Palindrome

S = {New Sequence init}
for E in Xs do
    {S insertFirst(E)}
end

fun {Check}
    local A B C in
        {S isEmpty(A)}
        if A then true
        else
            {S first(B)}
            {S last(C)}
            if B == C then
                {S removeFirst}
                {S removeLast}
                {Check}
            else
            false
            end
        end
    end
end
in
    {Check}