anchor.diff:             |> Array.mapi (fun i s -> s.LastIndexOf(lookup.[i]) = int lookup.[i] - int 'A' + n - 1)
              |> Array.forall id)
   
  +       .&. "The first and last lines should contain one letter, all others two" @| (
  +           lines
  +           |> Array.mapi (fun i s -> (s |> String.filter (fun c -> c <> ' ') |> String.length) = if (i = 0 || i = lookup.Length-1) then 1 else 2)
  +           |> Array.forall id)
  +
   
   
       [<Property(MaxTest=1)>]
  
positive.code:         |> String.concat "\n"
  
      let diamond4 (ch:char) =
          let n = int ch - int 'A'
          [ 0 .. n] @ [ n - 1 .. -1 .. 0 ]
          |> List.map (fun x -> string (char (int 'A' + x)))
          |> List.toArray
          |> String.concat "\n"
  
      let diamond5 (ch:char) =
          let n = charNum ch
          let pad i = String.replicate i " "
          [ 0 .. n] @ [ n - 1 .. -1 .. 0 ]
          |> List.map (fun x -> sprintf "%s%c" (pad (n - x)) (char (int 'A' + x)))
          |> List.toArray
          |> String.concat "\n"
  
      let diamond6 (ch:char) =
          let n = charNum ch
          let pad i = String.replicate i " "
          [ 0 .. n] @ [ n - 1 .. -1 .. 0 ]
          |> List.map (fun x -> sprintf "%s%c" (pad (n - x)) (char (int 'A' + x)))
          |> List.toArray
          |> String.concat "\n"
  
  
negative.code: 
      let charNum ch = int ch - int 'A'
  
      let numChar x = char <| int 'A' + x
  
      let pad = String.replicate
  
      let diamond1 (ch:char) =
          ""
  
  