sig lists2. type append (list A) -> (list A) -> (list A) -> o. type reverse (list A) -> (list A) -> o. type cons A -> (list A) -> (list A). type null (list A).
sig lists2. type append (list A) -> (list A) -> (list A) -> o. type reverse (list A) -> (list A) -> o. type cons A -> (list A) -> (list A). type null (list A).