AST refactoring

ASTPlayground/MainForm.pas

@@ -312,7 +312,7 @@ begin
     result := root.Accept(visitor);
     sw.Stop;
 
-    if not result.IsUndefined then
+    if not result.IsVoid then
         Memo1.Lines.Add(Format('Result: %s (calculated in %d ms)', [result.ToString, sw.ElapsedMilliseconds]))
     else
         Memo1.Lines.Add(Format('<undefined result> (calculated in %d ms)', [sw.ElapsedMilliseconds]));

Src/AST/Myc.Ast.Evaluator.pas

@@ -176,9 +176,9 @@ begin
     if Assigned(Node.Initializer) then
         initValue := Node.Initializer.Accept(Self)
     else
-        initValue := TAstValue.Undefined;
+        initValue := TAstValue.Void;
     FScope.SetValue(varName, initValue);
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TEvaluatorVisitor.VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue;
@@ -202,16 +202,13 @@ begin
     calleeValue := Node.Callee.Accept(Self);
     arguments := Node.Arguments;
 
-    if not calleeValue.IsClosure then
-    begin
+    if calleeValue.Kind <> avkClosure then
         raise EArgumentException.Create('Expression is not a callable closure.');
-    end;
+
     closure := calleeValue.AsClosure;
 
     if (arguments.Count <> Length(closure.Parameters)) then
-    begin
         raise EArgumentException.CreateFmt('Argument count mismatch: expected %d, got %d', [Length(closure.Parameters), arguments.Count]);
-    end;
 
     callScope := T_ExecutionScope.Create(closure.ClosureScope);
 
@@ -236,7 +233,10 @@ begin
     leftValue := Node.Left.Accept(Self);
     rightValue := Node.Right.Accept(Self);
 
-    if not leftValue.IsScalar or not rightValue.IsScalar then
+    if leftValue.Kind <> rightValue.Kind then
+        raise ENotSupportedException.Create('Binary operations are only supported for compatible types.');
+
+    if leftValue.Kind <> avkScalar then
     begin
         raise ENotSupportedException.Create('Binary operations are only supported for scalar types.');
     end;
@@ -284,10 +284,8 @@ var
     rightScalar: TScalar;
 begin
     rightValue := Node.Right.Accept(Self);
-    if not rightValue.IsScalar then
-    begin
+    if rightValue.Kind <> avkScalar then
         raise ENotSupportedException.Create('Unary operations are only supported for scalar types.');
-    end;
 
     rightScalar := rightValue.AsScalar;
 
@@ -321,7 +319,7 @@ var
     expression: IExpressionNode;
     lastValue: TAstValue;
 begin
-    lastValue := TAstValue.Undefined;
+    lastValue := TAstValue.Void;
     for expression in Node.Expressions do
     begin
         lastValue := expression.Accept(Self);

Src/AST/Myc.Ast.Nodes.pas

@@ -20,7 +20,8 @@ type
         function ToString: string;
     end;
 
-    TAstValueKind = (avkUndefined, avkScalar, avkClosure);
+    // Added avkText to represent a string value.
+    TAstValueKind = (avkUndefined, avkScalar, avkClosure, avkText);
 
     // --- Forward Declarations to break cycles ---
     IExecutionScope = interface;
@@ -56,23 +57,21 @@ type
     private
         FKind: TAstValueKind;
         FScalar: TScalar;
-        FClosure: IEvaluatorClosure;
+        FInterface: IInterface;
         function GetKind: TAstValueKind; inline;
-        function GetIsScalar: Boolean; inline;
-        function GetIsClosure: Boolean; inline;
-        function GetIsUndefined: Boolean; inline;
+        function GetIsVoid: Boolean; inline;
     public
         class operator Initialize(out Dest: TAstValue);
-        class function Undefined: TAstValue; static;
+        class function Void: TAstValue; static;
         class function FromScalar(const AValue: TScalar): TAstValue; static;
         class function FromClosure(const AValue: IEvaluatorClosure): TAstValue; static;
+        class function FromText(const AValue: String): TAstValue; static;
         function AsScalar: TScalar;
         function AsClosure: IEvaluatorClosure;
+        function AsText: String;
         function ToString: String;
+        property IsVoid: Boolean read GetIsVoid;
         property Kind: TAstValueKind read GetKind;
-        property IsScalar: Boolean read GetIsScalar;
-        property IsClosure: Boolean read GetIsClosure;
-        property IsUndefined: Boolean read GetIsUndefined;
     end;
 
     IExecutionScope = interface(IInterface)
@@ -198,19 +197,51 @@ type
 
 implementation
 
+uses
+    System.Classes;
+
+type
+    // Private interface to encapsulate a string value for reference counting.
+    IAstTextValue = interface(IInterface)
+        function GetValue: string;
+        property Value: string read GetValue;
+    end;
+
+    // Implementation of the text value interface.
+    TAstTextValue = class(TInterfacedObject, IAstTextValue)
+    private
+        FValue: string;
+        function GetValue: string;
+    public
+        constructor Create(const AValue: string);
+    end;
+
+{ TAstTextValue }
+
+constructor TAstTextValue.Create(const AValue: string);
+begin
+    inherited Create;
+    FValue := AValue;
+end;
+
+function TAstTextValue.GetValue: string;
+begin
+    Result := FValue;
+end;
+
 { TAstValue }
 
 class operator TAstValue.Initialize(out Dest: TAstValue);
 begin
     Dest.FKind := avkUndefined;
-    Dest.FClosure := nil;
+    Dest.FInterface := nil;
 end;
 
 function TAstValue.AsClosure: IEvaluatorClosure;
 begin
     if (FKind <> avkClosure) then
         raise EInvalidCast.Create('Cannot read value as a Closure.');
-    Result := FClosure;
+    Result := IEvaluatorClosure(FInterface);
 end;
 
 function TAstValue.AsScalar: TScalar;
@@ -220,10 +251,17 @@ begin
     Result := FScalar;
 end;
 
+function TAstValue.AsText: String;
+begin
+    if (FKind <> avkText) then
+        raise EInvalidCast.Create('Cannot read value as Text.');
+    Result := IAstTextValue(FInterface).Value;
+end;
+
 class function TAstValue.FromClosure(const AValue: IEvaluatorClosure): TAstValue;
 begin
     Result.FKind := avkClosure;
-    Result.FClosure := AValue;
+    Result.FInterface := AValue;
     Result.FScalar := Default(TScalar);
 end;
 
@@ -231,20 +269,17 @@ class function TAstValue.FromScalar(const AValue: TScalar): TAstValue;
 begin
     Result.FKind := avkScalar;
     Result.FScalar := AValue;
-    Result.FClosure := nil;
+    Result.FInterface := nil;
 end;
 
-function TAstValue.GetIsClosure: Boolean;
+class function TAstValue.FromText(const AValue: String): TAstValue;
 begin
-    Result := FKind = avkClosure;
+    Result.FKind := avkText;
+    Result.FInterface := TAstTextValue.Create(AValue);
+    Result.FScalar := Default(TScalar);
 end;
 
-function TAstValue.GetIsScalar: Boolean;
-begin
-    Result := FKind = avkScalar;
-end;
-
-function TAstValue.GetIsUndefined: Boolean;
+function TAstValue.GetIsVoid: Boolean;
 begin
     Result := FKind = avkUndefined;
 end;
@@ -259,13 +294,14 @@ begin
     case FKind of
         avkScalar: Result := FScalar.ToString;
         avkClosure: Result := '<closure>';
+        avkText: Result := AsText;
         avkUndefined: Result := '<void>';
     else
         Result := '[Unknown AstValue]';
     end;
 end;
 
-class function TAstValue.Undefined: TAstValue;
+class function TAstValue.Void: TAstValue;
 begin
     Result := Default(TAstValue);
 end;

Src/AST/Myc.Ast.Printer.pas

@@ -80,13 +80,13 @@ end;
 function TPrettyPrintVisitor.VisitConstant(const Node: IConstantNode): TAstValue;
 begin
     AppendLine(Format('Constant (%s)', [Node.Value.ToString]));
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitIdentifier(const Node: IIdentifierNode): TAstValue;
 begin
     AppendLine(Format('Identifier (%s)', [Node.Name]));
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitBinaryExpression(const Node: IBinaryExpressionNode): TAstValue;
@@ -96,7 +96,7 @@ begin
     Node.Left.Accept(Self);
     Node.Right.Accept(Self);
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitUnaryExpression(const Node: IUnaryExpressionNode): TAstValue;
@@ -105,7 +105,7 @@ begin
     Indent;
     Node.Right.Accept(Self);
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitIfExpression(const Node: IIfExpressionNode): TAstValue;
@@ -125,7 +125,7 @@ begin
     Node.ElseBranch.Accept(Self);
     Unindent;
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue;
@@ -148,7 +148,7 @@ begin
     Node.Body.Accept(Self);
     Unindent;
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitFunctionCall(const Node: IFunctionCallNode): TAstValue;
@@ -167,7 +167,7 @@ begin
         arg.Accept(Self);
     Unindent;
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitBlockExpression(const Node: IBlockExpressionNode): TAstValue;
@@ -179,7 +179,7 @@ begin
     for expr in Node.Expressions do
         expr.Accept(Self);
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitVariableDeclaration(const Node: IVariableDeclarationNode): TAstValue;
@@ -191,7 +191,7 @@ begin
         Node.Initializer.Accept(Self);
         Unindent;
     end;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 function TPrettyPrintVisitor.VisitAssignment(const Node: IAssignmentNode): TAstValue;
@@ -201,7 +201,7 @@ begin
     Indent;
     Node.Value.Accept(Self);
     Unindent;
-    Result := TAstValue.Undefined;
+    Result := TAstValue.Void;
 end;
 
 end.