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• Freeing memory with Pointer Arithmetic

  - by Breedly

  C++ newb here. I'm trying to write my own implementation of an array using only pointers, and I've hit a wall I don't know how to get over. My constructor throws this error array.cpp:40:35: error: invalid conversion from ‘int*’ to ‘int’ [-fpermissive] When my array initializes I want it to free up all the spaces in the array for ints. Array::Array(int theSize){ size = theSize; int *arrayPointer = new int; int index = 0; while(theSize > index){ *(arrayPointer + index) = new int; //This is the trouble line. ++index; } } What am I doing wrong stackoverflow?

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• C++ boost thread id and Singleton

  - by aaa

  hi. Sorry to flood so many questions this week. I assume thread index returned by thread.get_id is implementation specific. In case of the pthreads, is index reused? IE, if thread 0 runs and joins, is thread launched afterwords going to have a different ID? the reason I ask this is a need to implement Singleton pattern with a twist: each thread gets its own instance. I know it sounds very crazy, but threads control hardware (cuda) which does not permit device memory sharing. What is a good way to implement such pattern?

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• Does "Value Restriction" practically mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• Javascript Autocomplete Text

  - by WPS

  Hi All, I need to implement an autocomplete text field using JavaScript and JSF. When the user types some character in a text field, I need to make an AJAX request and get the values based on the values entered. I've an input text field, on "keyup" I'm triggering a function which submits the value to the server side. var timeoutid = 0; function intitiateTypeAhead(){ clearTimeout(timeoutid); if (document.getElementById("inputText").value.length >= 2) { timeoutid = setTimeout('clickButton', 500); } return false; } function clickButton(){ //submits the value to the server } <h:inputText id="inputText" onkeyup="intitiateTypeAhead()"></h:inputText> This works properly, but certain times the request is made for each character entered by the user. I'm not sure if there is anything wrong with the implementation. Can someone please help me to fix this?

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• Efficiently draw a grid in Windows Forms

  - by Joel

  I'm writing an implementation of Conway's Game of Life in C#. This is the code I'm using to draw the grid, it's in my panel_Paint event. g is the graphics context. for (int y = 0; y < numOfCells * cellSize; y += cellSize) { for (int x = 0; x < numOfCells * cellSize; x += cellSize) { g.DrawLine(p, x, 0, x, y + numOfCells * cellSize); g.DrawLine(p, 0, x, y + size * drawnGrid, x); } } When I run my program, it is unresponsive until it finishes drawing the grid, which takes a few seconds at numOfCells = 100 & cellSize = 10. Removing all the multiplication makes it faster, but not by very much. Is there a better/more efficient way to draw my grid? Thanks

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• WebView not responding when called from a method

  - by AragornSG

  I have an app with tabbar and webview. I'm trying to make the app come back to default url each time user taps the bar. Right now I'm intercepting taps and launching a method, however it's not affecting my webview. The same syntax for calling webview from awakeFromNib works, so I don't have a clue what's up. I suspect it's something to do with how I call the method, but I don't know what. Here is the code: #import "SecondViewController.h" @implementation SecondViewController - (void)awakeFromNib { NSString *loadURL = [NSString stringWithFormat:@"http://pageurl"]; // [secondView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:loadURL]]]; SecondViewController *ptr = [[SecondViewController alloc] init]; [ptr goToPage]; } - (void) goToPage { NSLog(@"go to page"); NSString *newURL = [NSString stringWithFormat:@"http://pageurl"]; [secondView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:newURL]]]; } Thanks fot your help!

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• GWT : NULL Session

  - by jidma

  I'm using spring4gwt in my project. I have the following login service implementation: @Service("loginService") public class LoginServiceImpl extends RemoteServiceServlet implements LoginService { @Override @Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class) public UserBean checkUser(String userName, String password) throws Exception { HttpSession httpSession = getThreadLocalRequest().getSession(); } } When i call the loginService.checkUser("test","test") (In hosted mode), I get a null pointer exception, as getThreadLocalRequest() returns NULL instead of the actual session. I didn't try in web mode yet. Why would I get a null session ? Does it have something to do with spring4gwt ? Thank you

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• Why exactly is calling the destructor for the second time undefined behavior in C++?

  - by sharptooth

  As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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• Please explain class methods

  - by user1209902

  I'm finding it difficult to understand when it is necessary to create class methods. From what I've read, they are important for creating new objects, but I do not see how. The following class create a simple shape black rectangle. Can anyone show me how to incorporate a class method to do something that I could not do with an instance method? Shape.h #import <UIKit/UIKit.h> @interface Shape : UIView; - (id) initWithX: (int)xVal andY: (int)yVal; @end Shape.m #import "Shape.h" @implementation Shape - (id) initWithX:(int )xVal andY:(int)yVal { self = [super init]; UIView *shape = [[UIView alloc] initWithFrame:CGRectMake(xVal, yVal, 10, 10)]; shape.backgroundColor = [UIColor blackColor]; [self addSubview:shape]; return self; } @end

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• has_many relation doesn't seems right or logical in business perceptive, needed some thing like belo

  - by Vijendra

  My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end It works, but "user has many companies" doesn't looks logically meaningful. It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? Can some one please suggest the right way for representing these relationships?

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• an error "variable of field declared void"

  - by lego69

  I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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• What's the best way to return different cells depending on position in a UITableView

  - by Robert Conn

  I have a grouped UITableView that has 3 sections and a number of cells in each section that each need to be a different custom cell, with different display requirements. I currently have a large if statement in cellForRowAtIndexPath, with each branch instantiating and returning the appropriate custom cell based on interrogating the indexPath's section and row properties. e.g. if (indexPath.section == 0 && indexPath.row == 0) { // instantiate and return cell A } else if (indexPath.section == 1 && indexPath.row == 2) { // instantiate and return cell B } //etc etc What is best practice for this scenario? A large if statement does the job, but is it the best implementation?

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• what is serialization and how it works

  - by Rozer

  I know the serialization process but have't implemented it. In my application i have seen there are various classes that has been implemented serilizable interface. consider following class public class DBAccessRequest implements Serializable { private ActiveRequest request = null; private Connection connection = null; private static Log log = LogFactory.getLog(DBAccessRequest.class); public DBAccessRequest(ActiveRequest request,Connection connection) { this.request = request; this.connection = connection; } /** * @return Returns the DB Connection object. */ public Connection getConnection() { return connection; } /** * @return Returns the active request object for the db connection. */ public ActiveRequest getRequest() { return request; } } just setting request and connection in constructor and having getter setter for them. so what is the use of serilizable implementation over here...

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• Object initialization sequence in Objective-C

  - by Alex

  Hello everyone. The Cocoa framework has a convention to always call self = [super init] in the init method of an inherited class, because [super init] may return a new instance. What will happen if I do this? @interface MyClass : NSObject /* or any other class */ { int ivar_; } @end @implementation MyClass - (id)init { ivar_ = 12345; if ((self = [super init])) { NSLog(@"ivar_'s value is %d", ivar_); } return self; } @end In the case when [super init] returns a new instance, what will I see in the console? ivar_'s value is 0? I can't think of a way to check this myself, because I don't know which class may return a new instance from its init method. Also, can't seem to find explicit clarification for this scenario in the docs. Could anyone help me out? Thanks!

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• Objective C - Custom Getter with inheritance

  - by anhdat

  Recently I have worked with Core Data. When I want to set a default value for some fields, I came up with this problem: So I made a simple represent: We have 2 class Parent and Child, in which Child inherit from Parent. // Parent.h @interface Parent : NSObject @property (strong, nonatomic) NSString *lastName; // Child.h @interface Child : Parent In Parent class, I made a custom getter to set a default value when nothing is set: // Parent.h - (NSString *)lastName { if (_lastName) { return _lastName; } else { return @"Parent Default Name"; } } But I cannot make a custom default value for the field "name" which Child inherits from its Parent. // Child.h @implementation Child - (NSString *)lastname { if (super.lastName) { return super.lastName; } else { return @"Child Default Name"; } } Apparently, this method is never called. So my question here is: How can I set a custom getter for the field the Child class inherits from Parent without define an overriding property?

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• Better to extend a class or modify it directly?

  - by primehunter326

  Hi, So I'm working on creating a visualization for a data structure in Java. I already have the implementation of the data structure (Binary Search Tree) to start with, but I need to add some additional functionality to the included node class. As far as conventions and best practices are concerned, should I create a subclass of the node with this added functionality or should I just modify what I have and document it there? My question is similar to what's asked here but that's a little over my head. I know it probably doesn't matter much for what I'm doing, so I'm asking this more as a general thing.

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• How to test if an array contains a pair of numbers whose product is odd?

  - by John

  How can I write a function that takes an array of integers and returns true if their exists a pair of numbers whose product is odd? What are the properties of odd integers? And of course, how do you write this function in Java? Also, maybe a short explanation of how you went about formulating an algorithm for the actual implementation. Yes, this is a function out of a textbook. No, this is not homework—I'm just trying to learn, so please no "do your own homework comments."

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• Cocoa multhithreads, locks don't work

  - by Igor

  I have a threadMethod which shows in console robotMotorsStatus every 0.5 sec. But when I try to change robotMotorsStatus in changeRobotStatus method I receive an exception. Where I need to put locks in that program. #import "AppController.h" @implementation AppController extern char *robotMotorsStatus; - (IBAction)runThread:(id)sender { [self performSelectorInBackground:@selector(threadMethod) withObject:nil]; } - (void)threadMethod { char string_to_send[]="QFF001100\r"; //String prepared to the port sending (first inintialization) string_to_send[7] = robotMotorsStatus[0]; string_to_send[8] = robotMotorsStatus[1]; while(1){ [theLock lock]; usleep(500000); NSLog (@"Robot status %s", robotMotorsStatus); [theLock unlock]; } } - (IBAction)changeRobotStatus:(id)sender { robotMotorsStatus[0]='1'; }

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• Windows Phone: Updating backend datastore (via web service) while keeping UI very responsive

  - by will

  I am developing a Windows Phone app where users can update a list. Each update, delete, add etc need to be stored in a database that sits behind a web service. As well as ensuring all the operations made on the phone end up in the cloud, I need to make sure the app is really responsive and the user doesn’t feel any lag time whatsoever. What’s the best design to use here? Each check box change, each text box edit fires a new thread to contact the web service? Locally store a list of things that need to be updated then send to the server in batch every so often (what about the back button)? Am I missing another even easier implementation? Thanks in advance,

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• Remove duplicates in entries, scala way

  - by andersbohn

  I have a list of entries stating a production value in a given interval. Entries stating the exact same value at a later time adds no information and can safely be left out. case class Entry(minute:Int, production:Double) val entries = List(Entry(0, 100.0), Entry(5, 100.0), Entry(10, 100.0), Entry(20, 120.0), Entry(30, 100.0), Entry(180, 0.0)) Experimenting with the scala 2.8 collection functions, so far I have this working implementation: entries.foldRight(List[Entry]()) { (entry, list) => list match { case head :: tail if (entry.production == head.production) => entry :: tail case head :: tail => entry :: list case List() => entry :: List() } } res0: List[Entry] = List(Entry(0,100.0), Entry(20,120.0), Entry(30,100.0), Entry(180,0.0)) Any comments? Am I missing out on some scala magic?

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• Mixing LINQ to SQL with properties of objects in a generic list

  - by BPotocki

  I am trying to accomplish something like this query: var query = from a in DatabaseTable where listOfObjects.Any(x => x.Id == a.Id) select a; Basically, I want to filter the results where a.Id equals a property of one of the objects in the generic list "listOfObjects". I'm getting the error "Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator." Any ideas on how to filter this in an easily readable way using "contains" or another method? Thanks in advance.

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• Is there any disadvantage to putting API code into a JAR along with the classes?

  - by Adam Gent

  In Java if you package the source code (.java) files into the jar along with classes (.class) most IDE's like eclipse will show the javadoc comments for code completion. IIRC there are few open-source projects that do this like JMock. Lets say I have cleanly separated my API code from implementation code so that I have something like myproject-api.jar and myproject-impl.jar is there any reason why I should not put the source code in my myproject-api.jar ? Because of Performance? Size? Why don't other projects do this?

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• Zend_Form: Is this really the way we should be doing things?

  - by Francis Daigle

  OK. I understand how to use Zend_Form and it's implementation of the decorator pattern. My question is, is this the best way to be going about creating forms? Shouldn't a documents forms be left to to the front-end rather than generating forms programmatically? Doesn't this kinda violate the whole idea of keeping things separate? I mean, really, even providing that you have a good understanding of the methodology being employed, does it really save one that much time? I guess what I'm looking for is some guidance as to what might be considered 'best practice'. I'm not saying that Zend_Form doesn't have it's place, I'm just wondering if it should be used in all cases (or not). And this has nothing to do with validation. I'm just thinking that something more akin to using the 'ViewScript' approach might be more appropriate in most cases. Your thoughts?

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• Passing a NSString to another ViewController using classes

  - by Jeff Kranenburg

  I know this insanely simple, but I am re-teaching myself the basics and trying to get my head around this:-) I have one ViewController called MainVC and I have one called ClassVC In ClassVC I have this code: @interface ClassVC : UIViewController { NSString *mainLine; } @property (nonatomic, retain) NSString *mainLine; @end and I have this in the implementation file: @synthesize mainLine = _mainLine; -(NSString *)_mainLine { _mainLine = @"This a string from a Class"; return _mainLine; } Now I was thinking that if I #import the ClassVC into MainVC I would be able to transfer that string along as well like so: This code is in the viewDidLoad _mainLabel.text = _secondClass.mainLine; NSLog(@"%@", _secondClass.mainLine); But that is not working - so cannot I not pass strings in through this way???

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• How do you deal with the more mundane parts of programming tasks?

  - by Uri

  My experience as a developer is that many projects or tickets are a mix of a short and focused very interesting task (e.g., designing some API or a platform to solve something) and a lot of repetitive and mundane tasks that cannot be automated (such as certain refactorings to use the API or platform, implementation of certain tests, some GUI handling, etc). I believe that this is the nature of our profession, unless we are high-level architects or managements and can delegate this work. The only item in my personal arsenal when dealing with these tasks is to devote some of my attention to radio or audiobooks (preferably not in English as I find it hard to concentrate on two "streams" of English at the same time). I maintain sufficient attention to carry the task and don't lose concentration as fast. I'm wondering how others cope with these and maintain concentration.

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