+
+2. Do the same with lists. That is, given an arbitrary type
+'a, let the boxed type be ['a], i.e., a list of objects of type 'a. The singleton
+is `\p.[p]`, and the composition operator is
+
+ >=> (first:P->[Q]) (second:Q->[R]) :(P->[R]) = List.flatten (List.map f (g a))
+
+For example:
+
+ f p = [p, p+1]
+ s q = [q*q, q+q]
+ >=> f s 7 = [49, 14, 64, 16]
+