Recursion

// Recursive frames have independent parameters and locals.
pure funcra fib(n: integer) -> integer
    needs n >= 0;
{
    if n <= 1 { return n; }
    return fib(n - 1) + fib(n - 2);
}

pure funcra even(n: integer) -> boolean {
    if n == 0 { return true; }
    return odd(n - 1);
}

pure funcra odd(n: integer) -> boolean {
    if n == 0 { return false; }
    return even(n - 1);
}

print(fib(10));
print(even(8), odd(8));