Matching neighbouring words of a pattern using Regex

Discussion in 'Perl' started by CV, Aug 30, 2004.

  1. CV

    CV Guest

    How can I match 'n' number of neighbouring words of a pattern using regular
    expressions?

    For example, suppose I am looking for the pattern "length xyz cm" in some
    text. where xyz is a number - integer or fraction or decimal point. How can
    I also grab about 3-5 words on either side of the pattern "length xyz cm"?
    The surrounding words are not always constant & may be variable. Also, the
    original text to be matched is not just a single sentence, but lines from a
    file concatenated together - so the text has many newline characters too. I
    only want the words on the same line as the pattern.

    I have tried using regex of the form
    /\b(\w*)\b(\w*)\b(\w*)\b($pattern)\b(\w*)\b(\w*)\b(\w*), but this doesn't
    work for some reason. Could someone please offer some suggestions?

    thanks!
    CV, Aug 30, 2004
    #1
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  2. CV wrote:
    > How can I match 'n' number of neighbouring words of a pattern using
    > regular expressions?


    This group is defunct. See reply in comp.lang.perl.misc.

    --
    Gunnar Hjalmarsson
    Email: http://www.gunnar.cc/cgi-bin/contact.pl
    Gunnar Hjalmarsson, Aug 30, 2004
    #2
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  3. In article <>,
    CV <> wrote:
    >How can I match 'n' number of neighbouring words of a pattern using regular
    >expressions?
    >
    >For example, suppose I am looking for the pattern "length xyz cm" in some
    >text. where xyz is a number - integer or fraction or decimal point. How can
    >I also grab about 3-5 words on either side of the pattern "length xyz cm"?
    >The surrounding words are not always constant & may be variable. Also, the
    >original text to be matched is not just a single sentence, but lines from a
    >file concatenated together - so the text has many newline characters too. I
    >only want the words on the same line as the pattern.
    >
    >I have tried using regex of the form
    >/\b(\w*)\b(\w*)\b(\w*)\b($pattern)\b(\w*)\b(\w*)\b(\w*), but this doesn't
    >work for some reason. Could someone please offer some suggestions?
    >


    You may be confused about the \b assertion. Did you intend for
    something with \w and \W..? Also, what if the pattern falls
    at the beginning or end of the line... do you want to capture
    the patterns that may not have 3-5 surrounding words?

    One possibility presuming you intend to capture 3-5 surrounding
    words:


    my $text = "...";
    my $pattern = 'length ... cm ';

    my $words = '(?:\w+[^\w\n]+){3,5}';
    #my $words = '(?:\w+[^\w\n]+){0,5}'; # to catch every pattern

    print $1 while /($words$pattern$words)/g;


    [ Note the 3-5 surrounding words may consume another
    adjacent $pattern instance but you don't specify what
    to do in that case. }


    hth,
    --
    Charles DeRykus
    Charles DeRykus, Aug 31, 2004
    #3
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