f == CHOOSE f \in [Int \X Int -> Int]:
\A <<x, y>> \in DOMAIN f:
f[x, y] = f[y, x]
Which is expressing that `f` is some commutative function, but we don't care which. Could be multiplication, could be addition, could be average, could be euclidian distance from origin, could just be the 0 function.
f == CHOOSE f \in [Int \X Int -> Int]: \A <<x, y>> \in DOMAIN f: f[x, y] = f[y, x]
Which is expressing that `f` is some commutative function, but we don't care which. Could be multiplication, could be addition, could be average, could be euclidian distance from origin, could just be the 0 function.