
                                      >
                                      > Trouble solved within 2 min. No debugging why vim does not behave the
                                      > way you expect. This guard would be trival to implement. if []
                                      > collections are negated and contain \n show the message.

                                      If you don't want that, use :set cpo+=l

                                      > And it would not break backward compatibility. Which is the use case for
                                      > allowing '[^\n]' at all?

                                      It is a perfect valid regular expression. What is the reason to forbid
                                      its use?

                                      Anyway, I just made a patch, that should match your expectations.


                                      regards,
                                      Christian
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                                    • Marc Weber
                                      I want Vim defaults to be - sane - follow the principle of least surprise. (I d like nocompatible to be set by default, but that s another story) Christian:
                                      Message 18 of 28 , Feb 19, 2013
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                                        I want Vim defaults to be
                                        - sane
                                        - follow the principle of least surprise.
                                        (I'd like nocompatible to be set by default, but that's another story)

                                        Christian: :set cpo+=l still makes my test cases fail:
                                        [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                                        [2] echo len(matchstr("\n","\\zs[^\n]\\ze")

                                        You explained it by \n not being chr(10), so what is it?

                                        Let's try by understanding \n's behaviour:
                                        ==========================================

                                        case 1) vim buf
                                        To my undestanding $ matches end of line (in a vim buffer) without eating that
                                        end of line whereas \n does both: it matches and eats the end of line.
                                        Eg try /..\n.. and :set hlsearch

                                        Thus \n is the same as $\n when applying regex to vim buffers. dos 1310 usually
                                        is encoded in a ff setting, so \n does what you want if you want it.

                                        case 2) matchstr, matchall, substitute =~ and whatnot (?)

                                        So if \n is not chr(10), what is it then in this case?

                                        echo len(matchstr("\n",'\zs[^\n]\ze'))

                                        clearly indicates it matches \n and and I agree on Erik which called it this way

                                        Sorry, [^\n] can never match \n ; not even in pink. That is broken
                                        behaviour.

                                        So from this point of view I'd say \n behavior is broken when regex get applied
                                        to strings only (which your patch is supposed to fix - I'll test it
                                        later)

                                        Is there more to fix?
                                        =====================

                                        issue 1)

                                        docs state:
                                        [] (with 'nomagic': \[]) */[]* */\[]* */\_[]* */collection*
                                        \_[]

                                        Well - try /[] - it will not be treated as collection, it'll match [], because
                                        its empty!! So there should be a comment that collections must contain at least
                                        one char to be seen as one.

                                        issue 2)
                                        With "\_" prepended the collection also includes the end-of-line - why does it exist, because
                                        [\n] is accepted and works as expected?

                                        So can \_[] syntax be deprecated?


                                        Marc Weber

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                                      • Christian Brabandt
                                        Hi Marc! ... Well, you need to prevent that expr-quote (:h expr-quote) is being evaluated. You need to escape the then. ... No. Please read again what I
                                        Message 19 of 28 , Feb 19, 2013
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                                          Hi Marc!

                                          On Di, 19 Feb 2013, Marc Weber wrote:

                                          > I want Vim defaults to be
                                          > - sane
                                          > - follow the principle of least surprise.
                                          > (I'd like nocompatible to be set by default, but that's another story)
                                          >
                                          > Christian: :set cpo+=l still makes my test cases fail:
                                          > [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                                          > [2] echo len(matchstr("\n","\\zs[^\n]\\ze")

                                          Well, you need to prevent that expr-quote (:h expr-quote) is being
                                          evaluated. You need to escape the \ then.

                                          > You explained it by \n not being chr(10), so what is it?

                                          No. Please read again what I wrote. I am not going to repeat myself.

                                          > Let's try by understanding \n's behaviour:
                                          > ==========================================
                                          >
                                          > case 1) vim buf
                                          > To my undestanding $ matches end of line (in a vim buffer) without eating that
                                          > end of line whereas \n does both: it matches and eats the end of line.
                                          > Eg try /..\n.. and :set hlsearch
                                          >
                                          > Thus \n is the same as $\n when applying regex to vim buffers. dos 1310 usually
                                          > is encoded in a ff setting, so \n does what you want if you want it.
                                          >
                                          > case 2) matchstr, matchall, substitute =~ and whatnot (?)
                                          >
                                          > So if \n is not chr(10), what is it then in this case?
                                          >
                                          > echo len(matchstr("\n",'\zs[^\n]\ze'))
                                          >
                                          > clearly indicates it matches \n and and I agree on Erik which called it this way
                                          >

                                          Vim internals do not distinguish between evaluating functions and
                                          buffers. They work on matching a regular pattern on a string of text. In
                                          Vim buffers, lines are distinguished in memory by NUL and that is the
                                          only thing, that '.' does not match and so does [^\n] so that in a
                                          buffer a search for /[^\n] will match any char (even control codes like
                                          CR or LF)

                                          What you want is, that in a text /[^\n] also does not match LF character
                                          and that is what my patch provides thus it should do what you want.

                                          > Is there more to fix?
                                          > =====================
                                          >
                                          > issue 1)
                                          >
                                          > docs state:
                                          > [] (with 'nomagic': \[]) */[]* */\[]* */\_[]* */collection*
                                          > \_[]
                                          >
                                          > Well - try /[] - it will not be treated as collection, it'll match [], because
                                          > its empty!! So there should be a comment that collections must contain at least
                                          > one char to be seen as one.

                                          I would call this a bug as well. I think, this should give an error.

                                          > issue 2)
                                          > With "\_" prepended the collection also includes the end-of-line - why does it exist, because
                                          > [\n] is accepted and works as expected?
                                          >
                                          > So can \_[] syntax be deprecated?

                                          Why is this an issue? I don't see a problem with \_ syntax at all.

                                          Mit freundlichen Grüßen
                                          Christian
                                          --
                                          Dem großen Publikum ist ein Buch nicht leicht zu schlecht, sehr
                                          leicht aber zu gut.
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                                        • Marc Weber
                                          ... Let me tell you. People get to know Vim. Vim is a tool to serve users. They want to edit text, get their job done (At least that s what I assume). For this
                                          Message 20 of 28 , Feb 19, 2013
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                                            > Why is this an issue? I don't see a problem with \_ syntax at all.
                                            Let me tell you. People get to know Vim. Vim is a tool to serve users.
                                            They want to edit text, get their job done (At least that's what I
                                            assume). For this reason every construct such as \_ which requires you
                                            to lookup help is going to take your time - time which should be spent
                                            on the wiki or the homepage (yes - there is much to improve).

                                            So from technical point of view there is nothing wrong: Something is
                                            documentented, and it works as expected.

                                            If you look at the ruby community there are some voices which
                                            dislike some aspects about ruby: That there are so many ways to do
                                            something ..

                                            If you look at the whole ecosystem it is wrong, because its
                                            wasting resources in many ways (human resources being the most
                                            expensive ones). You may disagree on this - but its true.
                                            The best docs are the ones you don't have to read.

                                            I'm not proposing dropping it (if Vim was my projcet I'd do so - showing
                                            an error message instead) - but maybe docs can be adjusted so that
                                            people use [\n] and maybe even miss the Vim only special case on the
                                            first glance.

                                            Christian, thanks for your support.

                                            Marc Weber

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                                          • Christian Brabandt
                                            ... Attached is an updated patch, that also prevents /[] matching [] (a collation cannot be empty, so I think it should return an error and other vi clones do,
                                            Message 21 of 28 , Feb 19, 2013
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                                              On Di, 19 Feb 2013, Christian Brabandt wrote:

                                              > On Mo, 18 Feb 2013, Marc Weber wrote:
                                              > > I don't think that additional threads are going to help
                                              > > There is an issue, and we should find a way to fix (IMHO).
                                              > > Let me summarize again - and tell me if you feel differently.
                                              > >
                                              > > Test cases:
                                              > > [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                                              > > [2] echo len(matchstr("\n","\\zs[^\n]\\ze"))
                                              > >
                                              > > I expect both do the same, the difference is that the second as chr(10) in [^],
                                              > > while the first has \n (which should be translated to chr(10).
                                              > >
                                              > > However I obsorve that [2] returns 0 as expected , but [1] does return
                                              > > 1, thus it matches \n even though I told Vim that I do not want to match
                                              > > it. People told me this was because '.' is equal to [^\n].
                                              > >
                                              > >
                                              > > Current situation: at least to be fixed
                                              > > 1:
                                              > > No matter whether '.' should behave like [^\n]
                                              > > [1] and [2] should behave the same, right?
                                              > > 2:
                                              > > This should be documented.
                                              > > (Do you all at least agree these two statments?)
                                              >
                                              > Bram, here is a patch, making [^\n] not match NL within the text and
                                              > that also documents, that '.' matches CR and LF within the text.
                                              >
                                              > This makes both [1] and [2] behave the same and seems to better match
                                              > the users expectations.

                                              Attached is an updated patch, that also prevents /[] matching []
                                              (a collation cannot be empty, so I think it should return an error and
                                              other vi clones do, also grep and perl throw an error).

                                              Included are tests as well.

                                              regards,
                                              Christian
                                              --
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                                            • Marc Weber
                                              ... We should discuss whether /[] is a bug or feature. docs state that /[abc matches [abc by purpose (which could also be treated as error because there is no
                                              Message 22 of 28 , Feb 19, 2013
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                                                > [..] patch, [..] prevents /[] matching []
                                                > other vi clones do, also grep and perl throw an error).
                                                :) You start comparing Vim against what other tools do.

                                                We should discuss whether /[] is a bug or feature. docs state that /[abc
                                                matches [abc by purpose (which could also be treated as error because
                                                there is no closing ]. And I actually might agree on this being useful.

                                                Marc Weber

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                                              • Ben Fritz
                                                ... Sometimes the meaning is clearer. What if you re searching for a sequence of certain characters including newlines, where the first character is NOT a
                                                Message 23 of 28 , Feb 19, 2013
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                                                  On Monday, February 18, 2013 4:38:56 PM UTC-6, MarcWeber wrote:
                                                  >
                                                  > So why should anybody write [^\n] if you can use '.'? So why make [^\n]
                                                  >
                                                  > behave the same way?

                                                  Sometimes the meaning is clearer.

                                                  What if you're searching for a sequence of certain characters including newlines, where the first character is NOT a newline?

                                                  I'd probably want to use:

                                                  /[^\n]\&[a-f0-9\n]\+

                                                  which is equivalent to, but clearer in meaning than:

                                                  /.\&[a-f0-9\n]\+

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                                                • Erik Christiansen
                                                  ... Christian, many thanks for the work you have done, and for putting users first. It is heartily appreciated. The consolation may be small, but vim is now
                                                  Message 24 of 28 , Feb 20, 2013
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                                                    On 19.02.13 10:23, Christian Brabandt wrote:
                                                    > Bram, here is a patch, making [^\n] not match NL within the text and
                                                    > that also documents, that '.' matches CR and LF within the text.
                                                    >
                                                    > This makes both [1] and [2] behave the same and seems to better match
                                                    > the users expectations.

                                                    Christian, many thanks for the work you have done, and for putting users
                                                    first. It is heartily appreciated.

                                                    The consolation may be small, but vim is now consistent with awk:

                                                    »
                                                    . This matches any single character, including the newline character.

                                                    « - xpdf gawk.pdf # "Effective AWK Programming"

                                                    O'Reilly's "Mastering Regular Expressions" has it as varying between
                                                    tools. (OK, we knew that. :-)

                                                    Regards,
                                                    Erik

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                                                  • Bram Moolenaar
                                                    ... This isn t right, there are no NL characters in the text. There are NUL characters which are stored as NL characters. That s an implementation detail,
                                                    Message 25 of 28 , Feb 20, 2013
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                                                      Christian Brabandt wrote:

                                                      > Hi Marc!
                                                      >
                                                      > On Mo, 18 Feb 2013, Marc Weber wrote:
                                                      >
                                                      > > I don't think that additional threads are going to help
                                                      > > There is an issue, and we should find a way to fix (IMHO).
                                                      > > Let me summarize again - and tell me if you feel differently.
                                                      > >
                                                      > > Test cases:
                                                      > > [1] echo len(matchstr("\n",'\zs[^\n]\ze'))
                                                      > > [2] echo len(matchstr("\n","\\zs[^\n]\\ze"))
                                                      > >
                                                      > > I expect both do the same, the difference is that the second as chr(10) in [^],
                                                      > > while the first has \n (which should be translated to chr(10).
                                                      > >
                                                      > > However I obsorve that [2] returns 0 as expected , but [1] does return
                                                      > > 1, thus it matches \n even though I told Vim that I do not want to match
                                                      > > it. People told me this was because '.' is equal to [^\n].
                                                      > >
                                                      > >
                                                      > > Current situation: at least to be fixed
                                                      > > 1:
                                                      > > No matter whether '.' should behave like [^\n]
                                                      > > [1] and [2] should behave the same, right?
                                                      > > 2:
                                                      > > This should be documented.
                                                      > > (Do you all at least agree these two statments?)
                                                      >
                                                      > Bram, here is a patch, making [^\n] not match NL within the text and
                                                      > that also documents, that '.' matches CR and LF within the text.
                                                      >
                                                      > This makes both [1] and [2] behave the same and seems to better match
                                                      > the users expectations.

                                                      This isn't right, there are no NL characters in the text. There are NUL
                                                      characters which are stored as NL characters. That's an implementation
                                                      detail, which sometimes becomes visible to the user.

                                                      It's good to explain this in the docs. I'm not sure we actually should
                                                      change the behavior, it might not really take away much confusion.


                                                      --
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                                                    • Marc Weber
                                                      Hi Bram, thanks for joining the discussion and participating. echo len(nr2char(0)) returns 0, where is the 0 char stored as n .. So please take care about the
                                                      Message 26 of 28 , Feb 20, 2013
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                                                        Hi Bram,

                                                        thanks for joining the discussion and participating.

                                                        echo len(nr2char(0))
                                                        returns 0, where is the 0 char stored as \n ..
                                                        So please take care about the use case: I'm not talking about buffers,
                                                        I'm talking about matchstr, substitute etc and viml strings.

                                                        I'm aware that both should be tested and documented which becomes clear
                                                        reading my later summary.

                                                        Anyway [^\n] matching \n is a very very unexpected behaviour.
                                                        Having \_[ syntax doesn't make sense, either. Because [\n] works and is
                                                        standard. And this should be visible in docs.

                                                        Marc Weber

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                                                      • Erik Christiansen
                                                        ... Bram, is that meant to be There are NL characters which are stored as NUL characters ? Because if there are no NL characters in the text , then nothing
                                                        Message 27 of 28 , Feb 20, 2013
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                                                          On 20.02.13 13:32, Bram Moolenaar wrote:
                                                          > Christian Brabandt wrote:
                                                          > > Bram, here is a patch, making [^\n] not match NL within the text and
                                                          > > that also documents, that '.' matches CR and LF within the text.
                                                          > >
                                                          > > This makes both [1] and [2] behave the same and seems to better match
                                                          > > the users expectations.
                                                          >
                                                          > This isn't right, there are no NL characters in the text. There are NUL
                                                          > characters which are stored as NL characters.

                                                          Bram, is that meant to be "There are NL characters which are stored as
                                                          NUL characters"? Because if "there are no NL characters in the text",
                                                          then nothing can be stored as them, can it?

                                                          > That's an implementation detail, which sometimes becomes visible to
                                                          > the user.

                                                          OK, but the actual problem is corruption of a regex syntax snippet in
                                                          one quoting context. Letting "[^\n]" not be the same as '[^\n]' is the
                                                          mark of a broken regex implementation. Other regex engines manage \n
                                                          without their syntax breaking, so it is possible with Vim too.

                                                          Vim has '.' to represent "any character", and so does not require a
                                                          second representation for that. But if [^\n] is the same as '.', because
                                                          there are no newlines present, then that must _always_ be the case,
                                                          regardless of a bit of quoting flim-flam.

                                                          > It's good to explain this in the docs.

                                                          Yes, knowing that there are no newlines can help us avoid looking for
                                                          them.

                                                          Another fix is needed, though, for the problem that quote flavour is
                                                          allowed to corrupt the regex in one case, causing behaviour contrary to
                                                          the quoted regex syntax. That is an illogicality boobytrap to torment
                                                          the user.

                                                          > I'm not sure we actually should change the behavior, it might not
                                                          > really take away much confusion.

                                                          Excuse me, Bram but removing the broken behaviour of "[^\n]" not being
                                                          the same as '[^\n]' does remove a mind boggling logical nonsense, and so
                                                          does do away with major confusion.

                                                          Deep knowledge if Vim internals is an asset when it fosters effective
                                                          and robust fixes, but tends toward a liability if it blinds one to the
                                                          failings of a self-contradicting user interface, I think.

                                                          In all that we construct, it is _what_ should happen which guides _how_
                                                          it is made to happen. Arguments defending the current broken status
                                                          repeatedly refer to _how_ usurping _what_, as an implementational
                                                          side effect, and accepting that as a justification. That is not
                                                          intelligent design, and has here led to impaired functionality.

                                                          Vim's supremacy would be improved by removing the user interface
                                                          deficiency.

                                                          Erik

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                                                          You have all eternity to be cautious in when you're dead.
                                                          - Lois Platford

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