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• Simplified INotifyPropertyChanged Implementation with WeakReference Support and Typed Property Acces

  - by Daniel Cazzulino

  I've grown a bit tired of implementing INotifyPropertyChanged. I've tried ways to improve it before (like this "ViewModel" custom tool which even generates strong-typed event accessors). But my fellow Clarius teammate Mariano thought it was overkill and didn't like that tool much. He mentioned an alternative approach also, which I didn't like too much because it relied on the consumer changing his typical interaction with the object events, but also because it has a substantial design flaw that causes handlers not to be called at all after a garbage collection happens. A very simple unit test will showcase this bug....Read full article

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• Implementation of Diffie-Hellman algorithm of key exchange

  The article is devoted to the development of the library that implements the Diffie – Hellman cryptographic algorithm of key exchange.

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• Using heavyweight ORM implementation for light based games

  - by Holland

  I'm just about to engulf myself in an MVC-based/Component architecture in C#, using MySQL's connector/Net for the data storage, and probably some NHibernate/FluentNHibernate Object-relational-mapping to map out the data structure. The goal is to build a scalable 2D RPG. Then I think about it...and I can't help but think this seems a little "heavy weight" for a 2D RPG, especially one which, while I plan to incorporate a lot of functionality and entertaining gameplay, may be ported to something like Windows Phone or Android in the future. Yet, on the other hand even a 2-Dimensional RPG can become very complicated, and therefore must incorporate a lot of functionality. While this can be accomplished with text/XML/JSON for data storage, is there a better way? Is something such as Object-Relational-Mapping useful in such an application? So, what do you think? Would you say that there is a place for such technologies? I don't know what to think...

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• Dynamic Tab Implementation in ADF

  - by Vijay Mohan

  Well, this can be a common usecase across apps to open tabs dynamically at runtime based on the request.Well, in order to achieve this you can have a parent container, lets say a panelTab component.Inside panelTab , u can have a showDetailItem inside an af:foreach or an af:iterator binded to a bean static list which will have as many show detail items as you wish to be shown.something like this.private static List = { new showDetailItem("1"),new ShowDetailItem("2") ...};now in the backing bean you can have a method that takes care of rendering and disclosing an specific tab based on the index.public void openMyTab(){List<MyItems> list = refToParentContainer.getChildren();int indexOfTabToBeOpened = //Write a method that will compute the tab index of the next //tab.list.get(index).setRendered(true);list.get(index).setDisclosed(true);similarly you can set other properties too.}Else, instead of having af:foreach/iterator iterating through the SD items , you can go for static SDs in the page with render property set to false and then you can follow the same approach to render/disclose it at runtime.

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• Octree implementation for fustrum culling

  - by Manvis

  I'm learning modern (=3.1) OpenGL by coding a 3D turn based strategy game, using C++. The maps are composed of 100x90 3D hexagon tiles that range from 50 to 600 tris (20 different types) + any player units on those tiles. My current rendering technique involves sorting meshes by shaders they use (minimizing state changes) and then calling glDrawElementsInstanced() for drawing. Still get solid 16.6 ms/frame on my GTX 560Ti machine but the game struggles (45.45 ms/frame) on an old 8600GT card. I'm certain that using an octree and fustrum culling will help me here, but I have a few questions before I start implementing it: Is it OK for an octree node to have multiple meshes in it (e.g. can a soldier and the hex tile he's standing on end up in the same octree node)? How is one supposed to treat changes in object postion (e.g. several units are moving 3 hexes down)? I can't seem to find good a explanation on how to do it. As I've noticed, soting meshes by shaders is a really good way to save GPU. If I put node contents into, let's say, std::list and sort it before rendering, do you think I would gain any performance, or would it just create overhead on CPU's end? I know that this sounds like early optimization and implementing + testing would be the best way to find out, but perhaps someone knows from experience?

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• Rich Snippets - LocalBusiness - Photos - Correct Implementation

  - by user32622

  Does somebody know, how this is supposed to be implemented correctly? In my local business full page, I have a carousel with several images, so what I did is that on the container of this carousel i have written the following: "itemprop='photos' itemscope itemtype="http://schema.org/ImageObject"", i.e. <div class="tourism-product-media-gallery" itemprop='photos' itemscope itemtype="http://schema.org/ImageObject"> and then on each and every image i have written the following: "itemprop="contentURL"", i.e. <img src="@mediaItem.NormalImage" alt="@mediaItemCaption" itemprop="contentURL"/> But i am not convinced that this is the way it should be. Anyone has any insight on this and more knowledge? Thanks Note: here are the results from the rich snippet google testing tool: click here

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• Clean way to use mutable implementation of Immutable interfaces for encapsulation

  - by dsollen

  My code is working on some compost relationship which creates a tree structure, class A has many children of type B, which has many children of type C etc. The lowest level class, call it bar, also points to a connected bar class. This effectively makes nearly every object in my domain inter-connected. Immutable objects would be problematic due to the expense of rebuilding almost all of my domain to make a single change to one class. I chose to go with an interface approach. Every object has an Immutable interface which only publishes the getter methods. I have controller objects which constructs the domain objects and thus has reference to the full objects, thus capable of calling the setter methods; but only ever publishes the immutable interface. Any change requested will go through the controller. So something like this: public interface ImmutableFoo{ public Bar getBar(); public Location getLocation(); } public class Foo implements ImmutableFoo{ private Bar bar; private Location location; @Override public Bar getBar(){ return Bar; } public void setBar(Bar bar){ this.bar=bar; } @Override public Location getLocation(){ return Location; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); if(foo!=null) foo.addBar(bar); return foo; } } I felt the basic approach seems sensible, however, when I speak to others they always seem to have trouble envisioning what I'm describing, which leaves me concerned that I may have a larger design issue then I'm aware of. Is it problematic to have domain objects so tightly coupled, or to use the quasi-mutable approach to modifying them? Assuming that the design approach itself isn't inherently flawed the particular discussion which left me wondering about my approach had to do with the presence of business logic in the domain objects. Currently I have my setter methods in the mutable objects do error checking and all other logic required to verify and make a change to the object. It was suggested that this should be pulled out into a service class, which applies all the business logic, to simplify my domain objects. I understand the advantage in mocking/testing and general separation of logic into two classes. However, with a service method/object It seems I loose some of the advantage of polymorphism, I can't override a base class to add in new error checking or business logic. It seems, if my polymorphic classes were complicated enough, I would end up with a service method that has to check a dozen flags to decide what error checking and business logic applies. So, for example, if I wanted to have a childFoo which also had a size field which should be compared to bar before adding par my current approach would look something like this. public class Foo implements ImmutableFoo{ public void addBar(Bar bar){ if(!getLocation().equals(bar.getLocation()) throw new LocationException(); this.bar=bar; } } public interface ImmutableChildFoo extends ImmutableFoo{ public int getSize(); } public ChildFoo extends Foo implements ImmutableChildFoo{ private int size; @Override public int getSize(){ return size; } @Override public void addBar(Bar bar){ if(getSize()<bar.getSize()){ throw new LocationException(); super.addBar(bar); } My colleague was suggesting instead having a service object that looks something like this (over simplified, the 'service' object would likely be more complex). public interface ImmutableFoo{ ///original interface, presumably used in other methods public Location getLocation(); public boolean isChildFoo(); } public interface ImmutableSizedFoo implements ImmutableFoo{ public int getSize(); } public class Foo implements ImmutableSizedFoo{ public Bar bar; @Override public void addBar(Bar bar){ this.bar=bar; } @Override public int getSize(){ //default size if no size is known return 0; } @Override public boolean isChildFoo return false; } } public ChildFoo extends Foo{ private int size; @Override public int getSize(){ return size; } @Override public boolean isChildFoo(); return true; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableSizedFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); service.addBarToFoo(foo, bar); returned foo; } public class Service{ public static void addBarToFoo(Foo foo, Bar bar){ if(foo==null) return; if(!foo.getLocation().equals(bar.getLocation())) throw new LocationException(); if(foo.isChildFoo() && foo.getSize()<bar.getSize()) throw new LocationException(); foo.setBar(bar); } } } Is the recommended approach of using services and inversion of control inherently superior, or superior in certain cases, to overriding methods directly? If so is there a good way to go with the service approach while not loosing the power of polymorphism to override some of the behavior?

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• Ord function implementation in Delphi

  - by Federico Zancan

  Purely as an exercise at home, aimed to better understand some language basics, I tried to reimplement the Ord function, but I came across a problem. In fact, the existing Ord function can accept arguments of a variety of different types (AnsiChar, Char, WideChar, Enumeration, Integer, Int64) and can return Integer or Int64. I can't figure out how to declare multiple versions of the same function. How should this be coded in Delphi?

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• A star algorithm implementation problems

  - by bryan226

  I’m having some trouble implementing the A* algorithm in a 2D tile based game. The problem is basically that the algorithm gets stuck when something gets in its direct way (e.g. walls) Note that it only allows Horizontal and Vertical movement. Here's a picture as it works fine across the map without something in its direct way: (Green tile = destination, Blue = In closed list, Green = in open list) This is what happens if I try to walk 'around' a wall: I calculate costs with the F = G + H formula: G = 1 Cost per Step H = 10 Cost per Step //Count how many tiles are between current-tile & destination-tile The functions: short c_astar::GuessH(short Startx,short Starty,short Destinationx,short Destinationy) { hgeVector Start, Destination; Start.x = Startx; Start.y = Starty; Destination.x = Destinationx; Destination.y = Destinationy; short a = 0; short b = 0; if(Start.x > Destination.x) a = Start.x - Destination.x; else a = Destination.x - Start.x; if(Start.y > Destination.y) b = Start.y - Destination.y; else b = Destination.y - Start.y; return (a+b)*10; } short c_astar::GuessG(short Startx,short Starty,short Currentx,short Currenty) { hgeVector Start, Destination; Start.x = Startx; Start.y = Starty; Destination.x = Currentx; Destination.y = Currenty; short a = 0; short b = 0; if(Start.x > Destination.x) a = Start.x - Destination.x; else a = Destination.x - Start.x; if(Start.y > Destination.y) b = Start.y - Destination.y; else b = Destination.y - Start.y; return (a+b); } At the end of the loop I check which tile is the cheapest to go according to its F value: Then some quick checks are done for each tile (UP,DOWN,LEFT,RIGHT): //...CX are holding the F value of the TILE specified // Info: C0 = Center (Current) // C1 = UP // C2 = DOWN // C3 = LEFT // C4 = RIGHT //Quick checks if(((C1 < C2) && (C1 < C3) && (C1 < C4))) { Current.y -= 1; bSimilar = false; if(DEBUG) hge->System_Log("C1 < ALL"); } //.. same for C2,C3 & C4 If there are multiple tiles with the same F value: It’s actually a switch for DOWNLEFT,UPRIGHT.. etc. Here’s one of it: case UPRIGHT: { //UP Temporary = Current; Temporary.y -= 1; bTileStatus[0] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[0]) { //Proceed normal we are OK & walkable Tilex.Tile = map.at(Temporary.y).at(Temporary.x); //Search in lists if(SearchInClosedList(Tilex.Tile.ID,C0)) bFoundInClosedList[0] = true; if(SearchInOpenList(Tilex.Tile.ID,C0)) bFoundInOpenList[0] = true; //RIGHT Temporary = Current; Temporary.x += 1; bTileStatus[1] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[1]) { //Proceed normal we are OK & walkable Tilex.Tile = map.at(Temporary.y).at(Temporary.x); //Search in lists if(SearchInClosedList(Tilex.Tile.ID,C0)) bFoundInClosedList[1] = true; if(SearchInOpenList(Tilex.Tile.ID,C0)) bFoundInOpenList[1] = true; //************************************************* // Purpose: ClosedList behavior //************************************************* if(bFoundInClosedList[0] && !bFoundInClosedList[1]) { //UP found in ClosedList. Go RIGHT return RIGHT; } if(!bFoundInClosedList[0] && bFoundInClosedList[1]) { //RIGHT found in ClosedList. Go UP return UP; } if(bFoundInClosedList[0] && bFoundInClosedList[1]) { //Both found in ClosedList. Random value switch(hge->Random_Int(8,9)) { case 8: return UP; break; case 9: return RIGHT; break; } } //************************************************* // Purpose: OpenList behavior //************************************************* if(bFoundInOpenList[0] && !bFoundInOpenList[1]) { //UP found in OpenList. Go RIGHT return RIGHT; } if(!bFoundInOpenList[0] && bFoundInOpenList[1]) { //RIGHT found in OpenList. Go UP return UP; } if(bFoundInOpenList[0] && bFoundInOpenList[1]) { //Both found in OpenList. Random value switch(hge->Random_Int(8,9)) { case 8: return UP; break; case 9: return RIGHT; break; } } } else if(!bTileStatus[1]) { //RIGHT is not walkable OR out of range //Choose UP return UP; } } else if(!bTileStatus[0]) { //UP is not walkable OR out of range //Fast check RIGHT Temporary = Current; Temporary.x += 1; bTileStatus[1] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[1]) { return RIGHT; } else return FAILED; //Failed, no valid path found! } } break; A log for the second picture: (Cut down to ten passes, because it’s just repeating itself) ----------------------------------------------------- PASS: 1 | C1: 211 | C2: 191 | C3: 211 | C4: 191 DOWN + RIGHT SIMILAR Going DOWN ----------------------------------------------------- PASS: 2 | C1: 200 | C2: 182 | C3: 202 | C4: 182 DOWN + RIGHT SIMILAR Going DOWN ----------------------------------------------------- PASS: 3 | C1: 191 | C2: 193 | C3: 193 | C4: 173 C4 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 4 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going UP Tile(12.000000,5.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 5 | C1: 191 | C2: 173 | C3: 191 | C4: 999 C2 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 6 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going UP Tile(12.000000,5.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 7 | C1: 191 | C2: 173 | C3: 191 | C4: 999 C2 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 8 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going LEFT ----------------------------------------------------- PASS: 9 | C1: 191 | C2: 193 | C3: 193 | C4: 173 C4 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 10 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going LEFT ----------------------------------------------------- Its always going after the cheapest F value, which seems to be wrong. If someone could point me to the right direction I'd be thankful. Regards, bryan226

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• Requiring multithreading/concurrency for implementation of scripting language

  - by Ricky Stewart

  Here's the deal: I'm looking at designing my own scripting/interpreted language for fun. I'm only in the planning stages right now; I want to make sure I have a very strong hold on exactly how I will implement everything before I start coding. What I'm currently struggling with is concurrency. It seems to me like an easy way to avoid the unpredictable performance that comes with garbage collection would be to put the garbage collector in its own thread, and have it run concurrently with the interpreter itself. (To be clear, I don't plan to allow the scripts to be multithreaded themselves; I would simply put a garbage collector to work in a different thread than the interpreter.) This doesn't seem to be a common strategy for many popular scripting languages, probably for portability reasons; I would probably write the interpreter in the UNIX/POSIX threading framework initially and then port it to other platforms (Windows, etc.) if need be. Does anyone have any thoughts in this issue? Would whatever gains I receive by exploiting concurrency be nullified by the portability issues that will inevitably arise? (On that note, am I really correct in my assumption that I would experience great performance gains with a concurrent garbage collector?) Should I move forward with this strategy or step away from it?

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• Question on the implementation of my Entity System

  - by miguel.martin

  I am currently creating an Entity System, in C++, it is almost completed (I have all the code there, I just have to add a few things and test it). The only thing is, I can't figure out how to implement some features. This Entity System is based off a bit from the Artemis framework, however it is different. I'm not sure if I'll be able to type this out the way my head processing it. I'm going to basically ask whether I should do something over something else. Okay, now I'll give a little detail on my Entity System itself. Here are the basic classes that my Entity System uses to actually work: Entity - An Id (and some methods to add/remove/get/etc Components) Component - An empty abstract class ComponentManager - Manages ALL components for ALL entities within a Scene EntitySystem - Processes entities with specific components Aspect - The class that is used to help determine what Components an Entity must contain so a specific EntitySystem can process it EntitySystemManager - Manages all EntitySystems within a Scene EntityManager - Manages entities (i.e. holds all Entities, used to determine whether an Entity has been changed, enables/disables them, etc.) EntityFactory - Creates (and destroys) entities and assigns an ID to them Scene - Contains an EntityManager, EntityFactory, EntitySystemManager and ComponentManager. Has functions to update and initialise the scene. Now in order for an EntitySystem to efficiently know when to check if an Entity is valid for processing (so I can add it to a specific EntitySystem), it must recieve a message from the EntityManager (after a call of activate(Entity& e)). Similarly the EntityManager must know when an Entity is destroyed from the EntityFactory in the Scene, and also the ComponentManager must know when an Entity is created AND destroyed. I do have a Listener/Observer pattern implemented at the moment, but with this pattern I may remove a Listener (which is this case is dependent on the method being called). I mainly have this implemented for specific things related to a game, i.e. Teams, Tagging of entities, etc. So... I was thinking maybe I should call a private method (using friend classes) to send out when an Entity has been activated, deleted, etc. i.e. taken from my EntityFactory void EntityFactory::killEntity(Entity& e) { // if the entity doesn't exsist in the entity manager within the scene if(!getScene()->getEntityManager().doesExsist(e)) { return; // go back to the caller! (should throw an exception or something..) } // tell the ComponentManager and the EntityManager that we killed an Entity getScene()->getComponentManager().doOnEntityWillDie(e); getScene()->getEntityManager().doOnEntityWillDie(e); // notify the listners for(Mouth::iterator i = getMouth().begin(); i != getMouth().end(); ++i) { (*i)->onEntityWillDie(*this, e); } _idPool.addId(e.getId()); // add the ID to the pool delete &e; // delete the entity } As you can see on the lines where I am telling the ComponentManager and the EntityManager that an Entity will die, I am calling a method to make sure it handles it appropriately. Now I realise I could do this without calling it explicitly, with the help of that for loop notifying all listener objects connected to the EntityFactory's Mouth (an object used to tell listeners that there's an event), however is this a good idea (good design, or what)? I've gone over the PROS and CONS, I just can't decide what I want to do. Calling Explicitly: PROS Faster? Since these functions are explicitly called, they can't be "removed" CONS Not flexible Bad design? (friend functions) Calling through Listener objects (i.e. ComponentManager/EntityManager inherits from a EntityFactoryListener) PROS More Flexible? Better Design? CONS Slower? (virtual functions) Listeners can be removed, i.e. may be removed and not get called again during the program, which could cause in a crash. P.S. If you wish to view my current source code, I am hosting it on BitBucket.

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• ICopyHook implementation

  Implementing ICopyHook Windows extension

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• File system implementation in MongoDB with GridFS

  - by Ralph

  I am working on two projects that will both implement a Webdav server backed by a MongoDB GridFS. In each case, there is the potential for the system to store tens of millions of files spread across thousands of hierarchical directories. I can come up with two different ways of storing the directory structure: As a "true" hierarchical file system, with directories containing the IDs (_id) of subdirectories and regular files. The paths will be separated by slashes (/) as in a POSIX-compliant file system. The path /a/b/c will be represented as a directory a containing a directory b containing a file c. As a flat file system, where file names include the slashes. The path /a/b/c will be stored as a single file with the name /a/b/c What are the advantages and disadvantages of each, with respect to a "real" folder-based file system?

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• Just another deep cloning implementation

  Deep cloning in .NET via reflection

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• Software Architecture - From design to sucessful implementation

  - by user20358

  As the subject goes; once a software architect puts down the high level design and approach to a software that is to be developed from scratch, how does the team ensure that it is implemented successfully? To my mind the following things will need to be done Proper understanding of requirements Setting down coding practices and guidelines Regular code reviews to ensure the guidelines are being adhered to Revisiting the requirements phase and making necessary changes to design based on client inputs if there are any changes to requirements Proper documentation of what is being done in code Proper documentation of requirements and changes to them Last but not the least, implementing the design via object oriented code where appropriate Did I miss anything? Would love to hear any mistakes that you have learned from in your project experiences. What went wrong, what could have been done better. Thanks for taking the time..

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• Negamax implementation doesn't appear to work with tic-tac-toe

  - by George Jiglau

  I've implemented Negamax as it can be found on wikipedia, which includes alpha/beta pruning. However, it seems to favor a losing move, which should be an invalid result. The game is Tic-Tac-Toe, I've abstracted most of the game play so it should be rather easy to spot an error within the algorithm. Here is the code, nextMove, negamax or evaluate are probably the functions that contain the fault: #include <list> #include <climits> #include <iostream> //#define DEBUG 1 using namespace std; struct Move { int row, col; Move(int row, int col) : row(row), col(col) { } Move(const Move& m) { row = m.row; col = m.col; } }; struct Board { char player; char opponent; char board[3][3]; Board() { } void read(istream& stream) { stream >> player; opponent = player == 'X' ? 'O' : 'X'; for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { char playa; stream >> playa; board[row][col] = playa == '_' ? 0 : playa == player ? 1 : -1; } } } void print(ostream& stream) { for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { switch(board[row][col]) { case -1: stream << opponent; break; case 0: stream << '_'; break; case 1: stream << player; break; } } stream << endl; } } void do_move(const Move& move, int player) { board[move.row][move.col] = player; } void undo_move(const Move& move) { board[move.row][move.col] = 0; } bool isWon() { if (board[0][0] != 0) { if (board[0][0] == board[0][1] && board[0][1] == board[0][2]) return true; if (board[0][0] == board[1][0] && board[1][0] == board[2][0]) return true; } if (board[2][2] != 0) { if (board[2][0] == board[2][1] && board[2][1] == board[2][2]) return true; if (board[0][2] == board[1][2] && board[1][2] == board[2][2]) return true; } if (board[1][1] != 0) { if (board[0][1] == board[1][1] && board[1][1] == board[2][1]) return true; if (board[1][0] == board[1][1] && board[1][1] == board[1][2]) return true; if (board[0][0] == board[1][1] && board[1][1] == board[2][2]) return true; if (board[0][2] == board [1][1] && board[1][1] == board[2][0]) return true; } return false; } list<Move> getMoves() { list<Move> moveList; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board[row][col] == 0) moveList.push_back(Move(row, col)); return moveList; } }; ostream& operator<< (ostream& stream, Board& board) { board.print(stream); return stream; } istream& operator>> (istream& stream, Board& board) { board.read(stream); return stream; } int evaluate(Board& board) { int score = board.isWon() ? 100 : 0; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board.board[row][col] == 0) score += 1; return score; } int negamax(Board& board, int depth, int player, int alpha, int beta) { if (board.isWon() || depth <= 0) { #if DEBUG > 1 cout << "Found winner board at depth " << depth << endl; cout << board << endl; #endif return player * evaluate(board); } list<Move> allMoves = board.getMoves(); if (allMoves.size() == 0) return player * evaluate(board); for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, -player); int val = -negamax(board, depth - 1, -player, -beta, -alpha); board.undo_move(*it); if (val >= beta) return val; if (val > alpha) alpha = val; } return alpha; } void nextMove(Board& board) { list<Move> allMoves = board.getMoves(); Move* bestMove = NULL; int bestScore = INT_MIN; for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, 1); int score = -negamax(board, 100, 1, INT_MIN + 1, INT_MAX); board.undo_move(*it); #if DEBUG cout << it->row << ' ' << it->col << " = " << score << endl; #endif if (score > bestScore) { bestMove = &*it; bestScore = score; } } if (!bestMove) return; cout << bestMove->row << ' ' << bestMove->col << endl; #if DEBUG board.do_move(*bestMove, 1); cout << board; #endif } int main() { Board board; cin >> board; #if DEBUG cout << "Starting board:" << endl; cout << board; #endif nextMove(board); return 0; } Giving this input: O X__ ___ ___ The algorithm chooses to place a piece at 0, 1, causing a guaranteed loss, do to this trap(nothing can be done to win or end in a draw): XO_ X__ ___ Perhaps it has something to do with the evaluation function? If so, how could I fix it?

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• My approach towards SEO implementation needs improvements. [closed]

  - by Eritrea

  I have always copy/paste this below code as a template for meta tags on project, but I think they are not effective as they could possible be. So, I need to know if there is anyway I can improve it. suppose I have a site called coop.com for a company called Coopm and we do import and export as a business in France. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> <meta name="rpbots" content="index, follow" /> <meta name="description" content="ccop is a major import and export company" /> <meta name="keywords" content="coop, coop.com coop company, import export, import export france, " /> <meta name='REVISIT-AFTER' content='30 DAYS'> <title>coop is an import and export company located in France</title> </head> The reason I am asking, is because I want to know if there are better ways of constructing your SEO tags, and construction.

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• Version control implementation advice on legacy websites?

  - by Eric

  Assuming no experience with version control systems, just local to live web development. I've been dropped in on a few legacy website projects, and want an easier and more robust way to be able to quickly push and revert changes en masse. I'm currently the only developer on these projects, but more may be added in the future and I think it would be beneficial to set up a system that others can use.

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• Dynamic body implementation

  - by ArturoVM

  I am writing a 2D game where one of the characters has some very particular requirements. This character is a body with no particular shape (similar to a fluid, but not so much), it has to be able to grow and shrink (as in actually growing, not just scaling), and it has to have collision detection (even if it's basic). Because of this requirements, it obviously can't be based on a sprite, so direct rendering of the shape should be the logical thing to do. I assume this is no easy task, but I just couldn't find a good physics engine that covers these requirements (or at least no tutorial on how to do it; I particularly searched for Box2D tutorials). Is there a way of doing this with Box2D, SDL, or any other physics or game engine out there? If not, what's a good place to start? I am really clueless as far as soft-body physics are concerned.

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• Implementation of instance testing in Java, C++, C#

  - by Jake

  For curiosity purposes as well as understanding what they entail in a program, I'm curious as to how instance testing (instanceof/is/using dynamic_cast in c++) works. I've tried to google it (particularly for java) but the only pages that come up are tutorials on how to use the operator. How do the implementations vary across those langauges? How do they treat classes with identical signatures? Also, it's been drilled into my head that using instance testing is a mark of bad design. Why exactly is this? When is that applicable, instanceof should still be used in methods like .equals() and such right? I was also thinking of this in the context of exception handling, again particularly in Java. When you have mutliple catch statements, how does that work? Is that instance testing or is it just resolved during compilation where each thrown exception would go to?

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• Confused about javascript module pattern implementation

  - by Damon

  I have a class written on a project I'm working on that I've been told is using the module pattern, but it's doing things a little differently than the examples I've seen. It basically takes this form: (function ($, document, window, undefined) { var module = { foo : bar, aMethod : function (arg) { className.bMethod(arg); }, bMethod : function (arg) { console.log('spoons'); } }; window.ajaxTable = ajaxTable; })(jQuery, document, window); I get what's going on here. But I'm not sure how this relates to most of the definitions I've seen of the module (or revealing?) module pattern. like this one from briancray var module = (function () { // private variables and functions var foo = 'bar'; // constructor var module = function () { }; // prototype module.prototype = { constructor: module, something: function () { } }; // return module return module; })(); var my_module = new module(); Is the first example basically like the second except everything is in the constructor? I'm just wrapping my head around patterns and the little things at the beginnings and endings always make me not sure what I should be doing.

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• Tetris Movement - Implementation

  - by James Brauman

  Hi gamedev, I'm developing a Tetris clone and working on the input at the moment. When I was prototyping, movement was triggered by releasing a directional key. However, in most Tetris games I've played the movement is a bit more complex. When a directional key is pressed, the shape moves one space in that direction. After a short interval, if the key is still held down, the shape starts moving in the direction continuously until the key is released. In the case of the down key being pressed, there is no pause between the initial movement and the subsequent continuous movement. I've come up with a solution, and it works well, but it's totally over-engineered. Hey, at least I can recognize when things are getting silly, right? :) public class TetrisMover { List registeredKeys; Dictionary continuousPressedTime; Dictionary totalPressedTime; Dictionary initialIntervals; Dictionary continousIntervals; Dictionary keyActions; Dictionary initialActionDone; KeyboardState currentKeyboardState; public TetrisMover() { *snip* } public void Update(GameTime gameTime) { currentKeyboardState = Keyboard.GetState(); foreach (Keys currentKey in registeredKeys) { if (currentKeyboardState.IsKeyUp(currentKey)) { continuousPressedTime[currentKey] = TimeSpan.Zero; totalPressedTime[currentKey] = TimeSpan.Zero; initialActionDone[currentKey] = false; } else { if (initialActionDone[currentKey] == false) { keyActions[currentKey](); initialActionDone[currentKey] = true; } totalPressedTime[currentKey] += gameTime.ElapsedGameTime; if (totalPressedTime[currentKey] = initialIntervals[currentKey]) { continuousPressedTime[currentKey] += gameTime.ElapsedGameTime; if (continuousPressedTime[currentKey] = continousIntervals[currentKey]) { keyActions[currentKey](); continuousPressedTime[currentKey] = TimeSpan.Zero; } } } } } public void RegisterKey(Keys key, TimeSpan initialInterval, TimeSpan continuousInterval, Action keyAction) { if (registeredKeys.Contains(key)) throw new InvalidOperationException( string.Format("The key %s is already registered.", key)); registeredKeys.Add(key); continuousPressedTime.Add(key, TimeSpan.Zero); totalPressedTime.Add(key, TimeSpan.Zero); initialIntervals.Add(key, initialInterval); continousIntervals.Add(key, continuousInterval); keyActions.Add(key, keyAction); initialActionDone.Add(key, false); } public void UnregisterKey(Keys key) { *snip* } } I'm updating it every frame, and this is how I'm registering keys for movement: tetrisMover.RegisterKey( Keys.Left, keyHoldStartSpecialInterval, keyHoldMovementInterval, () = { Move(Direction.Left); }); tetrisMover.RegisterKey( Keys.Right, keyHoldStartSpecialInterval, keyHoldMovementInterval, () = { Move(Direction.Right); }); tetrisMover.RegisterKey( Keys.Down, TimeSpan.Zero, keyHoldMovementInterval, () = { PerformGravity(); }); Issues that this doesn't address: If both left and right are held down, the shape moves back and forth really quick. If a directional key is held down and the turn finishes and the shape is replaced by a new one, the new one will move quickly in that direction instead of the little pause it is supposed to have. I could fix the issues, but I think it will make the solution even worse. How would you implement this?

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• OpenID implementation - PHP, Javascript, MySQL

  - by Marc A.

  Hello, I've started doing some research on the technologies that I will need for my website. I'm trying to implement a really simple website with OpenID user registration. The website will store a block of text for each user. I imagine this means that I will need a database with: User ID Open ID url Data Having said that, I'm still having trouble deciding what I really need to do this. I know that I will need the following for the actual site: Javascript JQuery CSS But on the back end, I'm kind of lost at the moment. I've been looking at the OpenID-Selector, which is coded in Javascript. It seems like it's exactly what is used on this site. Will I actually need PHP? MySQL for the data and user registration? Thanks for the kickstart!

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• Les accesseurs et les détails d'implémentation, un billet de Guillaume Belz

  C'est une discussion qui revient régulièrement sur le chat de Developpez.com. Une personne demande comment fait-on pour accéder aux variables membres privées d'une classe et on lui répond de créer des getter et setter. Viens alors un C++ien moyen (c'est-à-dire un casse-pied, en général moi) qui hurle au scandale et sort l'adage bien connu : "les accesseurs, c'est le mal". S'en suit une discussion sur pourquoi les accesseurs sont à éviter, quand j'ai le temps et l'humeur.

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• implementation of text editor in shell programming

  - by Arka Ghosh

  i have made a text editor in C. when i am changing the extension of that file from .c to .sh and compiling the file in the terminal,some error is shown,like for the global variables an external error is shown,and for the functions i have declared errors are shown there also.please help me to solve this. I am sending my code.. include include include int i,j,ec,fg,ec2; char fn[20],e,c,d; FILE *fp1,*fp2,fp; void Create(); void Append(); void Delete(); void Display(); int main() { do { printf("\n\t\t** TEXT EDITOR *"); printf("\n\n\tMENU:\n\t..\n "); printf("\n\t1.CREATE\n\t2.DISPLAY\n\t3.APPEND\n\t4.DELETE\n\t5.EXIT\n"); printf("\n\tEnter your choice: "); scanf("%d",&ec); switch(ec) { case 1: Create(); break; case 2: Display(); break; case 3: Append(); break; case 4: Delete(); break; case 5: exit(1); } }while(1); } void Create() { fp1=fopen("temp.txt","w"); printf("\n\tEnter the text and press '.' to save\n\n\t"); while(1) { c=getchar(); fputc(c,fp1); if(c == '.') { fclose(fp1); printf("\n\tEnter then new filename: "); scanf("%s",fn); fp1=fopen("temp.txt","r"); fp2=fopen(fn,"w"); while(!feof(fp1)) { c=getc(fp1); putc(c,fp2); } fclose(fp2); break; }} } void Display() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end1; } while(!feof(fp1)) { c=getc(fp1); printf("%c",c); } end1: fclose(fp1); printf("\n\n\tPress any key to continue.."); } void Delete() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end2; } fclose(fp1); if(remove(fn)==0) { printf("\n\n\tFile has been deleted successfully!"); goto end2; } else printf("\n\tError!\n"); end2: printf("\n\n\tPress any key to continue.."); getchar(); } void Append() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end3; } while(!feof(fp1)) { c=getc(fp1); printf("%c",c); } fclose(fp1); printf("\n\tType the text and press 'Ctrl+s' to append.\n"); fp1=fopen(fn,"a"); while(1) { c=getchar(); if(c==19) goto end3; if(c==13) { d='\n'; fputc(d,fp1); } else { fputc(c,fp1); } } end3: fclose(fp1); }

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