From: William James <w_a_x_man@...>
Date: 2005-09-28T19:26:44+09:00
Subject: Re: Splitting a string with escapable separator?

Michael Schuerig wrote:
> I'm trying to come up with an *elegant* way to split a string into an
> array at a separator with the additional feature that the separators
> can be escaped. It should work like this
>
>   "Hello\, World,Hi".split_escapable(',' '\')
>   # => ["Hello, World", "Hi"]
>
> Through a number of permutations with regexps, scan and the rest of the
> family, I was unable to find a solution. I could parse the given string
> myself, going though it character by character, but I'd prefer a less
> pedestrian approach.


class String
  def split_escapable( splitter, escaper )
    escaper = escaper*2 if escaper=='\\'
    re = %r{ \G
             # Make sure at least 1 character remains.
             (?= . )
             (
               (?:
                 [^#{ splitter }#{ escaper }]
                 |
                 (?:  #{ escaper } .  )
               ) *
             )
             (?:
               #{ splitter }
               |
               \Z
             )

           }xm
    scan( re ).map{|x| x.first.gsub( /#{escaper}(.)/, '\1' ) }
  end
end

s = <<HERE
Hello@, World!,Hi.
Alarm rings@, lights flash.,One escaper @@
HERE
s.split("\n").each {|x|a=x.split_escapable(',','@');p a; puts a}
puts "----"

s = <<'HERE'
Hello\, World!,Hi.
Alarm rings\, lights flash.,One escaper \\
HERE
s.split("\n").each {|x|a=x.split_escapable(',','\\');p a; puts a}