elem :: Int -> [Int] -> Bool
-- testing 4 combinations of argument values
-- pruning with 40/53 rules
-- 2 candidates of size 1
-- 0 candidates of size 2
-- 0 candidates of size 3
-- 0 candidates of size 4
-- 4 candidates of size 5
-- 0 candidates of size 6
-- 0 candidates of size 7
-- 16 candidates of size 8
-- tested 19 candidates
elem x []  =  False
elem x (y:xs)  =  x == y || elem x xs

set :: [Int] -> Bool
-- testing 4 combinations of argument values
-- pruning with 39/49 rules
-- 2 candidates of size 1
-- 0 candidates of size 2
-- 0 candidates of size 3
-- 2 candidates of size 4
-- 0 candidates of size 5
-- 0 candidates of size 6
-- 4 candidates of size 7
-- 8 candidates of size 8
-- tested 10 candidates
set []  =  True
set (x:xs)  =  not (elem x xs) && set xs