takes a number as argument n and returns true if n is even and false if n is not even.
So X1 must have the behavior of the `even` function. Fortunately, it's easy to write
such a function without using any fixed-point combinators...
takes a number as argument n and returns true if n is even and false if n is not even.
So X1 must have the behavior of the `even` function. Fortunately, it's easy to write
such a function without using any fixed-point combinators...