data Either a b = Left a | Right b hsdata Three = A | B | C
Either Three Three
-- これが取りうるのは
-- ①Right A
-- ②Right B
-- ③Rihgt C
-- ④Left A
-- ⑤Left B
-- ⑥Left C
-- よって6つhs data Week = Sun | Mon | Tue | Wed | Thu | Fri | Sathsdata Either a b = Left a | Right b