Functional Programming, Haskell, Computer Science, Lambda Calculus, Algorithms.
left unbound. We could replace it by f0, but then f1 would be unbound. If we replace it by f1, then f0 would be unbound. Either way that’d be a bug. The problem here is that, after copying a λ, the “same” bound variable will exist in two different places, but its occurrence remains in a single