// Fibonacci sequence

`export fib_recursive : {[I64.n]
    ? {
        n < 0 { %.error ~ "#BOLD#RED#Invalid n Got %#" `format n }
        n = 0 { 0 }
        n < 2 { 1 }
        { + (fib `sync n - 1; fib `sync n - 2) }
    }
}

`export fib_iterative : {[I64.n]
    ? n < 0 {
        `return.error ~ "#BOLD#RED#Invalid n Got %#" `format n
    }
    a : 0
    b : 1
    @ 0 .. n {
        c : b
        b : a + b
        a : c
    }
    a
}

`export fib_array : {[I64.n]
    ? {
        n < 0 {
            `return.error ~ "#BOLD#RED#Invalid n Got %#" `format n
        }
        n > 0 { n :- 1 }
    }
    arr : Array $ (0; 1)
    @ 0 .. n {
        arr `push + (arr `get -2; arr `get -1)
    }
    arr
}