factorial :: Int -> Int
-- testing 4 combinations of argument values
-- pruning with 27/65 rules
-- looking through 3 candidates of size 1
-- looking through 4 candidates of size 2
-- looking through 13 candidates of size 3
-- looking through 34 candidates of size 4
-- looking through 75 candidates of size 5
-- looking through 183 candidates of size 6
-- looking through 577 candidates of size 7
-- tested 343 candidates
factorial 0  =  1
factorial x  =  x * factorial (x - 1)

factorial :: Int -> Int
-- testing 4 combinations of argument values
-- pruning with 32/72 rules
-- looking through 3 candidates of size 1
-- looking through 4 candidates of size 2
-- looking through 13 candidates of size 3
-- looking through 34 candidates of size 4
-- looking through 75 candidates of size 5
-- looking through 247 candidates of size 6
-- tested 172 candidates
factorial x  =  foldr (*) 1 [1..x]