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• iPhone CALayer Stacking Order

  - by Brian

  I'm using CALayers to draw to a UITableViewCell. I'm trying to figure out how layers are ordered with the content of the UITableViewCell. For instance: I add labels to the UITableViewCell in my cellForRow:atIndexPath method In the drawRect method of UITableViewCell I draw some content using the current context Also, in drawRect I add a few sublayers So what would be the order of these elements. I know I have zPosition on the CALayers but I'm not sure if they are always on top of any subviews of the UITableViewCell. And I'm not sure where the content that is drawn in drawRect comes in the order. Any help or links to documentation would be great. I have read through the Core Animation Programming Guide and didn't see anywhere where this would be answered.

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• PHP protected classes and properties, protected from whom?

  - by Andrew Heath

  I'm just getting started with OOP PHP via PHP Object-Oriented Solutions and am a little curious about the notion of protection in OOP. The author clearly explains how protection works, but the bit about not wanting others to be able to change properties falls a bit flat. I'm having a hard time imagining a situation where it is ever possible to prevent others from altering your classes, since they could just open up your class.php and manually tweak whatever they pleased seeing as how PHP is always in plaintext. Caution: all of the above written by a beginner with a beginner's understanding of programming...

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• Can we represent bit fields in JSON/BSON?

  - by zubair

  We have a dozen simulators talking to each other on UDP. The interface definition is managed in a database. The simulators are written using different languages; mostly C++, some in Java and C#. Currently, when systems engineer makes changes in the interface definition database, simulator developers manually update the communication data structures in their code. The data is mostly 2-5 bytes with bit fields for each signal. What I want to do is to generate one file from interface definition database describing byte and bit field definitions and let each developer add it to his simulator code with minimal fuss. I looked at JSON/BSON but couldn't find a way to represent bit fields in it. Thanks Zubair

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• How do I do automatic data serialization of data objects in Haskell

  - by Adam Gent

  One of the huge benefits in languages that have some sort of reflection/introspecition is that objects can be automatically constructed from a variety of sources. For example in Java I can use the same objects for persisting to a db (with Hibernate) serializing to XML (with JAXB) or serializing to JSON (json-lib). You can do the same in Ruby and Python also usually following some simple rules for properties or annotations for Java. Thus I don't need lots "Domain Transfer Objects". I can concentrate on the domain I am working in. It seems in very strict FP like Haskell and Ocaml this is not possible. Particularly Haskell. The only thing I have seen is doing some sort of preprocessing or meta-programming (ocaml). Is it just accepted that you have to do all the transformations from the bottom upwards? In other words you have to do lot of boring work to turn a data type in haskell into JSON/XML/DB Row object and back again into a data object.

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• Service Layer Patter - Could we avoid the service layer on a specific case?

  - by lidermin

  Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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• Service Layer Patter - Could we avoid the service layer on a specific case?

  - by lidermin

  Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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• Which sector in IT industry best suites my career needs?

  - by Shailesh Tainwala

  I am a student of software engineering and will be graduating in a years time. I want to get a few years of work experience before considering further studies. I like the idea of working on projects developing end-to-end systems for medium/large enterprises in different domains. My area of special interest is AI and data-mining. ERP and MIS are terms that closely resemble what I am driving at. What type of companies should I be ideally looking at?

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• malloc()/free() behavior differs between Debian and Redhat

  - by StasM

  I have a Linux app (written in C) that allocates large amount of memory (~60M) in small chunks through malloc() and then frees it (the app continues to run then). This memory is not returned to the OS but stays allocated to the process. Now, the interesting thing here is that this behavior happens only on RedHat Linux and clones (Fedora, Centos, etc.) while on Debian systems the memory is returned back to the OS after all freeing is done. Any ideas why there could be the difference between the two or which setting may control it, etc.?

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• Ethics of assisting other programmers, where do we draw the line?

  - by Chris

  In general, not just in relation to stackoverflow, sometimes I'm asked a programming question for which the answer will probably be used for good purposes, but there is a chance that it could not be. Two recent examples which reminded me of some real world questions I've been asked are: Send email to many users, and keep a formless application from closing for a keyboard hook Though I don't believe the intent of the authors of those questions is in any way nefarious, occasionally someone does ask such a question for purposes of aiding a spamming effort, or creating a keylogger. Even though the questioner and answerers had good intent, a 3rd party could pervert those answers to create a piece of malware or a spam utility. Should we always trust the questioner to use the answer for good? Should we feel obligated to ask the purpose of a question, and how the answer will be used? And how can we prevent answers from being overheard (when asked verbally) or being referenced (when posted publicly online) and then used for unsavory purposes?

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• Do I assign different or the same class id to 32-bit and 64-bit versions of the same IFilter?

  - by sharptooth

  I've implemented my own Microsoft Search IFilter. I need two versions of it - 32-bit and 64-bit for deploying them on corresponding systems. In case of IFilters for any file extension I can only register one IFilter class id. Which means I can only use one version on any system. So having two class ids seems useless - it only makes the automatic installer more complex. Do I reuse the same COM class id for both or do I use different class ids?

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• Is there a sample set of web log data available for testing analysis against?

  - by Peter

  Sorry if this isn't strictly speaking a programming question, but I figure my best chance of success would be to ask here. I'm developing some web log file analysis algorithms, but to date I only have access to a fairly small amount of web log data to process. One algorithm I want to use makes some assumptions about 'the shape' of typical web log data, and so I'd like to test it against a larger 'exemplar' - perhaps the logs of a busy site with a good distribution of traffic from different sources etc. Is there a set of such data available somewhere? Thanks for any help.

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• Using Python tuples as vectors

  - by Etaoin

  I need to represent immutable vectors in Python ("vectors" as in linear algebra, not as in programming). The tuple seems like an obvious choice. The trouble is when I need to implement things like addition and scalar multiplication. If a and b are vectors, and c is a number, the best I can think of is this: tuple(map(lambda x,y: x + y, a, b)) # add vectors 'a' and 'b' tuple(map(lambda x: x * c, a)) # multiply vector 'a' by scalar 'c' which seems inelegant; there should be a clearer, simpler way to get this done -- not to mention avoiding the call to tuple, since map returns a list. Is there a better option?

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• How to write a shell in Python

  - by panzi

  I've written a small console application that can perform certain tasks. The user interface is similar to things like version control systems or yum etc. So basically you can think of it as a domain specific language. Now I'd like to write a (bash like) shell that can execute and auto-complete this language and has a command history (so I do not have to load and save the quite large xml files on each command). In a nutshell I want something like ipython but not for executing python code but my own DSL. Are there any libraries that help me doing this? I see that there is a readline and rlcompleter module in python but its documentation seems to indicate that this is only for use with the python shell itself, or did I miss something there?

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• Synchronising scripts / db / files from dev system to web server

  - by Spoonface

  I work as a freelance web dev, and up until now have been ftping my scripts / databases / static files to my web server manually, but I'm finding that is too error prone. So I'm looking for an app to automate uploading new and updated scripts / files / databases / etc. I know a lot of independent devs use WinSCP or Unison, but I don't think those apps can synch databases. Does anyone have any other suggestions? It doesn't need to be anything overly feature rich as I'm not working within a team or across multiple operating systems or anything like that. I can purchase any reasonably priced license if necesary. My work is primarily for PHP / MySQL / Apache on a Windows system, and then uploaded to a Linux / Apache server. thanks for your time!

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• How can I tell if a given hWnd is still valid?

  - by Ian P

  Please forgive my ignorance, I'm completely new when it comes to winforms programming. I'm using a third-party class that spawns an instance of Internet Explorer. This class has a property, hWnd, that returns the hWnd of the process. Later on down the line, I may want to reuse the instance of the application if it still exists, so I need to tell my helper class to attach to it. Prior to doing that, I'd like to know if the given hWnd is still valid, otherwise I'll spawn another instance. How can I do this in C# & .NET 3.5? Thanks for the help and I apologize if my winforms nomenclature is all wacky.. haha Ian

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• Java text classification problem

  - by yox

  Hello, I have a set of Books objects, classs Book is defined as following : Class Book{ String title; ArrayList<tags> taglist; } Where title is the title of the book, example : Javascript for dummies. and taglist is a list of tags for our example : Javascript, jquery, "web dev", .. As I said a have a set of books talking about different things : IT, BIOLOGY, HISTORY, ... Each book has a title and a set of tags describing it.. I have to classify automaticaly those books into separated sets by topic, example : IT BOOKS : Java for dummies Javascript for dummies Learn flash in 30 days C++ programming HISTORY BOOKS : World wars America in 1960 Martin luther king's life BIOLOGY BOOKS : .... Do you guys know a classification algorithm/method to apply for that kind of problems ? A solution is to use an external API to define the category of the text, but the problem here is that books are in different languages : french, spanish, english ..

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• A Question About the Expressive Power of Higher-Order Logical Reasoning Formalisms.

  - by Bubba88

  Hi! I do not really know if this is scientifically proven, but I've read in a book (It was a relatively modern AI book by Peter Norvig) that secon-order logical programming could be more expressive than existing first-order languages. The question is: Is it statistically/symbolically proven that higher-order predicate logics exceed first-order predicates in their expressive power? Or they just bring the modularity/convenience/maintainability to your knowledge bases? Additionally: If there is some kind of firm direction in which I could go seeking more expressive power than I have (I mean exactly the descriptive potential of the symbols I write in given semantics/syntax) - then I would be glad to hear just almost everything :) Thank you.

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• java runtime tracing library to replace system.out.println

  - by Grzegorz Oledzki

  Have you heard of any library which would allow me to set up a tracing for specific methods at runtime? Instead of adding (and removing) lots of System.out.println in my code (and having to re-compile and re-deploy) I would like to have a magic thing which would print out a line for each call of selected method without any change in the code. This would work without re-compiling, so some kind of JVM agent (or some non-standard JVM would be needed?). Sounds like a job for aspect programming? A typical scenario would be to start an application, configure the traced methods dynamically (in a separate file or similar) and then everytime a selected method is called a line with its name (and arguments) is printed out to System.out (or some log file). Naturally one could think of tens of additional features, but this basic set would be a great tool. BTW, I use Eclipse interactive debugger too, not only the System.out tracing technique, but both have some advantages and sometimes Eclipse is not enough.

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• Is it possible to programmatically talk to MSN messenger / Live messenger?

  - by Ceilingfish

  Hi chaps, I've been researching how to interact with the MSN messenger / Live messenger service programmatically and I can't find any real documentation on this. The documentation for the Live services only seem to implement in Javascript (they're here: http://dev.live.com/Messenger/) It would be possible to reverse engineer this API to obtain the web services that it is actually using, but I am guessing that they didn't provide the sources for a reason (which means that those web services aren't meant for direct access). However I can't find any other official APIs that allow programmatic access (more specifically no APIs that mention sockets, web services, or a proper programming language like Java or .Net). Does anyone know if an API like that exists?

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• What is the best way to interoperably serialize a message?

  - by iwein

  I'm considering message serialization support for spring-integration. This would be useful for various wire level transports to implement guaranteed delivery, but also to allow interoperability with other messaging systems (e.g. through AMQP). The fundamental problem that arises is that a message containing Java object in it's payload and headers should be converted to a byte[] and/or written to a stream. Java's own serialization is clearly not going to cut it because that is not interoperable. My preference would be to create an interface that allows the user to implement the needed logic for all Objects that take part in serialization. Is this a sensible idea and what would the interface look like? Is there a standard interoperable way to serialize Objects that would make sense in this context?

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• Must See Conference Videos for Python/Django Developers

  - by Koobz

  There's lots of good conference videos online regarding Python and Django development. Instead of watching ST:TNG at the computer, I figure it'd more productive to hone my knowledge . Fire away with some of your most inspiring and educational Python, Django, or simply programming related talks. Provide an explanation of why you found the talk useful. Examples: James Bennet on Re-usable Apps - Got me to take a serious look at django apps. Put together a fairly robust site in two days afterwards with django-cms, django-photologue, django-contact-form. Good advice on when your app is crossing boundaries and why it's good to err on the site of 'make it a separate app.'

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• Embedded Linux: Memory Fragmentation

  - by waffleman

  In many embedded systems, memory fragmentation is a concern. Particularly, for software that runs for long periods of time (months, years, etc...). For many projects, the solution is to simply not use dynamic memory allocation such as malloc/free and new/delete. Global memory is used whenever possible and memory pools for types that are frequently allocated and deallocated are good strategies to avoid dynamic memory management use. In Embedded Linux how is this addressed? I see many libraries use dynamic memory. Is there mechanism that the OS uses to prevent memory fragmentation? Does it clean up the heap periodically? Or should one avoid using these libraries in an embedded environment?

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• Portable way of finding total disk size in Java (pre java 6)

  - by Wouter Lievens

  I need to find the total size of a drive in Java 5 (or 1.5, whatever). I know that Java 6 has a new method in java.io.File, but I need it to work in Java 5. Apache Commons IO has org.apache.commons.io.FileSystemUtils to provide the free disk space, but not the total disk space. I realize this is OS dependant and will need to depend on messy command line invocation. I'm fine with it working on "most" systems, i.e. windows/linux/macosx. Preferably I'd like to use an existing library rather than write my own variants. Any thoughts? Thanks.

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• Function Object in Java .

  - by Tony

  I wanna implement a javascript like method in java , is this possible ? Say , I have a Person class : public class Person { private String name ; private int age ; // constructor ,accessors are omitted } And a list with Person objects: Person p1 = new Person("Jenny",20); Person p2 = new Person("Kate",22); List<Person> pList = Arrays.asList(new Person[] {p1,p2}); I wanna implement a method like this: modList(pList,new Operation (Person p) { incrementAge(Person p) { p.setAge(p.getAge() + 1)}; }); modList receives two params , one is a list , the other is the "Function object", it loops the list ,and apply this function to every element in the list. In functional programming language,this is easy , I don't know how java do this? Maybe could be done through dynamic proxy, does that have a performance trade off?

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• Encrypt text using a number

  - by Adam Matan

  Project Euler I have recently begun to solve some of the Project Euler riddles. I found the discussion forum in the site a bit frustrating (most of the discussions are closed and poorly-threaded), So I have decided to publish my Python solutions on launchpad for discussion. The problem is that it seems quite unethical to publish these solutions, as it would let other people gain reputation without doing the programming work, which the site deeply discourages. My Encryption problem I want to encrypt my answers so that only those who have already solved the riddles can see my code. The logical key would be the answer to the riddle, which is always numeric. In order to prevent brute-force attacks on my answers, I want to find an encryption algorithm that takes a significantly long time (few seconds) to run. Do you know any such algorithm? I would fancy a Python package, which I can attach to the code, over an external program that might have portability issues. Thanks, Adam

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