CHANGES.

CHANGES.md

 # Changes
 
+## 2020/10/01
+
+* Change the signature `SolverSig.OUTPUT` so as to make `tyvar` an abstract
+  type. An injection function `solver_tyvar : int -> tyvar` is introduced.
+
+* Add n-ary products to the System F demo.
+  (Contributed by Gabriel Scherer and Olivier Martinot.)
+
+* Some cleanup in the directory structure.
+
 ## 2019/09/24
 
 * Use `dune` instead of `ocamlbuild`. All necessary library files