# (fib n) = the nth Fibonacci number
\fib=
    (
    \loop==
        (\x\y\n
        le n 0 x;
        \z=(+ x y)
        \n=(- n 1)
        loop y z n
        )
    loop 0 1
    )


# Now test it:
for 0 20 (\n say (fib n))