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• Android: Capturing the return of an activity.

  - by Chrispix

  I have a question regarding launching new activities. It boils down to this. I have 3 tabs on a view A) contains gMap activity B) camera activity C) some random text fields. Requirement is that the application runs in Portrait mode. All 3 tabs work as expected w/ the exception of the Camera Preview Surface (B). It is rotated 90 degrees. They only way to make it correct is to set the app to landscape which throws all my tabs around, and is pretty much unworkable. My solution is this : replace my camera activity with a regular activity that is empty w/ the exception of Intent i = new Intent(this,CameraActivity.class); startActivity(i); This launches my CameraActivity. And that works fine. I had to do a linear layout and include 3 images that look like real tabs, so I can try and mimic the operation of the tabs while rotating the screen to landscape and keep the visuals as portrait. The user can click one of the images(buttons) to display the next tab. This is my issue. It should exit my 'camera activity' returning to the 'blank activity' in a tab, where it should be interpreted to click the desiered tab from my image. The main thing is, when it returns, it returns to a blank (black) page under a tab (because it is 'empty'). How can I capture the return event back to the page that called the activity, and then see what action they performed? I can set an onclicklistener where I can respond to the fake tabs (images) being clicked to exit out of the camera activity. On exit, the tab should update so that is where you return. any Suggestions? Thanks,

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• Load images into separate movie clips from a XML, Flash, Actionscript 3.0

  - by James Dunay

  I have an xml image bank, pretty standard, and I have a loader, along with movie clips that I want the images loaded into, the problem that I am running into is I want the images to load into separate movie clips, so I’m using a case statement to specify where they go. However, I can only get them to load into a single movie clip, I assume they are loading ontop of each other and I don’t know how to get them to separate out. I’ll post my code. It doesn’t make any sense to me but if you have any suggestions that would be real great. I can make separate loaders and then just do 1 image per loader, but that just doesn’t sound right to me. var counterNumber:Number = 0; function callThumbs():void{ for (var i:Number = 0; i <3; i++){ thumbLoaded(); counterNumber++; } } function thumbLoaded(){ var photoLoader = new Loader(); switch (counterNumber){ case 1: photoLoader.load(new URLRequest(MovieClip(this.parent).xml.photos.imageOne.image.@url[0])); whole.boxOne.pictureLoader.addChild(photoLoader); trace("1Done"); break; case 2: photoLoader.load(new URLRequest(MovieClip(this.parent).xml.photos.imageTwo.image.@url[0])); whole.boxTwo.pictureLoader.addChild(photoLoader); trace("2Done"); break; } }

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• Stopping cookies being set from a domain (aka "cookieless domain") to increase site performance

  - by Django Reinhardt

  I was reading in Google's documentation about improving site speed. One of their recommendations is serving static content (images, css, js, etc.) from a "cookieless domain": Static content, such as images, JS and CSS files, don't need to be accompanied by cookies, as there is no user interaction with these resources. You can decrease request latency by serving static resources from a domain that doesn't serve cookies. Google then says that the best way to do this is to buy a new domain and set it to point to your current one: To reserve a cookieless domain for serving static content, register a new domain name and configure your DNS database with a CNAME record that points the new domain to your existing domain A record. Configure your web server to serve static resources from the new domain, and do not allow any cookies to be set anywhere on this domain. In your web pages, reference the domain name in the URLs for the static resources. This is pretty straight forward stuff, except for the bit where it says to "configure your web server to serve static resources from the new domain, and do not allow any cookies to be set anywhere on this domain". From what I've read, there's no setting in IIS that allows you to say "serve static resources", so how do I prevent ASP.NET from setting cookies on this new domain? At present, even if I'm just requesting a .jpg from the new domain, it sets a cookie on my browser, even though our application's cookies are set to our old domain. For example, ASP.NET sets an ".ASPXANONYMOUS" cookie that (as far as I'm aware) we're not telling it to do. Apologies if this is a real newb question, I'm new at this! Thanks.

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• How to build a simulation of a login hardware token in .Net

  - by Michel

  Hi, i have a hardware token for remote login to some citrix environment. When i click the button on the device, i get an id and i can use that to login to the citrix farm. I can click the button as much as i like, and every time a new code gets generated, and they all work. Now i want to secure my private website likewise, but not with the hardware token, but with a 'token app' on my phone. So i run an app on my phone, generate a key, and use that to (partly) authenticate myself on the server. But here's the point: i don't know how it works! How can i generate 1, 2 or 100 keys at one time which i can see (on the server) are all valid, but without the server and the phone app having contact (the hardware token also is an 'offline' solution). Can you help me with a hint how i would do this? This is what i thought of so far: the phone app and the server app know (hardcoded) the same encryption key. The phone app encrypts the current time. The server app decrypts the string to the current time and if the diff between that time and the actual server time is less than 10 minutes it's an ok. Difficult for other users to fake a key, but encryption gives such nasty strings to enter, and the hardware token gives me nice things like 'H554TU8' And this is probably not how the real hardware token works, because the server and the phone app must 'know' the same encryption key. Michel

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• How to get the most out of a 3 month intern?

  - by firoso

  We've got a software engineering intern coming in who's fairly competent and shows promise. There's one catch: we have him for 3 months full time and can't count on anything past that. He still has a year of school left, which is why we can't say for sure that we have him past 3 months. We have a specific project we're putting him on. How can we maximize his productivity while still giving him a positive learning experience? He wants to learn about development cycles and real-world software engineering. Anything that you think would be critical that you wish you had learned earlier? Nearly six months later: He's preformed admirably and even I have learned a lot from him. Thank you all for the input. Now I want to provide feedback to YOU! He has benefited most from sitting down and writing code. However, he has had a nasty history of bad software engineering practices which I'm trying to replace with good habits (properly finishing a method before moving on, not hacking code together, proper error channeling, etc). He has also really gained a lot by feeling involved in design decisions, even if most of the time they're related to my own design plans.

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• Java abstract visitor - guarantueed to succeed? If so, why?

  - by disown

  I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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• designing an ASP.NET MVC partial view - showing user choices within a large set of choices

  - by p.campbell

  Consider a partial view whose job is to render markup for a pizza order. The desire is to reuse this partial view in the Create, Details, and Update views. It will always be passed an IEnumerable<Topping>, and output a multitude of checkboxes. There are lots... maybe 40 in all (yes, that might smell). A-OK so far. Problem The question is around how to include the user's choices on the Details and Update views. From the datastore, we've got a List<ChosenTopping>. The goal is to have each checkbox set to true for each chosen topping. What's the easiest to read, or most maintainable way to achieve this? Potential Solutions Create a ViewModel with the List and List. Write out the checkboxes as per normal. While writing each, check whether the ToppingID exists in the list of ChosenTopping. Create a new ViewModel that's a hybrid of both. Perhaps call it DisplayTopping or similar. It would have property ID, Name and IsUserChosen. The respective controller methods for Create, Update, and Details would have to create this new collection with respect to the user's choices as they see fit. The Create controller method would basically set all to false so that it appears to be a blank slate. The real application isn't pizza, and the organization is a bit different from the fakeshot, but the concept is the same. Is it wise to reuse the control for the 3 different scenarios? How better can you display the list of options + the user's current choices? Would you use jQuery instead to show the user selections? Any other thoughts on the potential smell of splashing up a whole bunch of checkboxes?

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• [OT a bit] Flex+JEE what is it good for?

  - by Zenzen

  Ok so sorry for being, I guess, a bit off topic but still I think this is the best place to ask. My new semester just started (don't worry I won't ask you to do my homework) and this time we have a rather cool subject about www programming in general where we have to do a web service, web abb - whatever as long as it's "web". Here's the problem though, my team and I want to do it with Flex and JEE but we don't have much experience about what are they actually used for. I mean we know you can do virtually anything with it, but we don't really want to lose time on doing something useless. My first idea was to do a "brainstorming" 3D room/service - a place where people could log in have a video conference, a whiteboard, a place to upload pictures everyone could see, some toolbars for google, youtube etc. plus some other features which would make real-time brainstorming easy when you can't get everyone in one place. But is Flex+JEE really suitable? I mean I'm 99% sure it's doable but is it really worth doing it in Flex+JEE or was the whole purpose of JEE completely different? @EDIT: well this was only one of our ideas obviously. I do know the basics of JSP, Servlets, JPA etc. of course but yeah the main goal of this project is to get some actual experience. The problem is we don't really know is it worth doing something like let's say a social network (something like extended facebook) for gamers (doesn't really matter if it already exists) in JEE or would it only look ridiculous (because PHP or whatever would be a far better choice)? Bottom line is that we are wondering are only large scale applications (for banks etc.) written in JEE or is it good for anything (even the smaller projects)?

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• How to track auto-generated id's in select-insert statement

  - by k rey

  I have two tables detail and head. The detail table will be written first. Later, the head table will be written. The head is a summary of the detail table. I would like to keep a reference from the detail to the head table. I have a solution but it is not elegant and requires duplicating the joins and filters that were used during summation. I am looking for a better solution. The below is an example of what I currently have. In this example, I have simplified the table structure. In the real world, the summation is very complex. -- Preparation create table #detail ( detail_id int identity(1,1) , code char(4) , amount money , head_id int null ); create table #head ( head_id int identity(1,1) , code char(4) , subtotal money ); insert into #detail ( code, amount ) values ( 'A', 5 ); insert into #detail ( code, amount ) values ( 'A', 5 ); insert into #detail ( code, amount ) values ( 'B', 2 ); insert into #detail ( code, amount ) values ( 'B', 2 ); -- I would like to somehow simplify the following two queries insert into #head ( code, subtotal ) select code, sum(amount) from #detail group by code update #detail set head_id = h.head_id from #detail d inner join #head h on d.code = h.code -- This is the desired end result select * from #detail Desired end result of detail table: detail_id code amount head_id 1 A 5.00 1 2 A 5.00 1 3 B 2.00 2 4 B 2.00 2

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• Using callback functions for error handling in C

  - by Earlz

  Hi, I have been thinking about the difficulty incurred with C error handling.. like who actually does if(printf("hello world")==-1){exit(1);} But you break common standards by not doing such verbose, and usually useless coding. Well what if you had a wrapper around the libc? like so you could do something like.. //main... error_catchall(my_errors); printf("hello world"); //this will automatically call my_errors on an error of printf ignore=1; //this makes it so the function will return like normal and we can check error values ourself if(fopen.... //we want to know if the file opened or not and handle it ourself. } int my_errors(){ if(ignore==0){ _exit(1); //exit if we aren't handling this error by flagging ignore } return 0; //this is called when there is an error anywhere in the libc } ... I am considering making such a wrapper as I am synthesizing my own BSD licensed libc(so I already have to touch the untouchable..), but I would like to know what people think about it.. would this actually work in real life and be more useful than returning -1?

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• PHP MySQLi isn't letting me alter a table (adding a new column)

  - by asdasd

  Well thats pretty much it. This is my query: $query = 'ALTER TABLE permissions ADD '.$name.' INT NOT NULL DEFAULT \'0\''; Where $name is already checked to exist with only lower case alpha letters, and not more than 20 length. Im just starting this out with very simple names. The next 4 lines of code after that one are: if($stmt = $db -> prepare($query)) { $success = $stmt -> execute(); $stmt -> close(); if(!$success) echo 'ERROR: Unsuccessful query: ',$db->error,PHP_EOL; } And I get back, every time ERROR: Unsuccessful query: And no error message. Is there a way to get more error messages so I can see what is failing? I can add new columns through phpmyadmin, but that really doesnt help me at all. The $db is fine, i do lots of stuff before and after this one section. It is only adding new column to the table that fails. side question: prepare() rejected my query every time when i tried to make those 2 variables, the $name and the 0 value as ? ? prepared statement values. Thats why they are in the real query and not bound later. If i could change that too I would like that.

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• Is there a way to force ContourPlot re-check all the points on the each stage of it's recursion algorithm?

  - by Alexey Popkov

  Hello, Thanks to this excellent analysis of the Plot algorithm by Yaroslav Bulatov, I now understand the reason why Plot3D and ContourPlot fail to draw smoothly functions with breaks and discontinuities. For example, in the following case ContourPlot fails to draw contour x^2 + y^2 = 1 at all: ContourPlot[Abs[x^2 + y^2 - 1], {x, -1, 1}, {y, -1, 1}, Contours -> {0}] It is because the algorithm does not go deeply into the region near x^2 + y^2 = 1. It "drops" this region on an initial stage and do not tries to investigate it further. Increasing MaxRecursion does nothing in this sense. And even undocumented option Method -> {Refinement -> {ControlValue -> .01 \[Degree]}} does not help (but makes Plot3D a little bit smoother). The above function is just a simple example. In real life I'm working with very complicated implicit functions that cannot be solved analytically. Is there a way to get ContourPlot to go deeply into such regions near breaks and discontinuities?

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• Generics vs inheritance (when no collection classes are involved)

  - by Ram

  This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also validate the above statement. Can someone give a valid use of generics in a real-life scenario which does not involve any collections ? Pedantically, I was thinking about making an example which does not involve collections public class Animal<T> { public void Speak() { Console.WriteLine("I am an Animal and my type is " + typeof(T).ToString()); } public void Eat() { //Eat food } } public class Dog { public void WhoAmI() { Console.WriteLine(this.GetType().ToString()); } } and "An Animal of type Dog" will be Animal<Dog> magic = new Animal<Dog>(); It is entirely possible to have Dog getting inherited from Animal (Assuming a non-generic version of Animal)Dog:Animal Therefore Dog is an Animal Another example I was thinking was a BankAccount. It can be BankAccount<Checking>,BankAccount<Savings>. This can very well be Checking:BankAccount and Savings:BankAccount. Are there any best practices to determine if we should go with generics or with inheritance ?

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• Big trouble after app update. CoreData migration error

  - by MrBr

  this morning we had a big trouble with our iphone app. We had to even take it off the store. The thing is that we made real small changes to our xcdatamodel. We thought that the update process is automatically taking care about exchanging it the right way until we found out something like CoreData migration exists. We are using the UIManagedDocument to connect to the persistent store. How is it possible to exchange this file with the new one? While we were developing we just uninstalled the whole app from the device and then installed it again and everything worked. How can we simulate this process in the app store with updates? UPDATE I try to set the migration option like this _database = [[UIIManagedDocument alloc] init]; NSMutableDictionary *options = [[NSMutableDictionary alloc] init]; [options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption], _database.persistentStoreOptions = options; but the app is still crashing with ** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores. It cannot perform a save operation.'

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• Is .NET 4.0 just a show?

  - by Will Marcouiller

  I went to a presentation about the .NET Framework and Visual Studio 2010, last night. The topis were: ASP.NET 4 - Some of the new features of ASP.NET 4 More control over ClientID's in WebForms; Output Caching; ... // Some other stuff I don't really remember being more in framework and WinForms world. Entity Framework 2.0 (.NET 4.0) T4 Templates; Domain driven development; Data driven development; Contexts (edmx files); Some of real-world limitations of EF4 (projects with over 70 to 75 tables); Better POCO support, despite there are still these hidden EntityObject and StructuralObject, but used differently in comparison to EF 1.0 so that it doesn't take off your inheritance; Allows to easily choose how to persist the hierarchy into the underlying database; Code only (start working with EF4 directly from your code!); Design by Contract (DbC). The most interesting feature is, and only, as far as I'm concerned, all related to parallelism made easier. Which really works! No additional assembly references to add. In conclusion, I'm far from impressed about .NET Framework 4.0, apart that it makes some things easier to do. But when you're used to make it a way, it doesn't really change much, in my opinion. Is it me who cannot foresee what .NET 4.0 has to offer? What would you guys base your decision on to migrate to .NET 4.0, in a practical way?

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• Validating JSP's and HTML Forms, Server-side or Client-side, or both?

  - by CitadelCSAlum

  I am aware that I can Google "HTML Form Validation" and would get a billion tutorials. I am well aware that I can use simple JavaScript to validate form input, but I have been told that this is not necessarily an efficient method. I have also heard that it is a best practice to validate both client and server-side code. OK! Well, What exactly does this mean besides writing code on both? Does it mean I do some with JavaScript and other with Servlet's or does it mean that I write identical validation methods on both? My real question is can anybody give me insight and direction as how to go about validation my HTML forms. I am using JSP's and Servlet's and I have tons of form validation to do. I have already done minor form validation with regex in Java, but want to figure out if Im heading in the right track before I write any more code. Only productive answers please, If I wanted negative feedback on how inexperienced I was, I would have gone to Reddit. Thanks!

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• Getting the avg of the top 10 students from each school

  - by dave

  Hi all -- We have a school district with 38 elementary schools. The kids took a test. The averages for the schools are widely dispersed, but I want to compare the averages of JUST THE TOP 10 students from each school. Requirement: use temporary tables only. I have done this in a very work-intensive, error-prone sort of way as follows. (sch_code = e.g., 9043; -- schabbrev = e.g., "Carter"; -- totpct_stu = e.g., 61.3) DROP TEMPORARY TABLE IF EXISTS avg_top10 ; CREATE TEMPORARY TABLE avg_top10 ( sch_code VARCHAR(4), schabbrev VARCHAR(75), totpct_stu DECIMAL(5,1) ); INSERT INTO avg_top10 SELECT sch_code , schabbrev , totpct_stu FROM test_table WHERE sch_code IN ('5489') ORDER BY totpct_stu DESC LIMIT 10; -- I do that last query for EVERY school, so the total -- length of the code is well in excess of 300 lines. -- Then, finally... SELECT schabbrev, ROUND( AVG( totpct_stu ), 1 ) AS top10 FROM avg_top10 GROUP BY schabbrev ORDER BY top10 ; -- OUTPUT: ----------------------------------- schabbrev avg_top10 ---------- --------- Goulding 75.4 Garth 77.7 Sperhead 81.4 Oak_P 83.7 Spring 84.9 -- etc... Question: So this works, but isn't there a lot better way to do it? Thanks! PS -- Looks like homework, but this is, well...real.

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• What does this structure actually do?

  - by LGTrader

  I found this structure code in a Julia Set example from a book on CUDA. I'm a newbie C programmer and cannot get my head around what it's doing, nor have I found the right thing to read on the web to clear it up. Here's the structure: struct cuComplex { float r; float i; cuComplex( float a, float b ) : r(a), i(b) {} float magnitude2( void ) { return r * r + i * i; } cuComplex operator*(const cuComplex& a) { return cuComplex(r*a.r - i*a.i, i*a.r + r*a.i); } cuComplex operator+(const cuComplex& a) { return cuComplex(r+a.r, i+a.i); } }; and it's called very simply like this: cuComplex c(-0.8, 0.156); cuComplex a(jx, jy); int i = 0; for (i=0; i<200; i++) { a = a * a + c; if (a.magnitude2() > 1000) return 0; } return 1; So, the code did what? Defined something of structure type 'cuComplex' giving the real and imaginary parts of a number. (-0.8 & 0.156) What is getting returned? (Or placed in the structure?) How do I work through the logic of the operator stuff in the struct to understand what is actually calculated and held there? I think that it's probably doing recursive calls back into the stucture float magnitude2 (void) { return return r * r + i * i; } probably calls the '*' operator for r and again for i, and then the results of those two operations call the '+' operator? Is this correct and what gets returned at each step? Just plain confused. Thanks!

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• How to put JFrame into existing JPanel in Java Swing?

  - by suud

  I have an open-source java swing application like this: http://i47.tinypic.com/dff4f7.jpg You can see in the screenshot, there is a JPanel divided into two area, left and right area. The left area has many text links. When I click the SLA Criteria link, it will pop-up the SLA Criteria window. The pop-up window is JFrame object. Now, I'm trying to put the pop-up window into right area of the JPanel, so that means no pop-up window anymore, i.e. when I click the SLA Criteria link, its contents will be displayed at the right area of the JPanel. The existing content of the right area of JPanel will not be used anymore. The example illustration (note: it's made and edited using image editor, this is not the real screenshot of working application) is like this: http://i48.tinypic.com/5vrxaa.jpg So, I would like to know is there a way to put JFrame into JPanel? I'm thinking of using JInternalFrame, is it possible? Or is there another way? UPDATE: Source code: http://pastebin.com/tiqRbWP8 (VTreePanel.java, this is the JPanel) http://pastebin.com/330z3yuT (CPanel.java, this is the super class of VTreePanel) http://pastebin.com/MkNsbtjh (AWindow.java, this is the JFrame, pop-up window) http://pastebin.com/2rsppQeE (CFrame.java, this is the super class of AWindow)

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• What's the best way of accessing a DRb object (e.g. Ruby Queue) from Scala (and Java)?

  - by Tom Morris

  I have built a variety of little scripts using Ruby's very simple Queue class, and share the Queue between Ruby and JRuby processes using DRb. It would be nice to be able to access these from Scala (and maybe Java) using JRuby. I've put together something Scala and the JSR-223 interface to access jruby-complete.jar. import javax.script._ class DRbQueue(host: String, port: Int) { private var engine = DRbQueue.factory.getEngineByName("jruby") private var invoker = engine.asInstanceOf[Invocable] engine.eval("require \"drb\" ") private var queue = engine.eval("DRbObject.new(nil, \"druby://" + host + ":" + port.toString + "\")") def isEmpty(): Boolean = invoker.invokeMethod(this.queue, "empty?").asInstanceOf[Boolean] def size(): Long = invoker.invokeMethod(this.queue, "length").asInstanceOf[Long] def threadsWaiting: Long = invoker.invokeMethod(this.queue, "num_waiting").asInstanceOf[Long] def offer(obj: Any) = invoker.invokeMethod(this.queue, "push", obj.asInstanceOf[java.lang.Object]) def poll(): Any = invoker.invokeMethod(this.queue, "pop") def clear(): Unit = { invoker.invokeMethod(this.queue, "clear") } } object DRbQueue { var factory = new ScriptEngineManager() } (It conforms roughly to java.util.Queue interface, but I haven't declared the interface because it doesn't implement the element and peek methods because the Ruby class doesn't offer them.) The problem with this is the type conversion. JRuby is fine with Scala's Strings - because they are Java strings. But if I give it a Scala Int or Long, or one of the other Scala types (List, Set, RichString, Array, Symbol) or some other custom type. This seems unnecessarily hacky: surely there has got to be a better way of doing RMI/DRb interop without having to use JSR-223 API. I could either make it so that the offer method serializes the object to, say, a JSON string and takes a structural type of only objects that have a toJson method. I could then write a Ruby wrapper class (or just monkeypatch Queue) to would parse the JSON. Is there any point in carrying on with trying to access DRb from Java/Scala? Might it just be easier to install a real message queue? (If so, any suggestions for a lightweight JVM-based MQ?)

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• MemoryFailPoint fires to early in WinXP 64

  - by msedi

  Hello, I have created a volume class (called VoxelVolume) with a self-organizing memory management, since the GC in C# didn't provide a good mechanism for managing contents of the volume for mapping, unmapping and remapping. Although I could have used the mechanisms of virtual memory, the problem is that the files are often too large to fit into the page file and I don't want to force the users to increase the pagefile size. Currently this system is working quite well and there is no problem in lacking resources and OutOfMemoryExceptions since the InsufficientMemoryException using the MemoryFailPoint works quite well. This was all testes on a 32bit WinXP system with 2GB of main memory. Running the same mechanism on 64bit system with 32GB of main memory also works well, but when the application runs the MemoryFailPoint suddenly throws an exception although 24GB of main memory are still free. Another point is when the MemoryFailPoint has fired once, it fires everytime and there is no chance to get rid of it. What I have read so far, that there is a small object and a large object heap (SOH and LOH). But only for the SOH the GC takes real care of and I can free the SOH from unused objects by applying GC.Collect() and GC.WaitForPendingFinalizers. The MemoryFailPoint is obviously the only way to get a little bit of control for the LOH, but since there is enough memory left on the system I see no reason why the MemoryFilePoint should fire. Is there any experience around here using the MemoryFailPoint? Thank you for your help Martin

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• Fun with casting and inheritance

  - by Vaccano

  NOTE: This question is written in a C# like pseudo code, but I am really going to ask which languages have a solution. Please don't get hung up on syntax. Say I have two classes: class AngleLabel: CustomLabel { public bool Bold; // code to allow the label to be on an angle } class Label: CustomLabel { public bool Bold; // Code for a normal label // Maybe has code not in an AngleLabel (align for example). } They both decend from this class: class CustomLabel: Control { protected bool Bold; } The bold field is exposed as public in the descended classes. No interfaces are available on the classes. Now, I have a method that I want to beable to pass in a CustomLabel and set the Bold property. Can this be done without having to 1) find out what the real class of the object is and 2) cast to that object and then 3) make seperate code for each variable of each label type to set bold. Kind of like this: public void SetBold(customLabel: CustomLabel) { AngleLabel angleLabel; NormalLabel normalLabel; if (angleLabel is AngleLabel ) { angleLabel= customLabel as AngleLabel angleLabel.Bold = true; } if (label is Label) { normalLabel = customLabel as Label normalLabel .Bold = true; } } It would be nice to maybe make one cast and and then set bold on one variable. What I was musing about was to make a fourth class that just exposes the bold variable and cast my custom label to that class. Would that work? If so, which languages would it work for? (This example is drawn from an old version of Delphi (Delphi 5)). I don't know if it would work for that language, (I still need to try it out) but I am curious if it would work for C++, C# or Java. If not, any ideas on what would work? (Remember no interfaces are provided and I can not modify the classes.) Any one have a guess?

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• Architecture for database analytics

  - by David Cournapeau

  Hi, We have an architecture where we provide each customer Business Intelligence-like services for their website (internet merchant). Now, I need to analyze those data internally (for algorithmic improvement, performance tracking, etc...) and those are potentially quite heavy: we have up to millions of rows / customer / day, and I may want to know how many queries we had in the last month, weekly compared, etc... that is the order of billions entries if not more. The way it is currently done is quite standard: daily scripts which scan the databases, and generate big CSV files. I don't like this solutions for several reasons: as typical with those kinds of scripts, they fall into the write-once and never-touched-again category tracking things in "real-time" is necessary (we have separate toolset to query the last few hours ATM). this is slow and non-"agile" Although I have some experience in dealing with huge datasets for scientific usage, I am a complete beginner as far as traditional RDBM go. It seems that using column-oriented database for analytics could be a solution (the analytics don't need most of the data we have in the app database), but I would like to know what other options are available for this kind of issues.

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• iPhone: Helpful Classes or extended Subclasses which should have been in the SDK

  - by disp

  This is more a community sharing post than a real question. In my iPhone OS projects I'm always importing a helper class with helpful methods which I can use for about every project. So I thought it might be a good idea, if everyone shares some of their favorite methods, which should have been in everyones toolcase. I'll start with an extension of the NSString class, so I can make strings with dates on the fly providing format and locale. Maybe someone can find some need in this. @implementation NSString (DateHelper) +(NSString *) stringWithDate:(NSDate*)date withFormat:(NSString *)format withLocaleIdent:(NSString*)localeString{ NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; //For example @"de-DE", or @"en-US" NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:localeString]; [dateFormatter setLocale:locale]; // For example @"HH:mm" [dateFormatter setDateFormat:format]; NSString *string = [dateFormatter stringFromDate:date]; [dateFormatter release]; [locale release]; return string; } @end I'd love to see some of your tools.

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