double :: Int -> Int
-- testing 4 combinations of argument values
-- looking through 3 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 5 candidates of size 3
double x  =  x + x

add :: Int -> Int -> Int
-- testing 4 combinations of argument values
-- looking through 4 candidates of size 1
-- looking through 0 candidates of size 2
-- looking through 29 candidates of size 3
add x y  =  x + y

square :: Int -> Int
-- testing 3 combinations of argument values
-- looking through 3 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 5 candidates of size 3
square x  =  x * x

tnpo :: Int -> Int
-- testing 3 combinations of argument values
-- looking through 3 candidates of size 1
-- looking through 3 candidates of size 2
-- looking through 5 candidates of size 3
-- looking through 20 candidates of size 4
-- looking through 13 candidates of size 5
-- looking through 97 candidates of size 6
-- looking through 42 candidates of size 7
tnpo x  =  x + (x + (x + 1))