lsubst n new (LOp op args) = let args' = map (lsubst n new) args in
                                 LOp op args'
lsubst n new (LOp op args) = let args' = map (lsubst n new) args in
                                 LOp op args'
lsubst n new (LOp op args) = let args' = map (lsubst n new) args in
                                 LOp op args'