third :: [Int] -> Int
-- testing 60 combinations of argument values
-- looking through 2/11 candidates of size 1
-- looking through 2/8 candidates of size 2
-- looking through 3/11 candidates of size 3
-- looking through 5/18 candidates of size 4
third xs  =  head (tail (tail xs))

product :: [Int] -> Int
-- testing 60 combinations of argument values
-- looking through 2/11 candidates of size 1
-- looking through 2/8 candidates of size 2
-- looking through 3/11 candidates of size 3
-- looking through 5/18 candidates of size 4
-- looking through 13/33 candidates of size 5
-- looking through 26/68 candidates of size 6
-- looking through 63/143 candidates of size 7
-- looking through 152/336 candidates of size 8
-- looking through 358/783 candidates of size 9
-- looking through 860/1835 candidates of size 10
product xs  =  if null xs then 1 else head xs * product (tail xs)

product :: [Int] -> Int
-- testing 60 combinations of argument values
-- looking through 2/12 candidates of size 1
-- looking through 2/10 candidates of size 2
-- looking through 3/15 candidates of size 3
-- looking through 8/26 candidates of size 4
product xs  =  foldr (*) 1 xs