Today s Topics. Program Realisation 2. How code and configuration data of forms are organized.

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1 Program Realisation Today s Topics hemerik/ip0/ Lecture 9 Kees Hemerik Tom Verhoeff Technische Universiteit Eindhoven Faculteit Wiskunde en Informatica Software Engineering & Technology Feedback to T.Verhoeff@TUE.NL How code and configuration data of forms are organized Event mechanism in Delphi Call-Back routines to reduce coupling Memory leaks, dangling references UML: Unified Modeling Language Final Assignment part 3: Backtracking to solve packing puzzles Conclusion c 007, T. TUE.NL 1 Program Realization : Lecture 9 c 007, T. TUE.NL Program Realization : Lecture 9 Code Organization of Forms and Controls in Unit1.pas 1 unit Unit1; 3 interface 4 5 uses 6..., Forms,...; 7 8 type 9 TForm1 = class(tform) 10 (* Controls and other components, managed by Delphi IDE *) (* Event handlers declarations, managed by Delphi IDE *) c 007, T. TUE.NL 3 Program Realization : Lecture 9 Code Organization of Forms and Controls in Unit1.pas 15 // Additional fields & methods, declared by appl. developer 16 private public end; 1 var 3 Form1: TForm1; 4 5 implementation 6 // Event handler implementations, provided by appl. developer 7 // Additional method implementations by appl developer end. c 007, T. TUE.NL 3 Program Realization : Lecture 9

2 Main.pas of Final Assignment Configuration Parameters of Forms and Controls in Unit1.dfm 1 uses..., Forms,..., Base, PuzzleIO,...; 3 type 4 TForm1 = class(tform) 5 PiecesGrid: TStringGrid; procedure PiecesGridDrawCell(Sender: TObject; ACol, ARow: Integer; 8 Rect: TRect; State: TGridDrawState); public 11 FPuzzle: TPuzzle; // the puzzle being manipulated 1 13 // Globals to support dragging of a piece 14 FDragOldPosition: TPosition; // position of piece at start of drag 15 FDragPlacement: TPlacement; // piece and orientation being dragged end; 1 object Form1: TForm1 Left = 9 3 Top = Width = Height = Caption = Form object PiecesGrid: TStringGrid 9 Left = 5 10 Top = Width = Height = ColCount = end end c 007, T. TUE.NL 4 Program Realization : Lecture 9 c 007, T. TUE.NL 5 Program Realization : Lecture 9 Event Mechanism in Delphi: Main Event Loop 1 program PuzzleProject; 3 uses 4 Forms, 5 Main in Main.pas {Form1}, 6 Base in Base.pas ; 7 8 begin 9 Application.Initialize; 10 Application.CreateForm(TForm1, Form1); 11 Application.Run; 1 end. Application.Run starts the main event loop The main event loop waits for an event and calls its event handler c 007, T. TUE.NL 6 Program Realization : Lecture 9 Event Mechanism in Delphi: Event Events are triggered by user actions and object state changes Events are implemented as private fields with method pointers, e.g. of type TNotifyEvent TNotifyEvent = procedure (Sender: TObject) of object; Procedure types Cannot be accommodated in the static call graph c 007, T. TUE.NL 7 Program Realization : Lecture 9

3 Event Handlers Configured in Main.dfm of Final Assignment Adding Automatic Solvers to Final Assignment 1 object Form1: TForm object PiecesGrid: TStringGrid OnDragDrop = PiecesGridDragDrop 6 OnDragOver = PiecesGridDragOver 7 OnDrawCell = PiecesGridDrawCell 8 OnEndDrag = PiecesGridEndDrag 9 OnMouseDown = PiecesGridMouseDown 10 OnStartDrag = PiecesGridStartDrag 11 end end Problem : provide unit Solvers, finding solutions and showing them on the main form Dilemma : Main.pas needs to use Solvers.pas to invoke a solver Solvers.pas needs to access Main.pas to show solutions This could result in mutual dependence: tight coupling Tight coupling reduces maintainability c 007, T. TUE.NL 8 Program Realization : Lecture 9 c 007, T. TUE.NL 9 Program Realization : Lecture 9 Using Call-Backs to User Interface to reduce coupling In Solvers.pas, define OnFound: TNotifyEvent, which the solver invokes to signal that a solution is found Main.pas uses Solvers.pas and configures OnFound with a local handler Main.pas invokes the solver when user clicks FindAll button Solvers.pas does not need to know where OnFound is handled Solvers.pas does not use Main.pas; both use Classes (TNotifyEvent) and Base.pas (FPuzzle) c 007, T. TUE.NL 10 Program Realization : Lecture 9 1 unit Solvers; 3 interface 4 5 uses Call-Back in Solvers.pas 6 Classes, Base; (* does not use Main *) 7 8 type 9 TSolver = class(tobject) 10 protected 11 FPuzzle: TPuzzle; 1 FSolutionCount: Integer; 13 FOnFound: TNotifyEvent; 14 procedure SolutionFound; c 007, T. TUE.NL 11 Program Realization : Lecture 9

4 15 public Call-Back in Solvers.pas 16 // construction/destruction constructor Create(APuzzle: TPuzzle); 18 { create a solver for APuzzle, calling OnFound for each sol 19 // commands procedure FindAll; virtual; abstract; 1 // pre: FPuzzle <> nil // post: all solutions have been found, and 3 // SolutionFound has been called for each of them. 4 5 property Puzzle: TPuzzle read FPuzzle write FPuzzle; 6 property SolutionCount: Integer read FSolutionCount; 7 property OnFound: TNotifyEvent read FOnFound write FOnFound; 8 end; c 007, T. TUE.NL 11 Program Realization : Lecture implementation Call-Back in Solvers.pas 34 procedure TSolver.SolutionFound; 35 begin 36 FSolutionCount := FSolutionCount + 1; 37 if Assigned(FOnFound) 38 then FOnFound(Self); 39 end; c 007, T. TUE.NL 11 Program Realization : Lecture 9 Setting up Call-Back in Main.pas 1 FSolver: TSolver; // the selected automatic solver... 3 procedure TForm1.SolutionFound(Sender: TObject); 4 begin 5 UpdateViews; 6 LogBoxState( Format( Solution: %d, [FSolver.SolutionCount])); 7 end; 8 9 procedure TForm1.ShowSolutionsCheckBoxClick(Sender: TObject); 10 begin 11 if ShowSolutionsCheckBox.Checked 1 then FSolver.OnFound := SolutionFound 13 else FSolver.OnFound := nil; 14 end; c 007, T. TUE.NL 1 Program Realization : Lecture 9 Memory Leaks and Dangling References Memory leak : after p := q or New(p) or p :=...Create(...), (old p)ˆ is possibly still allocated but unreachable The amount of usable memory has diminished ( leaked away) GetHeapStatus reports some memory statistics (e.g. TotalAllocated) Dangling references : after Dispose(p) or p.free, other references could still point to (old p)ˆ References to disposed/freed objects are called dangling The objects pointed to are no longer valid and must not be used c 007, T. TUE.NL 13 Program Realization : Lecture 9

5 Memory Leaks and Dangling References: Examples See final assignment, Main.pas: 1 procedure TForm1.DoReadPuzzle(AFileName: String); begin 3 ClearPiecesGrid; 4 FPuzzle.Free; 5 FPuzzle := ReadPuzzle(AFileName); 6 end; Omitting FPuzzle.Free causes a memory leak after line 5 Omitting ClearPiecesGrid, causes the placements in PiecesGrid.Objects to contain dangling references after line 4 It is an (implicit) invariant that PiecesGrid.Objects contains placements referring to FPuzzle. c 007, T. TUE.NL 14 Program Realization : Lecture 9 Differences between Dispose, Destroy, Free, FreeAndNil procedure Dispose(p: Pointer) frees dynamic variable pˆ created by New destructor Destroy; virtual; cleans up memory; override in descendant for additional clean-up; do not call directly procedure Free (method) invokes Destroy if Self <> nil procedure FreeAndNil(var Obj) frees Obj and sets it to nil c 007, T. TUE.NL 15 Program Realization : Lecture 9 UML: Unified Modeling Language Standard graphical language for modeling object-oriented software Final Assignment: Part 3 Process (count, show) each solution of packing puzzle P once Syntax: Diagrams, but also textual representation (OCL) Semantics: somewhat controversial For (static) structure and (dynamic) behavior Extensible, still evolving Not a design method c 007, T. TUE.NL 16 Program Realization : Lecture 9 Generalization: once process each solution of P that is an extension of partial solution Q Original problem: Q = Trivial when Q is total solution: box full or all pieces used Step: extend partial solution with a placement Various options: occupy unoccupied cell or use available piece c 007, T. TUE.NL 17 Program Realization : Lecture 9

6 Final Assignment: Backtracking ingredients Backtracking optimizations 1. Determine whether a partial solution is total. Process a solution 3. Traverse all unoccupied box cells C 4. Traverse all available pieces 5. For each available piece, traverse all its orientations 6. For each orientation, traverse all its possible placements at C 7. Determine whether a placement fits 8. Do a placement 9. Remove a placement c 007, T. TUE.NL 18 Program Realization : Lecture 9 Which unoccupied cell to occupy? Which placements to try of an available piece? Most placements can be eliminated, when taking into account the shape constraint of the occupied region and the order of positions in an orientation... Note: Currently no order constraint on positions in an orientation c 007, T. TUE.NL 19 Program Realization : Lecture 9 Finishing IP0 Main Theme: Modular Structure Registered in PEACH for PR/0607 Sufficient results for all lab assignments Final Assignment: individual work Submission deadline first round: Sun 1 July 007 at 3:00 Manage Complexity Separation of Concerns Divide and Conquer Design by Contract Submission deadline second round: Sun 30 Sept 007 at 3:00 c 007, T. TUE.NL 0 Program Realization : Lecture 9 c 007, T. TUE.NL 1 Program Realization : Lecture 9

7 Why Modular Structure? How to Design Correct construction Manage complexity Team construction Reduce development time Verification Errors are inevitable Adaptation Change is inevitable Reuse Reduce budget c 007, T. TUE.NL Program Realization : Lecture 9 During design, many decisions must be made Design guidelines, principles, and methods are needed Modular structure: how to find the modules Top-down design, stepwise refinement, functional decomposition Bottom-up design Functionality versus data as basis for modularity c 007, T. TUE.NL 3 Program Realization : Lecture 9 Main Themes What Next? Abstract Data Types and object-oriented programming Recursion, both in control and in data Event-driven, interactive Graphical User Interfaces Borland Delphi with Object Pascal New curriculum... Algorithms and Data Structures Threads, Network communication, database connection c 007, T. TUE.NL 4 Program Realization : Lecture 9 c 007, T. TUE.NL 5 Program Realization : Lecture 9

Programming, Block C. Today s Topics. wstomv/2ip05/ Branching dynamic data structures with pointers: Lecture 15.

Programming, Block C. Today s Topics. wstomv/2ip05/ Branching dynamic data structures with pointers: Lecture 15. Programming, Block C Today s Topics http://www.win.tue.nl/ wstomv/2ip05/ Lecture 15 Tom Verhoeff Kees Hemerik Technische Universiteit Eindhoven Faculteit Wiskunde en Informatica Software Engineering &