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491Re: [NTS] Probably a basic regexp question on ^[^,]

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  • mycroftj
    Jan 31, 2011
      --- In ntb-scripts@yahoogroups.com, Sheri <silvermoonwoman@...> wrote:
      > On 1/28/2011 5:57 PM, mycroftj wrote:
      > > I HOPE this is not something I should easily see.
      > >
      > > I am using NTL 6.2
      > >
      > > This is the FIND command, not a clip.
      > > I wanted a regular expression to find lines that did not begin with a comma.
      > >
      > > I did NOT mess around with look aheads because I thought ^[^,] would work but each click of the FIND NEXT button finds every character on a line up to the end of the line or a comma. ^, finds each line that DOES begin with a comma so why doesn't the negation work?
      > >
      > > In a similar way, why does ^[adfg] find the first a in asefasdf (which I expected) and the first d in the next line (which I expected) but also all the rest of the chars in dgdfgdf? I thought this would find a,d,f or g if they were the first char on a line.
      > >
      > > Thanks for explaining!
      > >
      > > Joy
      > >
      > Hi Joy,
      > If you are looking for whole lines that begin with one of those
      > characters, the cursor needs to start at the beginning of a line and
      > your pattern needs to match the entire line. Otherwise, after a match,
      > you need to move the cursor to the beginning of the next line before
      > re-running. The metacharacter "^" matches at the beginning of each line
      > and also at the beginning of the subject passed for matching. For the
      > Find function, after your pattern has matched, the next subject getting
      > tested begins with the next character following the match.
      > Another possibility would be to look for the characters only when they
      > follow a line break e.g.,
      > \R\K[adfg]
      > Obviously that can't possibly match at the start of the first line.
      > This is an area where NoteTab Pro has a different behavior (which
      > actually is not to my liking). If NoteTab Pro notices a pattern begins
      > with "^" it moves to the beginning of the next line before testing. So
      > NTP makes it appear that ^ matches only at the beginning of a line.
      > There are workarounds to keep NTP from doing that.
      > There are other functions (e.g., Replace All) that treat the portion of
      > the document following the cursor as one subject. If you use one of
      > those functions, your pattern will behave more like you expected.
      > However you should ensure that the cursor is at the top of the document
      > or at the beginning of a line when you start one of those functions.
      > Alternatively you can enable the Whole document (aka "All") option.
      > Hope this helps explain what you saw.
      > Regards,
      > Sheri

      Thanks so much for the explanation. I've been reading and studying and have never noticed any place that points out what you said about the metacharacter "^" will also match at the beginning of the subject passed for matching and not just at the start of a line.

      When I manage a difficult regexp string and then fail on a 'simple' one, I start to wonder if it's my computer or myself. So far, it's always been myself and mostly concerning strange quirks of regexps I seem to be good at stumbling upon.

      Thanks again.

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