There are really cool things that you can achieve in Lisp with macros that are cumbersome (if possible) in Haskell. Take for example the `memoize' macro (see Chapter 9 of Peter Norvig's PAIP). With it, you can define a function, say foo, and then simply evaluate (memoize 'foo), which replaces foo's global definition with a memoized version. Can you achieve the same effect in Haskell with higher-order functions?