class Ecu::SignalListComparison

def names(criterion)
  @names[criterion] ||= \
    case criterion
    when :left_exclusive  then left - right
    when :right_exclusive then right - left
    when :common          then left & right
    when :equal           then left & right
    when :nonequal        then []
    else fail "Unknown criterion #{criterion}"
    end
end