fix small typo in presentation

diff --git a/pres.mtask.tex b/pres.mtask.tex
index 4b6f7d6..52115ae 100644 (file)
--- a/pres.mtask.tex
+++ b/pres.mtask.tex
@@ -124,12 +124,12 @@ Plus x y = \e -> x e + y e
 :: Evaluator a = Evaluator (Env -> a)
 :: PrettyPrinter a = PP String
 
-class intArith where
+class intArith v where
        lit   :: t -> v t | toString t
        add   :: (v t) (v t) -> (v t) | + t
        minus :: (v t) (v t) -> (v t) | - t
 
-class boolArith where ...
+class boolArith v where ...
 
 instance intArith Evaluator where
        lit x   = Evaluator \e->x