anchor.diff:  
   // PART 1
   
  -let pTxt  = charsToString <!> many letter
  -let pTxt1 = charsToString <!> many1 letter
  +let pword  = manySatisfy System.Char.IsLetter
  +let pword1 = many1Satisfy System.Char.IsLetter
   
   let pIntPair = pint32 <* pchar 'x' <**> pint32
   
  
positive.code: 
  let pCodeExpr = pCode >>= mkSubP
  
  let expr = pTxt1 <|> ((+) <!> pCodeExpr <*> pTxt)
  
  let grammar = strJoin >> strLen64 <!> many expr
  
  // PART 2
  
  let pStrLen  = strLen64 <!> pTxt
  let pStr1Len = strLen64 <!> pTxt1
  
  let rec mkSubPLen (x, y) =
    (fun str ->
  
negative.code: open FParsec
  open FParsecOp
  
  let strJoin (xs : string list) =
    xs |> List.fold (+) ""
  let strLen64 = String.length >> int64
  