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in reply to Regular Expression Question

    /^(?:(?:\d+|\d+-\d+|a)(,\s*|$))+$/

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Re: Re: Regular Expression Question
by SquireJames (Monk) on Dec 09, 2003 at 07:16 UTC
    That's excellent, thanks muchly.

    Now all I have to do is work out what it's doing....
[reply]
      use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(qr/^(?:(?:\d+|\d+-\d+|a)(,\s*|$))+$/)-
+>explain;

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      outputs: 
      The regular expression:

(?-imsx:^(?:(?:\d+|\d+-\d+|a)(,\s*|$))+$)

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (?:                      group, but do not capture (1 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    (?:                      group, but do not capture:
----------------------------------------------------------------------
      \d+                      digits (0-9) (1 or more times
                               (matching the most amount possible))
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      \d+                      digits (0-9) (1 or more times
                               (matching the most amount possible))
----------------------------------------------------------------------
      -                        '-'
----------------------------------------------------------------------
      \d+                      digits (0-9) (1 or more times
                               (matching the most amount possible))
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      a                        'a'
----------------------------------------------------------------------
    )                        end of grouping
----------------------------------------------------------------------
    (                        group and capture to \1:
----------------------------------------------------------------------
      ,                        ','
----------------------------------------------------------------------
      \s*                      whitespace (\n, \r, \t, \f, and " ")
                               (0 or more times (matching the most
                               amount possible))
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      $                        before an optional \n, and the end of
                               the string
----------------------------------------------------------------------
    )                        end of \1
----------------------------------------------------------------------
  )+                       end of grouping
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

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      --

      flounder

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