Michael Schimmel
644 lines
23 KiB
ObjectPascal
644 lines
23 KiB
ObjectPascal
unit Myc.Ast.Evaluator;
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interface
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uses
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System.SysUtils,
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System.Classes,
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System.Generics.Collections,
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Myc.Data.Scalar,
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Myc.Data.Value,
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Myc.Ast.Nodes,
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Myc.Ast.Scope;
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type
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// The standard AST evaluator for production use.
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// This class inherits directly from TInterfacedObject as it is an
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// Interpreter (AST -> TDataValue), not a Transformer (AST -> IAstNode).
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TEvaluatorVisitor = class(TInterfacedObject, IAstVisitor, IEvaluatorVisitor)
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private
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FScope: IExecutionScope;
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protected
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// IAstVisitor methods made virtual for TDebugEvaluatorVisitor to override
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function VisitConstant(const Node: IConstantNode): TDataValue; virtual;
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function VisitIdentifier(const Node: IIdentifierNode): TDataValue; virtual;
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function VisitKeyword(const Node: IKeywordNode): TDataValue; virtual;
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function VisitIfExpression(const Node: IIfExpressionNode): TDataValue; virtual;
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function VisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue; virtual;
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function VisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue; virtual;
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function VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue; virtual;
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function VisitQuasiquote(const Node: IQuasiquoteNode): TDataValue; virtual;
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function VisitUnquote(const Node: IUnquoteNode): TDataValue; virtual;
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function VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue; virtual;
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function VisitFunctionCall(const Node: IFunctionCallNode): TDataValue; virtual;
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function VisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue; virtual;
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function VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue; virtual;
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function VisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue; virtual;
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function VisitAssignment(const Node: IAssignmentNode): TDataValue; virtual;
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function VisitIndexer(const Node: IIndexerNode): TDataValue; virtual;
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function VisitMemberAccess(const Node: IMemberAccessNode): TDataValue; virtual;
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function VisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue; virtual;
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function VisitCreateSeries(const Node: ICreateSeriesNode): TDataValue; virtual;
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function VisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue; virtual;
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function VisitSeriesLength(const Node: ISeriesLengthNode): TDataValue; virtual;
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function VisitRecurNode(const Node: IRecurNode): TDataValue; virtual;
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function VisitNop(const Node: INopNode): TDataValue; virtual;
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function IsTruthy(const AValue: TDataValue): Boolean; inline;
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// Returns a closure that can create the correct type of visitor for a lambda's body.
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function CreateVisitorFactory: TEvaluatorFactory; virtual;
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property Scope: IExecutionScope read FScope;
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public
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constructor Create(const AScope: IExecutionScope);
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// Executes an AST with proper TCO handling. This is the main entry point.
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function Execute(const RootNode: IAstNode): TDataValue;
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class procedure HandleTCO(var ResultValue: TDataValue); static;
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end;
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implementation
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uses
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System.TypInfo,
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System.Generics.Defaults,
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Myc.Ast,
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Myc.Data.Keyword,
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Myc.Data.Decimal,
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Myc.Data.Series,
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Myc.Data.Scalar.JSON,
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Myc.Ast.Types;
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// Helper type for TCO via trampolining.
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type
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TThunk = record
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Callee: TDataValue;
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Args: TArray<TDataValue>;
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Recur: Boolean;
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constructor Create(const ACallee: TDataValue; const AArgs: TArray<TDataValue>; ARecur: Boolean);
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end;
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constructor TThunk.Create(const ACallee: TDataValue; const AArgs: TArray<TDataValue>; ARecur: Boolean);
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begin
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Callee := ACallee;
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Args := AArgs;
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Recur := ARecur;
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end;
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{ TDynamicRecord }
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type
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// Runtime implementation for generic records using linear search
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TDynamicRecord = class(TInterfacedObject, IKeywordMapping<TDataValue>)
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private
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FFields: TArray<TPair<IKeyword, TDataValue>>;
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function GetFields: TArray<TPair<IKeyword, TDataValue>>;
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public
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constructor Create(const AFields: TArray<TPair<IKeyword, TDataValue>>);
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function IndexOf(const Key: IKeyword): Integer;
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end;
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constructor TDynamicRecord.Create(const AFields: TArray<TPair<IKeyword, TDataValue>>);
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begin
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inherited Create;
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FFields := AFields;
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end;
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function TDynamicRecord.GetFields: TArray<TPair<IKeyword, TDataValue>>;
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begin
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Result := FFields;
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end;
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function TDynamicRecord.IndexOf(const Key: IKeyword): Integer;
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begin
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// Linear search (O(n)) as requested
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for Result := 0 to High(FFields) do
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begin
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if FFields[Result].Key.Idx = Key.Idx then
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exit;
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end;
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Result := -1;
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end;
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{ TEvaluatorVisitor }
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constructor TEvaluatorVisitor.Create(const AScope: IExecutionScope);
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begin
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inherited Create;
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Assert(Assigned(AScope));
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FScope := AScope;
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end;
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function TEvaluatorVisitor.Execute(const RootNode: IAstNode): TDataValue;
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begin
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if not Assigned(RootNode) then
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exit(TDataValue.Void);
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Result := RootNode.Accept(Self);
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HandleTCO(Result);
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end;
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function TEvaluatorVisitor.CreateVisitorFactory: TEvaluatorFactory;
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begin
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// The production visitor returns a factory that creates another production visitor.
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Result := function(const AScope: IExecutionScope): IEvaluatorVisitor begin Result := TEvaluatorVisitor.Create(AScope); end;
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end;
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class procedure TEvaluatorVisitor.HandleTCO(var ResultValue: TDataValue);
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begin
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// This is the central trampoline loop for Tail Call Optimization.
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// It runs as long as the evaluation returns a thunk.
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while ResultValue.Kind = vkGeneric do
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begin
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var thunk := ResultValue.AsGeneric<TThunk>;
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var callee := thunk.Callee.AsMethod();
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ResultValue := callee(thunk.Args);
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end;
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end;
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function TEvaluatorVisitor.IsTruthy(const AValue: TDataValue): Boolean;
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begin
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// Other types (Text, Series, etc.) are considered "false" in a boolean context
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if (AValue.Kind <> vkScalar) then
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exit(false);
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case AValue.AsScalar.Kind of
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TScalar.TKind.Ordinal: Result := AValue.AsScalar.Value.AsInt64 <> 0;
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TScalar.TKind.Float: Result := AValue.AsScalar.Value.AsDouble <> 0.0;
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TScalar.TKind.Keyword: Result := AValue.AsScalar.Value.AsInt64 <> 0;
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TScalar.TKind.Boolean: Result := AValue.AsScalar.Value.AsInt64 <> 0;
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else
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Result := false;
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end;
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end;
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function TEvaluatorVisitor.VisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
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var
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capturedCells: TArray<IValueCell>;
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i: Integer;
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closureScope: IExecutionScope;
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visitorFactory: TEvaluatorFactory;
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begin
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// 1. Capture Upvalues
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// The Node.Upvalues array contains the physical addresses in the *current* scope (FScope)
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// that map to the closure's upvalues.
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if Node.Upvalues <> nil then
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begin
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SetLength(capturedCells, Length(Node.Upvalues));
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for i := 0 to High(Node.Upvalues) do
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capturedCells[i] := FScope.Capture(Node.Upvalues[i]);
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end
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else
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capturedCells := nil;
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// 2. Determine Parent Scope for Closure
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// Memory optimization: a lambda's scope does not need to be kept alive as a parent
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// if it contains no nested lambdas that might need to capture from it later.
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// (Assuming HasNestedLambdas flag is set correctly by Binder)
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if Node.HasNestedLambdas then
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closureScope := FScope
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else
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closureScope := nil;
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// 3. Prepare Visitor Factory
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visitorFactory := CreateVisitorFactory();
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// 4. Capture Metadata for Closure
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var descriptor := Node.Descriptor; // Runtime Descriptor (contains types + layout)
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var params := Node.Parameters;
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var cNode: ILambdaExpressionNode := Node;
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// [unsafe] prevents a reference cycle since the closure captures itself for 'recur'.
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var [unsafe] closure: TDataValue.TFunc;
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closure :=
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function(const ArgValues: TArray<TDataValue>): TDataValue
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var
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lambdaScope: IExecutionScope;
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bodyVisitor: IAstVisitor;
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i: Integer;
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adr: TResolvedAddress;
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begin
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if (Length(ArgValues) <> Length(params)) then
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raise EArgumentException.CreateFmt('Argument count mismatch: expected %d, got %d', [Length(params), Length(ArgValues)]);
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// Create the new execution scope for this function call.
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lambdaScope := TScope.CreateScope(closureScope, descriptor, capturedCells);
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// Capture the closure itself in slot 0 for 'recur' to find it (if needed).
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// Note: The Binder reserves Slot 0 for <self>.
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adr.Kind := akLocalOrParent;
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adr.ScopeDepth := 0;
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adr.SlotIndex := 0;
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lambdaScope[adr] := TDataValue(closure); // Explicit cast
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// Populate the scope with the actual parameters passed to the function.
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for i := 0 to High(ArgValues) do
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begin
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// Parameters are bound to specific slots by the Binder.
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// We access them via the Address stored in the parameter node.
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adr := params[i].Address;
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// Defensive check: Ensure we are writing to local scope
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Assert(adr.ScopeDepth = 0);
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lambdaScope[adr] := ArgValues[i];
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end;
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// Create a visitor with the new scope and execute the lambda's body.
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bodyVisitor := visitorFactory(lambdaScope);
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Result := cNode.Body.Accept(bodyVisitor);
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end;
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// The result of visiting a lambda node is the callable closure itself.
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Result := TDataValue(closure); // Explicit cast
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end;
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function TEvaluatorVisitor.VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
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begin
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// Macro definitions are compile-time constructs.
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// The Evaluator ignores them (treated as Void).
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Result := TDataValue.Void;
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end;
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function TEvaluatorVisitor.VisitQuasiquote(const Node: IQuasiquoteNode): TDataValue;
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begin
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raise Exception.Create('Quasiquote nodes are a compile-time construct and cannot be evaluated at runtime.');
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end;
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function TEvaluatorVisitor.VisitUnquote(const Node: IUnquoteNode): TDataValue;
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begin
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raise Exception.Create('Unquote nodes are a compile-time construct and cannot be evaluated at runtime.');
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end;
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function TEvaluatorVisitor.VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
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begin
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raise Exception.Create('Unquote-splicing nodes are a compile-time construct and cannot be evaluated at runtime.');
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end;
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function TEvaluatorVisitor.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
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var
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calleeValue: TDataValue;
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argValues: TArray<TDataValue>;
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i: Integer;
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argNodes: TArray<IAstNode>;
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begin
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if Assigned(Node.StaticTarget) then
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begin
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// --- Static Path (Optimized) ---
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// 1. Evaluate arguments
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argNodes := Node.Arguments;
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SetLength(argValues, Length(argNodes));
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for i := 0 to High(argNodes) do
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begin
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// Assuming arguments passed type check
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argValues[i] := argNodes[i].Accept(Self);
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end;
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// 2. Call the static target directly
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Result := Node.StaticTarget(argValues);
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// 3. Handle TCO
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HandleTCO(Result);
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end
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else
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begin
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// --- Dynamic Path (Default) ---
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calleeValue := Node.Callee.Accept(Self);
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if calleeValue.Kind <> vkMethod then
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raise EArgumentException.Create('Expression is not invokable in this context.');
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argNodes := Node.Arguments;
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SetLength(argValues, Length(argNodes));
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for i := 0 to High(argNodes) do
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argValues[i] := argNodes[i].Accept(Self);
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if Node.IsTailCall then
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begin
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// This is a tail call. Return a thunk to be processed by the trampoline.
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Result := TDataValue.FromGeneric<TThunk>(TThunk.Create(calleeValue, argValues, false));
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end
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else
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begin
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// This is a non-tail call. It must execute the call and act as the trampoline.
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Result := (calleeValue.AsMethod)(argValues);
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HandleTCO(Result);
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end;
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end;
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end;
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function TEvaluatorVisitor.VisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
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begin
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// The evaluator simply "unwraps" the macro expansion node
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// and executes the expanded body it contains.
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Result := Node.ExpandedBody.Accept(Self);
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end;
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function TEvaluatorVisitor.VisitRecurNode(const Node: IRecurNode): TDataValue;
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var
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argValues: TArray<TDataValue>;
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calleeAddress: TResolvedAddress;
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calleeValue: TDataValue;
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i: Integer;
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begin
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// The binder ensures this is only in a tail position.
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SetLength(argValues, Length(Node.Arguments));
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for i := 0 to High(Node.Arguments) do
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argValues[i] := Node.Arguments[i].Accept(Self);
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// The callee is the current function, stored in slot 0 of the current scope.
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calleeAddress.Kind := akLocalOrParent;
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calleeAddress.ScopeDepth := 0;
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calleeAddress.SlotIndex := 0;
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calleeValue := FScope[calleeAddress];
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// Recur always returns a thunk for the trampoline.
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Result := TDataValue.FromGeneric<TThunk>(TThunk.Create(calleeValue, argValues, true));
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end;
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function TEvaluatorVisitor.VisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue;
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var
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itemValue, lookbackValue, seriesVar: TDataValue;
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lookback: Int64;
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begin
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seriesVar := FScope[Node.Series.Address];
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itemValue := Node.Value.Accept(Self);
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lookback := -1;
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if Assigned(Node.Lookback) then
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begin
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lookbackValue := Node.Lookback.Accept(Self);
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if (lookbackValue.Kind <> vkScalar) or (lookbackValue.AsScalar.Kind <> TScalar.TKind.Ordinal) then
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raise EArgumentException.Create('Lookback parameter must be an integer.');
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lookback := lookbackValue.AsScalar.Value.AsInt64;
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end;
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case seriesVar.Kind of
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vkRecordSeries:
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begin
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if (itemValue.Kind <> vkRecord) then
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raise EArgumentException.Create('Can only add record values to a TScalarRecordSeries.');
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with seriesVar.AsRecordSeries do
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begin
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Add(itemValue.AsRecord, lookback);
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end;
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end;
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else
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raise EArgumentException.Create('"add" operation is only supported for series types.');
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end;
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Result := TDataValue.Void;
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end;
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function TEvaluatorVisitor.VisitAssignment(const Node: IAssignmentNode): TDataValue;
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begin
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if Node.Target.Kind <> akIdentifier then
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raise ETypeException.Create('Runtime Error: Assignment target must be an identifier.');
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// Evaluate value
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Result := Node.Value.Accept(Self);
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// Assign
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FScope[Node.Target.AsIdentifier.Address] := Result;
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end;
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function TEvaluatorVisitor.VisitConstant(const Node: IConstantNode): TDataValue;
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begin
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Result := Node.Value;
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end;
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function TEvaluatorVisitor.VisitKeyword(const Node: IKeywordNode): TDataValue;
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begin
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// Return the keyword as a TScalar value
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Result := TDataValue(TScalar.FromKeyword(Node.Value)); // Explicit cast
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end;
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function TEvaluatorVisitor.VisitCreateSeries(const Node: ICreateSeriesNode): TDataValue;
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var
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def: string;
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begin
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def := Node.Definition.Trim;
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if def.StartsWith('[') then
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begin
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var recordDef := TRttiAstHelper.JsonToRecordDefinition(def);
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if Length(recordDef.Fields) = 0 then
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raise EArgumentException.Create('Failed to parse record definition from JSON array.');
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var recordSeries := TScalarRecordSeries.Create(recordDef);
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Result := TDataValue.FromRecordSeries(recordSeries);
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end
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else
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begin
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var scalarKind := TScalar.StringToKind(def);
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Result := TDataValue.FromSeries(TScalarSeries.Create(scalarKind));
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end;
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end;
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function TEvaluatorVisitor.VisitIdentifier(const Node: IIdentifierNode): TDataValue;
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begin
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// The scope's GetValues implementation handles unboxing and parent lookup.
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Result := FScope[Node.Address];
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end;
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function TEvaluatorVisitor.VisitIndexer(const Node: IIndexerNode): TDataValue;
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var
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baseValue, indexValue: TDataValue;
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index: Int64;
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series: ISeries;
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recSeries: IRecordSeries;
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i, fieldCount: Integer;
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values: TArray<TScalar.TValue>;
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key: IKeyword;
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memberSeries: ISeries;
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scalarValue: TScalar;
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rec: TScalarRecord;
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begin
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baseValue := Node.Base.Accept(Self);
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indexValue := Node.Index.Accept(Self);
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if (indexValue.Kind <> vkScalar) or (indexValue.AsScalar.Kind <> TScalar.TKind.Ordinal) then
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raise EArgumentException.Create('Indexer `[]` requires an integer argument.');
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index := indexValue.AsScalar.Value.AsInt64;
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case baseValue.Kind of
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vkSeries:
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begin
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series := baseValue.AsSeries;
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if (index < 0) or (index >= series.TotalCount) then
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raise EArgumentException.CreateFmt('Index %d is out of bounds for series with %d elements.', [index, series.TotalCount]);
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Result := TDataValue(series.Items[Integer(index)]); // Explicit cast
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end;
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vkRecordSeries:
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begin
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recSeries := baseValue.AsRecordSeries;
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if (index < 0) or (index >= recSeries.TotalCount) then
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raise EArgumentException.CreateFmt('Index %d is out of bounds for series with %d elements.', [index, recSeries.TotalCount]);
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// Materialize the TScalarRecord by accessing each member series by index
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fieldCount := Length(recSeries.Def.Fields);
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SetLength(values, fieldCount);
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for i := 0 to fieldCount - 1 do
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begin
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key := recSeries.Def.Fields[i].Key;
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memberSeries := recSeries[key];
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scalarValue := memberSeries[index];
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values[i] := scalarValue.Value;
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end;
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rec := TScalarRecord.Create(recSeries.Def, values);
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Result := TDataValue.FromRecord(rec);
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end;
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else
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raise EArgumentException.Create('Indexer `[]` is not supported for this value type.');
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end;
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end;
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function TEvaluatorVisitor.VisitMemberAccess(const Node: IMemberAccessNode): TDataValue;
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var
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baseValue: TDataValue;
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begin
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baseValue := Node.Base.Accept(Self);
|
|
|
|
case baseValue.Kind of
|
|
vkRecordSeries: Result := TDataValue.FromSeries(baseValue.AsRecordSeries[Node.Member.Value]);
|
|
|
|
vkRecord: Result := TDataValue(baseValue.AsRecord[Node.Member.Value]); // Explicit cast
|
|
|
|
vkGenericRecord:
|
|
begin
|
|
var rec := baseValue.AsGenericRecord;
|
|
var fieldIndex := rec.IndexOf(Node.Member.Value);
|
|
if fieldIndex < 0 then
|
|
raise EArgumentException.CreateFmt('Member ":%s" not found in record.', [Node.Member.Value.Name]);
|
|
|
|
Result := rec.Fields[fieldIndex].Value;
|
|
end;
|
|
else
|
|
raise EArgumentException.Create('Member access operator `.` is not supported for this value type.');
|
|
end;
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue;
|
|
var
|
|
i: Integer;
|
|
begin
|
|
// Use the properties populated by the TypeChecker/Binder
|
|
if Assigned(Node.GenericDefinition) then
|
|
begin
|
|
// --- GENERIC RECORD PATH ---
|
|
var genFields: TArray<TPair<IKeyword, TDataValue>>;
|
|
SetLength(genFields, Length(Node.Fields));
|
|
|
|
for i := 0 to High(Node.Fields) do
|
|
begin
|
|
genFields[i] :=
|
|
TPair<IKeyword, TDataValue>.Create(
|
|
Node.Fields[i].Key.Value,
|
|
Node.Fields[i].Value.Accept(Self) // Evaluate expression
|
|
);
|
|
end;
|
|
|
|
var dynRec := TDynamicRecord.Create(genFields);
|
|
Result := TDataValue.FromGenericRecord(dynRec);
|
|
end
|
|
else if Assigned(Node.ScalarDefinition) then
|
|
begin
|
|
// --- SCALAR RECORD PATH ---
|
|
var values: TArray<TScalar.TValue>;
|
|
SetLength(values, Length(Node.Fields));
|
|
|
|
for i := 0 to High(Node.Fields) do
|
|
begin
|
|
var valData := Node.Fields[i].Value.Accept(Self);
|
|
values[i] := valData.AsScalar.Value;
|
|
end;
|
|
|
|
var rec := TScalarRecord.Create(Node.ScalarDefinition, values);
|
|
Result := TDataValue.FromRecord(rec);
|
|
end
|
|
else
|
|
raise EInvalidOpException.Create('RecordLiteral has no definition (Binder/TypeChecker failure).');
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
|
|
var
|
|
address: TResolvedAddress;
|
|
begin
|
|
if Node.Target.Kind <> akIdentifier then
|
|
raise ETypeException.Create('Runtime Error: Variable declaration target must be an identifier.');
|
|
|
|
// 1. Evaluate Initializer
|
|
if Assigned(Node.Initializer) then
|
|
Result := Node.Initializer.Accept(Self)
|
|
else
|
|
Result := TDataValue.Void;
|
|
|
|
// 2. Get Address (assigned by Binder)
|
|
address := Node.Target.AsIdentifier.Address;
|
|
|
|
// 3. Store Value
|
|
if Node.IsBoxed then
|
|
begin
|
|
// Capture (heap alloc)
|
|
Assert(address.ScopeDepth = 0);
|
|
FScope.DefineBoxed(address.SlotIndex, Result);
|
|
end
|
|
else
|
|
begin
|
|
// Stack alloc
|
|
FScope[address] := Result;
|
|
end;
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitIfExpression(const Node: IIfExpressionNode): TDataValue;
|
|
begin
|
|
if IsTruthy(Node.Condition.Accept(Self)) then
|
|
Result := Node.ThenBranch.Accept(Self)
|
|
else if Assigned(Node.ElseBranch) then
|
|
Result := Node.ElseBranch.Accept(Self)
|
|
else
|
|
Result := TDataValue.Void;
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
|
|
begin
|
|
if IsTruthy(Node.Condition.Accept(Self)) then
|
|
Result := Node.ThenBranch.Accept(Self)
|
|
else
|
|
Result := Node.ElseBranch.Accept(Self);
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
|
|
var
|
|
expression: IAstNode;
|
|
begin
|
|
Result := TDataValue.Void;
|
|
for expression in Node.Expressions do
|
|
Result := expression.Accept(Self);
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitNop(const Node: INopNode): TDataValue;
|
|
begin
|
|
Result := TDataValue.Void;
|
|
end;
|
|
|
|
function TEvaluatorVisitor.VisitSeriesLength(const Node: ISeriesLengthNode): TDataValue;
|
|
var
|
|
seriesValue: TDataValue;
|
|
len: Int64;
|
|
begin
|
|
seriesValue := FScope[Node.Series.Address];
|
|
|
|
case seriesValue.Kind of
|
|
vkSeries: len := seriesValue.AsSeries.Count;
|
|
vkRecordSeries: len := seriesValue.AsRecordSeries.Count;
|
|
else
|
|
raise EArgumentException.CreateFmt('Cannot get length of type %s.', [GetEnumName(TypeInfo(TDataValueKind), Ord(seriesValue.Kind))]);
|
|
end;
|
|
|
|
Result := TDataValue(TScalar.FromInt64(len)); // Explicit cast
|
|
end;
|
|
|
|
end.
|