Not a monad (Wadler); would be if the types were
Neverthless, obeys the monad laws.
+Oh, one more thing: because natural language allows the functor to be
+on the left or on the right, we replace the type arrow -> with a
+left-leaning version \ and a right-leaning version, as follows:
+
+ α/β β = α
+ β β\α = α
+
+This means we need two versions of ¢ too (see Barker and Shan 2014
+chapter 1 for full details).
+
This is (almost) all we need to get some significant linguistic work
done.