fix(smtlib): handle "xor"

src/smtlib/Form.ml

@@ -134,6 +134,7 @@ let imply_l st xs y = match xs with
   | _ -> T.app_fun st Funs.imply (IArray.of_list @@ y :: xs)
 
 let imply st a b = imply_a st (IArray.singleton a) b
+let xor st a b = not_ st (equiv st a b)
 
 let distinct_l tst l =
   match l with

src/smtlib/Typecheck.ml

@@ -144,6 +144,10 @@ let rec conv_term (ctx:Ctx.t) (t:PA.term) : T.t =
             errorf_ctx ctx "expected term, not type; got `%s`" f
         end
     end
+  | PA.App ("xor", [a;b]) ->
+    let a = conv_term ctx a in
+    let b = conv_term ctx b in
+    Form.xor ctx.tst a b
   | PA.App (f, args) ->
     let args = List.map (conv_term ctx) args in
     begin match find_id_ ctx f with