isLeft :: Either A A -> Bool
-- testing 4 combinations of argument values
-- pruning with 0/0 rules
-- 2 candidates of size 1
-- 1 candidates of size 2
-- tested 3 candidates
isLeft (Left x) = True
isLeft (Right x) = False
isRight :: Either A A -> Bool
-- testing 4 combinations of argument values
-- pruning with 0/0 rules
-- 2 candidates of size 1
-- 1 candidates of size 2
-- tested 3 candidates
isRight (Left x) = False
isRight (Right x) = True
fromLeft :: A -> Either A A -> A
-- testing 5 combinations of argument values
-- pruning with 0/0 rules
-- 1 candidates of size 1
-- 1 candidates of size 2
-- tested 2 candidates
fromLeft x (Left y) = y
fromLeft x (Right y) = x
fromLeft :: A -> Either A A -> A
-- testing 5 combinations of argument values
-- pruning with 0/0 rules
-- 1 candidates of size 1
-- 1 candidates of size 2
-- tested 2 candidates
fromLeft x (Left y) = x
fromLeft x (Right y) = y
either :: (A -> A) -> (A -> A) -> Either A A -> A
-- pruning with 0/0 rules
-- 0 candidates of size 1
-- 1 candidates of size 2
-- 4 candidates of size 3
-- 12 candidates of size 4
-- tested 11 candidates
either f g (Left x) = f x
either f g (Right x) = g x
lefts :: [Either A A] -> [A]
-- testing 5 combinations of argument values
-- pruning with 0/0 rules
-- 1 candidates of size 1
-- 0 candidates of size 2
-- tested 1 candidates
lefts = undefined -- search exhausted