def test_tagged(c, x, y, z):
if c > 0:
return tagged(x)
elif c == 0:
return tagged(y)
else:
return tagged(z)
def countdown(n):
if n == 0:
return tagged(None)
else:
return tagged(Pair(n, countdown(n - 1)))
def make_tree(depth, x):
if depth == 0:
return tagged(x)
else:
return tagged(
Pair(make_tree(depth - 1, x * 2), make_tree(depth - 1, x * 2 + 1)))