f = Const("f")
a = Const("a")
print(f(f(a)))
print(mk_lambda("x", Const("N"), Var(0)))
assert(tostring(f(a)) == "f a")
x = Const("x")
y = Const("y")
N = Const("N")
print(fun(x, N, y, N, f(x, y)))
a = {x, N, x, Y}
print(a[1])
print(fun({{x, N}, {y, N}}, f(x, y)))
print(Pi({{x, N}, {y, N}}, f(x, y)))