[alexpac26]

Код:

// стандарт строки 1,2,3,5,7
function NumParser2(numstr: string; rz: char = ','):string;
var s: TStringList; i: integer; ok : boolean;
begin
  s := TStringList.Create;
  ExtractStrings([rz],[' '],PChar(numstr),s);
  result:='';
  // преобразование
  ok := false;
  for i:=s.Count-2 downto 1 do
    if ((s[i-1] = '-') or (strtoint(s[i-1])+1 = strtoint(s[i]))) and
       ((s[i+1] = '-') or (strtoint(s[i+1])-1 = strtoint(s[i]))) then begin
          s[i] := '-';
          if ok then s.Delete(i);
          ok:=true;
    end else
      ok:=false;
  // end for
  s.Delimiter:=rz;
  result:=StringReplace(s.DelimitedText,rz+'-'+rz,'-',[rfReplaceAll]);
  s.free;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(NumParser2('1,2,3,5,7'));
  ShowMessage(NumParser2('1,2,3,5,7,10,11,12,13'));
  ShowMessage(NumParser2('1,2,3,4,5,7,13,70,71,72,73,80'));
end;