Array#classify for String elements using Regexp

array_classify.rb

# -*- coding: utf-8 -*-

class Array
  #
  # classift( /()/ )
  #
  # [
  #   [grouped by same \1],
  #   [grouped by same \1],
  #   [grouped by same \1],
  #   [others]
  # ]
  #
  # two-clause BSD
  #
  def classify( re, strict = false )
    c = {}
    o = []
    k = []

    self.each { |e|
      e.match( re )
      if ( $1 )
        if ( !c.has_key?( $1 ) )
          k << $1
          c[$1] = []
        end
        c[$1] << e
      else
        o << e
      end
    }

    vals  = []
    vals += k.map { |e| c[e] }

    return ( strict ) ? vals : vals + o
  end
end