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  • Nullpointerexcption & abrupt IOStream closure with inheritence and subclasses

    - by user1401652
    A brief background before so we can communicate on the same wave length. I've had about 8-10 university courses on programming from data structure, to one on all languages, to specific ones such as java & c++. I'm a bit rusty because i usually take 2-3 month breaks from coding. This is a personal project that I started thinking of two years back. Okay down to the details, and a specific question, I'm having problems with my mutator functions. It seems to be that I am trying to access a private variable incorrectly. The question is, am I nesting my classes too much and trying to mutate a base class variable the incorrect way. If so point me in the way of the correct literature, or confirm this is my problem so I can restudy this information. Thanks package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Date { private int hour, minute, day, month, year; Date() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What's the hour? (Use 1-24 military notation"); hour = Integer.parseInt(keyboard.readLine()); System.out.println("what's the minute? "); minute = Integer.parseInt(keyboard.readLine()); System.out.println("What's the day of the month?"); day = Integer.parseInt(keyboard.readLine()); System.out.println("Which month of the year is it, use an integer"); month = Integer.parseInt(keyboard.readLine()); System.out.println("What year is it?"); year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (IOException e) { System.out.println("Yo houston we have a problem"); } } public void setHour(int hour) { this.hour = hour; } public void setHour() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What hour, use military notation?"); this.hour = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getHour() { return hour; } public void setMinute(int minute) { this.minute = minute; } public void setMinute() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What minute?"); this.minute = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ": doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": minute shall not cooperate"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the setMinute function of the Date class"); } } public int getMinute() { return minute; } public void setDay(int day) { this.day = day; } public void setDay() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What day 0-6?"); this.day = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getDay() { return day; } public void setMonth(int month) { this.month = month; } public void setMonth() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What month 0-11?"); this.month = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getMonth() { return month; } public void setYear(int year) { this.year = year; } public void setYear() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What year?"); this.year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getYear() { return year; } public void set() { setMinute(); setHour(); setDay(); setMonth(); setYear(); } public Vector<Integer> get() { Vector<Integer> holder = new Vector<Integer>(5); holder.add(hour); holder.add(minute); holder.add(month); holder.add(day); holder.add(year); return holder; } }; That is the Date class obviously, next is the other base class Location. package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Location { String streetName, state, city, country; int zipCode, address; Location() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What is the street name"); streetName = keyboard.readLine(); System.out.println("Which state?"); state = keyboard.readLine(); System.out.println("Which city?"); city = keyboard.readLine(); System.out.println("Which country?"); country = keyboard.readLine(); System.out.println("Which zipcode?");//if not u.s. continue around this step zipCode = Integer.parseInt(keyboard.readLine()); System.out.println("What address?"); address = Integer.parseInt(keyboard.readLine()); } catch (IOException e) { System.out.println(e.toString()); } } public void setZipCode(int zipCode) { this.zipCode = zipCode; } public void setZipCode() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What zipCode?"); this.zipCode = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public void set() { setAddress(); setCity(); setCountry(); setState(); setStreetName(); setZipCode(); } public int getZipCode() { return zipCode; } public void setAddress(int address) { this.address = address; } public void setAddress() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.address = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getAddress() { return address; } public void setStreetName(String streetName) { this.streetName = streetName; } public void setStreetName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.streetName = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getStreetName() { return streetName; } public void setState(String state) { this.state = state; } public void setState() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.state = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getState() { return state; } public void setCity(String city) { this.city = city; } public void setCity() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.city = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCity() { return city; } public void setCountry(String country) { this.country = country; } public void setCountry() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.country = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCountry() { return country; } }; their parent(What is the proper name?) class package GroceryReceiptProgram; import java.io.*; public class FoodGroup { private int price, count; private Date purchaseDate, expirationDate; private Location location; private String name; public FoodGroup() { try { setPrice(); setCount(); expirationDate.set(); purchaseDate.set(); location.set(); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the constructor of the FoodGroup class"); } } public void setPrice(int price) { this.price = price; } public void setPrice() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What Price?"); price = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setPrice function"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class. SetPrice()"); } } public int getPrice() { return price; } public void setCount(int count) { this.count = count; } public void setCount() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What count?"); count = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setCount()"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class, setCount"); } } public int getCount() { return count; } public void setName(String name) { this.name = name; } public void setName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.name = keyboard.readLine(); } catch (IOException e) { System.out.println(e.toString()); } } public String getName() { return name; } public void setLocation(Location location) { this.location = location; } public Location getLocation() { return location; } public void setPurchaseDate(Date purchaseDate) { this.purchaseDate = purchaseDate; } public void setPurchaseDate() { this.purchaseDate.set(); } public Date getPurchaseDate() { return purchaseDate; } public void setExpirationDate(Date expirationDate) { this.expirationDate = expirationDate; } public void setExpirationDate() { this.expirationDate.set(); } public Date getExpirationDate() { return expirationDate; } } and finally the main class, so I can get access to all of this work. package GroceryReceiptProgram; public class NewMain { public static void main(String[] args) { FoodGroup test = new FoodGroup(); } } If anyone is further interested, here is a link the UML for this. https://www.dropbox.com/s/1weigjnxih70tbv/GRP.dia

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  • Inheritance issue

    - by VenkateshGudipati
    hi Friends i am facing a issue in Inheritance i have a interface called Irewhizz interface irewhzz { void object save(object obj); void object getdata(object obj); } i write definition in different class like public user:irewhzz { public object save(object obj); { ....... } public object getdata(object obj); { ....... } } this is antoher class public client:irewhzz { public object save(object obj); { ....... } public object getdata(object obj); { ....... } } now i have different classes like public partial class RwUser { #region variables IRewhizzDataHelper irewhizz; IRewhizzRelationDataHelper irewhizzrelation; private string _firstName; private string _lastName; private string _middleName; private string _email; private string _website; private int _addressId; private string _city; private string _zipcode; private string _phone; private string _fax; //private string _location; private string _aboutMe; private string _username; private string _password; private string _securityQuestion; private string _securityQAnswer; private Guid _user_Id; private long _rwuserid; private byte[] _image; private bool _changepassword; private string _mobilephone; private int _role; #endregion //IRewhizz is the interface and its functions are implimented by UserDataHelper class //RwUser Class is inheriting the UserDataHelper Properties and functions. //Here UserDataHelper functions are called with Irewhizz Interface Object but not with the //UserDataHelper class Object It will resolves the unit testing conflict. #region Constructors public RwUser() : this(new UserDataHelper(), new RewhizzRelationalDataHelper()) { } public RwUser(IRewhizzDataHelper repositary, IRewhizzRelationDataHelper relationrepositary) { irewhizz = repositary; irewhizzrelation = relationrepositary; } #endregion #region Properties public int Role { get { return _role; } set { _role = value; } } public string MobilePhone { get { return _mobilephone; } set { _mobilephone = value; } } public bool ChangePassword { get { return _changepassword; } set { _changepassword = value; } } public byte[] Image { get { return _image; } set { _image = value; } } public string FirstName { get { return _firstName; } set { _firstName = value; } } public string LastName { get { return _lastName; } set { _lastName = value; } } public string MiddleName { get { return _middleName; } set { _middleName = value; } } public string Email { get { return _email; } set { _email = value; } } public string Website { get { return _website; } set { _website = value; } } public int AddressId { get { return _addressId; } set { _addressId = value; } } public string City { get { return _city; } set { _city = value; } } public string Zipcode { get { return _zipcode; } set { _zipcode = value; } } public string Phone { get { return _phone; } set { _phone = value; } } public string Fax { get { return _fax; } set { _fax = value; } } //public string Location //{ // get // { // return _location; // } // set // { // _location = value; // } //} public string AboutMe { get { return _aboutMe; } set { _aboutMe = value; } } public string username { get { return _username; } set { _username = value; } } public string password { get { return _password; } set { _password = value; } } public string SecurityQuestion { get { return _securityQuestion; } set { _securityQuestion = value; } } public string SecurityQAnswer { get { return _securityQAnswer; } set { _securityQAnswer = value; } } public Guid UserID { get { return _user_Id; } set { _user_Id = value; } } public long RwUserID { get { return _rwuserid; } set { _rwuserid = value; } } #endregion #region MemberFunctions // DataHelperDataContext db = new DataHelperDataContext(); // RewhizzDataHelper rwdh=new RewhizzDataHelper(); //It saves user information entered by user and returns the id of that user public object saveUserInfo(RwUser userObj) { userObj.UserID = irewhizzrelation.GetUserId(username); var res = irewhizz.saveData(userObj); return res; } //It returns the security questions for user registration } public class Agent : RwUser { IRewhizzDataHelper irewhizz; IRewhizzRelationDataHelper irewhizzrelation; private int _roleid; private int _speclisationid; private int[] _language; private string _brokaragecompany; private int _loctionType_lk; private string _rolename; private int[] _specialization; private string _agentID; private string _expDate; private string _regstates; private string _selLangs; private string _selSpels; private string _locations; public string Locations { get { return _locations; } set { _locations = value; } } public string SelectedLanguages { get { return _selLangs; } set { _selLangs = value; } } public string SelectedSpecialization { get { return _selSpels; } set { _selSpels = value; } } public string RegisteredStates { get { return _regstates; } set { _regstates = value; } } //private string _registeredStates; public string AgentID { get { return _agentID; } set { _agentID = value; } } public string ExpDate { get { return _expDate; } set { _expDate = value; } } private int[] _registeredStates; public SelectList RegisterStates { set; get; } public SelectList Languages { set; get; } public SelectList Specializations { set; get; } public int[] RegisterdStates { get { return _registeredStates; } set { _registeredStates = value; } } //public string RegisterdStates //{ // get // { // return _registeredStates; // } // set // { // _registeredStates = value; // } //} public int RoleId { get { return _roleid; } set { _roleid = value; } } public int SpeclisationId { get { return _speclisationid; } set { _speclisationid = value; } } public int[] Language { get { return _language; } set { _language = value; } } public int LocationTypeId { get { return _loctionType_lk; } set { _loctionType_lk = value; } } public string BrokarageCompany { get { return _brokaragecompany; } set { _brokaragecompany = value; } } public string Rolename { get { return _rolename; } set { _rolename = value; } } public int[] Specialization { get { return _specialization; } set { _specialization = value; } } public Agent() : this(new AgentDataHelper(), new RewhizzRelationalDataHelper()) { } public Agent(IRewhizzDataHelper repositary, IRewhizzRelationDataHelper relationrepositary) { irewhizz = repositary; irewhizzrelation = relationrepositary; } public void inviteclient() { //Code related to mailing } //DataHelperDataContext dataObj = new DataHelperDataContext(); //#region IRewhizzFactory Members //public List<object> getAgentInfo(string username) //{ // var res=dataObj.GetCompleteUserDetails(username); // return res.ToList(); // throw new NotImplementedException(); //} //public List<object> GetRegisterAgentData(string username) //{ // var res= dataObj.RegisteredUserdetails(username); // return res.ToList(); //} //public void saveAgentInfo(string username, string password, string firstname, string lastname, string middlename, string securityquestion, string securityQanswer) //{ // User userobj=new User(); // var result = dataObj.rw_Users_InsertUserInfo(firstname, middlename, lastname, dataObj.GetUserId(username), securityquestion, securityquestionanswer); // throw new NotImplementedException(); //} //#endregion public Agent updateData(Agent objectId) { objectId.UserID = irewhizzrelation.GetUserId(objectId.username); objectId = (Agent)irewhizz.updateData(objectId); return objectId; } public Agent GetAgentData(Agent agentodj) { agentodj.UserID = irewhizzrelation.GetUserId(agentodj.username); agentodj = (Agent)irewhizz.getData(agentodj); if (agentodj.RoleId != 0) agentodj.Rolename = (string)(string)irewhizzrelation.getValue(agentodj.RoleId); if (agentodj.RegisterdStates.Count() != 0) { List<SelectListItem> list = new List<SelectListItem>(); string regstates = ""; foreach (int i in agentodj.RegisterdStates) { SelectListItem listitem = new SelectListItem(); listitem.Value = i.ToString(); listitem.Text = (string)irewhizzrelation.getValue(i); list.Add(listitem); regstates += (string)irewhizzrelation.getValue(i) + ","; } SelectList selectlist = new SelectList(list, "Value", "Text"); agentodj.RegisterStates = selectlist; if(regstates!=null) agentodj.RegisteredStates = regstates.Remove(regstates.Length - 1); } if (agentodj.Language.Count() != 0) { List<SelectListItem> list = new List<SelectListItem>(); string selectedlang = ""; foreach (int i in agentodj.Language) { SelectListItem listitem = new SelectListItem(); listitem.Value = i.ToString(); listitem.Text = (string)irewhizzrelation.getValue(i); list.Add(listitem); selectedlang += (string)irewhizzrelation.getValue(i) + ","; } SelectList selectlist = new SelectList(list, "Value", "Text"); agentodj.Languages = selectlist; // agentodj.SelectedLanguages = selectedlang; } if (agentodj.Specialization.Count() != 0) { List<SelectListItem> list = new List<SelectListItem>(); string selectedspel = ""; foreach (int i in agentodj.Specialization) { SelectListItem listitem = new SelectListItem(); listitem.Value = i.ToString(); listitem.Text = (string)irewhizzrelation.getValue(i); list.Add(listitem); selectedspel += (string)irewhizzrelation.getValue(i) + ","; } SelectList selectlist = new SelectList(list, "Value", "Text"); agentodj.Specializations = selectlist; //agentodj.SelectedSpecialization = selectedspel; } return agentodj; } public void SaveImage(byte[] pic, String username) { irewhizzrelation.SaveImage(pic, username); } } now the issue is when ever i am calling agent class it is given error like null reference exception for rwuser class can any body give the solution thanks in advance

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  • Random movement of wandering monsters in x & y axis in LibGDX

    - by Vishal Kumar
    I am making a simple top down RPG game in LibGDX. What I want is ... the enemies should wander here and there in x and y directions in certain interval so that it looks natural that they are guarding something. I spend several hours doing this but could not achieve what I want. After a long time of coding, I came with this code. But what I observed is when enemies come to an end of x or start of x or start of y or end of y of the map. It starts flickering for random intervals. Sometimes they remain nice, sometimes, they start flickering for long time. public class Enemy extends Sprite { public float MAX_VELOCITY = 0.05f; public static final int MOVING_LEFT = 0; public static final int MOVING_RIGHT = 1; public static final int MOVING_UP = 2; public static final int MOVING_DOWN = 3; public static final int HORIZONTAL_GUARD = 0; public static final int VERTICAL_GUARD = 1; public static final int RANDOM_GUARD = 2; private float startTime = System.nanoTime(); private static float SECONDS_TIME = 0; private boolean randomDecider; public int enemyType; public static final float width = 30 * World.WORLD_UNIT; public static final float height = 32 * World.WORLD_UNIT; public int state; public float stateTime; public boolean visible; public boolean dead; public Enemy(float x, float y, int enemyType) { super(x, y); state = MOVING_LEFT; this.enemyType = enemyType; stateTime = 0; visible = true; dead = false; boolean random = Math.random()>=0.5f ? true :false; if(enemyType == HORIZONTAL_GUARD){ if(random) velocity.x = -MAX_VELOCITY; else velocity.x = MAX_VELOCITY; } if(enemyType == VERTICAL_GUARD){ if(random) velocity.y = -MAX_VELOCITY; else velocity.y = MAX_VELOCITY; } if(enemyType == RANDOM_GUARD){ //if(random) //velocity.x = -MAX_VELOCITY; //else //velocity.y = MAX_VELOCITY; } } public void update(Enemy e, float deltaTime) { super.update(deltaTime); e.stateTime+= deltaTime; e.position.add(velocity); // This is for updating the Animation for Enemy Movement Direction. VERY IMPORTANT FOR REAL EFFECTS updateDirections(); //Here the various movement methods are called depending upon the type of the Enemy if(e.enemyType == HORIZONTAL_GUARD) guardHorizontally(); if(e.enemyType == VERTICAL_GUARD) guardVertically(); if(e.enemyType == RANDOM_GUARD) guardRandomly(); //quadrantMovement(e, deltaTime); } private void guardHorizontally(){ if(position.x <= 0){ velocity.x= MAX_VELOCITY; velocity.y= 0; } else if(position.x>= World.mapWidth-width){ velocity.x= -MAX_VELOCITY; velocity.y= 0; } } private void guardVertically(){ if(position.y<= 0){ velocity.y= MAX_VELOCITY; velocity.x= 0; } else if(position.y>= World.mapHeight- height){ velocity.y= -MAX_VELOCITY; velocity.x= 0; } } private void guardRandomly(){ if (System.nanoTime() - startTime >= 1000000000) { SECONDS_TIME++; if(SECONDS_TIME % 5==0) randomDecider = Math.random()>=0.5f ? true :false; if(SECONDS_TIME>=30) SECONDS_TIME =0; startTime = System.nanoTime(); } if(SECONDS_TIME <=30){ if(randomDecider && position.x >= 0) velocity.x= -MAX_VELOCITY; else{ if(position.x < World.mapWidth-width) velocity.x= MAX_VELOCITY; else velocity.x= -MAX_VELOCITY; } velocity.y =0; } else{ if(randomDecider && position.y >0) velocity.y= -MAX_VELOCITY; else velocity.y= MAX_VELOCITY; velocity.x =0; } /* //This is essential so as to keep the enemies inside the boundary of the Map if(position.x <= 0){ velocity.x= MAX_VELOCITY; //velocity.y= 0; } else if(position.x>= World.mapWidth-width){ velocity.x= -MAX_VELOCITY; //velocity.y= 0; } else if(position.y<= 0){ velocity.y= MAX_VELOCITY; //velocity.x= 0; } else if(position.y>= World.mapHeight- height){ velocity.y= -MAX_VELOCITY; //velocity.x= 0; } */ } private void updateDirections() { if(velocity.x > 0) state = MOVING_RIGHT; else if(velocity.x<0) state = MOVING_LEFT; else if(velocity.y>0) state = MOVING_UP; else if(velocity.y<0) state = MOVING_DOWN; } public Rectangle getBounds() { return new Rectangle(position.x, position.y, width, height); } private void quadrantMovement(Enemy e, float deltaTime) { int temp = e.getEnemyQuadrant(e.position.x, e.position.y); boolean random = Math.random()>=0.5f ? true :false; switch(temp){ case 1: velocity.x = MAX_VELOCITY; break; case 2: velocity.x = MAX_VELOCITY; break; case 3: velocity.x = -MAX_VELOCITY; break; case 4: velocity.x = -MAX_VELOCITY; break; default: if(random) velocity.x = MAX_VELOCITY; else velocity.y =-MAX_VELOCITY; } } public float getDistanceFromPoint(float p1,float p2){ Vector2 v1 = new Vector2(p1,p2); return position.dst(v1); } private int getEnemyQuadrant(float x, float y){ Rectangle enemyQuad = new Rectangle(x, y, 30, 32); if(ScreenQuadrants.getQuad1().contains(enemyQuad)) return 1; if(ScreenQuadrants.getQuad2().contains(enemyQuad)) return 2; if(ScreenQuadrants.getQuad3().contains(enemyQuad)) return 3; if(ScreenQuadrants.getQuad4().contains(enemyQuad)) return 4; return 0; } } Is there a better way of doing this. I am new to game development. I shall be very grateful to any help or reference.

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  • Maintaining shared service in ASP.NET MVC Application

    - by kazimanzurrashid
    Depending on the application sometimes we have to maintain some shared service throughout our application. Let’s say you are developing a multi-blog supported blog engine where both the controller and view must know the currently visiting blog, it’s setting , user information and url generation service. In this post, I will show you how you can handle this kind of case in most convenient way. First, let see the most basic way, we can create our PostController in the following way: public class PostController : Controller { public PostController(dependencies...) { } public ActionResult Index(string blogName, int? page) { BlogInfo blog = blogSerivce.FindByName(blogName); if (blog == null) { return new NotFoundResult(); } IEnumerable<PostInfo> posts = postService.FindPublished(blog.Id, PagingCalculator.StartIndex(page, blog.PostPerPage), blog.PostPerPage); int count = postService.GetPublishedCount(blog.Id); UserInfo user = null; if (HttpContext.User.Identity.IsAuthenticated) { user = userService.FindByName(HttpContext.User.Identity.Name); } return View(new IndexViewModel(urlResolver, user, blog, posts, count, page)); } public ActionResult Archive(string blogName, int? page, ArchiveDate archiveDate) { BlogInfo blog = blogSerivce.FindByName(blogName); if (blog == null) { return new NotFoundResult(); } IEnumerable<PostInfo> posts = postService.FindArchived(blog.Id, archiveDate, PagingCalculator.StartIndex(page, blog.PostPerPage), blog.PostPerPage); int count = postService.GetArchivedCount(blog.Id, archiveDate); UserInfo user = null; if (HttpContext.User.Identity.IsAuthenticated) { user = userService.FindByName(HttpContext.User.Identity.Name); } return View(new ArchiveViewModel(urlResolver, user, blog, posts, count, page, achiveDate)); } public ActionResult Tag(string blogName, string tagSlug, int? page) { BlogInfo blog = blogSerivce.FindByName(blogName); if (blog == null) { return new NotFoundResult(); } TagInfo tag = tagService.FindBySlug(blog.Id, tagSlug); if (tag == null) { return new NotFoundResult(); } IEnumerable<PostInfo> posts = postService.FindPublishedByTag(blog.Id, tag.Id, PagingCalculator.StartIndex(page, blog.PostPerPage), blog.PostPerPage); int count = postService.GetPublishedCountByTag(tag.Id); UserInfo user = null; if (HttpContext.User.Identity.IsAuthenticated) { user = userService.FindByName(HttpContext.User.Identity.Name); } return View(new TagViewModel(urlResolver, user, blog, posts, count, page, tag)); } } As you can see the above code heavily depends upon the current blog and the blog retrieval code is duplicated in all of the action methods, once the blog is retrieved the same blog is passed in the view model. Other than the blog the view also needs the current user and url resolver to render it properly. One way to remove the duplicate blog retrieval code is to create a custom model binder which converts the blog from a blog name and use the blog a parameter in the action methods instead of the string blog name, but it only helps the first half in the above scenario, the action methods still have to pass the blog, user and url resolver etc in the view model. Now lets try to improve the the above code, first lets create a new class which would contain the shared services, lets name it as BlogContext: public class BlogContext { public BlogInfo Blog { get; set; } public UserInfo User { get; set; } public IUrlResolver UrlResolver { get; set; } } Next, we will create an interface, IContextAwareService: public interface IContextAwareService { BlogContext Context { get; set; } } The idea is, whoever needs these shared services needs to implement this interface, in our case both the controller and the view model, now we will create an action filter which will be responsible for populating the context: public class PopulateBlogContextAttribute : FilterAttribute, IActionFilter { private static string blogNameRouteParameter = "blogName"; private readonly IBlogService blogService; private readonly IUserService userService; private readonly BlogContext context; public PopulateBlogContextAttribute(IBlogService blogService, IUserService userService, IUrlResolver urlResolver) { Invariant.IsNotNull(blogService, "blogService"); Invariant.IsNotNull(userService, "userService"); Invariant.IsNotNull(urlResolver, "urlResolver"); this.blogService = blogService; this.userService = userService; context = new BlogContext { UrlResolver = urlResolver }; } public static string BlogNameRouteParameter { [DebuggerStepThrough] get { return blogNameRouteParameter; } [DebuggerStepThrough] set { blogNameRouteParameter = value; } } public void OnActionExecuting(ActionExecutingContext filterContext) { string blogName = (string) filterContext.Controller.ValueProvider.GetValue(BlogNameRouteParameter).ConvertTo(typeof(string), Culture.Current); if (!string.IsNullOrWhiteSpace(blogName)) { context.Blog = blogService.FindByName(blogName); } if (context.Blog == null) { filterContext.Result = new NotFoundResult(); return; } if (filterContext.HttpContext.User.Identity.IsAuthenticated) { context.User = userService.FindByName(filterContext.HttpContext.User.Identity.Name); } IContextAwareService controller = filterContext.Controller as IContextAwareService; if (controller != null) { controller.Context = context; } } public void OnActionExecuted(ActionExecutedContext filterContext) { Invariant.IsNotNull(filterContext, "filterContext"); if ((filterContext.Exception == null) || filterContext.ExceptionHandled) { IContextAwareService model = filterContext.Controller.ViewData.Model as IContextAwareService; if (model != null) { model.Context = context; } } } } As you can see we are populating the context in the OnActionExecuting, which executes just before the controllers action methods executes, so by the time our action methods executes the context is already populated, next we are are assigning the same context in the view model in OnActionExecuted method which executes just after we set the  model and return the view in our action methods. Now, lets change the view models so that it implements this interface: public class IndexViewModel : IContextAwareService { // More Codes } public class ArchiveViewModel : IContextAwareService { // More Codes } public class TagViewModel : IContextAwareService { // More Codes } and the controller: public class PostController : Controller, IContextAwareService { public PostController(dependencies...) { } public BlogContext Context { get; set; } public ActionResult Index(int? page) { IEnumerable<PostInfo> posts = postService.FindPublished(Context.Blog.Id, PagingCalculator.StartIndex(page, Context.Blog.PostPerPage), Context.Blog.PostPerPage); int count = postService.GetPublishedCount(Context.Blog.Id); return View(new IndexViewModel(posts, count, page)); } public ActionResult Archive(int? page, ArchiveDate archiveDate) { IEnumerable<PostInfo> posts = postService.FindArchived(Context.Blog.Id, archiveDate, PagingCalculator.StartIndex(page, Context.Blog.PostPerPage), Context.Blog.PostPerPage); int count = postService.GetArchivedCount(Context.Blog.Id, archiveDate); return View(new ArchiveViewModel(posts, count, page, achiveDate)); } public ActionResult Tag(string blogName, string tagSlug, int? page) { TagInfo tag = tagService.FindBySlug(Context.Blog.Id, tagSlug); if (tag == null) { return new NotFoundResult(); } IEnumerable<PostInfo> posts = postService.FindPublishedByTag(Context.Blog.Id, tag.Id, PagingCalculator.StartIndex(page, Context.Blog.PostPerPage), Context.Blog.PostPerPage); int count = postService.GetPublishedCountByTag(tag.Id); return View(new TagViewModel(posts, count, page, tag)); } } Now, the last thing where we have to glue everything, I will be using the AspNetMvcExtensibility to register the action filter (as there is no better way to inject the dependencies in action filters). public class RegisterFilters : RegisterFiltersBase { private static readonly Type controllerType = typeof(Controller); private static readonly Type contextAwareType = typeof(IContextAwareService); protected override void Register(IFilterRegistry registry) { TypeCatalog controllers = new TypeCatalogBuilder() .Add(GetType().Assembly) .Include(type => controllerType.IsAssignableFrom(type) && contextAwareType.IsAssignableFrom(type)); registry.Register<PopulateBlogContextAttribute>(controllers); } } Thoughts and Comments?

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  • OBJ model loaded in LWJGL has a black area with no texture

    - by gambiting
    I have a problem with loading an .obj file in LWJGL and its textures. The object is a tree(it's a paid model from TurboSquid, so I can't post it here,but here's the link if you want to see how it should look like): http://www.turbosquid.com/FullPreview/Index.cfm/ID/701294 I wrote a custom OBJ loader using the LWJGL tutorial from their wiki. It looks like this: public class OBJLoader { public static Model loadModel(File f) throws FileNotFoundException, IOException { BufferedReader reader = new BufferedReader(new FileReader(f)); Model m = new Model(); String line; Texture currentTexture = null; while((line=reader.readLine()) != null) { if(line.startsWith("v ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); float z = Float.valueOf(line.split(" ")[3]); m.verticies.add(new Vector3f(x,y,z)); }else if(line.startsWith("vn ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); float z = Float.valueOf(line.split(" ")[3]); m.normals.add(new Vector3f(x,y,z)); }else if(line.startsWith("vt ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); m.texVerticies.add(new Vector2f(x,y)); }else if(line.startsWith("f ")) { Vector3f vertexIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[0]), Float.valueOf(line.split(" ")[2].split("/")[0]), Float.valueOf(line.split(" ")[3].split("/")[0])); Vector3f textureIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[1]), Float.valueOf(line.split(" ")[2].split("/")[1]), Float.valueOf(line.split(" ")[3].split("/")[1])); Vector3f normalIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[2]), Float.valueOf(line.split(" ")[2].split("/")[2]), Float.valueOf(line.split(" ")[3].split("/")[2])); m.faces.add(new Face(vertexIndicies,textureIndicies,normalIndicies,currentTexture.getTextureID())); }else if(line.startsWith("g ")) { if(line.length()>2) { String name = line.split(" ")[1]; currentTexture = TextureLoader.getTexture("PNG", ResourceLoader.getResourceAsStream("res/" + name + ".png")); System.out.println(currentTexture.getTextureID()); } } } reader.close(); System.out.println(m.verticies.size() + " verticies"); System.out.println(m.normals.size() + " normals"); System.out.println(m.texVerticies.size() + " texture coordinates"); System.out.println(m.faces.size() + " faces"); return m; } } Then I create a display list for my model using this code: objectDisplayList = GL11.glGenLists(1); GL11.glNewList(objectDisplayList, GL11.GL_COMPILE); Model m = null; try { m = OBJLoader.loadModel(new File("res/untitled4.obj")); } catch (Exception e1) { e1.printStackTrace(); } int currentTexture=0; for(Face face: m.faces) { if(face.texture!=currentTexture) { currentTexture = face.texture; GL11.glBindTexture(GL11.GL_TEXTURE_2D, currentTexture); } GL11.glColor3f(1f, 1f, 1f); GL11.glBegin(GL11.GL_TRIANGLES); Vector3f n1 = m.normals.get((int) face.normal.x - 1); GL11.glNormal3f(n1.x, n1.y, n1.z); Vector2f t1 = m.texVerticies.get((int) face.textures.x -1); GL11.glTexCoord2f(t1.x, t1.y); Vector3f v1 = m.verticies.get((int) face.vertex.x - 1); GL11.glVertex3f(v1.x, v1.y, v1.z); Vector3f n2 = m.normals.get((int) face.normal.y - 1); GL11.glNormal3f(n2.x, n2.y, n2.z); Vector2f t2 = m.texVerticies.get((int) face.textures.y -1); GL11.glTexCoord2f(t2.x, t2.y); Vector3f v2 = m.verticies.get((int) face.vertex.y - 1); GL11.glVertex3f(v2.x, v2.y, v2.z); Vector3f n3 = m.normals.get((int) face.normal.z - 1); GL11.glNormal3f(n3.x, n3.y, n3.z); Vector2f t3 = m.texVerticies.get((int) face.textures.z -1); GL11.glTexCoord2f(t3.x, t3.y); Vector3f v3 = m.verticies.get((int) face.vertex.z - 1); GL11.glVertex3f(v3.x, v3.y, v3.z); GL11.glEnd(); } GL11.glEndList(); The currentTexture is an int - it contains the ID of the currently used texture. So my model looks absolutely fine without textures: (sorry I cannot post hyperlinks since I am a new user) i.imgur.com/VtoK0.png But look what happens if I enable GL_TEXTURE_2D: i.imgur.com/z8Kli.png i.imgur.com/5e9nn.png i.imgur.com/FAHM9.png As you can see an entire side of the tree appears to be missing - and it's not transparent, since it's not in the colour of the background - it's rendered black. It's not a problem with the model - if I load it using Kanji's OBJ loader it works fine(but the thing is,that I need to write my own OBJ loader) i.imgur.com/YDATo.png this is my OpenGL init section: //init display try { Display.setDisplayMode(new DisplayMode(Support.SCREEN_WIDTH, Support.SCREEN_HEIGHT)); Display.create(); Display.setVSyncEnabled(true); } catch (LWJGLException e) { e.printStackTrace(); System.exit(0); } GL11.glLoadIdentity(); GL11.glEnable(GL11.GL_TEXTURE_2D); GL11.glClearColor(1.0f, 0.0f, 0.0f, 1.0f); GL11.glShadeModel(GL11.GL_SMOOTH); GL11.glEnable(GL11.GL_DEPTH_TEST); GL11.glDepthFunc(GL11.GL_LESS); GL11.glDepthMask(true); GL11.glEnable(GL11.GL_NORMALIZE); GL11.glMatrixMode(GL11.GL_PROJECTION); GLU.gluPerspective (90.0f,800f/600f, 1f, 500.0f); GL11.glMatrixMode(GL11.GL_MODELVIEW); GL11.glEnable(GL11.GL_CULL_FACE); GL11.glCullFace(GL11.GL_BACK); //enable lighting GL11.glEnable(GL11.GL_LIGHTING); ByteBuffer temp = ByteBuffer.allocateDirect(16); temp.order(ByteOrder.nativeOrder()); GL11.glMaterial(GL11.GL_FRONT, GL11.GL_DIFFUSE, (FloatBuffer)temp.asFloatBuffer().put(lightDiffuse).flip()); GL11.glMaterialf(GL11.GL_FRONT, GL11.GL_SHININESS,(int)material_shinyness); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_DIFFUSE, (FloatBuffer)temp.asFloatBuffer().put(lightDiffuse2).flip()); // Setup The Diffuse Light GL11.glLight(GL11.GL_LIGHT2, GL11.GL_POSITION,(FloatBuffer)temp.asFloatBuffer().put(lightPosition2).flip()); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_AMBIENT,(FloatBuffer)temp.asFloatBuffer().put(lightAmbient).flip()); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_SPECULAR,(FloatBuffer)temp.asFloatBuffer().put(lightDiffuse2).flip()); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_CONSTANT_ATTENUATION, 0.1f); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_LINEAR_ATTENUATION, 0.0f); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_QUADRATIC_ATTENUATION, 0.0f); GL11.glEnable(GL11.GL_LIGHT2); Could somebody please help me?

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  • readonly keyword

    - by nmarun
    This is something new that I learned about the readonly keyword. Have a look at the following class: 1: public class MyClass 2: { 3: public string Name { get; set; } 4: public int Age { get; set; } 5:  6: private readonly double Delta; 7:  8: public MyClass() 9: { 10: Initializer(); 11: } 12:  13: public MyClass(string name = "", int age = 0) 14: { 15: Name = name; 16: Age = age; 17: Initializer(); 18: } 19:  20: private void Initializer() 21: { 22: Delta = 0.2; 23: } 24: } I have a couple of public properties and a private readonly member. There are two constructors – one that doesn’t take any parameters and the other takes two parameters to initialize the public properties. I’m also calling the Initializer method in both constructors to initialize the readonly member. Now when I build this, the code breaks and the Error window says: “A readonly field cannot be assigned to (except in a constructor or a variable initializer)” Two things after I read this message: It’s such a negative statement. I’d prefer something like: “A readonly field can be assigned to (or initialized) only in a constructor or through a variable initializer” But in my defense, I AM assigning it in a constructor (only indirectly). All I’m doing is creating a method that does it and calling it in a constructor. Turns out, .net was not ‘frameworked’ this way. We need to have the member initialized directly in the constructor. If you have multiple constructors, you can just use the ‘this’ keyword on all except the default constructors to call the default constructor. This default constructor can then initialize your readonly members. This will ensure you’re not repeating the code in multiple places. A snippet of what I’m talking can be seen below: 1: public class Person 2: { 3: public int UniqueNumber { get; set; } 4: public string Name { get; set; } 5: public int Age { get; set; } 6: public DateTime DateOfBirth { get; set; } 7: public string InvoiceNumber { get; set; } 8:  9: private readonly string Alpha; 10: private readonly int Beta; 11: private readonly double Delta; 12: private readonly double Gamma; 13:  14: public Person() 15: { 16: Alpha = "FDSA"; 17: Beta = 2; 18: Delta = 3.0; 19: Gamma = 0.0989; 20: } 21:  22: public Person(int uniqueNumber) : this() 23: { 24: UniqueNumber = uniqueNumber; 25: } 26: } See the syntax in line 22 and you’ll know what I’m talking about. So the default constructor gets called before the one in line 22. These are known as constructor initializers and they allow one constructor to call another. The other ‘myth’ I had about readonly members is that you can set it’s value only once. This was busted as well (I recall Adam and Jamie’s show). Say you’ve initialized the readonly member through a variable initializer. You can over-write this value in any of the constructors any number of times. 1: public class Person 2: { 3: public int UniqueNumber { get; set; } 4: public string Name { get; set; } 5: public int Age { get; set; } 6: public DateTime DateOfBirth { get; set; } 7: public string InvoiceNumber { get; set; } 8:  9: private readonly string Alpha = "asdf"; 10: private readonly int Beta = 15; 11: private readonly double Delta = 0.077; 12: private readonly double Gamma = 1.0; 13:  14: public Person() 15: { 16: Alpha = "FDSA"; 17: Beta = 2; 18: Delta = 3.0; 19: Gamma = 0.0989; 20: } 21:  22: public Person(int uniqueNumber) : this() 23: { 24: UniqueNumber = uniqueNumber; 25: Beta = 3; 26: } 27:  28: public Person(string name, DateTime dob) : this() 29: { 30: Name = name; 31: DateOfBirth = dob; 32:  33: Alpha = ";LKJ"; 34: Gamma = 0.0898; 35: } 36:  37: public Person(int uniqueNumber, string name, int age, DateTime dob, string invoiceNumber) : this() 38: { 39: UniqueNumber = uniqueNumber; 40: Name = name; 41: Age = age; 42: DateOfBirth = dob; 43: InvoiceNumber = invoiceNumber; 44:  45: Alpha = "QWER"; 46: Beta = 5; 47: Delta = 1.0; 48: Gamma = 0.0; 49: } 50: } In the above example, every constructor over-writes the values for the readonly members. This is perfectly valid. There is a possibility that based on the way the object is instantiated, the readonly member will have a different value. Well, that’s all I have for today and read this as it’s on a related topic.

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  • Multicast delegates in c#

    - by Jalpesh P. Vadgama
    In yesterday’s post We learn about Delegates and how we can use delegates in C#. In today’s blog post we are going to learn about Multicast delegates. What is Multicast Delegates? As we all know we can assign methods as object to delegate and later on we can call that method with the help delegates. We can also assign more then methods to delegates that is called Multicast delegates. It’s provide functionality to execute more then method at a time. It’s maintain delegates as invocation list (linked list). Let’s understands that via a example. We are going to use yesterday’s example and then we will extend that code multicast delegates. Following code I have written to demonstrate the multicast delegates. using System; namespace Delegates { class Program { public delegate void CalculateNumber(int a, int b); static void Main(string[] args) { int a = 5; int b = 5; CalculateNumber addNumber = new CalculateNumber(AddNumber); CalculateNumber multiplyNumber = new CalculateNumber(MultiplyNumber); CalculateNumber multiCast = (CalculateNumber)Delegate.Combine (addNumber, multiplyNumber); multiCast.Invoke(a,b); Console.ReadLine(); } public static void AddNumber(int a, int b) { Console.WriteLine("Adding Number"); Console.WriteLine(5 + 6); } public static void MultiplyNumber(int a, int b) { Console.WriteLine("Multiply Number"); Console.WriteLine(5 + 6); } } } As you can see in the above code I have created two method one for adding two numbers and another for multiply two number. After that I have created two same CalculateNumber delegates addNumber and multiplyNumber then I have create a multicast delegates multiCast with combining two delegates. Now I want to call this both method so I have used Invoke method to call this delegates. As now our code is let’s run the application. Following is a output as expected. As you can we can execute multiple methods with multicast delegates the only thing you need to take care is that we need to type for both delegates. That’s it. Hope you like it. Stay tuned for more.. Till then happy programming.

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  • Using set operation in LINQ

    - by vik20000in
    There are many set operation that are required to be performed while working with any kind of data. This can be done very easily with the help of LINQ methods available for this functionality. Below are some of the examples of the set operation with LINQ. Finding distinct values in the set of data. We can use the distinct method to find out distinct values in a given list.     int[] factorsOf300 = { 2, 2, 3, 5, 5 };     var uniqueFactors = factorsOf300.Distinct(); We can also use the set operation of UNION with the help of UNION method in the LINQ. The Union method takes another collection as a parameter and returns the distinct union values in  both the list. Below is an example.     int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };    int[] numbersB = { 1, 3, 5, 7, 8 };    var uniqueNumbers = numbersA.Union(numbersB); We can also get the set operation of INTERSECT with the help of the INTERSECT method. Below is an example.     int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };     int[] numbersB = { 1, 3, 5, 7, 8 };         var commonNumbers = numbersA.Intersect(numbersB);  We can also find the difference between the 2 sets of data with the help of except method.      int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };     int[] numbersB = { 1, 3, 5, 7, 8 };         IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB);  Vikram

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  • The internal storage of a DATETIME value

    - by Peter Larsson
    SELECT  [Now],         BinaryFormat,         SUBSTRING(BinaryFormat, 1, 4) AS DayPart,         SUBSTRING(BinaryFormat, 5, 4) AS TimePart,         CAST(SUBSTRING(BinaryFormat, 1, 4) AS INT) AS [Days],         DATEADD(DAY, CAST(SUBSTRING(BinaryFormat, 1, 4) AS INT), 0) AS [Today],         CAST(SUBSTRING(BinaryFormat, 5, 4) AS INT) AS [Ticks],         DATEADD(MILLISECOND, 1000.E / 300.E * CAST(SUBSTRING(BinaryFormat, 5, 4) AS INT), 0) AS Peso FROM    (             SELECT  GETDATE() AS [Now],                     CAST(GETDATE() AS BINARY(8)) AS BinaryFormat         ) AS d

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  • Android, how important is deltaTime?

    - by iQue
    Im making a game that is getting pretty big and sometimes my thread has to skip a frame, so far I'm not using deltaTime for setting the speed of my different objects in the game because it's still not a big enough game for it to matter imo. But its getting bigger then I planned, so my question is, how important is delta Time? If I should use delta time there is a problem, since speedX and speedY are integers(they have to be for eclipse to let you make a rectangle of them), I cant add delta time very functionally as far as I understand, but might be wrong? Ive tried adding deltaTime to the code below, and sometimes my enemies just not move after spawn, they just stand there and run in the same place Will add an some code for how I set / use speed: public void update(int dx, int dy) { double theta = 180.0 / Math.PI * Math.atan2(-(y - controls.pointerPosition.y), controls.pointerPosition.x - x); x +=dx * Math.cos(Math.toRadians(theta)); y +=dy * Math.sin(Math.toRadians(theta)); currentFrame = ++currentFrame % BMP_COLUMNS; } public void draw(Canvas canvas) { int srcX = currentFrame * width; int srcY = 1 * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bitmap, src, dst, null); } So if someone with some experience with this has any thoughts, please share. Thank you! Changed code: public void update(int dx, int dy, float delta) { double theta = 180.0 / Math.PI * Math.atan2(-(y - controls.pointerPosition.y), controls.pointerPosition.x - x); double speedX = delta * dx * Math.cos(Math.toRadians(theta)); double speedY = delta * dy * Math.sin(Math.toRadians(theta)); x += speedX; y += speedY; currentFrame = ++currentFrame % BMP_COLUMNS; } public void draw(Canvas canvas) { int srcX = currentFrame * width; int srcY = 1 * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bitmap, src, dst, null); } with this code my enemies move like before, except they wont move to the right (wont increment x), all other directions work.

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  • problem in array of shooter sprites which contain different colour bubbles

    - by prakash s
    everyone i am developing bubble shooter game in cocos2d I have placed shooter array which contain different color bubbles like this 00000000 it is 8 bubbles array if i tap the screen, first bubbles should move for shooting the target .png .And if i again tap the screen again 2nd position bubble should move for shooting the target.png bubbles,how it will possible for me because i have already created the array of target which contain different color bubbles, here i write the code : - (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { // Choose one of the touches to work with UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:[touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; // Set up initial location of projectile CGSize winSize = [[CCDirector sharedDirector] winSize]; NSMutableArray * movableSprites = [[NSMutableArray alloc] init]; NSArray *images = [NSArray arrayWithObjects:@"1.png", @"2.png", @"3.png", @"4.png",@"5.png",@"6.png",@"7.png", @"8.png", nil]; for(int i = 0; i < images.count; ++i) { int index = (arc4random() % 8)+1; NSString *image = [NSString stringWithFormat:@"%d.png", index]; CCSprite*projectile = [CCSprite spriteWithFile:image]; //CCSprite *projectile = [CCSprite spriteWithFile:@"3.png" rect:CGRectMake(0, 0,256,256)]; [self addChild:projectile]; [movableSprites addObject:projectile]; float offsetFraction = ((float)(i+1))/(images.count+1); //projectile.position = ccp(20, winSize.height/2); //projectile.position = ccp(18,0 ); //projectile.position = ccp(350*offsetFraction, 20.0f); projectile.position = ccp(10/offsetFraction, 20.0f); // projectile.position = ccp(projectile.position.x,projectile.position.y); // Determine offset of location to projectile int offX = location.x - projectile.position.x; int offY = location.y - projectile.position.y; // Bail out if we are shooting down or backwards if (offX <= 0) return; // Ok to add now - we've double checked position //[self addChild:projectile]; // Determine where we wish to shoot the projectile to int realX = winSize.width + (projectile.contentSize.width/2); float ratio = (float) offY / (float) offX; int realY = (realX * ratio) + projectile.position.y; CGPoint realDest = ccp(realX, realY); // Determine the length of how far we're shooting int offRealX = realX - projectile.position.x; int offRealY = realY - projectile.position.y; float length = sqrtf((offRealX*offRealX)+(offRealY*offRealY)); float velocity = 480/1; // 480pixels/1sec float realMoveDuration = length/velocity; // Move projectile to actual endpoint [projectile runAction:[CCSequence actions: [CCMoveTo actionWithDuration:realMoveDuration position:realDest], [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)], nil]]; // Add to projectiles array projectile.tag = 1; [_projectiles addObject:projectile]; } }

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  • How can I implement collision detection for these tiles?

    - by Fiona
    I am wondering how this would be possible, if at all. In the image below: http://i.stack.imgur.com/d8cO3.png The light brows tiles are ground, while the dark brown is background, so the player can pass over those tiles. Here's the for loops that draws the level: float scale = 1f; for (row = 0; row < currentLevel.Rows; row++) { for (column = 0; column < currentLevel.Columns; column++) { Tile tile = (Tile)currentLevel.GetTile(row, column); if (tile == null) { continue; } Texture2D texture = tile.Texture; spriteBatch.Draw(texture, new Microsoft.Xna.Framework.Rectangle( (int)(column * currentLevel.CellSize.X * scale), (int)(row * currentLevel.CellSize.Y * scale), (int)(currentLevel.CellSize.X * scale), (int)(currentLevel.CellSize.Y * scale)), Microsoft.Xna.Framework.Color.White); } } Here's what I have so far to determine where to create a Rectangle: Microsoft.Xna.Framework.Rectangle[,,,] groundBounds = new Microsoft.Xna.Framework.Rectangle[?, ?, ?, ?]; int tileSize = 20; int screenSizeInTiles = 30; var tilePositions = new System.Drawing.Point[screenSizeInTiles, screenSizeInTiles]; for (int x = 0; x < screenSizeInTiles; x++) { for (int y = 0; y < screenSizeInTiles; y++) { tilePositions[x, y] = new System.Drawing.Point(x * tileSize, y * tileSize); groundBounds[x, y, tileSize, tileSize] = new Microsoft.Xna.Framework.Rectangle(x, y, 20, 20); } } First off, I'm not sure how to initialize the array groundBounds (I don't know how big to make it). Also, I'm not entirely sure how to go about adding information to groundBounds. I want to add a Rectangle for each tile in the level. Preferably I'd only make a Rectangle for those tiles accessible by the player, and not background tiles, but that's for a different day. FYI, the map was made with a freeware program called Realm Factory.

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  • What makes signed integers behave differently?

    - by 000
    In this example of x86_64 hex/disassembled code I see: 48B80000000000000000 mov rax, 0x0 Signed Byte 52 Unsigned Byte 52 Signed Short 14388 Unsigned Short 14388 Signed Int 943863860 Unsigned Int 943863860 Signed Int64 3472328296363079732 Unsigned Int64 3472328296363079732 Float 4.630555e-05 Double 1.39804332763832e-76 String 48B80000000000000000 which to me appears to have the same functionality as: 48C7C000000000 mov rax, 0x0 48C7C000000000 Signed Byte 52 Unsigned Byte 52 Signed Short 14388 Unsigned Short 14388 Signed Int 927152180 Unsigned Int 927152180 Signed Int64 3472328377950746676 Unsigned Int64 3472328377950746676 Float 1.163599e-05 Double 1.39806836023098e-76 String 48C7C000000000 How is the first example treated differently from the second example?

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  • Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

    - by stoney78us
    I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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  • Yet another use of OUTER APPLY in defensive programming

    - by Alexander Kuznetsov
    When a SELECT is used to populate variables from a subquery, it fails to change them if the subquery returns nothing - and that can lead to subtle bugs. We shall use OUTER APPLY to eliminate this problem. Prerequisites All we need is the following mock function that imitates a subquery: CREATE FUNCTION dbo.BoxById ( @BoxId INT ) RETURNS TABLE AS RETURN ( SELECT CAST ( 1 AS INT ) AS [Length] , CAST ( 2 AS INT ) AS [Width] , CAST ( 3 AS INT ) AS [Height] WHERE @BoxId = 1 ) ; Let us assume that this...(read more)

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  • JGridView (Part 2)

    - by Geertjan
    The second sample in the JGrid download is a picture viewer that needs to be seen to be believed. Here it is, integrated into a NetBeans Platform application (click to enlarge it): When you mouse over the images, they change, showing several different images instantaneously. Here's the explorer view above, mainly making use of code from the sample: public class JGridView extends JScrollPane { @Override public void addNotify() { super.addNotify(); final ExplorerManager em = ExplorerManager.find(this); if (em != null) { final JGrid grid = new JGrid(); Node root = em.getRootContext(); final Node[] nodes = root.getChildren().getNodes(); final PicViewerObject[] pics = new PicViewerObject[nodes.length]; for (int i = 0; i < nodes.length; i++) { Node node = nodes[i]; pics[i] = node.getLookup().lookup(PicViewerObject.class); } grid.getCellRendererManager().setDefaultRenderer(new PicViewerRenderer()); grid.setModel(new DefaultListModel() { @Override public int getSize() { return pics.length; } @Override public Object getElementAt(int i) { return pics[i]; } }); grid.setFixedCellDimension(160); grid.addMouseMotionListener(new MouseAdapter() { int lastIndex = -1; @Override public void mouseMoved(MouseEvent e) { if (lastIndex >= 0) { Object o = grid.getModel().getElementAt(lastIndex); if (o instanceof PicViewerObject) { Rectangle r = grid.getCellBounds(lastIndex); if (r != null && !r.contains(e.getPoint())) { ((PicViewerObject) o).setMarker(false); grid.repaint(r); } } } int index = grid.getCellAt(e.getPoint()); if (index >= 0) { Object o = grid.getModel().getElementAt(index); if (o instanceof PicViewerObject) { Rectangle r = grid.getCellBounds(index); if (r != null) { ((PicViewerObject) o).setFraction(((float) e.getPoint().x - (float) r.x) / (float) r.width); ((PicViewerObject) o).setMarker(true); lastIndex = index; grid.repaint(r); } } } } }); grid.getSelectionModel().addListSelectionListener(new ListSelectionListener() { @Override public void valueChanged(ListSelectionEvent e) { //Somehow compare the selected item //with the list of books and find a matching book: int selectedIndex = grid.getSelectedIndex(); for (int i = 0; i < nodes.length; i++) { int picId = pics[i].getId(); if (selectedIndex == picId) { try { em.setSelectedNodes(new Node[]{nodes[i]}); } catch (PropertyVetoException ex) { Exceptions.printStackTrace(ex); } } } } }); setViewportView(grid); } } } The next step is to create a generic JGridView that will handle any kind of object automatically.

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  • libgdx arrays onTouch() method and delays for objects

    - by johnny-b
    i am trying to create random bullets but it is not working for some reason. also how can i make a delay so the bullets come every 30 seconds or 1 minute???? also the onTouch method does not work and it is not taking the bullet away???? shall i put the array in the GameRender class? thanks public class GameWorld { public static Ball ball; private Bullet bullet1; private ScrollHandler scroller; private Array<Bullet> bullets = new Array<Bullet>(); public GameWorld() { ball = new Ball(280, 273, 32, 32); bullet = new Bullet(-300, 200); scroller = new ScrollHandler(0); bullets.add(new Bullet(bullet.getX(), bullet.getY())); bullets = new Array<Bullet>(); Bullet bullet = null; float bulletX = 0.0f; float bulletY = 0.0f; for (int i=0; i < 10; i++) { bulletX = MathUtils.random(-10, 10); bulletY = MathUtils.random(-10, 10); bullet = new Bullet(bulletX, bulletY); bullets.add(bullet); } } public void update(float delta) { ball.update(delta); bullet.update(delta); scroller.update(delta); } public static Ball getBall() { return ball; } public ScrollHandler getScroller() { return scroller; } public Bullet getBullet1() { return bullet1; } } i also tried this and it is not working, i used this in the GameRender class Array<Bullet> enemies=new Array<Bullet>(); //in the constructor of the class enemies.add(new Bullet(bullet.getX(), bullet.getY())); // this throws an exception for some reason??? this is in the render method for(int i=0; i<bullet.size; i++) bullet.get(i).draw(batcher); //this i am using in any method that will allow me from the constructor to update to render for(int i=0; i<bullet.size; i++) bullet.get(i).update(delta); this is not taking the bullet out @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { for(int i=0; i<bullet.size; i++) if(bullet.get(i).getBounds().contains(screenX,screenY)) bullet.removeIndex(i--); return false; } thanks for the help anyone.

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  • draw bullet at the end of the barrel

    - by Alberto
    excuse my awkwardness, i have this code: [syntax="java"] int x2 = (int) (canon.getSceneCenterCoordinates()[0] + LENGTH_SPRITE/2* Math.cos(canon.getRotation())); int y2 = (int) (canon.getSceneCenterCoordinates()[1] + LENGTH_SPRITE/2* Math.sin(canon.getRotation())); projectile = new Sprite( (float) x2, (float) y2, mProjectileTextureRegion,this.getVertexBufferObjectManager() ); mMainScene.attachChild(projectile); [/syntax] and the bullet are drawn around the cannon in circle.. but not from the end of cannon :( help!

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  • How to make a queue switches from FIFO mode to priority mode?

    - by enzom83
    I would like to implement a queue capable of operating both in the FIFO mode and in the priority mode. This is a message queue, and the priority is first of all based on the message type: for example, if the messages of A type have higher priority than the messages of the B type, as a consequence all messages of A type are dequeued first, and finally the messages of B type are dequeued. Priority mode: my idea consists of using multiple queues, one for each type of message; in this way, I can manage a priority based on the message type: just take first the messages from the queue at a higher priority and progressively from lower priority queues. FIFO mode: how to handle FIFO mode using multiple queues? In other words, the user does not see multiple queues, but it uses the queue as if it were a single queue, so that the messages leave the queue in the order they arrive when the priority mode is disabled. In order to achieve this second goal I have thought to use a further queue to manage the order of arrival of the types of messages: let me explain better with the following code snippet. int NUMBER_OF_MESSAGE_TYPES = 4; int CAPACITY = 50; Queue[] internalQueues = new Queue[NUMBER_OF_MESSAGE_TYPES]; Queue<int> queueIndexes = new Queue<int>(CAPACITY); void Enqueue(object message) { int index = ... // the destination queue (ie its index) is chosen according to the type of message. internalQueues[index].Enqueue(message); queueIndexes.Enqueue(index); } object Dequeue() { if (fifo_mode_enabled) { // What is the next type that has been enqueued? int index = queueIndexes.Dequeue(); return internalQueues[index].Dequeue(); } if (priority_mode_enabled) { for(int i=0; i < NUMBER_OF_MESSAGE_TYPES; i++) { int currentQueueIndex = i; if (!internalQueues[currentQueueIndex].IsEmpty()) { object result = internalQueues[currentQueueIndex].Dequeue(); // The following statement is fundamental to a subsequent switching // from priority mode to FIFO mode: the messages that have not been // dequeued (since they had lower priority) remain in the order in // which they were queued. queueIndexes.RemoveFirstOccurrence(currentQueueIndex); return result; } } } } What do you think about this idea? Are there better or more simple implementations?

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  • Brute force algorithm implemented for sudoku solver in C [closed]

    - by 0cool
    This is my code that I have written in C.. It could solve certain level of problems but not the harder one.. I could not locate the error in it, Can you please find that.. # include <stdio.h> # include "sudoku.h" extern int sudoku[size][size]; extern int Arr[size][size]; int i, j, n; int BruteForceAlgorithm (void) { int val; for (i=0; i<size; i++) { for (j=0; j<size; j++) { if (sudoku[i][j]==0) { for (n=1; n<nmax; n++) { val = check (i,j,n); if ( val == 1) { sudoku[i][j]=n; // output(); break; } else if ( val == 0 && n == nmax-1 ) get_back(); } } } } } int get_back (void) { int p,q; int flag=0; for ( p=i; p>=0; p-- ) { for (q=j; q>=0; q-- ) { flag=0; if ( Arr[p][q]==0 && !( p==i && q==j) ) { if ( sudoku[p][q]== nmax-1 ) sudoku[p][q]=0; else { n = sudoku[p][q]; sudoku[p][q]=0; i = p; j = q; flag = 1; break; } } } if ( flag == 1) break; } } Code description: Sudoku.h has definitions related to sudoku solver. 1. size = 9 nmax = 10 2. check(i,j,n) returns 1 if a number "n" can be placed at (i,j) or else "0". What does this code do ? The code starts iterating from sudoku[0][0] to the end... if it finds a empty cell ( we take cell having "0" ), it starts checking for n=1 to n=9 which can be put in that.. as soon as a number can be put in that which is checked by check() it assigns it and breaks from loop and starts finding another empty cell. In case for a particular cell if it doesn't find "n" which can be assigned to sudoku cell.. it goes back to the previous empty cell and start iterating from where it stopped and assigns the next value and continues, Here comes the function get_back(). it iterates back..

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  • ArrayList of Entites Random Movement

    - by opiop65
    I have an arraylist of entites that I want to move randomly. No matter what I do, they won't move. Here is my female class: import java.awt.Graphics2D; import java.awt.Image; import java.awt.Rectangle; import java.util.Random; import javax.swing.ImageIcon; public class Female extends Entity { static int femaleX = 0; static int femaleY = 0; double walkSpeed = .1f; Random rand = new Random(); int random; int dir; Player player; public Female(int posX, int posY) { super(posX, posY); } public void update() { posX += femaleX; posY += femaleY; } public void draw(Graphics2D g2d) { g2d.drawImage(getFemaleImg(), posX, posY, null); if (Player.showBounds == true) { g2d.draw(getBounds()); } } public Image getFemaleImg() { ImageIcon ic = new ImageIcon("res/female.png"); return ic.getImage(); } public Rectangle getBounds() { return new Rectangle(posX, posY, getFemaleImg().getHeight(null), getFemaleImg().getWidth(null)); } public void moveFemale() { random = rand.nextInt(3); System.out.println(random); if (random == 0) { dir = 0; posX -= (int) walkSpeed; } } } And here is how I update the female class in the main class: public void actionPerformed(ActionEvent ae) { player.update(); for(int i = 0; i < females.size(); i++){ Female tempFemale = females.get(i); tempFemale.update(); } repaint(); } If I do something like this(in the female update method): public void update() { posX += femaleX; posY += femaleY; posX -= walkSpeed; } The characters move with no problem. Why is this?

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  • Write a program using 3 threads, one prints 10 'A's and the second prints 'B's and the third prints 10 'C's with synchrornization

    - by user132967
    Iam try to implement this questions using threads and mutex this is my code : include include include include include define Num_thread 3 pthread_mutex_t lett[Num_thread]; void Sleep_rand(double max) { struct timespec delai; delai.tv_sec=max; delai.tv_nsec=0; nanosleep(&delai,NULL); } void *Print_Sequence(); int main() { int i; pthread_t tid[Num_thread];// this is threads identifier for(i=0;i<Num_thread;i++) pthread_mutex_init(&lett[i],0); for(i=0;i<Num_thread;i++) { printf("i=%d\n",i); /* create the threads / pthread_create(&tid[i], / This variable will have the thread is after successful creation / NULL, / send the thread attributes / Print_Sequence, / the function the thread will run / &i/ send the parameter's address to the function */); } /* Wait till threads are complete and join before main continues */ for (i = 0; i pthread_join(tid[i], NULL); } return 0; } /* The thread will begin control in this function */ void Print_Sequence(void param) { int i,j=(int)param; printf("j=%d\n",(*j)); int max; pthread_mutex_lock(&lett[0]); pthread_mutex_lock(&lett[1]); for (i = 1; i <= 10; i++) { max=(int) (8*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("A"); } pthread_mutex_unlock(&lett[0]); pthread_mutex_lock(&lett[2]); for (i = 1; i <= 10; i++) { max=(int) (2*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("B"); } for (i = 1; i <= 10; i++) { max=(int) (15*rand()/(RAND_MAX+1.0)); Sleep_rand( max); printf("C"); } pthread_mutex_unlock(&lett[1]); pthread_mutex_unlock(&lett[2]); pthread_exit(0); } and the o/p is like : AAAAAAAAAABBBBBBBBBBCCCCCCCCCCAAAAAAAAAABBBBBBBBBBCCCCCCCCCCAAAAAAAAAABBBBBBBBBBCCCCCCCCCC COULD ANYONE PLEASE EXPLAIN WHAT IS THE WRONG WITH CODE ??

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  • Wi-Fi triangulation using android smartphone

    - by user1887020
    How to make application for wifi triangulation using android platform? This project will be implemented inside the building. No GPS needed. Just using wifi only and doing triangulation to get the current position of the user inside the building. I got minimum 3 access point to implement it. But how to start code in android and integrate triangulation inside android coding? I got the algorithm to do it.. but is there any chance that I can get it done? Because this project is actually want to replace the floor directory board into a smartphone floor directory so that user can find their way to their room for example to the lab. public class Triangulation { public Triangulation() { int dist_1, dist_2, dist_3; //variable for the distances int x1, x2, x3; //coordinates of x int y1, y2, y3; //coordinates of y int final_dist1, final_dist2; //final distance after calc dist_1 = 1; dist_2 = 2; dist_3 = 3; x1 = 5; //test inputs x2 = 2; x3 = 4; y1 = 2; y2 = 2; y3 = 5; final_dist1 = ((dist_1 * dist_1) - (dist_2 * dist_2) – (x1 * x1) + (x2 * x2) - (y1 * y1) + (y2 * y2)) / 2; final_dist2 = ((dist_2 * dist_2) - (dist_3 * dist_3) – (x2 * x2) + (x3 * x3) - (y2 * y2) + (y3 * y3)) / 2; initial_a1 = x1 - x2; initial_a2 = x2 - x3; initial_b1 = y1 - y2; initial_b2 = y2 - y3; //-----------------------STEP 1-------------------------------------- int a1 = initial_a1 / initial_a1; int a2 = initial_a2 / initial_a1; int b1 = initial_b1 / initial_a1; int b2 = initial_b2 / initial_a1; final_dist1 /= initial_a1; final_dist2 /= initial_a1; //-----------------------STEP 2-------------------------------------- a2 = a2 -a2; final_dist2 = -(initial_a2) * final_dist1 + final_dist2; //-----------------------STEP 3-------------------------------------- a2 /= b2; final_dist2 = final_dist2 / b2; b2 /= b2; //-------------------------STEP 4----------------------------------- b1 = b1 - b1; final_dist1 = -(initial_b1) * final_dist2 + final_dist1; } }

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  • Keep Getting Syntax Error C2199?

    - by DARK3ZOOZ
    Here's my problem I'm trying to define something, but keep getting a syntax error Code: #define R_RegisterShader 0x50C8A0 int (*trap_R_RegisterShader)( const char *name, int Arg_1 ) = (int (_cdecl *)(const char *, int ))R_RegisterShader; ^^^^^^^ This last part is where I keep getting the error if you need more lines of codes, just let me know. thanks http://gyazo.com/1a47ebc12cfbd6ea72feb72c686ae84d screenshot of error

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  • "Collection Wrapper" pattern - is this common?

    - by Prog
    A different question of mine had to do with encapsulating member data structures inside classes. In order to understand this question better please read that question and look at the approach discussed. One of the guys who answered that question said that the approach is good, but if I understood him correctly - he said that there should be a class existing just for the purpose of wrapping the collection, instead of an ordinary class offering a number of public methods just to access the member collection. For example, instead of this: class SomeClass{ // downright exposing the concrete collection. Things[] someCollection; // other stuff omitted Thing[] getCollection(){return someCollection;} } Or this: class SomeClass{ // encapsulating the collection, but inflating the class' public interface. Thing[] someCollection; // class functionality omitted. public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } We'll have this: // encapsulating the collection - in a different class, dedicated to this. class SomeClass{ CollectionWrapper someCollection; CollectionWrapper getCollection(){return someCollection;} } class CollectionWrapper{ Thing[] someCollection; public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } This way, the inner data structure in SomeClass can change without affecting client code, and without forcing SomeClass to offer a lot of public methods just to access the inner collection. CollectionWrapper does this instead. E.g. if the collection changes from an array to a List, the internal implementation of CollectionWrapper changes, but client code stays the same. Also, the CollectionWrapper can hide certain things from the client code - from example, it can disallow mutation to the collection by not having the methods setThing and removeThing. This approach to decoupling client code from the concrete data structure seems IMHO pretty good. Is this approach common? What are it's downfalls? Is this used in practice?

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