anchor.diff:      | Error of string
       | Project of string
       | OutputMode of OutputMode
  +    | CompilerLocation
       | Help
       | Quit
   
  
positive.code:     | null -> Quit
      | input ->
        let reader = Parsing.createForwardStringReader input 0
        let cmds = errors <|> outputmode <|> helptext <|> help <|> declarations <|> parse <|> project <|> completionTipOrDecl <|> quit <|> error
        reader |> Parsing.getFirst cmds
  
  // --------------------------------------------------------------------------------------
  
negative.code:       return HelpText sym
      }
  
    let compilerlocation = parser {
      let! _ = string "compilerlocation"
      return CompilerLocation
      }
  
    // Parses always and returns default error message
    let error = parser { return Error("Unknown command or wrong arguments") }
  
  