Scripting refinement

Src/AST/Myc.Ast.Script.pas

@@ -41,6 +41,10 @@ type
         tkError
     );
 
+    TTokenKindHelper = record helper for TTokenKind
+        function ToString: String;
+    end;
+
     TToken = record
         Kind: TTokenKind;
         Text: string;
@@ -63,6 +67,7 @@ type
     TExpr = record
         Token: TToken;
         Node: IAstNode;
+        Params: TArray<IIdentifierNode>;
     end;
 
     TParser = class
@@ -246,7 +251,7 @@ end;
 procedure TParser.Consume(AExpectedKind: TTokenKind);
 begin
     if FCurrentToken.Kind <> AExpectedKind then
-        raise Exception.CreateFmt('Syntax Error: Expected token %d, but found %d', [Ord(AExpectedKind), Ord(FCurrentToken.Kind)]);
+        raise Exception.CreateFmt('Syntax Error: Expected token %s, but found %s', [AExpectedKind.ToString, FCurrentToken.Kind.ToString]);
     NextToken;
 end;
 
@@ -259,6 +264,8 @@ begin
     try
         while FCurrentToken.Kind <> tkRightBracket do
         begin
+            if FCurrentToken.Kind = tkEOF then
+                raise Exception.Create('Syntax Error: Unexpected end of file.');
             if FCurrentToken.Kind <> tkIdentifier then
                 raise Exception.Create('Syntax Error: Expected identifier in parameter list.');
             params.Add(TAst.Identifier(FCurrentToken.Text));
@@ -284,7 +291,6 @@ function TParser.ParseList: IAstNode;
 var
     elements: TList<TExpr>;
     head: TExpr;
-    headIdent: IIdentifierNode;
     tailTokens: TArray<TToken>;
     tailNodes: TArray<IAstNode>;
 begin
@@ -295,7 +301,11 @@ begin
     elements := TList<TExpr>.Create;
     try
         while FCurrentToken.Kind <> tkRightParen do
+        begin
+            if FCurrentToken.Kind = tkEOF then
+                raise Exception.Create('Syntax Error: Unexpected end of file.');
             elements.Add(ParseExpression);
+        end;
 
         head := elements[0];
 
@@ -311,37 +321,59 @@ begin
         if head.Token.Kind = tkIdentifier then
         begin
             // Handle special forms
-            if SameText(headIdent.Name, 'if') then
+            if SameText(head.Token.Text, 'if') then
                 Result := TAst.IfExpr(tailNodes[0], tailNodes[1], IfThen(Length(tailNodes) > 2, tailNodes[2], nil))
-            else if SameText(headIdent.Name, 'def') then
+            else if SameText(head.Token.Text, 'def') then
             begin
-                var identNode: IIdentifierNode;
                 if tailTokens[0].Kind <> tkIdentifier then
                     raise Exception.Create('Syntax Error: Expected an identifier for def statement.');
-                Result := TAst.VarDecl(identNode, IfThen(Length(tailNodes) > 1, tailNodes[1], nil));
+                Result := TAst.VarDecl(IIdentifierNode(tailNodes[0]), IfThen(Length(tailNodes) > 1, tailNodes[1], nil));
             end
-            else if SameText(headIdent.Name, 'assign') then
+            else if SameText(head.Token.Text, 'assign') then
             begin
-                var identNode: IIdentifierNode;
                 if tailTokens[0].Kind <> tkIdentifier then
                     raise Exception.Create('Syntax Error: Expected an identifier for assignment.');
-                Result := TAst.Assign(identNode, tailNodes[1]);
+                Result := TAst.Assign(IIdentifierNode(tailNodes[0]), tailNodes[1]);
             end
-            else if SameText(headIdent.Name, 'fn') then
-                Result := TAst.LambdaExpr(ParseParameterList, tailNodes[0]) // Special parsing for params
-            else if SameText(headIdent.Name, 'do') then
+            else if SameText(head.Token.Text, 'fn') then
+                Result := TAst.LambdaExpr(elements[High(tailNodes)].Params, tailNodes[1])
+            else if SameText(head.Token.Text, 'do') then
                 Result := TAst.Block(tailNodes)
-            else if SameText(headIdent.Name, 'recur') then
+            else if SameText(head.Token.Text, 'recur') then
                 Result := TAst.Recur(tailNodes)
-            else if SameText(headIdent.Name, 'get') then
+            else if SameText(head.Token.Text, 'get') then
                 Result := TAst.Indexer(tailNodes[0], tailNodes[1])
-            else if (Length(headIdent.Name) > 1) and (headIdent.Name.StartsWith('.')) then
-                Result := TAst.MemberAccess(tailNodes[0], TAst.Identifier(headIdent.Name.Substring(1)))
+            else if (Length(head.Token.Text) > 1) and (head.Token.Text.StartsWith('.')) then
+                Result := TAst.MemberAccess(tailNodes[0], TAst.Identifier(head.Token.Text.Substring(1)))
             else
-                Result := TAst.FunctionCall(head.Node, tailNodes); // Default is a function call
-        end
-        else
-            Result := TAst.FunctionCall(head.Node, tailNodes); // Callee is a complex expression, e.g. ((fn [x] x) 1)
+            begin
+                if Length(tailNodes) = 1 then
+                begin
+                    for var op := Low(TScalar.TUnaryOp) to High(TScalar.TUnaryOp) do
+                    begin
+                        if head.Token.Text = op.ToString then
+                        begin
+                            Result := TAst.UnaryExpr(op, tailNodes[0]);
+                            break
+                        end;
+                    end;
+                end
+                else if Length(tailNodes) = 2 then
+                begin
+                    for var op := Low(TScalar.TBinaryOp) to High(TScalar.TBinaryOp) do
+                    begin
+                        if head.Token.Text = op.ToString then
+                        begin
+                            Result := TAst.BinaryExpr(tailNodes[0], op, tailNodes[1]);
+                            break
+                        end;
+                    end;
+                end;
+            end;
+        end;
+
+        if Result = nil then
+            Result := TAst.FunctionCall(head.Node, tailNodes);
 
     finally
         elements.Free;
@@ -378,15 +410,17 @@ begin
             NextToken;
         end;
         tkLeftParen: Result.Node := ParseList;
+        tkLeftBracket: Result.Params := ParseParameterList;
+        tkEOF: {nop};
     else
-        raise Exception.CreateFmt('Syntax Error: Unexpected token %d', [Ord(FCurrentToken.Kind)]);
+        raise Exception.CreateFmt('Syntax Error: Unexpected token %s', [FCurrentToken.Kind.ToString]);
     end;
 end;
 
 function TParser.Parse: IAstNode;
 begin
     var expr := ParseExpression;
-    if expr.Token.Kind <> tkEOF then
+    if FCurrentToken.Kind <> tkEOF then
         raise Exception.Create('Syntax Error: Unexpected characters after end of expression.');
     Result := expr.Node;
 end;
@@ -696,4 +730,20 @@ begin
     end;
 end;
 
+function TTokenKindHelper.ToString: String;
+begin
+    case Self of
+        tkLeftParen: Result := '(';
+        tkRightParen: Result := ')';
+        tkLeftBracket: Result := '[';
+        tkRightBracket: Result := ']';
+        tkIdentifier: Result := '<identifier>';
+        tkNumber: Result := '<number>';
+        tkString: Result := '<string>';
+        tkEOF: Result := '<EOF>';
+    else
+        Result := '<error>';
+    end;
+end;
+
 end.