(((List(a, b)~())~List(a))~List(b, c))
(((List(a, a, b, b)~())~List(a, a))~List(b, b, c, c))
(((List(a, a, a, b, b, b)~())~List(a, a, a))~List(b, b, b, c, c, c))
(((List(a, a, a, a, b, b, b, b)~())~List(a, a, a, a))~List(b, b, b, b, c, c, c, c))
Expected failure
``b'' expected but `c' found
end of input