> holds 100 $ id === (+0) &&& id === (id . id) True
> holds 100 $ id === (+0) ||| id === (id . id) True
prop_id_idempotent = id === id . id
> check $ id === (+0) +++ OK, passed 200 tests.
> check $ id === id . id +++ OK, passed 1 tests (exhausted).
> check $ id === (+1) *** Failed! Falsifiable (after 1 tests): 0
>>> fold (handles (filtered even) sum) [1..10] 30
>>> foldM (handlesM (filtered even) (Foldl.mapM_ print)) [1..10] 2 4 6 8 10
>>> extQ (const True) not True False
>>> extQ (const True) not 'a' True