posix.rb

def cmp(this, type=nil)
  type ||= this.class
  cmp_with_type(this, type)
end

def cmp_with_type(this, type)
  if type == String
    StringComparator.new(this)
  elsif type == Fixnum or type == Bignum
    NumberComparator.new(this)
  else
    raise "No comparator for #{type}"
  end
end