anchor.diff:  
       let charNum ch = int ch - int 'A'
   
  +    let numChar x = char <| int 'A' + x
  +
  +    let pad = String.replicate
  +
       let diamond1 (ch:char) =
           ""
   
  
positive.code:            |> Array.mapi (fun i s -> s.LastIndexOf(lookup.[i]) = int lookup.[i] - int 'A' + n - 1)
             |> Array.forall id)
  
  
  
      [<Property(MaxTest=1)>]
  
negative.code:     let ``Diamond 5`` (ch:char) = diamondTest diamond5
  
      [<Property(Arbitrary=[| typeof<Letter> |])>]
      let ``Diamond 6`` (ch:char) = diamondTest diamond6
  
      [<Property(Arbitrary=[| typeof<Letter> |])>]
      let ``Diamond 7`` (ch:char) = diamondTest diamond7