square :: Int -> Int
-- pruning with 14/25 rules
-- looking through 3 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 6 candidates of size 3
-- tested 9 candidates
square x = x * x
square :: Int -> Int
-- pruning with 14/25 rules
-- looking through 3 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 6 candidates of size 3
-- tested 9 candidates
square x = x * x
sum :: [Int] -> Int
-- pruning with 4/8 rules
-- looking through 1 candidates of size 1
-- looking through 2 candidates of size 2
-- looking through 3 candidates of size 3
-- looking through 4 candidates of size 4
-- looking through 5 candidates of size 5
-- tested 11 candidates
sum [] = 0
sum (x:xs) = x + sum xs
(++) :: [Int] -> [Int] -> [Int]
-- pruning with 3/3 rules
-- looking through 2 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 11 candidates of size 3
-- looking through 32 candidates of size 4
-- looking through 100 candidates of size 5
-- looking through 244 candidates of size 6
-- tested 234 candidates
[] ++ xs = xs
(x:xs) ++ ys = x:(xs ++ ys)