FPGDBMIDebugger: starting a parser for pascal expressions

git-svn-id: trunk@43196 -

debugger/fpgdbmidebugger.pp

@@ -5,12 +5,188 @@ unit FpGdbmiDebugger;
 interface
 
 uses
-  Classes, sysutils, FpDbgClasses, GDBMIDebugger, BaseDebugManager, Debugger, GDBMIMiscClasses,
-  GDBTypeInfo, maps, FpDbgLoader, FpDbgDwarf, FpDbgDwarfConst, LazLoggerBase,
-  LazLoggerProfiling;
+  Classes, sysutils, math, FpDbgClasses, GDBMIDebugger, BaseDebugManager, Debugger,
+  GDBMIMiscClasses, GDBTypeInfo, maps, LCLProc, FpDbgLoader, FpDbgDwarf, FpDbgDwarfConst,
+  LazLoggerBase, LazLoggerProfiling;
 
 type
 
+  TFpGDBMIExpressionPart = class;
+  TFpGDBMIExpressionPartClass = class of TFpGDBMIExpressionPart;
+
+  { TFpGDBMIExpression }
+
+  TFpGDBMIExpression = class
+  private
+    FError: String;
+    FTextExpression: String;
+    FExpressionPart: TFpGDBMIExpressionPart;
+    FValid: Boolean;
+    procedure Parse;
+    procedure SetError(AMsg: String);
+    function PosFromPChar(APChar: PChar): Integer;
+  protected
+    property ExpressionPart: TFpGDBMIExpressionPart read FExpressionPart;
+  public
+    constructor Create(ATextExpression: String);
+    destructor Destroy; override;
+    function DebugDump: String;
+    property Error: String read FError;
+    property Valid: Boolean read FValid;
+  end;
+
+  TFpGDBMIExpressionPartContainer = class;
+  TFpGDBMIExpressionPartBracket = class;
+  { TFpGDBMIExpressionPart }
+
+  TFpGDBMIExpressionPart = class
+  private
+    FEndChar: PChar;
+    FParent: TFpGDBMIExpressionPartContainer;
+    FStartChar: PChar;
+    FExpression: TFpGDBMIExpression;
+    function GetSurroundingBracket: TFpGDBMIExpressionPartBracket;
+    function GetTopParent: TFpGDBMIExpressionPart;
+    procedure SetEndChar(AValue: PChar);
+    procedure SetParent(AValue: TFpGDBMIExpressionPartContainer);
+    procedure SetStartChar(AValue: PChar);
+    function  GetText(AMaxLen: Integer=0): String;
+    procedure SetError(AMsg: String = '');
+    procedure SetError(APart: TFpGDBMIExpressionPart; AMsg: String = '');
+  protected
+    function DebugText(AIndent: String): String; virtual; // Self desc only
+    function DebugDump(AIndent: String): String; virtual;
+  protected
+    procedure Init; virtual;
+    Procedure ReplaceInParent(AReplacement: TFpGDBMIExpressionPart);
+    procedure DoHandleEndOfExpression; virtual;
+
+    function IsValidNextPart(APart: TFpGDBMIExpressionPart): Boolean; virtual;
+    function CanHaveBinaryOperatorAsNext: Boolean; virtual; // True
+  public
+    constructor Create(AExpression: TFpGDBMIExpression; AStartChar: PChar; AnEndChar: PChar = nil);
+    function  HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart; virtual;
+    procedure HandleEndOfExpression; virtual;
+    property StartChar: PChar read FStartChar write SetStartChar;
+    property EndChar: PChar read FEndChar write SetEndChar;
+    property Parent: TFpGDBMIExpressionPartContainer read FParent write SetParent;
+    property TopParent: TFpGDBMIExpressionPart read GetTopParent; // or self
+    property SurroundingBracket: TFpGDBMIExpressionPartBracket read GetSurroundingBracket; // incl self
+  end;
+
+  { TFpGDBMIExpressionPartContainer }
+
+  TFpGDBMIExpressionPartContainer = class(TFpGDBMIExpressionPart)
+  private
+    FList: TList;
+    function GetCount: Integer;
+    function GetItems(AIndex: Integer): TFpGDBMIExpressionPart;
+    function GetLastItem: TFpGDBMIExpressionPart;
+    procedure SetItems(AIndex: Integer; AValue: TFpGDBMIExpressionPart);
+    procedure SetLastItem(AValue: TFpGDBMIExpressionPart);
+  protected
+    procedure Init; override;
+    function DebugDump(AIndent: String): String; override;
+  public
+    destructor Destroy; override;
+    function Add(APart: TFpGDBMIExpressionPart): Integer;
+    function IndexOf(APart: TFpGDBMIExpressionPart): Integer;
+    procedure Clear;
+    property Count: Integer read GetCount;
+    property Items[AIndex: Integer]: TFpGDBMIExpressionPart read GetItems write SetItems;
+    property LastItem: TFpGDBMIExpressionPart read GetLastItem write SetLastItem;
+  end;
+
+  { TFpGDBMIExpressionPartIdentifer }
+
+  TFpGDBMIExpressionPartIdentifer = class(TFpGDBMIExpressionPartContainer)
+  // may >contain< "()" or "[]"
+  public
+  end;
+
+  TFpGDBMIExpressionPartBracket = class(TFpGDBMIExpressionPartContainer)
+  end;
+
+  { TFpGDBMIExpressionPartRoundBracket }
+
+  TFpGDBMIExpressionPartRoundBracket = class(TFpGDBMIExpressionPartBracket)
+  private
+    FIsClosed: boolean;
+    FIsClosing: boolean;
+  protected
+    procedure Init; override;
+    procedure DoHandleEndOfExpression; override;
+    function CanHaveBinaryOperatorAsNext: Boolean; override;
+  public
+    procedure CloseBracket;
+    function HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart; override;
+    procedure HandleEndOfExpression; override;
+    property IsClosed: boolean read FIsClosed;
+  end;
+
+  { TFpGDBMIExpressionPartOperator }
+
+  TFpGDBMIExpressionPartOperator = class(TFpGDBMIExpressionPartContainer)
+  private
+    FIsUnary: Boolean;
+    FPrecedence: Integer;
+  protected
+    function DebugText(AIndent: String): String; override;
+    function CanHaveBinaryOperatorAsNext: Boolean; override;
+    procedure DoHandleEndOfExpression; override;
+  public
+    function HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart; override;
+    function HandlePrevPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart; virtual;
+    property IsUnary: Boolean read FIsUnary;
+    property Precedence: Integer read FPrecedence;
+  end;
+
+  { TFpGDBMIExpressionPartUnaryOperator }
+
+  TFpGDBMIExpressionPartUnaryOperator = class(TFpGDBMIExpressionPartOperator)
+  protected
+    procedure Init; override;
+  public
+  end;
+
+  { TFpGDBMIExpressionPartBinaryOperator }
+
+  TFpGDBMIExpressionPartBinaryOperator = class(TFpGDBMIExpressionPartOperator)
+  protected
+    procedure Init; override;
+  public
+  end;
+
+  { TFpGDBMIExpressionPartOperatorAddressOf }
+
+  TFpGDBMIExpressionPartOperatorAddressOf = class(TFpGDBMIExpressionPartUnaryOperator)  // @
+  protected
+    procedure Init; override;
+  end;
+
+  { TFpGDBMIExpressionPartOperatorUnaryPlusMinus }
+
+  TFpGDBMIExpressionPartOperatorUnaryPlusMinus = class(TFpGDBMIExpressionPartUnaryOperator)  // + -
+  // Unary + -
+  protected
+    procedure Init; override;
+  end;
+
+  { TFpGDBMIExpressionPartOperatorPlusMinus }
+
+  TFpGDBMIExpressionPartOperatorPlusMinus = class(TFpGDBMIExpressionPartBinaryOperator)  // + -
+  // Binary + -
+  protected
+    procedure Init; override;
+  end;
+
+  { TFpGDBMIExpressionPartOperatorMulDiv }
+
+  TFpGDBMIExpressionPartOperatorMulDiv = class(TFpGDBMIExpressionPartBinaryOperator)    // * /
+  protected
+    procedure Init; override;
+  end;
+
   TFpGDBMIDebugger = class;
 
   { TFpGDBPTypeRequestCache }
@@ -96,6 +272,581 @@ type
     procedure Cancel(const ASource: String); override;
   end;
 
+{ TFpGDBMIExpressionPartRoundBracket }
+
+procedure TFpGDBMIExpressionPartRoundBracket.Init;
+begin
+  inherited Init;
+  FIsClosed := False;
+  FIsClosing := False;
+end;
+
+procedure TFpGDBMIExpressionPartRoundBracket.DoHandleEndOfExpression;
+begin
+  if not IsClosed then begin
+    SetError('Bracket not closed');
+    exit;
+  end;
+  inherited DoHandleEndOfExpression;
+end;
+
+function TFpGDBMIExpressionPartRoundBracket.CanHaveBinaryOperatorAsNext: Boolean;
+begin
+  Result := IsClosed;
+end;
+
+procedure TFpGDBMIExpressionPartRoundBracket.CloseBracket;
+begin
+  FIsClosing := True;
+  if LastItem <> nil then
+    LastItem.HandleEndOfExpression;
+  FIsClosing := False;
+  FIsClosed := True;
+end;
+
+function TFpGDBMIExpressionPartRoundBracket.HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart;
+begin
+  if IsClosed then begin
+    Result := inherited HandleNextPart(APart);
+    exit;
+  end;
+
+  Result := Self;
+  if Count > 0 then begin
+    SetError('To many expressions');
+    exit;
+  end;
+
+  Result := APart;
+  Add(APart);
+end;
+
+procedure TFpGDBMIExpressionPartRoundBracket.HandleEndOfExpression;
+begin
+  if not FIsClosing then
+    inherited HandleEndOfExpression;
+end;
+
+{ TFpGDBMIExpressionPartOperatorUnaryPlusMinus }
+
+procedure TFpGDBMIExpressionPartOperatorUnaryPlusMinus.Init;
+begin
+  FPrecedence := 1;
+  inherited Init;
+end;
+
+{ TFpGDBMIExpression }
+
+procedure TFpGDBMIExpression.Parse;
+var
+  CurPtr, EndPtr, TokenEndPtr: PChar;
+  CurPart, NewPart: TFpGDBMIExpressionPart;
+
+  procedure AddPart(AClass: TFpGDBMIExpressionPartClass);
+  begin
+    NewPart := AClass.Create(Self, CurPtr, TokenEndPtr-1);
+  end;
+
+  procedure AddPlusMinus;
+  begin
+    if (CurPart = nil) or (not CurPart.CanHaveBinaryOperatorAsNext)
+    then
+      AddPart(TFpGDBMIExpressionPartOperatorUnaryPlusMinus)
+    else
+      AddPart(TFpGDBMIExpressionPartOperatorPlusMinus);
+  end;
+
+  procedure AddConstChar;
+  begin
+  end;
+
+  procedure AddConstNumber;
+  begin
+  end;
+
+  procedure AddIdentifier;
+  begin
+    while TokenEndPtr^ in ['a'..'z', 'A'..'Z', '_', '0'..'9'] do
+      inc(TokenEndPtr);
+    // TODO: Check functions not, and, in, as, is ...
+    NewPart := TFpGDBMIExpressionPartIdentifer.Create(Self, CurPtr, TokenEndPtr-1);
+  end;
+
+  procedure CloseRounBracket;
+  begin
+    NewPart := CurPart.SurroundingBracket;
+    if NewPart = nil then begin
+      SetError('Closing bracket "(" found without opening')
+    end
+    else
+    if not (NewPart is TFpGDBMIExpressionPartRoundBracket) then begin
+      SetError('Mismatch bracket')
+    end
+    else begin
+      TFpGDBMIExpressionPartRoundBracket(NewPart).CloseBracket;
+      CurPart := nil;
+    end;
+  end;
+
+begin
+  if FTextExpression = '' then
+    exit;
+  CurPtr := @FTextExpression[1];
+  EndPtr := CurPtr + length(FTextExpression);
+  CurPart := nil;
+
+  While (CurPtr < EndPtr) and FValid do begin
+    if CurPtr^ in [' ', #9, #10, #13] then begin
+      while (CurPtr^ in [' ', #9, #10, #13]) and (CurPtr < EndPtr) do
+        Inc(CurPtr);
+      continue;
+    end;
+
+    NewPart := nil;
+    TokenEndPtr := CurPtr + 1;
+    case CurPtr^ of
+      '@' :      AddPart(TFpGDBMIExpressionPartOperatorAddressOf);
+      '+', '-' : AddPlusMinus;
+      '*', '/' : AddPart(TFpGDBMIExpressionPartOperatorMulDiv);
+      '(':       AddPart(TFpGDBMIExpressionPartRoundBracket);
+      ')':       CloseRounBracket;
+      //'[': ;
+      //'''':     AddConstChar;
+      //'0'..'9',
+      //'$', '%': AddConstNumber;
+      'a'..'z',
+      'A'..'Z', '_': AddIdentifier;
+      else begin
+          SetError(Format('Unexpected char ''%0:s'' at pos %1:s', [CurPtr^, PosFromPChar(CurPtr)])); // error
+          break;
+        end;
+    end;
+    if not FValid then
+      break;
+    assert(NewPart <> nil);
+
+debugln('=================================');
+DebugLn('NEWPART:  '+NewPart.DebugText(''));
+    if CurPart = nil
+    then CurPart := NewPart
+    else CurPart := CurPart.HandleNextPart(NewPart);
+DebugLn('CURPART:  '+CurPart.DebugText(''));
+
+    CurPtr :=  TokenEndPtr;
+  end; // While CurPtr < EndPtr do begin
+
+
+
+  if CurPart <> nil then begin
+    CurPart.HandleEndOfExpression;
+    CurPart := CurPart.TopParent;
+  end
+  else
+  if Valid then
+    SetError('No Expression');
+
+  FExpressionPart := CurPart;
+end;
+
+procedure TFpGDBMIExpression.SetError(AMsg: String);
+begin
+  FValid := False;
+  FError := AMsg;
+end;
+
+function TFpGDBMIExpression.PosFromPChar(APChar: PChar): Integer;
+begin
+  Result := APChar - @FTextExpression[1] + 1;
+end;
+
+constructor TFpGDBMIExpression.Create(ATextExpression: String);
+begin
+  FTextExpression := ATextExpression;
+  FValid := True;
+  Parse;
+end;
+
+destructor TFpGDBMIExpression.Destroy;
+begin
+  FreeAndNil(FExpressionPart);
+  inherited Destroy;
+end;
+
+function TFpGDBMIExpression.DebugDump: String;
+begin
+  Result := 'TFpGDBMIExpression: ' + FTextExpression + LineEnding +
+            'Valid: ' + dbgs(FValid) + '   Error: "' + FError + '"'+ LineEnding
+            ;
+  if FExpressionPart <> nil then
+    Result := Result + FExpressionPart.DebugDump('  ');
+end;
+
+{ TFpGDBMIExpressionPartContainer }
+
+function TFpGDBMIExpressionPartContainer.GetItems(AIndex: Integer): TFpGDBMIExpressionPart;
+begin
+  Result := TFpGDBMIExpressionPart(FList[AIndex]);
+end;
+
+function TFpGDBMIExpressionPartContainer.GetLastItem: TFpGDBMIExpressionPart;
+begin
+  if Count > 0 then
+    Result := Items[Count - 1]
+  else
+    Result := nil;
+end;
+
+procedure TFpGDBMIExpressionPartContainer.SetItems(AIndex: Integer;
+  AValue: TFpGDBMIExpressionPart);
+begin
+  AValue.Parent := Self;
+  FList[AIndex] := AValue;
+end;
+
+procedure TFpGDBMIExpressionPartContainer.SetLastItem(AValue: TFpGDBMIExpressionPart);
+begin
+  assert(Count >0);
+  Items[Count-1] := AValue;
+end;
+
+procedure TFpGDBMIExpressionPartContainer.Init;
+begin
+  FList := TList.Create;
+  inherited Init;
+end;
+
+function TFpGDBMIExpressionPartContainer.DebugDump(AIndent: String): String;
+var
+  i: Integer;
+begin
+  Result := inherited DebugDump(AIndent);
+  for i := 0 to Count - 1 do
+    Result := Result + Items[i].DebugDump(AIndent+'  ');
+end;
+
+function TFpGDBMIExpressionPartContainer.GetCount: Integer;
+begin
+  Result := FList.Count;
+end;
+
+destructor TFpGDBMIExpressionPartContainer.Destroy;
+begin
+  Clear;
+  FreeAndNil(FList);
+  inherited Destroy;
+end;
+
+function TFpGDBMIExpressionPartContainer.Add(APart: TFpGDBMIExpressionPart): Integer;
+begin
+  APart.Parent := Self;
+  Result := FList.Add(APart);
+end;
+
+function TFpGDBMIExpressionPartContainer.IndexOf(APart: TFpGDBMIExpressionPart): Integer;
+begin
+  Result := Count - 1;
+  while (Result >= 0) and (Items[Result] <> APart) do
+    dec(Result);
+end;
+
+procedure TFpGDBMIExpressionPartContainer.Clear;
+begin
+  while Count > 0 do begin
+    Items[0].Free;
+    FList.Delete(0);
+  end;
+end;
+
+{ TFpGDBMIExpressionPart }
+
+procedure TFpGDBMIExpressionPart.SetEndChar(AValue: PChar);
+begin
+  if FEndChar = AValue then Exit;
+  FEndChar := AValue;
+end;
+
+function TFpGDBMIExpressionPart.GetTopParent: TFpGDBMIExpressionPart;
+begin
+  Result := Self;
+  while Result.Parent <> nil do
+    Result := Result.Parent;
+end;
+
+function TFpGDBMIExpressionPart.GetSurroundingBracket: TFpGDBMIExpressionPartBracket;
+var
+  tmp: TFpGDBMIExpressionPart;
+begin
+  Result := nil;
+  tmp := Self;
+  while (tmp <> nil) and not(tmp is TFpGDBMIExpressionPartBracket) do
+    tmp := tmp.Parent;
+  if tmp <> nil then
+    Result := TFpGDBMIExpressionPartBracket(tmp);
+end;
+
+procedure TFpGDBMIExpressionPart.SetParent(AValue: TFpGDBMIExpressionPartContainer);
+var
+  Old: TFpGDBMIExpressionPart;
+begin
+  if FParent = AValue then Exit;
+  Old := FParent;
+  FParent := AValue;
+end;
+
+procedure TFpGDBMIExpressionPart.SetStartChar(AValue: PChar);
+begin
+  if FStartChar = AValue then Exit;
+  FStartChar := AValue;
+end;
+
+function TFpGDBMIExpressionPart.GetText(AMaxLen: Integer): String;
+var
+  Len: Integer;
+begin
+  if FEndChar <> nil
+  then Len := FEndChar - FStartChar + 1
+  else Len := min(AMaxLen, 10);
+  if (AMaxLen > 0) and (Len > AMaxLen) then
+    Len := AMaxLen;
+  Result := Copy(FStartChar, 1, Len);
+end;
+
+procedure TFpGDBMIExpressionPart.SetError(AMsg: String);
+begin
+  if AMsg = '' then
+    AMsg := 'Invalid Expression';
+  FExpression.SetError(Format('%0:s at %1:d: "%2:s"', [AMsg, FExpression.PosFromPChar(FStartChar), GetText(20)]));
+end;
+
+procedure TFpGDBMIExpressionPart.SetError(APart: TFpGDBMIExpressionPart; AMsg: String);
+begin
+  if APart <> nil
+  then APart.SetError(AMsg)
+  else Self.SetError(AMsg);
+end;
+
+procedure TFpGDBMIExpressionPart.Init;
+begin
+  //
+end;
+
+procedure TFpGDBMIExpressionPart.ReplaceInParent(AReplacement: TFpGDBMIExpressionPart);
+var
+  i: Integer;
+begin
+  if Parent = nil then exit;
+  i := Parent.IndexOf(Self);
+  Assert(i >= 0);
+  Parent.Items[i] := AReplacement;
+  Parent := nil;
+end;
+
+procedure TFpGDBMIExpressionPart.DoHandleEndOfExpression;
+begin
+  //
+end;
+
+function TFpGDBMIExpressionPart.IsValidNextPart(APart: TFpGDBMIExpressionPart): Boolean;
+begin
+  Result := True;
+  if (APart is TFpGDBMIExpressionPartOperator) and
+     (not TFpGDBMIExpressionPartOperator(APart).IsUnary)
+  then
+    Result := Result and CanHaveBinaryOperatorAsNext;
+//TODO move
+  if (Parent <> nil) and (Parent is TFpGDBMIExpressionPartOperator) and
+     (not TFpGDBMIExpressionPartOperator(APart).IsUnary) and
+     (APart is TFpGDBMIExpressionPartOperator)
+  then
+    Result := False; //Result and CanHaveBinaryOperatorAsNext;
+end;
+
+function TFpGDBMIExpressionPart.CanHaveBinaryOperatorAsNext: Boolean;
+begin
+  Result := True;
+end;
+
+function TFpGDBMIExpressionPart.DebugText(AIndent: String): String;
+begin
+  Result := Format('%s%s at %d: "%s"',
+                   [AIndent, ClassName, FExpression.PosFromPChar(FStartChar), GetText])
+                   + LineEnding;
+end;
+
+function TFpGDBMIExpressionPart.DebugDump(AIndent: String): String;
+begin
+  Result := DebugText(AIndent);
+end;
+
+constructor TFpGDBMIExpressionPart.Create(AExpression: TFpGDBMIExpression; AStartChar: PChar;
+  AnEndChar: PChar);
+begin
+  FExpression := AExpression;
+  FStartChar := AStartChar;
+  FEndChar := AnEndChar;
+  Init;
+end;
+
+function TFpGDBMIExpressionPart.HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart;
+begin
+  if (APart is TFpGDBMIExpressionPartOperator) and IsValidNextPart(APart) then begin
+    Result := TFpGDBMIExpressionPartOperator(APart).HandlePrevPart(Self);
+    exit;
+  end;
+
+  if Parent <> nil then begin
+    Result := Parent.HandleNextPart(APart);
+    exit;
+  end;
+
+  SetError(APart, 'Unexpected ');
+  APart.Free;
+  Result := Self;
+end;
+
+procedure TFpGDBMIExpressionPart.HandleEndOfExpression;
+begin
+  DoHandleEndOfExpression;
+  if Parent <> nil then
+    Parent.HandleEndOfExpression;
+end;
+
+{ TFpGDBMIExpressionPartOperator }
+
+function TFpGDBMIExpressionPartOperator.DebugText(AIndent: String): String;
+begin
+  Result := inherited DebugText(AIndent);
+  while Result[Length(Result)] in [#10, #13] do SetLength(Result, Length(Result)-1);
+  Result := Result +
+    ' IsUnary:' + dbgs(FIsUnary) +
+    ' Precedence:' + dbgs(FPrecedence) +
+    LineEnding;
+end;
+
+function TFpGDBMIExpressionPartOperator.CanHaveBinaryOperatorAsNext: Boolean;
+begin
+  if IsUnary then
+    Result := (Count = 1) and Items[0].CanHaveBinaryOperatorAsNext
+  else
+    Result := (Count = 2) and Items[1].CanHaveBinaryOperatorAsNext;
+end;
+
+procedure TFpGDBMIExpressionPartOperator.DoHandleEndOfExpression;
+begin
+  if (IsUnary and (Count < 1)) or
+     (not IsUnary and (Count < 2))
+  then
+    SetError(Self, 'Not enough operands')
+  else
+    inherited DoHandleEndOfExpression;
+end;
+
+function TFpGDBMIExpressionPartOperator.HandleNextPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart;
+begin
+  Result := Self;
+  if (IsUnary and (Count > 0)) or (Count > 1) then begin
+    Result := inherited HandleNextPart(APart);
+    exit;
+  end;
+  if not IsValidNextPart(APart) then begin
+    SetError(APart, 'Not possible after Operator '+GetText+': ');
+    APart.Free;
+    exit;
+  end;
+
+  Add(APart);
+  Result := APart;
+end;
+
+function TFpGDBMIExpressionPartOperator.HandlePrevPart(APart: TFpGDBMIExpressionPart): TFpGDBMIExpressionPart;
+var
+  OpPart: TFpGDBMIExpressionPartOperator;
+begin
+  Result := Self;
+  if IsUnary or     // Unary has no previous // TODO deref ^
+     (Count > 0) or // Previous already set
+     (not APart.CanHaveBinaryOperatorAsNext) // can not have 2 operators follow each other
+  then begin
+    SetError(APart, 'Can not apply operator '+GetText+': ');
+    APart.Free;
+    Result := Self;
+    exit
+  end;
+
+  // precedence: 1 = highest
+  if APart is TFpGDBMIExpressionPartOperator then begin
+    OpPart := TFpGDBMIExpressionPartOperator(APart);
+
+    while true do begin
+      if OpPart.LastItem = nil then begin
+        SetError(APart, 'Internal parser error for operator '+GetText+': ');
+        APart.Free;
+        Result := Self;
+        exit
+      end;
+
+      if OpPart.Precedence > Self.Precedence then begin
+        if (OpPart.LastItem is TFpGDBMIExpressionPartOperator) and
+           (TFpGDBMIExpressionPartOperator(OpPart.LastItem).Precedence > Self.Precedence)
+        then begin
+          OpPart := TFpGDBMIExpressionPartOperator(OpPart.LastItem);
+          continue;
+        end;
+
+        // APart := OpPart.LastItem; break;
+        Add(OpPart.LastItem);
+        OpPart.LastItem := Self;
+        exit;
+      end;
+
+      break;
+    end;
+  end;
+
+  APart.ReplaceInParent(Self);
+  Add(APart);
+end;
+
+{ TFpGDBMIExpressionPartUnaryOperator }
+
+procedure TFpGDBMIExpressionPartUnaryOperator.Init;
+begin
+  FIsUnary := True;
+  inherited Init;
+end;
+
+{ TFpGDBMIExpressionPartBinaryOperator }
+
+procedure TFpGDBMIExpressionPartBinaryOperator.Init;
+begin
+  FIsUnary := False;
+  inherited Init;
+end;
+
+{ TFpGDBMIExpressionPartOperatorAddressOf }
+
+procedure TFpGDBMIExpressionPartOperatorAddressOf.Init;
+begin
+  FPrecedence := 1; // highest
+  inherited Init;
+end;
+
+{ TFpGDBMIExpressionPartOperatorPlusMinus }
+
+procedure TFpGDBMIExpressionPartOperatorPlusMinus.Init;
+begin
+  FPrecedence := 3;
+  inherited Init;
+end;
+
+{ TFpGDBMIExpressionPartOperatorMulDiv }
+
+procedure TFpGDBMIExpressionPartOperatorMulDiv.Init;
+begin
+  FPrecedence := 2;
+  inherited Init;
+end;
+
 { TFpGDBPTypeRequestCache }
 
 constructor TFpGDBPTypeRequestCache.Create(ADebugger: TFpGDBMIDebugger);