anchor.diff:  
   let literal s = pstring s .>> ws
   
  -//keywords
  -
   
   let (pVAR : Parser<string, unit>)  =
       let idStr = many1Satisfy isLower .>> ws // [a-z]+
  
positive.code: let ch c =   skipChar c >>. ws
  let str s =  pstring s .>> ws
  
  let pLETTER: Parser<string, unit> = (many1Satisfy isLower .>> ws) <|> (many1Satisfy isUpper .>> ws) <|> str "_" <|> str "$" 
  
  
  let pNUMBER: Parser<float, unit> =  pfloat .>>  ws 
  
  let pPLUS: Parser<string, unit> = str "+"
  
  
negative.code:         else // reconstruct error
              Reply(reply.Status, reply.Error, reply.State)
  
  
  