// A TreeElement is a block with one alternative and a root node
unit dpglib.TreeElem;

interface
uses
   dpgrtl.types,
   dpglib.types,
   dpglib.AlternativeBlock;

type
   TTreeElem = class(   TAlternativeBlock,
                        ITreeElem,
                        IGrammarElem)

      protected
         fRoot : IGrammarAtom;

      // ---------------------------------------------------------------
      // ITreeElem
      // ---------------------------------------------------------------
      protected
         function    GetRoot: IGrammarAtom;
         procedure   SetRoot( pRoot: IGrammarAtom);


      // ---------------------------------------------------------------
      // IGrammarElem
      // ---------------------------------------------------------------
      public
         procedure   Generate;
         function    Look( pK: integer): ILookahead;
         function    AsString          : AnsiString;

      public
         constructor Create(  Grammar  : IGrammar;
                              Start    : IToken;
                              Invert   : boolean);


   end;

implementation

{ TTreeElem }



// @@@: Construction / destruction ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                  Construction / destruction
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Constructor
// ================================================================================================
constructor TTreeElem.Create(Grammar: IGrammar; Start: IToken; Invert: boolean);
begin
   inherited
end;



// @@@: ITreeElem implementation ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                   ITreeElem implementation
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Get Root
// ================================================================================================
function TTreeElem.GetRoot: IGrammarAtom;
begin
   result := fRoot
end;

// ================================================================================================
// Set Root
// ================================================================================================
procedure TTreeElem.SetRoot(pRoot: IGrammarAtom);
begin
   fRoot := pRoot
end;



// @@@: IGrammarElem overrides ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//
//                                    IGrammarElem overrides
//
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// ================================================================================================
// Look
// ================================================================================================
function TTreeElem.Look(pK: integer): ILookahead;
begin
   result := fGrammar.LLkAnalyzer.Look( pK, self);
end;

// ================================================================================================
// Generate
// ================================================================================================
procedure TTreeElem.Generate;
begin
   fGrammar.Generator.Gen( self);
end;

// ================================================================================================
// As String
// ================================================================================================
function TTreeElem.AsString: AnsiString;
var
   alt   : IAlternative;
   elem  : IAlternativeElem;

begin
   result := ' #(';

   if Assigned(fRoot) then
      result := result +fRoot.AsString;

   alt   := fAlternatives.Items[0] as IAlternative;
   elem  := alt.Head;

   while Assigned(elem) do
   begin
      result := result + elem.AsString;
      elem   := elem.Next;
   end;

   result := result +')';
end;

end.