argument? Based on the excerpt `(u u) (tail xs)`, it appears that
`H`'s argument, `u`, should be a function that is ready to take itself
as an argument, and that returns a function that takes a list as an
argument. `H` itself fits the bill:
H H <~~> (\u \xs. (empty? xs) 0 (succ ((u u) (tail xs)))) H
argument? Based on the excerpt `(u u) (tail xs)`, it appears that
`H`'s argument, `u`, should be a function that is ready to take itself
as an argument, and that returns a function that takes a list as an
argument. `H` itself fits the bill:
H H <~~> (\u \xs. (empty? xs) 0 (succ ((u u) (tail xs)))) H