Learn F# - mastering “Seq.map” – decode to ASCII art

Script1.fsx

let code = "f8f8f8f8f7b2f8f63181f8f5c1318131f8f401318101f8f3c10131810131f8f202318102f8f1c10231810231f803718103f7c10211f1e10331f6810271f28103f5e10211f1b1f1e10331f40371c131f28103f3c10211f10131f2e10331f2810271e10131f38103f1e103f1810131f3c10371f1810211e10131f3810211f2e103f18131f2e10331f3810231e131f28103f4e103f1b1f1e10371f5810231f2810211f6e103f1e10331f7810231810211f8e10231810271f8f1810131810111f8f2e10131810131f8f381318111f8f4c1318171f8f53191f8f7b1f8f8f8f8f07"

let decodeIt (code:string) =

    let data = 
        [0..(code.Length/2)-1] 
        |> Seq.map (fun n -> code.Substring(n*2, 2))
        |> Seq.map (fun s -> new String(s.[0], Convert.ToInt32(string s.[1], 16)))
        |> Seq.toArray |> (fun a -> String.Join ("", a))

    [0..(data.Length/2)-1]
    |> Seq.map (fun n -> (n, data.Substring(n*2, 2)))
    |> Seq.map (fun (n,s) -> (n, Convert.ToByte(s, 16)))
    |> Seq.map (fun (n,i) -> (n, Convert.ToString(i,2).PadLeft(8,'0')))
    |> Seq.map (fun (n,s) -> (n, s.Replace('1', '*').Replace('0',' ')))
    |> Seq.map (fun (n,s) -> (if(n % 8 = 7)then printfn else printf) "%s" s)
    |> Seq.toArray |> ignore