/*
    Fibonacci sequence
    n can be any signed or unsigned integer type
*/

`export fib : Fn[n] $ (
    t : `type n
    ? {
        t = Int[Any; .signed; Any] {
            ? n <= 0 { `return 0 }
        }
        t = Int[Any; .unsigned; Any] {
            ? n = 0 { `return 0 }
        }
        { `panic "n must be a signed or unsigned Int" }
    }
    ? {
        n < 3 { 2 }
        { `sync(fib; n - 1) + fib `sync n - 2 }
    }
)

`export fib_string Fn[n] $ (
    String $ ("fib("; n; ") = "; fib `sync n; "\n")
)

`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"
         )
    }
    `print fib_string `sync I64 $ args `get -1
)