module Regexp::Parser

def self.anchor(token)
  case token.token
  when :bol
    @node << Anchor::BeginningOfLine.new(token)
  when :eol
    @node << Anchor::EndOfLine.new(token)
  when :bos
    @node << Anchor::BOS.new(token)
  when :eos
    @node << Anchor::EOS.new(token)
  when :eos_ob_eol
    @node << Anchor::EOSobEOL.new(token)
  when :word_boundary
    @node << Anchor::WordBoundary.new(token)
  when :nonword_boundary
    @node << Anchor::NonWordBoundary.new(token)
  when :match_start
    @node << Anchor::MatchStart.new(token)
  else
    raise UnknownTokenError.new('Anchor', token)
  end
end