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Re: How to split into paragraphs?

by ikegami (Pope)
on Nov 16, 2006 at 05:39 UTC ( #584376=note: print w/ replies, xml ) Need Help??


in reply to How to split into paragraphs?

If you're reading from a file, $/ = '' sets paragraph mode.

local $/ = ''; print OUT ("<$_>") while <IN>;

Alternatively, here's a solution that works for strings:

$out = join '', map { "<$_>" } map { /\G((?:(?!\n\n).)*\n+|.+\z)/sg } $in;


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Re^2: How to split into paragraphs?
by jrw (Scribe) on Nov 16, 2006 at 12:25 UTC
    Ikegami, see clarification above. I am partitioning based on being able to detect the start of each substring, not based on a separator between substrings.
Re^2: How to split into paragraphs?
by jrw (Scribe) on Nov 16, 2006 at 12:36 UTC
    ikegami: I hadn't thought of using map to generate a list when given only a single input -- that's an interesting idea.

    One thing I'm trying to do is avoid repeating the pattern used for detecting the start of each substring. When I try to capture using m//, I end up having to repeat the pattern to stop each match:

    /(START_PATTERN.*?)(?!START_PATTERN)/g

    split seems to say what I want: "here is the thing that separates the paragraphs from each other". But then I have to piece the parts back together again (see my original post's code) and I'm trying to avoid that.

      Ah, I see. Well, I've already provided the building blocks, but they are well hidden. Let me expose them.

      You need something along the lines of /[^$chars]*/, but instead of negatively matching chars, you want to negatively match a regexp.

      The direct equivalent of
      /[^$chars]*/
      for regexps is
      /(?:(?!$re).)*/

      In context,

      # Input the string. my $in = do { local $/; <DATA> }; # Must move "pos" on a match. # Zero-width match won't work. my $start_pat = qr/^\S+/m; # Break the input into paragraghs. my @paras = $in =~ / \G ( $start_pat (?: (?!$start_pat). )* ) /xgs; # Manipulate the paragraghs. @paras = map { "<$_>" } @paras; # Recombine the paragraphs. my $out = join '', @paras; # Output the string. print($out); __DATA__ abc: asdf1 asdf2 def: asdf3 ghi: asdf4 asdf5

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