anchor.diff:      | Post of int
       | Reply of int * AsyncReplyChannel<string>
   
  -let getState =
  +let postMessage =
       function // function-syntax pattern matching
       | Post i -> i
       | Reply (i, a) -> i
  
positive.code: // *********************************
  // Pipes vs. Composition
  // *********************************
  
  // Pipe operator
  let sum =
      [|1..10|] 
  
negative.code:     | SixPlus
      | Five
      | FiveS
  
  type Phone = { Manufacturer : string; Model : Model; OperatingSystem : string; Storage : int }
  
  let phones = [{ Manufacturer = "Apple"; Model = Model.Six; OperatingSystem = "iOS"; Storage = 64 };
  