anchor.diff:      let printArg = function
           | Some(attr) -> "["+(Source.toString attr)+"]"
           | None -> ""
  -    let printListBrackets  l_br r_br metaArgs =
  -        if (List.isEmpty metaArgs) then ""
  -        else l_br + (String.concat " " (List.map Source.toString metaArgs)) + r_br
  -    let printMetaArgs = printListBrackets "<<" ">>"
  -    let printArgs = printListBrackets "[" "]"
  +    let seqCount seq =
  +        Seq.fold(fun acc a -> acc+1) 0 seq
  +    let printSeqBrackets l_br r_br metaArgs =
  +        if (Seq.isEmpty metaArgs) then ""
  +        else if (seqCount metaArgs) > 1 then l_br + (String.concat " " (Seq.map Source.toString metaArgs)) + r_br
  +        else l_br + (Source.toString <| Seq.head metaArgs) + r_br
  +    let printMetaArgs = printSeqBrackets "<<" ">>"
  +    let printArgs = printSeqBrackets "[" "]"
       let rec priority = function 
           | PAlt(_) -> 1
           | PSeq([elem],None) -> 
  
positive.code:         | PToken(_) | PRef(_) | PMetaRef(_) | PLiteral(_) -> 100
          | PMany(_) | POpt(_) | PSome(_) -> 50
          | _ -> -1
      let rec printProduction (production:Production.t<Source.t,Source.t>) = 
          let printElem (elem:elem<Source.t,Source.t>) = 
              let binding = function
                  | Some x when String.forall System.Char.IsLetter (Source.toString x) -> (Source.toString x) + "="
                  | Some x  -> "<" + Source.toString x + ">="
                  | None -> ""
              let omit = if elem.omit then "-" else ""
              let needBrackets =  let prio = priority elem.rule in if elem.binding.IsSome then prio < 50 else prio = 1
              seq { yield Str(omit + binding elem.binding); yield! bracketsIf  needBrackets (printProduction elem.rule) }
          match production with
          | PAlt(alt1, alt2) -> seq {yield Tabbed(printProduction alt1); yield Line (seq {yield Str ("| "); yield! printProduction alt2})} //Альтернатива
          | PSeq(elem_seq,attr_option) -> seq {yield! (Seq.collect printElem elem_seq); yield Str(printAttr attr_option)} //Последовательность * атрибут.(атрибут всегда применяется к последовательности) 
          | PToken(source) -> to_seq <| Str (Source.toString source) //собственно токен
          | PRef(source, attr_option) -> to_seq <| Str (Source.toString source + printArg attr_option)  //Vanilla rule reference with an optional args list.
          | PMany(many) -> seq { yield! bracketsIf (priority many < 50) (printProduction many) ; yield Str "*"} //expr*
          | PMetaRef(rule_name, opt_arg, metaArgs) -> to_seq <| Str((Source.toString rule_name)+(printMetaArgs metaArgs)+(printArg opt_arg)) // Metarule reference like in "a: mr<x> y z"
          | PLiteral(source) -> to_seq <| Str (Source.toString source) //Литерал. Хочется в правилах явно писать ,например, .."if" expr "then" expr...
  //        |PRepet   of (t<'patt,'expr>) * int option * int option  //extended regexp repetition, "man egrep" for details
  //        |PPerm    of (t<'patt,'expr>) list //permutation (A || B || C)   
  ///// The following are obsolete and reduction to PRepet should be discussed.
          | PSome(some) -> seq {yield! (bracketsIf (priority some<50) (printProduction some)); yield Str("+")} //expr+
          | POpt(opt) -> seq {yield! (bracketsIf (priority opt<50) (printProduction opt)); yield Str("?")} //expr?
          | _ -> to_seq <| Str("ERROR")
  
      seq {yield Line(to_seq <| Str(startSign+rule.name+(printMetaArgs rule.metaArgs)+(printArgs rule.args)+": "));
          yield Tabbed(seq{yield! printProduction rule.body; yield Str(";")})}
  
  let generate (input_grammar:Definition.t<Source.t,Source.t>) =
      let tbSeq = Seq.collect (fun rule -> printRule rule) input_grammar.grammar
      printSourceOpt(input_grammar.head)+(printTextBox 4 4 80 tbSeq)+printSourceOpt(input_grammar.foot)
  
negative.code: open Yard.Core.IL
  open Yard.Core.IL.Production
  
  let printSourceOpt = function None -> "" | Some arg -> "\n{"+(fst arg)+"}\n\n"
  
  type TextBox =
  | Tabbed of seq<TextBox> 
  | Line of seq<TextBox>
  | StrSeq of seq<TextBox>
  | Str of string
  with 
    member x.IsTab with get() = match x with Tabbed _ -> true | _ -> false
    
  let to_seq x = seq { yield x }
  let printTextBox tabSize windowSize tbSeq =
  
      /// Return new sequence, what has the same elements, what tbSeq has,
      ///    with proper indent before each element.
      let rec printIndentedSeq tbSeq indent =
          Seq.collect (function
              | Str s -> to_seq (s, indent)
              | StrSeq tbSeq -> seq {yield! printIndentedSeq tbSeq (indent)}
              | Tabbed tbSeq | Line tbSeq as x -> 
               seq { yield ("\n", indent);
                     yield! printIndentedSeq tbSeq (indent + (if x.IsTab then tabSize else 0) ) } 
          ) tbSeq
  
      let strSeq = printIndentedSeq tbSeq 0
  
      // Return a string, consisting of established number of spaces
      let write_spaces i = String.replicate i " "
  
      /// Convert obtained sequence to resulting string.
      /// newline is true iff there was a line feed.
      let (text,_,_) = 
          Seq.fold (fun (str_acc, newline, chars_in_line) (word,indent) -> 
              if word="\n" then 
                  if newline then
                      (str_acc, true, 0)
                  else
                      (str_acc+word, true, 0)
              else
                  let spaces_count = if newline then indent else if word.Length=0 || word.[0]=';' || word.[0]=' ' then 0 else 1
                  if (String.length word <= windowSize - chars_in_line - spaces_count) then
                      let appended = (write_spaces spaces_count) + word
                      (str_acc + appended, false, chars_in_line + (String.length appended))
                  else
                      let newlineStr = (write_spaces (indent + tabSize)) + word
                      (str_acc + "\n" + newlineStr, false, String.length newlineStr)
              ) ("", true, 0) strSeq
      text
  