Ast Binding

Src/AST/Myc.Ast.pas

@@ -10,6 +10,7 @@ uses
 type
     // Record acting as a namespace for the factory functions.
     TAst = record
+        // --- Existing factory functions ---
         class function Constant(AValue: TScalar): IConstantNode; static;
         class function Identifier(AName: string): IIdentifierNode; static;
         class function BinaryExpr(
@@ -31,7 +32,7 @@ type
         class function Block(const AExpressions: array of IExpressionNode): IBlockExpressionNode; static;
         class function VarDecl(const AIdentifier: IIdentifierNode; AInitializer: IExpressionNode): IVariableDeclarationNode; static;
         class function Assign(const AIdentifier: IIdentifierNode; const AValue: IExpressionNode): IAssignmentNode; static;
-        class function AssignResult(const AValue: IExpressionNode): IAssignmentNode; static;
+        class function AssignResult(const AValue: IExpressionNode): IAssignmentNode; static; deprecated;
         class function Indexer(const ABase: IExpressionNode; const AIndex: IExpressionNode): IIndexerNode; static;
         class function MemberAccess(const ABase: IExpressionNode; const AMember: IIdentifierNode): IMemberAccessNode; static;
         class function CreateSeries(const ADefinition: String): ICreateSeriesNode; static;
@@ -40,8 +41,32 @@ type
             const AValue: IExpressionNode;
             const ALookback: IExpressionNode = nil
         ): IAddSeriesItemNode; static;
-        // Added the new factory function for SeriesLength
         class function SeriesLength(const ASeries: IIdentifierNode): ISeriesLengthNode; static;
+
+        // --- Static method to run the binder ---
+        // Traverses the AST and resolves all identifiers. This must be called before evaluating the AST.
+        class procedure Bind(const ARootNode: IExpressionNode); static;
+    end;
+
+    // TAstTraverser provides a default AST traversal implementation.
+    TAstTraverser = class abstract(TInterfacedObject, IAstVisitor)
+    public
+        function VisitConstant(const Node: IConstantNode): TAstValue; virtual;
+        function VisitIdentifier(const Node: IIdentifierNode): TAstValue; virtual;
+        function VisitBinaryExpression(const Node: IBinaryExpressionNode): TAstValue; virtual;
+        function VisitUnaryExpression(const Node: IUnaryExpressionNode): TAstValue; virtual;
+        function VisitIfExpression(const Node: IIfExpressionNode): TAstValue; virtual;
+        function VisitTernaryExpression(const Node: ITernaryExpressionNode): TAstValue; virtual;
+        function VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue; virtual;
+        function VisitFunctionCall(const Node: IFunctionCallNode): TAstValue; virtual;
+        function VisitBlockExpression(const Node: IBlockExpressionNode): TAstValue; virtual;
+        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): TAstValue; virtual;
+        function VisitAssignment(const Node: IAssignmentNode): TAstValue; virtual;
+        function VisitIndexer(const Node: IIndexerNode): TAstValue; virtual;
+        function VisitMemberAccess(const Node: IMemberAccessNode): TAstValue; virtual;
+        function VisitCreateSeries(const Node: ICreateSeriesNode): TAstValue; virtual;
+        function VisitAddSeriesItem(const Node: IAddSeriesItemNode): TAstValue; virtual;
+        function VisitSeriesLength(const Node: ISeriesLengthNode): TAstValue; virtual;
     end;
 
 implementation
@@ -69,13 +94,22 @@ type
     end;
 
     { TIdentifierNode }
+    // TIdentifierNode now includes fields for binder annotations.
     TIdentifierNode = class(TAstNode, IIdentifierNode)
     private
         FName: string;
+        // --- Annotation fields added for the binder ---
+        FIsResolved: Boolean;
+        FScopeDepth: Integer;
+        FSlotIndex: Integer;
         function GetName: string;
     public
         constructor Create(AName: string);
         function Accept(const Visitor: IAstVisitor): TAstValue; override;
+
+        function Resolve(out ScopeDepth: Integer; out SlotIndex: Integer): Boolean;
+
+        property Name: string read FName;
     end;
 
     { TBinaryExpressionNode }
@@ -205,7 +239,6 @@ type
     end;
 
     { TMemberAccessNode }
-    // Concrete implementation for the member access node.
     TMemberAccessNode = class(TAstNode, IMemberAccessNode)
     private
         FBase: IExpressionNode;
@@ -241,7 +274,6 @@ type
         function Accept(const Visitor: IAstVisitor): TAstValue; override;
     end;
 
-    // Added concrete class for the series length node.
     { TSeriesLengthNode }
     TSeriesLengthNode = class(TAstNode, ISeriesLengthNode)
     private
@@ -252,6 +284,40 @@ type
         function Accept(const Visitor: IAstVisitor): TAstValue; override;
     end;
 
+    // --- Binder Implementation ---
+
+    TSymbol = record
+        Name: string;
+        SlotIndex: Integer;
+    end;
+
+    TSymbolTable = class
+    private
+        FParent: TSymbolTable;
+        FSymbols: TDictionary<string, TSymbol>;
+        FNextSlotIndex: Integer;
+    public
+        constructor Create(AParent: TSymbolTable);
+        destructor Destroy; override;
+        function Define(const Name: string): TSymbol;
+        function Resolve(const Name: string; out Symbol: TSymbol; out Depth: Integer): Boolean;
+    end;
+
+    // TBinder inherits from the base traverser and overrides methods with specific binding logic.
+    TBinder = class(TAstTraverser)
+    private
+        FCurrentScope: TSymbolTable;
+        procedure EnterScope;
+        procedure ExitScope;
+    public
+        constructor Create;
+        destructor Destroy; override;
+        function VisitIdentifier(const Node: IIdentifierNode): TAstValue; override;
+        function VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue; override;
+        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): TAstValue; override;
+        function VisitBlockExpression(const Node: IBlockExpressionNode): TAstValue; override;
+    end;
+
 { TConstantNode }
 
 constructor TConstantNode.Create(AValue: TScalar);
@@ -276,6 +342,9 @@ constructor TIdentifierNode.Create(AName: string);
 begin
     inherited Create;
     FName := AName;
+    FIsResolved := False;
+    FScopeDepth := -1;
+    FSlotIndex := -1;
 end;
 
 function TIdentifierNode.Accept(const Visitor: IAstVisitor): TAstValue;
@@ -288,6 +357,16 @@ begin
     Result := FName;
 end;
 
+function TIdentifierNode.Resolve(out ScopeDepth: Integer; out SlotIndex: Integer): Boolean;
+begin
+    Result := FIsResolved;
+    if Result then
+    begin
+        ScopeDepth := FScopeDepth;
+        SlotIndex := FSlotIndex;
+    end;
+end;
+
 { TBinaryExpressionNode }
 
 constructor TBinaryExpressionNode.Create(ALeft: IExpressionNode; AOperator: TBinaryOperator; ARight: IExpressionNode);
@@ -650,8 +729,148 @@ begin
     Result := FSeries;
 end;
 
+{ TSymbolTable }
+
+constructor TSymbolTable.Create(AParent: TSymbolTable);
+begin
+    inherited Create;
+    FParent := AParent;
+    FSymbols := TDictionary<string, TSymbol>.Create;
+    FNextSlotIndex := 0;
+end;
+
+destructor TSymbolTable.Destroy;
+begin
+    FSymbols.Free;
+    inherited;
+end;
+
+function TSymbolTable.Define(const Name: string): TSymbol;
+begin
+    Result.Name := Name;
+    Result.SlotIndex := FNextSlotIndex;
+    inc(FNextSlotIndex);
+    FSymbols.Add(Name, Result);
+end;
+
+function TSymbolTable.Resolve(const Name: string; out Symbol: TSymbol; out Depth: Integer): Boolean;
+var
+    currentScope: TSymbolTable;
+begin
+    Depth := 0;
+    currentScope := Self;
+    while Assigned(currentScope) do
+    begin
+        if currentScope.FSymbols.TryGetValue(Name, Symbol) then
+            Exit(True);
+
+        inc(Depth);
+        currentScope := currentScope.FParent;
+    end;
+    Result := False;
+end;
+
+{ TBinder }
+
+constructor TBinder.Create;
+begin
+    inherited;
+    FCurrentScope := TSymbolTable.Create(nil); // Start with a global scope
+end;
+
+destructor TBinder.Destroy;
+begin
+    Assert(not Assigned(FCurrentScope.FParent), 'Scope leak in binder.');
+    FCurrentScope.Free;
+    inherited;
+end;
+
+procedure TBinder.EnterScope;
+begin
+    FCurrentScope := TSymbolTable.Create(FCurrentScope);
+end;
+
+procedure TBinder.ExitScope;
+var
+    oldScope: TSymbolTable;
+begin
+    oldScope := FCurrentScope;
+    FCurrentScope := FCurrentScope.FParent;
+    oldScope.Free;
+end;
+
+function TBinder.VisitBlockExpression(const Node: IBlockExpressionNode): TAstValue;
+begin
+    EnterScope;
+    try
+        // Default traversal of all expressions in the block
+        inherited VisitBlockExpression(Node);
+    finally
+        ExitScope;
+    end;
+end;
+
+function TBinder.VisitIdentifier(const Node: IIdentifierNode): TAstValue;
+var
+    symbol: TSymbol;
+    depth: Integer;
+    identNode: TIdentifierNode;
+begin
+    identNode := Node as TIdentifierNode;
+    if identNode.FIsResolved then
+        Exit;
+
+    if FCurrentScope.Resolve(identNode.Name, symbol, depth) then
+    begin
+        identNode.FIsResolved := True;
+        identNode.FScopeDepth := depth;
+        identNode.FSlotIndex := symbol.SlotIndex;
+    end
+    else
+        raise Exception.CreateFmt('Undefined identifier: "%s"', [identNode.Name]);
+end;
+
+function TBinder.VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue;
+var
+    param: IIdentifierNode;
+begin
+    EnterScope;
+    try
+        // 1. Define all parameters in the new scope.
+        for param in Node.Parameters do
+            FCurrentScope.Define(param.Name);
+
+        // 2. Now visit the parameter identifiers to resolve them to their new definitions,
+        //    and visit the body to resolve its identifiers.
+        inherited VisitLambdaExpression(Node);
+    finally
+        ExitScope;
+    end;
+end;
+
+function TBinder.VisitVariableDeclaration(const Node: IVariableDeclarationNode): TAstValue;
+begin
+    // 1. First, visit the initializer expression to resolve its identifiers.
+    if Assigned(Node.Initializer) then
+        Node.Initializer.Accept(Self);
+
+    // 2. Then, define the new variable in the current scope.
+    FCurrentScope.Define(Node.Identifier.Name);
+
+    // 3. Finally, visit the declaration's own identifier to resolve it.
+    Node.Identifier.Accept(Self);
+end;
+
 { TAst }
 
+class procedure TAst.Bind(const ARootNode: IExpressionNode);
+var
+    binder: IAstVisitor;
+begin
+    binder := TBinder.Create;
+    ARootNode.Accept(binder);
+end;
+
 class function TAst.AddSeriesItem(
     const ASeries: IIdentifierNode;
     const AValue: IExpressionNode;
@@ -741,4 +960,108 @@ begin
     Result := TVariableDeclarationNode.Create(AIdentifier, AInitializer);
 end;
 
+{ TAstTraverser }
+
+function TAstTraverser.VisitAddSeriesItem(const Node: IAddSeriesItemNode): TAstValue;
+begin
+    Node.Series.Accept(Self);
+    Node.Value.Accept(Self);
+    if Assigned(Node.Lookback) then
+        Node.Lookback.Accept(Self);
+end;
+
+function TAstTraverser.VisitAssignment(const Node: IAssignmentNode): TAstValue;
+begin
+    Node.Value.Accept(Self);
+    Node.Identifier.Accept(Self);
+end;
+
+function TAstTraverser.VisitBinaryExpression(const Node: IBinaryExpressionNode): TAstValue;
+begin
+    Node.Left.Accept(Self);
+    Node.Right.Accept(Self);
+end;
+
+function TAstTraverser.VisitBlockExpression(const Node: IBlockExpressionNode): TAstValue;
+var
+    expr: IExpressionNode;
+begin
+    for expr in Node.Expressions do
+        expr.Accept(Self);
+end;
+
+function TAstTraverser.VisitConstant(const Node: IConstantNode): TAstValue;
+begin
+end;
+
+function TAstTraverser.VisitCreateSeries(const Node: ICreateSeriesNode): TAstValue;
+begin
+end;
+
+function TAstTraverser.VisitFunctionCall(const Node: IFunctionCallNode): TAstValue;
+var
+    arg: IExpressionNode;
+begin
+    Node.Callee.Accept(Self);
+    for arg in Node.Arguments do
+        arg.Accept(Self);
+end;
+
+function TAstTraverser.VisitIdentifier(const Node: IIdentifierNode): TAstValue;
+begin
+end;
+
+function TAstTraverser.VisitIfExpression(const Node: IIfExpressionNode): TAstValue;
+begin
+    Node.Condition.Accept(Self);
+    Node.ThenBranch.Accept(Self);
+    if Assigned(Node.ElseBranch) then
+        Node.ElseBranch.Accept(Self);
+end;
+
+function TAstTraverser.VisitIndexer(const Node: IIndexerNode): TAstValue;
+begin
+    Node.Base.Accept(Self);
+    Node.Index.Accept(Self);
+end;
+
+function TAstTraverser.VisitLambdaExpression(const Node: ILambdaExpressionNode): TAstValue;
+var
+    param: IIdentifierNode;
+begin
+    for param in Node.Parameters do
+        param.Accept(Self);
+    Node.Body.Accept(Self);
+end;
+
+function TAstTraverser.VisitMemberAccess(const Node: IMemberAccessNode): TAstValue;
+begin
+    // Do not visit the member identifier, as it's not a variable in the current scope.
+    Node.Base.Accept(Self);
+end;
+
+function TAstTraverser.VisitSeriesLength(const Node: ISeriesLengthNode): TAstValue;
+begin
+    Node.Series.Accept(Self);
+end;
+
+function TAstTraverser.VisitTernaryExpression(const Node: ITernaryExpressionNode): TAstValue;
+begin
+    Node.Condition.Accept(Self);
+    Node.ThenBranch.Accept(Self);
+    Node.ElseBranch.Accept(Self);
+end;
+
+function TAstTraverser.VisitUnaryExpression(const Node: IUnaryExpressionNode): TAstValue;
+begin
+    Node.Right.Accept(Self);
+end;
+
+function TAstTraverser.VisitVariableDeclaration(const Node: IVariableDeclarationNode): TAstValue;
+begin
+    if Assigned(Node.Initializer) then
+        Node.Initializer.Accept(Self);
+    Node.Identifier.Accept(Self);
+end;
+
 end.