length :: [Int] -> Int
-- testing 38 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 1 candidates of size 2
-- looking through 2 candidates of size 3
-- looking through 3 candidates of size 4
-- looking through 5 candidates of size 5
-- looking through 11 candidates of size 6
-- looking through 22 candidates of size 7
-- looking through 53 candidates of size 8
-- looking through 101 candidates of size 9
length xs  =  if null xs then 0 else 1 + length (tail xs)

reverse :: [Int] -> [Int]
-- testing 38 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 4 candidates of size 2
-- looking through 9 candidates of size 3
-- looking through 24 candidates of size 4
-- looking through 65 candidates of size 5
-- looking through 215 candidates of size 6
-- looking through 673 candidates of size 7
-- looking through 2178 candidates of size 8
-- looking through 7154 candidates of size 9
-- looking through 23801 candidates of size 10
-- looking through 80160 candidates of size 11
reverse xs  =  if null xs then xs else reverse (tail xs) ++ unit (head xs)

sort :: [Int] -> [Int]
-- testing 30 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 4 candidates of size 2
-- looking through 6 candidates of size 3
-- looking through 12 candidates of size 4
-- looking through 31 candidates of size 5
-- looking through 98 candidates of size 6
-- looking through 287 candidates of size 7
-- looking through 792 candidates of size 8
-- looking through 2220 candidates of size 9
-- looking through 6516 candidates of size 10
sort xs  =  if null xs then xs else insert (head xs) (sort (tail xs))

length :: [Int] -> Int
-- testing 38 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 1 candidates of size 2
-- looking through 1 candidates of size 3
-- looking through 4 candidates of size 4
-- looking through 4 candidates of size 5
-- looking through 27 candidates of size 6
length xs  =  foldr (const (1 +)) 0 xs

reverse :: [Int] -> [Int]
-- testing 38 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 2 candidates of size 2
-- looking through 1 candidates of size 3
-- looking through 5 candidates of size 4
-- looking through 1 candidates of size 5
-- looking through 25 candidates of size 6
-- looking through 77 candidates of size 7
reverse xs  =  foldr (flip (++) . unit) [] xs

sort :: [Int] -> [Int]
-- testing 30 combinations of argument values
-- looking through 2 candidates of size 1
-- looking through 2 candidates of size 2
-- looking through 0 candidates of size 3
-- looking through 2 candidates of size 4
sort xs  =  foldr insert [] xs