third :: [Int] -> Int
-- testing 360 combinations of argument values
-- pruning with 14/25 rules
-- looking through 2 candidates of size 1
-- looking through 5 candidates of size 2
-- looking through 6 candidates of size 3
-- looking through 20 candidates of size 4
-- tested 18 candidates
third xs  =  head (tail (tail xs))

product :: [Int] -> Int
-- testing 360 combinations of argument values
-- pruning with 14/25 rules
-- looking through 2 candidates of size 1
-- looking through 5 candidates of size 2
-- looking through 6 candidates of size 3
-- looking through 20 candidates of size 4
-- looking through 34 candidates of size 5
-- tested 44 candidates
product []  =  1
product (x:xs)  =  x * product xs

product :: [Int] -> Int
-- testing 360 combinations of argument values
-- pruning with 15/26 rules
-- looking through 2 candidates of size 1
-- looking through 5 candidates of size 2
-- looking through 6 candidates of size 3
-- looking through 23 candidates of size 4
-- tested 20 candidates
product xs  =  foldr (*) 1 xs