+substVects :: Subst -> [CoreVect] -> [CoreVect]
+substVects subst = map (substVect subst)
+
+------------------
+substVect :: Subst -> CoreVect -> CoreVect
+substVect _subst (Vect v Nothing) = Vect v Nothing
+substVect subst (Vect v (Just rhs)) = Vect v (Just (simpleOptExprWith subst rhs))
+substVect _subst (NoVect v) = NoVect v
+
+------------------