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Re: syntax/man.vim: manSubHeading is a bit too general?

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  • Charles E Campbell Jr
    ... I suggest bringing up syntax highlighting issues for a specific filetype with the syntax highlighting file s maintainer. In this case, by looking at
    Message 1 of 8 , Apr 9 1:34 PM
      Nikolai Weibull wrote:

      > The manSubHeading is defined as
      >
      > syn match manSubHeading "^\s\{3\}[a-z][a-z ]*[a-z]$"
      >
      > This will, however, match more lines than I think is intended. It
      > will, for example, match the line
      >
      > \t returns are what are recorded and compared with the data git keeps
      >
      > where "\t" is a horizontal tabulation. I'm guessing that the actual
      > regex should be
      >
      > ^ \{3\}[a-z][a-z ]*[a-z]$
      >
      > but I'm not sure; I haven't been able to find a reference for the
      > display of manual pages.
      >
      > Anyone have any insight into this issue?

      I suggest bringing up syntax highlighting issues for a specific filetype
      with the syntax highlighting file's maintainer.
      In this case, by looking at syntax/man.vim, its: Gautam H. Mudunuri
      <gmudunur AT informatica.com>.

      Regards,
      Chip Campbell
    • Nikolai Weibull
      ... Yes, and it may be more correct as well, at least in the first and last instance. However, the second part may also contain a space, so l isn t correct
      Message 2 of 8 , Apr 9 2:55 PM
        On 4/9/07, Ian Tegebo <ian.tegebo@...> wrote:
        > On 4/9/07, Nikolai Weibull <now@...> wrote:

        > > ^ \{3\}[a-z][a-z ]*[a-z]$
        > I hope nobody minds if I take this opportunity to ask a question about
        > vim's pattern matching.
        >
        > After reading |pattern| I wonder if the following is more efficient:
        >
        > syn match manSubHeading '^ \{3\}\l\l\?\l$'

        Yes, and it may be more correct as well, at least in the first and
        last instance. However, the second part may also contain a space, so
        \l isn't correct there; and I don't know where you get that \? from.
        This is the correct pattern:

        ^ \{3}\l[[:alpha:] ]*\l$

        (I also noticed that the apparently accepted "\{m\}" is being used in
        this file instead of the documented "\{m}")

        One can of course ask oneself if a subsection heading must consist of
        at least two letters. I'm guessing that the intent was to force the
        line to end with a non-space:

        ^ \{3}\l\%([[:alpha:] ]*\l\)\=$

        In fact, I'd prefer it be written as

        ^ \{3}\a\%([[:alpha:] ]*\a\)\=$

        as 'syn case ignore' is on, \l and \a will be the same. However, \a
        meshes better with [:alpha:] and may, depending on how all this is
        implemented, be a miniscule amount faster.

        > Taken from |pattern|:
        >
        > - Matching with a collection can be slow, because each character in
        > the text has to be compared with each character in the collection.
        > Use one of the other atoms above when possible. Example: "\d" is
        > much faster than "[0-9]" and matches the same characters
        >
        > Do people find this to make a different for moderate file sizes, e.g.
        > the man page for 'less' being ~2000 lines?

        Probably not.

        nikolai
      • Charles E Campbell Jr
        ... (snip) The pattern you ve provided isn t matching the same thing. The current one: start the line with exactly three spaces or tabs, followed by a lower
        Message 3 of 8 , Apr 10 6:44 AM
          Ian Tegebo wrote:

          > On 4/9/07, Nikolai Weibull <now@...> wrote:
          >
          >> The manSubHeading is defined as
          >>
          >> syn match manSubHeading "^\s\{3\}[a-z][a-z ]*[a-z]$"
          >>
          >> This will, however, match more lines than I think is intended. It
          >> will, for example, match the line
          >>
          >> \t returns are what are recorded and compared with the data git keeps
          >>
          >> where "\t" is a horizontal tabulation. I'm guessing that the actual
          >> regex should be
          >>
          >> ^ \{3\}[a-z][a-z ]*[a-z]$
          >
          > I hope nobody minds if I take this opportunity to ask a question about
          > vim's pattern matching.
          >
          > After reading |pattern| I wonder if the following is more efficient:
          >
          > syn match manSubHeading '^ \{3\}\l\l\?\l$'

          (snip)

          The pattern you've provided isn't matching the same thing.
          The current one: start the line with exactly three spaces or tabs,
          followed by a lower case character, followed by any number of
          lower case characters or spaces, up to a lower case character
          at the end-of-line.

          example: <space><tab><space>aaaa aaa aaaaaa

          Nikolai W's modifies that to "start the line with exactly three spaces"; the
          rest is the same.

          example: <space><space><space>aaa aaaaaa aaa

          Yours: start the line with exactly three spaces, followed by two or three
          lower case characters, which then terminates the line.

          example: <space><space><space>aa

          > Do people find this to make a different for moderate file sizes, e.g.
          > the man page for 'less' being ~2000 lines?


          Depends on the line lengths. Your pattern would terminate quite
          quickly on each line, as only 5 or 6 characters may be at the beginning
          of matching lines; anything more is a mismatch. The original and NW's
          both examine the entire line; so if every line had 1GB of characters, these
          two patterns would take considerably longer than yours.

          Regards,
          Chip Campbell
        • Charles E Campbell Jr
          ... Whoops -- yes, you re quite right. Sorry bout that... Chip Campbell
          Message 4 of 8 , Apr 10 7:06 AM
            Nikolai Weibull wrote:

            > On 4/9/07, Charles E Campbell Jr <drchip@...> wrote:
            >
            >> In this case, by looking at syntax/man.vim, its: Gautam H. Mudunuri
            >> <gmudunur AT informatica.com>.
            >
            >
            > Actually, this was actually the wrong maintainer. Gautam was the
            > previous maintainer of this file. Nam SungHyun <namsh@...>
            > maintains it now.

            Whoops -- yes, you're quite right. Sorry 'bout that...

            Chip Campbell
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