(VAR n m l b r x y)
(RULES
isEmpty(empty) -> true
isEmpty(node(l,r)) -> false
left(empty) -> empty
left(node(l,r)) -> l
right(empty) -> empty
right(node(l,r)) -> r
inc(0) -> s(0)
inc(s(x)) -> s(inc(x))

count(n,x) -> if(isEmpty(n), isEmpty(left(n)), right(n), node(left(left(n)), node(right(left(n)),right(n))), x, inc(x))
if(true, b, n, m, x, y) -> x
if(false, false, n, m, x, y) -> count(m, x)
if(false, true, n, m, x, y) -> count(n, y)

nrOfNodes(n) -> count(n,0)
)
(COMMENT
counts the nr of nodes in a binary tree
)