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• Suggestions for entering mobile development -- pure iPhone SDK, Android SDK, Mono Touch or Titanium

  - by Tom Cabanski

  I am entering mobile development. I have been working primarily in .NET since 1.0 came out in beta. Before that, I was mostly a C++ and Delphi guy and still dabble in C++ from time to time. I do web apps quite a bit so I am reasonably proficient with Javascript, JQuery and CSS. I have also done a few Java applications. I started web programming with CGI and live mostly in the ASP.NET MVC world these days. I am trying to decide on which platform/OS and tool to select. I am concerned with the size of the market available for my applications as well as the marketibility of the skills I will pick up. The apps I have in mind would work on both phones and pads. Some aspects of what I have in mind will play better on the bigger screens that will be available on pads. Here are the options I am considering: Apple iPhone/iPad using pure Apple SDK (Objective-C) Apple iPhone/iPad using Mono Touch (C#) Android using pure Android SDK (Java) Multiple platforms using something like Titanium to generate native apps from web technologies (HTML, CSS and Javascript) Multiple platforms using HTML5 web applications that run in the browser (HTML, CSS and Javascript). Which option would you choose? Do you have a different suggestion? What are the pros and cons?

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• Algorithm to get through a maze

  - by Sam

  Hello, We are currently programming a game (its a pretty unknown language: modula 2), And the problem we encountered is the following: we have a maze (not a perfect maze) in a 17 x 12 grid. The computer has to generate a way from the starting point (9, 12) to the end point (9, 1). I found some algorithms but they dont work when the robot has to go back: xxxxx x => x x xxx or: xxxxx x xxxxxx x x x x x xxxxxx x => x xxxxxxxxx I found a solution for the first example type but then the second type couldn't be solved and the solution I made up for the second type would cause the robot to get stuck in the first type of situation. It's a lot of code so i'll give the idea: WHILE (end destination not reached) DO { try to go right, if nothing blocks you: go right if you encounter a block, try up until you can go right, if you cant go up anymore try going down until you can go right, (starting from the place you first were blocked), if you cant go down anymore, try one step left and fill the spaces you tested with blocks. } This works for the first type of problem ... not for the second one. Now it could be that i started wrong so i am open for better algorithms or solutions specificaly to how i could improve my algorithm. Thanks a lot!!

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• What do you do when your team leader doesn't know something simple?

  - by leppie

  What do you do when your team leader does not know why the following is wrong: a.SomeProp = a.SomeProp; // no funny side-effects, plain old property He claims 15 years of programming experience, and 7 years of C#/.NET. To me, someone of 3-6 months experience should know this. What I have done: Tried to make him understand why it is wrong. He told me not to criticize him. Told him it's not about criticism, but project risk. He got upset with me. I have addressed the risk of this person with our manager (few weeks back). I have addressed my concerns with this person with our manager several times, since 1 month after I started there (7 months now). Currently, I just feel like just not going back to work... I hardly have any nails left, and this is really just the tip of the iceberg. As nothing has changed after I have spoken to the manager for the last 6 months, I feel like I need to make some sort of ultimatum. Do you have any suggestions? PS: Please do not make this subjective. I have no need for arguing. The level of incompetence is pretty clear. I just need some advice before going insane. Update: Thanks for all the answers (trying to update before close, buggers). I think I will forward this thread to our manager :) Update 2: I sent my manager another mail with my concerns, and a link to this question. Awaiting response.

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• Is this error caused by a 64-bit library being accessed by a Java program running in a 32-bit JVM?

  - by Mike

  I'm trying to create a simple Java app that uses JNI to call some native functions. I've followed the examples in the JNI Programming Guide and can't seem to get them to work. I have the following Hello World program, written in Java: class HelloWorld { private native void print(); public static void main(String [] args) { new HelloWorld().print(); } static { System.load("/home/mike/Desktop/libHelloWorld.so"); } } I compile it using javac HelloWorld.java, just like normal. Then I run javah -jni HelloWorld, and finally the following: gcc34 -shared -fpic -o libHelloWorld.so -I/<path to JDK>/include -I/<path to JDK>/include/linux HelloWorld.c gcc34 is the name of the GCC program on my machine here at work (I don't control that) and I obviously place the real path to the JDK in that command. When I run my program, using the standard java HelloWorld, I get an error saying the following: Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/mike/Desktop/libHelloWorld.so: /home/mike/Desktop/libHelloWorld.so: wrong ELF class: ELFCLASS64 (Possible causes: architecture word width mismatch) at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1778) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1674) at java.lang.Runtime.load0(Runtime.java:770) at java.lang.System.load(System.java:1003) at HelloWorld.<clinit>(HelloWorld.java:8) Could not find the main class: HelloWorld. Program will exit. I know I'm running a 32-bit JVM (and unfortunately, as of right now, I'm not allowed to get a 64-bit JVM). I tried telling GCC to compile in 32-bit mode using the "-m32" option, but we don't have (and again, can't get) what we need for that. Does this sound like a 32/64-bit conflict or something else?

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• How do you use asynchronous ORMs without huge callback chains?

  - by hornairs

  I'm using the relatively immature Joose Javascript ORM plugin (project page) to persist objects in an Appcelerator Titanium (company page) mobile project. Since it's client side storage, the application has to check to see if the database is initialized before starting up the ORM since it inspects the DB tables to construct the classes. My problem is that this sequence of operations (and if this one is like this, other things down the road) takes a lot of callbacks to complete. I have a lot of jumping around in the code that isn't apparent to a maintainer and results in some complex call graphs and whatnot. So, I ask these questions: How would you asynchronously initialize a database and populate it with seed data using an ORM that needs the schema to be correct to function? Do you have any general strategies or links for async/event driven programming and keeping the call graph simple and understandable? Do you have any suggestions for Javascript ORMs/meta object systems that work with HTML 5 as a storage engine and are hopefully framework agnostic? Am I just a big newb and should be able to work this out with ease? Thanks folks!

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• Android: Creating a Scrollable Layout

  - by MD

  I'm trying to create a "scrollable" layout in Android. Even using developers.android.com, though, I feel a little bit lost at the moment. I'm somewhat new to Java, but not so much that I feel I should be having these issues--being new to Android is the bigger problem right now. The layout I'm trying to create should scroll in a sort of a "grid". I THINK what I'm looking for is the Gallery view, but I'm really lost as to how to implement it at the moment. I want it to "snap" to center the frame, like in the actual Gallery application. Essentially, if I had a photo gallery of 9 pictures, the idea is to scroll between them up/down AND side to side, in a 3x3 manner. Doesn't need to dynamically adjust, or anything like that, I just want a grid I can scroll through. I'm also not asking for anyone to give me explicit code for it--I'm trying to learn, more than anything. But pointing me in the right direction for helpful layout programming resources would be greatly appreciated, and confirming if it's a Gallery view I'm looking for would also be really helpful. EDIT: To clarify, the goal is to have ONE item on screen at a time. If you scroll between one item and the next, the previous one leaves the screen, and the new one snaps into place. So if it were a photo gallery, each spot on the grid would take up the entire screen size, approximately, and would be flung out of the viewable area when you slide across to the next photo, in either direction. (Photos are just an example for illustration purposes)

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• user input question

  - by jdbeverly87

  My program checks to test if a word or phrase is a palindrome (reads the same both backward and forward, ex "racecar"). The issue I'm having is after someone enters in "racecar" getting it to actually test. In the below code, I marked where if I type in "racecar" and run, Java returns the correct answer so I know I'm right there. But what am I missing as far as entering it into the console. I think my code is ok, but maybe I have something missing or in the wrong spot? Not really looking for a new answer unless I'm missing something, but if possible perhaps a pro at this moving my code to the correct area bc I'm stuck! `import java.util.*; public class Palindrome { public static void main(String[] args) { String myInput; Scanner in = new Scanner(System.in); System.out.println("Enter a word or phrase: "); **//this asks user for input but doesn't check for whether or not it is a palindrome** myInput = in.nextLine(); in.close(); System.out.println("You entered: " + myInput); } { String s="racecar"; **//I can type a word here and it works but I need** int i; **//I need it to work where I ask for the input** int n=s.length(); String str=""; for(i=n-1;i>=0;i--) str=str+s.charAt(i); if(str.equals(s)) System.out.println(s+ " is a palindrome"); else System.out.println(s+ " is not a palindrome"); } }` I'm new at programming so I'm hoping what I got is ok. I know the palindrome test works I'm just needing helping having it test thru where I'm entering it into the console. Thanks

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• Trouble with Rails has_many relationships

  - by Tchock

  I'm writing an app where a user can both create their own pages for people to post on, and follow posts on pages that users have created. Here is what my model relationships look like at the moment... class User < ActiveRecord::Base has_many :pages has_many :posts has_many :followings has_many :pages, :through => :followings, :source => :user class Page < ActiveRecord::Base has_many :posts belongs_to :user has_many :followings has_many :users, :through => :followings class Following < ActiveRecord::Base belongs_to :user belongs_to :page class Post < ActiveRecord::Base belongs_to :page belongs_to :user The trouble happens when I try to work my way down through the relationships in order to create a homepage of pages (and corresponding posts) a given user is following (similar to the way Twitter's user homepage works when you login - a page that provides you a consolidated view of all the latest posts from the pages you are following)... I get a "method not found" error when I try to call followings.pages. Ideally, I'd like to be able to call User.pages in a way that gets me the pages a user is following, rather than the pages they have created. I'm a programming and Rails newb, so any help would be much appreciated! I tried to search through as much of this site as possible before posting this question (along with numerous Google searches), but nothing seemed as specific as my problem...

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• Ruby Shoes packager including Shoes in the app

  - by user206481

  I can't seem to get the Ruby Shoes packager to correctly create an exe with Shoes included. I'm using the Raisins release (0.r1134), with the pack.rb replaced from github. The exe's the packager makes are all 70-80K files (they obviously don't include shoes or ruby). These exe's will run on my XP machine that already has Shoes on it. but when I copy them to another laptop they start a "Shoes is downloading" dialog that does nothing and then goes away. I need to make standalone Windows exe's, and my understanding was that the "Yes, I want Shoes included" option in the packager would do that. Did I misunderstand the intent? Is there a way to make this work? Hope so, because I love Shoes. As most women do. Hmm... maybe Shoes was _why's attempt at getting more women into programming as well as kids...but I digress. The other threads I've found here imply this will work: http://stackoverflow.com/questions/1390721/problem-in-ruby-shoes-packaging http://stackoverflow.com/questions/363218/shoes-packager-problem

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• Implementing Naïve Bayes algorithm in Java - Need some guidance

  - by techventure

  hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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• what type of bug causes a program to slowly use more processor power and all of a sudden go to 100%?

  - by reinier

  Hi, I was hoping to get some good ideas as to what might be causing a really nasty bug. This is a program which is transmitting data over a socket, and also receives messages back. I could explain lots more, but I don't think this will help here. I'm just searching for hypothetical problems which can cause the following behaviour: program runs processor time slowly accumulates (till around 60%) all of a sudden (could be after 30 but also after 60 seconds) the processor time shoots to 100%. the program halts completely In my syslog it always ends on one line with a memory allocation (something similar to: myArray = new byte[16384]) in the same thread. now here is the weird part: if I set the debugger anywhere...it immediately stops on that line. So just the act of setting a breakpoint, made the thread continue (it wasn't running since I saw no log output anymore) I was thinking 'deadlock' but that would not cause 100% processor power. If anything, the opposite. Also, setting a breakpoint would not cause a deadlock to end. anyone else a theoretical suggestion as to what kind of 'construct' might cause this effect? (apart from 'bad programming') ;^) thanks EDIT: I just noticed.... by setting the sendspeed slower, the problem shows itself much later than expected. I would think around the same amount of packets send...but no the amount of packets send is much higher this way before it has the same problem.

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• What is the recommended coding style for PowerShell?

  - by stej

  Is there any recommended coding style how to write PowerShell scripts? It's not about how to structure the code (how many functions, if to use module, ...). It's about 'how to write the code so that it is readable'. In programming languages there are some recommended coding styles (what to indent, how to indent - spaces/tabs, where to make new line, where to put braces,...), but I haven't seen any suggestion for PowerShell. What I'm interested particularly in: How to write parameters function New-XYZItem ( [string] $ItemName , [scriptblock] $definition ) { ... (I see that it's more like 'V1' syntax) or function New-PSClass { param([string] $ClassName ,[scriptblock] $definition )... or (why to add empty attribute?) function New-PSClass { param([Parameter()][string] $ClassName ,[Parameter()][scriptblock] $definition )... or (other formatting I saw maybe in Jaykul's code) function New-PSClass { param( [Parameter()] [string] $ClassName , [Parameter()] [scriptblock] $definition )... or ..? How to write complex pipeline Get-SomeData -param1 abc -param2 xyz | % { $temp1 = $_ 1..100 | % { Process-somehow $temp1 $_ } } | % { Process-Again $_ } | Sort-Object -desc or (name of cmdlet on new line) Get-SomeData -param1 abc -param2 xyz | % { $temp1 = $_ 1..100 | % { Process-somehow $temp1 $_ } } | % { Process-Again $_ } | Sort-Object -desc | and what if there are -begin -process -end params? how to make it the most readable? Get-SomeData -param1 abc -param2 xyz | % -begin { init } -process { Process-somehow2 ... } -end { Process-somehow3 ... } | % -begin { } .... or Get-SomeData -param1 abc -param2 xyz | % ` -begin { init } ` -process { Process-somehow2 ... } ` -end { Process-somehow3 ... } | % -begin { } .... the indentitation is important here and what element is put on new line as well. I have covered only questions that come on my mind very frequently. There are some others, but I'd like to keep this SO question 'short'. Any other suggestions are welcome.

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• Can you review my Perl rewrite of Cucumber?

  - by Evgeny

  There is a team working on acceptance testing X11 GUI application in our company, and they created a monstrous acceptance testing framework that drives the GUI as well as running scenarios. The framework is written using Perl 5, and scenario files look more like very complex Perl programs (thousands of lines long with procedural-programming style) than acceptance tests. I recently learned Ruby's Cucumber, and generally have been using Ruby for quite a lot of time. But unfortunately I can't just shove Ruby to replace Perl because the people who are writing all of this don't know Ruby and it's quite certain that they wont want "this" kind of interruption. So to bring Ruby's Cucumber a bit closer to their work, I rewrote it using Perl 5. Unfortunately I am really not a Perl programmer, and would love to get a code review and to hear suggestions from people who both know Perl and Cucumber. Hi Perl/Cucumber StackOverflow users - please help me create this "open source" attempt to re-create Cucumber for Perl! I would love to hear your comments and will accept any acceptable help. The minimal source code is here: http://github.com/kesor/p5-cucumber Thank you for your attention. For those not familiar with cucumber - please take just one small moment to take a look at this one small little page: http://wiki.github.com/aslakhellesoy/cucumber

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• Starter question of declarative style SQLAlchemy relation()

  - by jfding

  I am quite new to SQLAlchemy, or even database programming, maybe my question is too simple. Now I have two class/table: class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(40)) ... class Computer(Base): __tablename__ = 'comps' id = Column(Integer, primary_key=True) buyer_id = Column(None, ForeignKey('users.id')) user_id = Column(None, ForeignKey('users.id')) buyer = relation(User, backref=backref('buys', order_by=id)) user = relation(User, backref=backref('usings', order_by=id)) Of course, it cannot run. This is the backtrace: File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/state.py", line 71, in initialize_instance fn(self, instance, args, kwargs) File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 1829, in _event_on_init instrumenting_mapper.compile() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 687, in compile mapper._post_configure_properties() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 716, in _post_configure_properties prop.init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/interfaces.py", line 408, in init self.do_init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 716, in do_init self._determine_joins() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 806, in _determine_joins "many-to-many relation, 'secondaryjoin' is needed as well." % (self)) sqlalchemy.exc.ArgumentError: Could not determine join condition between parent/child tables on relation Package.maintainer. Specify a 'primaryjoin' expression. If this is a many-to-many relation, 'secondaryjoin' is needed as well. There's two foreign keys in class Computer, so the relation() callings cannot determine which one should be used. I think I must use extra arguments to specify it, right? And howto? Thanks

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• Thread resource sharing

  - by David

  I'm struggling with multi-threaded programming... I have an application that talks to an external device via a CAN to USB module. I've got the application talking on the CAN bus just fine, but there is a requirement for the application to transmit a "heartbeat" message every second. This sounds like a perfect time to use threads, so I created a thread that wakes up every second and sends the heartbeat. The problem I'm having is sharing the CAN bus interface. The heartbeat must only be sent when the bus is idle. How do I share the resource? Here is pseudo code showing what I have so far: TMainThread { Init: CanBusApi =new TCanBusApi; MutexMain =CreateMutex( "CanBusApiMutexName" ); HeartbeatThread =new THeartbeatThread( CanBusApi ); Execution: WaitForSingleObject( MutexMain ); CanBusApi->DoSomething(); ReleaseMutex( MutexMain ); } THeartbeatThread( CanBusApi ) { Init: MutexHeart =CreateMutex( "CanBusApiMutexName" ); Execution: Sleep( 1000 ); WaitForSingleObject( MutexHeart ); CanBusApi->DoHeartBeat(); ReleaseMutex( MutexHeart ); } The problem I'm seeing is that when DoHeartBeat is called, it causes the main thread to block while waiting for MutexMain as expected, but DoHeartBeat also stops. DoHeartBeat doesn't complete until after WaitForSingleObject(MutexMain) times out in failure. Does DoHeartBeat execute in the context of the MainThread or HeartBeatThread? It seems to be executing in MainThread. What am I doing wrong? Is there a better way? Thanks, David

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• Nested Routes and Parameters for Rails URLs (Best Practice)

  - by viatropos

  Hey there, I have a decent understanding of RESTful urls and all the theory behind not nesting urls, but I'm still not quite sure how this looks in an enterprise application, like something like Amazon, StackOverflow, or Google... Google has urls like this: http://code.google.com/apis/ajax/ http://code.google.com/apis/maps/documentation/staticmaps/ https://www.google.com/calendar/render?tab=mc Amazon like this: http://www.amazon.com/books-used-books-textbooks/b/ref=sa_menu_bo0?ie=UTF8&node=283155&pf_rd_p=328655101&pf_rd_s=left-nav-1&pf_rd_t=101&pf_rd_i=507846&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1PK4ZKN4YWJJ9B86ANC9 http://www.amazon.com/Ruby-Programming-Language-David-Flanagan/dp/0596516177/ref=sr_1_1?ie=UTF8&s=books&qid=1258755625&sr=1-1 And StackOverflow like this: http://stackoverflow.com/users/169992/viatropos http://stackoverflow.com/questions/tagged/html http://stackoverflow.com/questions/tagged?tagnames=html&sort=newest&pagesize=15 So my question is, what is best practice in terms of creating urls for systems like these? When do you start storing parameters in the url, when don't you? These big companies don't seem to be following the rules so hotly debated in the ruby community (that you should almost never nest URLs for example), so I'm wondering how you go about implementing your own urls in larger scale projects because it seems like the idea of not nesting urls breaks down at anything larger than a blog. Any tips?

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• How do I check to see if my subview is being touched?

  - by Amy

  I went through this tutorial about how to animate sprites: http://icodeblog.com/2009/07/24/iphone-programming-tutorial-animating-a-game-sprite/ I've been attempting to expand on the tutorial by trying to make Ryu animate only when he is touched. However, the touch is not even being registered and I believe it has something to do with it being a subview. Here is my code: -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{ UITouch *touch = [touches anyObject]; if([touch view] == ryuView){ NSLog(@"Touch"); } else { NSLog(@"No touch"); } } -(void) ryuAnims{ NSArray *imageArray = [[NSArray alloc] initWithObjects: [UIImage imageNamed:@"1.png"], [UIImage imageNamed:@"2.png"], [UIImage imageNamed:@"3.png"], [UIImage imageNamed:@"4.png"], [UIImage imageNamed:@"5.png"], [UIImage imageNamed:@"6.png"], [UIImage imageNamed:@"7.png"], [UIImage imageNamed:@"8.png"], [UIImage imageNamed:@"9.png"], [UIImage imageNamed:@"10.png"], [UIImage imageNamed:@"11.png"], [UIImage imageNamed:@"12.png"], nil]; ryuView.animationImages = imageArray; ryuView.animationDuration = 1.1; [ryuView startAnimating]; } -(void)viewDidLoad { [super viewDidLoad]; UIImageView *image = [[UIImageView alloc] initWithFrame: CGRectMake(100, 125, 150, 130)]; ryuView = image; ryuView.image = [UIImage imageNamed:@"1.png"]; ryuView.contentMode = UIViewContentModeBottomLeft; [self.view addSubview:ryuView]; [image release]; } This code compiles fine, however, when touching or clicking on ryu, nothing happens. I've also tried if([touch view] == ryuView.image) but that gives me this error: "Comparison of distinct Objective-C type 'struct UIImage *' and 'struct UIView *' lacks a cast." What am I doing wrong?

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• Why are floating point values so prolific?

  - by Kibbee

  So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster with floating point numbers, however, I can think of only a few cases that they actually the right data type would be using. If you sat back and think about every time you used a floating point value, how many times did you say, well, some error would be ok, as long as the result was a few microseconds faster. It really makes me think because Jeff was talking about NP completeness, and how heuristics give an answer that is kind of right. And well, computers shouldn't do that. They should give you the answer that is correct. Yet we see floating point values used in many applications where they are completely not valid. What really bugs me, isn't that floating point exists, but that in many languages, there isn't even a viable alternative, non-floating point, decimal value. A lot of programmers when doing financial applications have to fall back to storing the number of cents in an integer field. Which brings with it all kinds of other problems. Why do floats continue to be so prolific, even though they can't represent the real answer, and we expect computers to be accurate? [EDIT] Just to clarify, I was talking about Base 2 floating points, and not base 10 floating points. .Net offers the Decimal data type, which is a base 10 floating point value which offers a much better representation of the numbers we deal with on a daily basis in most computer programs. I find it hard to believe that even modern languages like Java don't support base 10 floating point values, unless you want to move into the realm of things like BigDecimal, which isn't really the right answer either in a lot of situations.

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• Extract known pattern substring from NSString (without regex)

  - by d11wtq

  I'm really tempted to drop RegexKit (or my own libpcre wrapper) into my project in order to do this, but before I do that I want to know how Cocoa developers manage to do half of this basic stuff without really convoluted code or without linking with RegexKit or another regular expression library. I find it gobsmacking that Cocoa does not include any regular expression matching features. I've so accustomed to using regular expressions for all kinds of things that I'm lost without them. I can do what I need without them, but the code would be rather convoluted. So, Cocoa devs, I ask you, what's the "Cocoa way" to do this... The problem is an everyday problem in programming as far as I'm concerned. Cocoa must have ways of doing this with the built-in features. Note that the position of the elements I want to match changes, and sometimes "quotes" are present. Whitespace is variable. Take the following strings: Content-Type: application/xml; charset=utf-8 Content-Type: text/html; charset="iso-8859-1" Content-Type: text/plain; charset=us-ascii Content-Type: text/plain; name="example.txt"; charset=utf-8 From all of these strings, how would you go about determining the mime type (e.g. text/plain) and the charset (e.g. utf-8) using just the built-in Cocoa classes? I'd end up performing a series of -rangeOfString: and substring calls, with conditional checks to deal with the optional quotes etc. Is there a way to do this with NSScanner? The NSScanner class seems to have a pretty naive API to me. Something like C's sscanf() that works for NSString objects would be an ideal fit. Most of my string parsing needs are simple such as this example so maybe regular expressions, while I'm accustomed to them, are overkill?

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• JMS equivalent in .Net

  - by rauts

  Hi All, I am trying to make an common abstract interface over the messaging infrastructure in our company. The design goal is to 2 fold. 1 is to hide the complexity of programming from the developers (i know its not very complex but still simplify it further) and 2 is to make the developers independent of the vendor specific messaging infrastructure (i.e. it can be MQSeries or EMS or MSMQ). The very common option is using the WCF layer over the messaging infrastructure. Use the MQSeries Custom channel for WCF or use EMS custom channle for WCF. But both are ruled out due to lack of proper version of MQSeries and EMS. Can someone please suggest what are the possible solutions to this problem. One which i can think of the to have a custom wrapper like JMS. Has anyone ever tried something similar before. Any help would be fantastic. by the way, i am trying to create this wrapper in C# 3.5. Regards

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• How to handle One View with multiple ViewModel and fire different Commands

  - by Naresh

  Hi All, I have senario in which one view and view has binding with multiple ViewModel. Eg. One View displaying Phone Detail and ViewModel as per bellow: Phone basic features- PhoneViewModel, Phone Price Detail- PhoneSubscriptionViewModel, Phone Accessories- PhoneAccessoryViewModel For general properties- PhoneDetailViewModel I have placed View's general properties to PhoneViewModel.Now senario is like this: By default View displays Phone Basic feaures which is bind with ObservationCollection of PhoneViewModel. My view have button - 'View Accessories', onclick of this button one popup screen- in my design I have display/hide Grid and bind it with ObservationCollection of PhoneAccessoryViewModel. Now problem begins- Accessory List also have button 'View Detail' onclick I have to open one popup screen, here also I had placed one Grid and Visible/Hide it. I have bind 'ViewAccessoryDetailCommand' command to 'View Detail' button. And on command execution one function fires and set property which Visible the Popup screen. Using such programming command fires, function calls but the property change not raises and so my view does not display popup. Summary: One View-- ViewModel1--Grid Bind view ViewModel2 --Grid Have Button and Onclick display new Grid which binded with ViewModel3-this Command fires but property not raises. I think there is some problem in my methodology, Please, give your suggetions.

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• How to force two process to run on the same CPU?

  - by kovan

  Context: I'm programming a software system that consists of multiple processes. It is programmed in C++ under Linux. and they communicate among them using Linux shared memory. Usually, in software development, is in the final stage when the performance optimization is made. Here I came to a big problem. The software has high performance requirements, but in machines with 4 or 8 CPU cores (usually with more than one CPU), it was only able to use 3 cores, thus wasting 25% of the CPU power in the first ones, and more than 60% in the second ones. After many research, and having discarded mutex and lock contention, I found out that the time was being wasted on shmdt/shmat calls (detach and attach to shared memory segments). After some more research, I found out that these CPUs, which usually are AMD Opteron and Intel Xeon, use a memory system called NUMA, which basically means that each processor has its fast, "local memory", and accessing memory from other CPUs is expensive. After doing some tests, the problem seems to be that the software is designed so that, basically, any process can pass shared memory segments to any other process, and to any thread in them. This seems to kill performance, as process are constantly accessing memory from other processes. Question: Now, the question is, is there any way to force pairs of processes to execute in the same CPU?. I don't mean to force them to execute always in the same processor, as I don't care in which one they are executed, altough that would do the job. Ideally, there would be a way to tell the kernel: If you schedule this process in one processor, you must also schedule this "brother" process (which is the process with which it communicates through shared memory) in that same processor, so that performance is not penalized.

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• Finding perfect numbers in C# (optimization)

  - by paradox

  I coded up a program in C# to find perfect numbers within a certain range as part of a programming challenge . However, I realized it is very slow when calculating perfect numbers upwards of 10000. Are there any methods of optimization that exist for finding perfect numbers? My code is as follows: using System; using System.Collections.Generic; using System.Linq; namespace ConsoleTest { class Program { public static List<int> FindDivisors(int inputNo) { List<int> Divisors = new List<int>(); for (int i = 1; i<inputNo; i++) { if (inputNo%i==0) Divisors.Add(i); } return Divisors; } public static void Main(string[] args) { const int limit = 100000; List<int> PerfectNumbers = new List<int>(); List<int> Divisors=new List<int>(); for (int i=1; i<limit; i++) { Divisors = FindDivisors(i); if (i==Divisors.Sum()) PerfectNumbers.Add(i); } Console.Write("Output ="); for (int i=0; i<PerfectNumbers.Count; i++) { Console.Write(" {0} ",PerfectNumbers[i]); } Console.Write("\n\n\nPress any key to continue . . . "); Console.ReadKey(true); } } }

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• Which Computer Organization & Architecture book is good for me?

  - by claws

  I'm always interested in learning the inner working of things. I started with C programming and then learnt Operating systems (from stallings) and then linkers & loaders and then assembly language after reading these now I want to go into little more depth. Computer Architecture. I feel that makes everything clear. As per SO archives these are the two good books: Computer Architecture: A Quantitative Approach, 4th Edition Computer Organization and Design, Fourth Edition, ~ David A. Patterson, John L. Hennessy But I've browsed through the contents of these books and found that they don't exactly meet my needs. I want to learn more about caches, Memory Management Unit , mapping b/w virtual memory & physical memory I'm no way interested in other ISAs like MIPS etc.. I'm IA32 and X86-64 fan and I want to stick to it. I'm not a hardware developer I don't want to details like circuit diagrams or How is L1, L2 & L3 caches are implemented? I want to know the parallel processing technologies like HyperThreading at the architecture level but again I don't want to design them. I liked the table of Contents of - Computer Architecture: A Quantitative Approach, 4th Edition but Quantitave Approach? Seriously?? I want to know the details of current technologies and I dont want to spend reading 200 pages of outdated old technologies ( I experienced this while learning ASM}

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• JAVA Regular Expression Errors

  - by Berkay

  I'm working on a simply password strength checker and i can not success applying regular expressions. In different resources different kinds of regular expressions are defined. i also find javascript regular expressions but had some problems to adapt. First, these are the regular expressions i need for JAVA: at least one lower case letter at least one upper case letter at least one number at least three numbers at least one special character at least two special characters both letters and numbers both upper and lower case letters, numbers, and special characters My goal is not being a regular expression expert i just want to use the parts i need.If you direct me good tutorials which discusses above for java, will be appreciated. Second, in this link some of them are mentioned but i'm getting problems to apply them. here does not catch the lower case letter (my pass: A5677a) if (passwd.matches("(?=.*[a-z])")) // [verified] at least one lower case letter {Score = Score+5;} Also here i'm getting error : illegal escape character. if (passwd.matches("(?=.*\d)")) // [verified] at least one number Finally, are these expressions all different in different kind of programming or script languages?

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