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  • NSMutableArray Vs Stack

    - by Chandan Shetty SP
    I am developing 2D game for iphone in Objectice-C.In this project I need to use stack, I can do it using STL(Standard template library) stacks or NSMutableArray, since this stack is widely used in the game which one is more efficient? @interface CarElement : NSObject { std::stack<myElement*> *mBats; } or @interface CarElement : NSObject { NSMutableArray *mBats; } Thanks,

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  • Object tree navigation language in Java

    - by lewap
    In the system which I'm currently developing I often have to navigate an object tree and based on its state and values take actions. In normal Java this results in tedious for loops, if statements etc... Are there alternative ways to achieve tree navigation, similar to XPath for XML? I know there is JXPath and OGNL, but do you know any other libraries for such purpose? Do you know any libraries which generate bytecodes for specific tree navigation expressions to make the processing as fast as Java native fors and ifs?

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  • Pattern for managing reference count and object life

    - by Gopalakrishnan Subramani
    We have a serial port which is connected to hundreds of physical devices on the same wire. We have protocols like Modbus and Hart to handle the request and response between the application and devices. The question is related to managing the reference count of the channel. When no device is using the channel, the channel should be closed. public class SerialPortChannel { int refCount = 0; public void AddReference() { refCount++; } public void ReleaseReference() { refCount--; if (refCount <= 0) this.ReleasePort(); //This close the serial port } } For each device connected, we create a object for the device like device = new Device(); device.Attach(channel); //this calls channel.AddReference() When the device disconnect, device.Detach(channel); //this calls channel.ReleaseReference() I am not convinced by the reference count model. Are there any better way to handle this problem in .NET World?

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  • (MyClassName)object vs. object as MyClassName

    - by Matthew Doyle
    Hello all, I was wondering what is the better method for Casting objects for C#: MyClassName test = (MyClassName)object; MyClassName test = object as MyClassName; I know already that if you do the first way, you get an exception, and the second way it sets test as null. However, I was wondering why do one over the other? I see the first way a lot, but I like how the second way because then I can check for null... If there isn't a 'better way' of doing it, what are the guidelines for using one way or the other?

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  • How are java.lang.Object's protected methods protected from subclasses?

    - by Adrian Lang
    The keyword protected grants access to classes in the same package and subclasses (http://java.sun.com/docs/books/tutorial/java/javaOO/accesscontrol.html). Now, every class has java.lang.Object as superclass (http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.html). Hence I conclude that every class may access java.lang.Object's methods even if they are protected. Take a look at the following example: public class Testclass { public Object getOne() throws CloneNotSupportedException { return this.clone(); } public Object getTwo() throws CloneNotSupportedException { return ((Object) this).clone(); } } While getOne() compiles fine, getTwo() gives Testclass.java:6: clone() has protected access in java.lang.Object return ((Object) this).clone(); I neither understand why getTwo() doesn't compile nor what's the difference (regarding the access of java.lang.Objects members) with getOne().

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  • Mysql 100% CPU + Slow query

    - by felipeclopes
    I'm using the RDS database from amazon with a some very big tables, and yesterday I started to face 100% CPU utilisation on the server and a bunch of slow query logs that were not happening before. I tried to check the queries that were running and faced this result from the explain command +----+-------------+-------------------------------+--------+----------------------------------------------------------------------------------------------+---------------------------------------+---------+-----------------------------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------------------+--------+----------------------------------------------------------------------------------------------+---------------------------------------+---------+-----------------------------------------------------------------+------+----------------------------------------------+ | 1 | SIMPLE | businesses | const | PRIMARY | PRIMARY | 4 | const | 1 | Using index; Using temporary; Using filesort | | 1 | SIMPLE | activities_businesses | ref | PRIMARY,index_activities_users_on_business_id,index_tweets_users_on_tweet_id_and_business_id | index_activities_users_on_business_id | 9 | const | 2252 | Using index condition; Using where | | 1 | SIMPLE | activities_b_taggings_975e9c4 | ref | taggings_idx | taggings_idx | 782 | const,myapp_production.activities_businesses.id,const | 1 | Using index condition; Using where | | 1 | SIMPLE | activities | eq_ref | PRIMARY,index_activities_on_created_at | PRIMARY | 8 | myapp_production.activities_businesses.activity_id | 1 | Using where | +----+-------------+-------------------------------+--------+----------------------------------------------------------------------------------------------+---------------------------------------+---------+-----------------------------------------------------------------+------+----------------------------------------------+ Also checkin in the process list, I got something like this: +----+-----------------+-------------------------------------+----------------------------+---------+------+--------------+------------------------------------------------------------------------------------------------------+ | Id | User | Host | db | Command | Time | State | Info | +----+-----------------+-------------------------------------+----------------------------+---------+------+--------------+------------------------------------------------------------------------------------------------------+ | 1 | my_app | my_ip:57152 | my_app_production | Sleep | 0 | | NULL | | 2 | my_app | my_ip:57153 | my_app_production | Sleep | 2 | | NULL | | 3 | rdsadmin | localhost:49441 | NULL | Sleep | 9 | | NULL | | 6 | my_app | my_other_ip:47802 | my_app_production | Sleep | 242 | | NULL | | 7 | my_app | my_other_ip:47807 | my_app_production | Query | 231 | Sending data | SELECT my_fields... | | 8 | my_app | my_other_ip:47809 | my_app_production | Query | 231 | Sending data | SELECT my_fields... | | 9 | my_app | my_other_ip:47810 | my_app_production | Query | 231 | Sending data | SELECT my_fields... | | 10 | my_app | my_other_ip:47811 | my_app_production | Query | 231 | Sending data | SELECT my_fields... | | 11 | my_app | my_other_ip:47813 | my_app_production | Query | 231 | Sending data | SELECT my_fields... | ... So based on the numbers, it looks like there is no reason to have a slow query, since the worst execution plan is the one that goes through 2k rows which is not much. Edit 1 Another information that might be useful is the slow query_log SET timestamp=1401457485; SELECT my_query... # User@Host: myapp[myapp] @ ip-10-195-55-233.ec2.internal [IP] Id: 435 # Query_time: 95.830497 Lock_time: 0.000178 Rows_sent: 0 Rows_examined: 1129387 Edit 2 After profiling, I got this result. The result have approximately 250 rows with two columns each. +----------------------+----------+ | state | duration | +----------------------+----------+ | Sending data | 272 | | removing tmp table | 0 | | optimizing | 0 | | Creating sort index | 0 | | init | 0 | | cleaning up | 0 | | executing | 0 | | checking permissions | 0 | | freeing items | 0 | | Creating tmp table | 0 | | query end | 0 | | statistics | 0 | | end | 0 | | System lock | 0 | | Opening tables | 0 | | logging slow query | 0 | | Sorting result | 0 | | starting | 0 | | closing tables | 0 | | preparing | 0 | +----------------------+----------+ Edit 3 Adding query as requested SELECT activities.share_count, activities.created_at FROM `activities_businesses` INNER JOIN `businesses` ON `businesses`.`id` = `activities_businesses`.`business_id` INNER JOIN `activities` ON `activities`.`id` = `activities_businesses`.`activity_id` JOIN taggings activities_b_taggings_975e9c4 ON activities_b_taggings_975e9c4.taggable_id = activities_businesses.id AND activities_b_taggings_975e9c4.taggable_type = 'ActivitiesBusiness' AND activities_b_taggings_975e9c4.tag_id = 104 AND activities_b_taggings_975e9c4.created_at >= '2014-04-30 13:36:44' WHERE ( businesses.id = 1 ) AND ( activities.created_at > '2014-04-30 13:36:44' ) AND ( activities.created_at < '2014-05-30 12:27:03' ) ORDER BY activities.created_at; Edit 4 There may be a chance that the indexes are not being applied due to difference in column type between the taggings and the activities_businesses, on the taggable_id column. mysql> SHOW COLUMNS FROM activities_businesses; +-------------+------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | activity_id | bigint(20) | YES | MUL | NULL | | | business_id | bigint(20) | YES | MUL | NULL | | +-------------+------------+------+-----+---------+----------------+ 3 rows in set (0.01 sec) mysql> SHOW COLUMNS FROM taggings; +---------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | tag_id | int(11) | YES | MUL | NULL | | | taggable_id | bigint(20) | YES | | NULL | | | taggable_type | varchar(255) | YES | | NULL | | | tagger_id | int(11) | YES | | NULL | | | tagger_type | varchar(255) | YES | | NULL | | | context | varchar(128) | YES | | NULL | | | created_at | datetime | YES | | NULL | | +---------------+--------------+------+-----+---------+----------------+ So it is examining way more rows than it shows in the explain query, probably because some indexes are not being applied. Do you guys can help m with that?

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  • Hibernate -using Table per subclass - how to link an existing superclass object to a sibclass object

    - by Chandni
    Hi, I have a User hibernate class, Clerk class and Consumer class. All these maps to their own tables in database. The User PK also acts as Clerk's and Consumer's PK. So now my problem is that if a user is initially a Clerk, he has a record in Users table and Clerks table. If that user wants to become a consumer, I want to link that User's record to the new Consumer's record. So even if I pass the userId to the consumer's record, it treats it as a new User to be persisted and gives a duplicate_key exception. How do I tell Hiernate to link the same user object with this new Consumer object. Thanks in advance, -Chandni

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  • Divide and conquer method to compute roots [SOLVED]

    - by hellsoul153
    Hello, Knowing that we can use Divide-and-Conquer algorithm to compute large exponents, for exemple 2 exp 100 = 2 exp(50) * 2 exp(50), which is quite more efficient, is this method efficient using roots ? For exemple 2 exp (1/100) = (2 exp(1/50)) exp(1/50) ? In other words, I'm wondering if (n exp(1/x)) is more efficient to (n exp(1/y)) for x < y and where x and y are integers.

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  • Is it good to subclass a class only to separate some functional parts?

    - by prostynick
    Suppose we have abstract class A (all examples in C#) public abstract class A { private Foo foo; public A() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //a lot of other stuff... } But we are able to split it into two classes A and B: public abstract class A { public A() { } //a lot of stuff... } public abstract class B : A { private Foo foo; public B() : base() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //nothing else or just some overrides of A stuff } That's good, but we are 99.99% sure, that no one will ever subclass A, because functionality in B is very important. Is it still good to have two separate classes only to split some code into two parts and to separate functional elements?

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  • Converting HTML TAG Object to JSON Object

    - by cooldude
    Hi, I want to convert the html tag objects to json object in the javascript in order to send them to the server from the javascript. As i have to save these objects at the Ruby on Rails server. These HTML objects is the canvas tag object and the graphics objects created using CAKE API. I have used the stringify function but it is not working. Here is my code: var CAKECanvas = new Canvas(document.body, 1000,1000); var canvas=CAKECanvas.canvas; var text=document.createElement('textarea'); text.id="text"; text.rows="100"; text.cols="200"; document.body.appendChild(text); canvas.style.borderStyle="solid"; canvas.style.borderColor="black"; var rect= new Circle(); rect.radius=100; rect.centered=true; rect.cx=Math.random() * 500; rect.cy= Math.random() * 300; rect.stroke= false; rect.fill= "red"; rect.xDir = Math.random() > 0.5?1:-1; rect.yDir = Math.random() > 0.5?1:-1; var obj=new Object; var count = 0,k; for (k in rect) { if (rect.hasOwnProperty(k)) { count++; obj[k]=rect[k]; } } alert(count); rect.addFrameListener(function(t, dt) { this.cx += this.xDir * 50 * dt/1000; this.cy += this.yDir * 50 * dt/1000; if (this.cx > 550) { this.xDir = -1; } if (this.cx < 50) { this.xDir = 1; } if (this.cy > 350) { this.yDir = -1; } if (this.cy < 50) { this.yDir = 1; } } ); CAKECanvas.append(rect); var carAsJSON = JSON.stringify(obj); /////////////////ERROR

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  • Creating an object relational schema from a Class diagram

    - by Caylem
    Hi Ladies and Gents. I'd like some help converting the following UML diagram: UML Diagram The diagram shows 4 classes and is related to a Loyalty card scheme for an imaginary supermarket. I'd like to create an object relational data base schema from it for use with Oracle 10g/11g. Not sure where to begin, if somebody could give me a head start that would be great. Looking for actually starting the schema, show abstraction, constraints, types(subtypes, supertypes) methods and functions. Note: I'm not looking for anyone to make any comments regarding the actual classes and whether changes should be made to the Diagram, just the schema. Thanks

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  • Unable to create unmanaged object using new keyword in managed C++

    - by chair79
    Hi all, I've created a class with a boost::unordered_map as a member, Linkage.h #ifndef LINKAGE_H #define LINKAGE_H #include <boost/unordered_map.hpp> class Linkage { private: boost::unordered_map<int, int> m_IOMap; public: .... }; Linkage.cpp #include "stdafx.h" ... // methods and in the managed side of C++, I try to create the pointer of the obj: private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) { Linkage* m_pLink = new Linkage(); ..... } However this produces errors: Error 4 error LNK2005: "private: static unsigned int const boost::detail::type_with_alignment_imp<4>::found" (?found@?$type_with_alignment_imp@$03@detail@boost@@$$Q0IB) already defined in Proj_Test.obj Linkage.obj ..... Error 7 fatal error LNK1169: one or more multiply defined symbols found Could anyone explain to me pls? Thanks.

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  • OO and Writing Drupal Modules

    - by Aaron
    Preface: Yes, I've read: http://drupal.org/node/547518 I am writing 'foo' module for Drupal6, where I am organizing the code in an OO fashion. There's a class called Foo that has a bunch of setters and accessors, and it is working quite well at abstracting some pretty nasty code and SQL. The question is is it common practice to expose a class for other modules, or is it better to wrap things in the more typical foo_myfnname()? For example, if I am writing the module's docs, should I tell people to do this: $foo = new Foo(); $something = $foo->get_something(); or tell them to call: foo_get_something(); which under the hood does: function foo_get_something() { $foo = new Foo(); return $foo->get_something(); }

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  • Change user name

    - by Giorgio
    Recently i've added new accounts in my PC, and for one of those need to change name: I've try to change it by "graphical procedure" from "account manager menu" but change only the name in LogIn screen and near the clock. If I open a Terminal the name remain the old one. I need to have this situation from Old name: franco@PC-Casa:~$ ----- I want obtain New name: francesco@PC-Casa:~$ o How i can do this without create a new one user and transfer all data? Can you explain me step by step the procedure?

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  • Approximate timings for various operations on a "typical desktop PC" anno 2010

    - by knorv
    In the article "Teach Yourself Programming in Ten Years" Peter Norvig (Director of Research, Google) gives the following approximate timings for various operations on a typical 1GHz PC back in 2001: execute single instruction = 1 nanosec = (1/1,000,000,000) sec fetch word from L1 cache memory = 2 nanosec fetch word from main memory = 10 nanosec fetch word from consecutive disk location = 200 nanosec fetch word from new disk location (seek) = 8,000,000 nanosec = 8 millisec What would the corresponding timings be for your definition of a typical PC desktop anno 2010?

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  • Returning a local object from a function

    - by pocoa
    Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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  • How to profile object creation in Java?

    - by gooli
    The system I work with is creating a whole lot of objects and garbage collecting them all the time which results in a very steeply jagged graph of heap consumption. I would like to know which objects are being generated to tune the code, but I can't figure out a way to dump the heap at the moment the garbage collection starts. When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. Any notes on how to track down excessive temporary object creation are welcome.

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  • JSP Problem ussing implicit object (session) in a function

    - by user234666
    Can the object of type HttpSession called session be accessed from a function? In a simple jsp page I have a function(see below) defined in the header of the page, and set to an onclick handle of for a button. When I press this button, I'll never see the second alert message. If I do something in the body of the page (like Session ID: <%= session.getId() % ) I have no trouble accessing it. What newbie mistake am I making? function doTest() { alert('Preforming test 122333232'); String sessionId = session.getId(); alert('After access'); if(sessionId == null) { alert('session id is null?'); } Thanks

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  • How to replace an object in an NSMutableArray at a given index with a new object

    - by shakeelw
    Hi guys. I have an NSMutableArray object(retained, synthesized as all) that is initiated just fine and I can easily add objects to it using the 'addObject:' method. But if I want to replace an object at a certain index with a new one in that NSMutableArray, it doesn't work. For example: ClassA.h @interface ClassA : NSObject { NSMutableArray *list; } @property (nonatomic, copy, readwrite) NSMutableArray *list; end ClassA.m import "ClassA.h" @implementation ClassA @synthesize list; (id)init { [super init]; NSMutableArray *localList = [[NSMutableArray alloc] init]; self.list = localList; [localList release]; //Add initial data [list addObject:@"Hello "]; [list addObject:@"World"]; } // Custom set accessor to ensure the new list is mutable (void)setList:(NSMutableArray *)newList { if (list != newList) { [list release]; list = [newList mutableCopy]; } } -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; [self.list replaceObjectAtIndex:i withObject:newTitle]; NSLog((NSString *)[self.list objectAtIndex:i]); // gives the correct output } However, the change remains true only inside the method. from any other method, the NSLog((NSString *)[self.list objectAtIndex:i]); gives the same old value. How can I actually get the old object replaced with the new one at a specific index so that the change can be noticed from within any other method as well. I even modified the method like this, but the result is the same: -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; NSMutableArray *localList = [[NSMutableArray alloc] init]; localList = [localList mutableCopy]; for(int j = 0; j < [list count]; j++) { if(j == i) { [localList addObject:newTitle]; NSLog(@"j == 1"); NSLog([NSString stringWithFormat:@"%d", j]); } else { [localList addObject:(NSString *)[self.list objectAtIndex:j]]; } } [self.list release]; //self.list = [localList mutableCopy]; [self setList:localList]; [localList release]; } Please help out guys :)

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  • Output of System.out.println(object)

    - by Shaarad Dalvi
    I want to know what exactly the output tells when I do the following : class data { int a=5; } class main { public static void main(String[] args) { data dObj=new data(); System.out.println(dObj); } } I know it gives something related to object as the output in my case is data@1ae73783. I guess the '1ae73783' is a hex number. I also did some work around and printed System.out.println(dObj.hashCode()); I got number 415360643. I got an integer value. I don't know what hashCode() returns, still out of curiosity, when I converted 1ae73783 to decimal, I got 415360643! That's why I am curious that what exactly is this number?? Is this some memory location of Java's sandbox or some other thing? Any light on this matter will be helpful..thanks! :)

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  • How to print object data in javascript

    - by rxzhang
    I have the following object data: var response = { "response": { "numFound": 7945, "docs": [{ "description": "target", "url": "target", "id": "269653", "score": 6.9186745 }, { "description": "Target Kent", "url": "Target_Kent", "id": "37275", "score": 4.3241715 }] }, "highlighting": { "269653": { "description": ["<em>target</em>"] }, "37275": { "description": ["<em>Target</em> Kent"] } } }; I can use response.response.docs[0].description to print out "target". But I don't know how to print out "<em>target</em>". Thanks.

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  • Is count(*) really expensive ?

    - by Anil Namde
    I have a page where I have 4 tabs displaying 4 different reports based off different tables. I obtain the row count of each table using a select count(*) from <table> query and display number of rows available in each table on the tabs. As a result, each page postback causes 5 count(*) queries to be executed (4 to get counts and 1 for pagination) and 1 query for getting the report content. Now my question is: are count(*) queries really expensive -- should I keep the row counts (at least those that are displayed on the tab) in the view state of page instead of querying multiple times? How expensive are COUNT(*) queries ?

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  • Declaring and creating an object then adding to collection VS Adding object to collection using new

    - by ZeeMan
    Ok so the title may have been confusing so i have posted 2 code snippets to illustrate what i mean. NOTE: allUsers is just a collection. RegularUser regUser = new RegularUser(userName, password, name, emailAddress); allUsers.Add(regUser); VS allUsers.Add(new RegularUser(userName, password, name, emailAddress)); Which snippet A or B is better and why? What are the advantages or disadvantages? The example i wrote was C# but does the language (C#, Java etc) make a difference?

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