in reply to regexp - replace spaces in quoted string

My thanks to you both. To help with my regexp education, would you mind expanding a little on the syntax?
  • Comment on Re: regexp - replace spaces in quoted string

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Re^2: regexp - replace spaces in quoted string
by planetscape (Chancellor) on Sep 06, 2005 at 10:43 UTC

    YAPE::Regex::Explain will help you:

    The regular expression:

(?-imsx:s/(".*?")/($x=$1)=~y: :_:, $x/ge)

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):
----------------------------------------------------------------------
  s/                       's/'
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    "                        '"'
----------------------------------------------------------------------
    .*?                      any character except \n (0 or more times
                             (matching the least amount possible))
----------------------------------------------------------------------
    "                        '"'
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  /                        '/'
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    x=                       'x='
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    1                        '1'
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
  =~y: :_:,                '=~y: :_:, '
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
  x/ge                     'x/ge'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

    [download]

    HTH,


    Update: See below for corrections. (Thanks, japhy!)

    planetscape
[reply]
[d/l]
      s/(".*?")/($x=$1)=~y: :_:, $x/ge)

[CUT]

  =~y: :_:,                '=~y: :_:, '
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
  x/ge                     'x/ge'

      [download]
      Hm... Is it good explanation??
      I'll try in my poor english: 
      s/(".*?")/($x=$1)=~y: :_:, $x/ge)
^^^^^^^^^1
          ^^^^^^^2
                  ^^^^^^^3
                          ^^4
                             ^^^5

      [download]
      1) take ALL between " and "
      2) So you have ALL in $1. $1 is read only, so copy $1 to $x. And now, for one moment forget about all and work only on $x (this is thanx /e which "wraps an eval{...} around the replacement string and the evaluated result is substituted for the matched substring".
      3)in $x replace all ' ' to '_'
      4)put replaced $x into first s/from/to/
      5)g - works globaly; e - eval the replacment string

      greets
      Uksza
[reply]
[d/l]
[select]

        While the explanation provided by YAPE::Regex::Explain will probably be inferior to that which a human well-versed in regexps could produce, the advantage in using the module is that an explanation can be produced without having access to the well-versed human. It is available to anyone with access to CPAN, and therefore can be quite useful to the learner. :-)

        planetscape
[reply]
Re^2: regexp - replace spaces in quoted string
by intel (Beadle) on Sep 06, 2005 at 10:55 UTC
    To explain the first response syntax: 
    #declarations
my ($quote_on,$output);

#default scalar is the data
$_ = q/this is a "test of some regexp" blah blah
this is another "test of some regexp" foo bar/;

#using $_ begin a for loop performing a split on each #element

for (split //) {

#quote_on is a boolean set to true when the increments reach
#a quote (and then off again when reaching another quote)

 $quote_on = ($quote_on ? 0 : 1) if (/\"/);

#if processing elements after a quote, then replace the
#whitespace with an underscore

 s/\s/_/g if $quote_on;

#assign all that to $output

  $output .= $_;
}

    [download]
    I didn't write the original post, but I was thinking about doing it a different way, although this one seems to be
    perfectly adequate and more importantly, maintainable, than a seemingly more elegant one-liner. Just IMHO
[reply]
[d/l]

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