// Fibonacci sequence for all numeric types

`export fib : Fn[n] $ (
    ? {
        n <= 0 { 0 }
        n < 3 { 2 }
        { `call_sync(fib; n - 1) + fib `call_sync n - 2 }
    }
)

`is_main Fn $ (
    ( args ) : `use "sys"
    ? 3 != `length args {
        `return `error String $ (
            "Got: "; " " `join args; "\n"
            "Usage: "; args `get 0; " "; args `get 1; " <number>\n"
         )
    }
    n : I64 $ args `get -1
    ( print ) : `use "io"
    print `call_sync String $ ("fib("; n; ") = "; fib `call_sync n; "\n")
)