added macrodef

Src/AST/Myc.Ast.Script.pas

@@ -108,6 +108,7 @@ type
         function VisitIfExpression(const Node: IIfExpressionNode): TDataValue;
         function VisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
         function VisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
+        function VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
         function VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
         function VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
         function VisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
@@ -359,6 +360,20 @@ begin
                     raise Exception.Create('Syntax Error: Expected an identifier for def statement.');
                 Result := TAst.VarDecl(IIdentifierNode(tailNodes[0]), IfThen(Length(tailNodes) > 1, tailNodes[1], nil));
             end
+            else if SameText(head.Token.Text, 'defmacro') then
+            begin
+                // (defmacro name [params] body)
+                if (Length(tailNodes) <> 3) or (tailTokens[0].Kind <> tkIdentifier) then
+                    raise Exception.Create('Syntax Error: ''defmacro'' requires a name, a parameter list, and a body.');
+                if elements[1].Node <> nil then
+                    raise Exception.Create('Syntax Error: Expected a parameter list [...] after macro name.');
+
+                var macroName := IIdentifierNode(tailNodes[0]);
+                var macroParams := elements[1].Params;
+                var macroBody := tailNodes[2];
+
+                Result := TAst.MacroDef(macroName, macroParams, macroBody);
+            end
             else if SameText(head.Token.Text, 'assign') then
             begin
                 if tailTokens[0].Kind <> tkIdentifier then
@@ -424,6 +439,19 @@ var
     i64: Int64;
     dbl: Double;
 begin
+    // TODO: Implement reader macros for quasiquoting here.
+    // The current lexer will tokenize `, ~, and ~@ as identifiers.
+    // Check for them here and wrap the subsequent expression accordingly.
+    // Example:
+    // if FCurrentToken.Text = '`' then
+    // begin
+    //   NextToken;
+    //   var exprToQuote := ParseExpression;
+    //   Result.Node := TAst.Quasiquote(exprToQuote.Node);
+    //   exit;
+    // end;
+    // (This requires IQuasiquoteNode and TAst.Quasiquote to be defined first).
+
     Result.Token := FCurrentToken;
     case FCurrentToken.Kind of
         tkNumber:
@@ -606,6 +634,33 @@ begin
     Result := TDataValue.Void;
 end;
 
+function TPrettyPrintVisitor.VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
+var
+    param: IIdentifierNode;
+    sb: TStringBuilder;
+begin
+    // Added visitor for pretty printing macro definitions.
+    sb := TStringBuilder.Create;
+    try
+        for param in Node.Parameters do
+            sb.Append(param.Name + ' ');
+        if sb.Length > 0 then
+            sb.Remove(sb.Length - 1, 1);
+
+        Append('(defmacro ' + Node.Name.Name + ' [' + sb.ToString + ']');
+    finally
+        sb.Free;
+    end;
+
+    Indent;
+    NewLine;
+    Node.Body.Accept(Self);
+    Unindent;
+    NewLine;
+    Append(')');
+    Result := TDataValue.Void;
+end;
+
 function TPrettyPrintVisitor.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
 var
     arg: IAstNode;