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• Interface extension

  - by user877329

  Suppose that I have an input stream interface, which defines a method for reading data. I also have a seekable interface which defines a method for seeking. A natural way of defining a input file is then to implement both input stream and seekable. I want to construct a data decoder from the input stream interface so I can read data from a file or from another stream. The problem is that I also want to implement seek functionality to the data decoder, since I want to be able to step individual records not raw bytes. This is not possible if I only provide an input stream, which does not have the bytewise seek method. Should I skip the seekable interface and add the seek method to input stream instead and force all streams to at least leave it as a nop.

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• Could someone explain in detail simplex /or perlin noise?

  - by Ryan Szemplinski

  I am really interested in perlin/simplex noise but I am having a difficult time understanding it. I am not very good at math but I am willing to learn because it interests me greatly. If someone is willing to dedicate there time into this I would be immensely appreciative of this. To be more concise, an explanation of functions and some calculation inside the functions would be nice to understand. Thanks in advance!

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• Preferred lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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• Help identify the pattern for reacting on updates

  - by Mike

  There's an entity that gets updated from external sources. Update events are at random intervals. And the entity has to be processed once updated. Multiple updates may be multiplexed. In other words there's a need for the most current state of entity to be processed. There's a point of no-return during processing where the current state (and the state is consistent i.e. no partial update is made) of entity is saved somewhere else and processing goes on independently of any arriving updates. Every consequent set of updates has to trigger processing i.e. system should not forget about updates. And for each entity there should be no more than one running processing (before the point of no-return) i.e. the entity state should not be processed more than once. So what I'm looking for is a pattern to cancel current processing before the point of no return or abandon processing results if an update arrives. The main challenge is to minimize race conditions and maintain integrity. The entity sits mainly in database with some files on disk. And the system is in .NET with web-services and message queues. What comes to my mind is a database queue-like table. An arriving update inserts row in that table and the processing is launched. The processing gathers necessary data before the point of no-return and once it reaches this barrier it looks into the queue table and checks whether there're more recent updates for the entity. If there are new updates the processing simply shuts down and its data is discarded. Otherwise the processing data is persisted and it goes beyond the point of no-return. Though it looks like a solution to me it is not quite elegant and I believe this scenario may be supported by some sort of middleware. If I would use message queues for this then there's a need to access the queue API in the point of no-return to check for the existence of new messages. And this approach also lacks elegance. Is there a name for this pattern and an existing solution?

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• Installing dgen removes Ubuntu-Desktop

  - by aliasbody

  I am trying to install "dgen" a Sega MegaDrive/Genesis emulator, available in the official Ubuntu repositories. But when I try to install, the package manager (USC or even apt-get), say's that he needs to remove those packages before installing : file-roller lintian ubuntu-desktop unzip winetricks Ubuntu always had problems with dependencies like this, and this was the main raison I started using Arch Linux instead of Ubuntu, but with the newest versions (mainly the 12.04 version), I was hopping that those kind of problems had complety dissapeared.. but no :S... So, How can I install this package without removing those packages ? And do I need to fill a bug report for this ?

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• Whats a good structure to save and retrieve locations of images?

  - by Goot

  I got a java-ee application, where I collect informations about movies. Im my backend I provide data like the name, description, genre and a random uuid. I also got lots of related files, which are stored on a file server. Including some screenshots, the dvd or bluRay cover and video trailers. My current approach is: When saving the files to the fileserver, I retrieve the movies random uuid (which is the primary key btw.). I then rename the files screenshot_[UUID]_1, screenshot_[UUID]_2 ... etc. Now, there are lots of other ways to handle this, like saving all filenames in a database or creating a dir structure on the fileserver for every uuid and, e.g., return all images in the "[uuid]/screenshots" folder via REST. I expect about 30k requests a day, so the service has to be pretty performant. Whats the best way to solve this?

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• Error while reomving the new kernel 2.6.37

  - by Tarek

  Hi! I tried to install the new kernel but something went wrong and I'm trying to remove it now. The error massege is: mhd@Tarek-Laptop:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED: linux-image-2.6.37-020637-generic 0 upgraded, 0 newly installed, 1 to remove and 9 not upgraded. 1 not fully installed or removed. After this operation, 111MB disk space will be freed. Do you want to continue [Y/n]? y (Reading database ... 188780 files and directories currently installed.) Removing linux-image-2.6.37-020637-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 2.6.37-020637-generic /boot/vmlinuz-2.6.37-020637-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 2.6.37-020637-generic /boot/vmlinuz-2.6.37-020637-generic /etc/default/grub: 33: Syntax error: EOF in backquote substitution run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 2 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-2.6.37-020637-generic.postrm line 328. dpkg: error processing linux-image-2.6.37-020637-generic (--remove): subprocess installed post-removal script returned error exit status 1 Errors were encountered while processing: linux-image-2.6.37-020637-generic E: Sub-process /usr/bin/dpkg returned an error code (1) The previous unsloved error is on this bug.

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• Making it myself vs. modifying someone else's code as a beginner

  - by JamesGold

  I just started getting into open source projects mainly for the learning experience. I've made a few tiny contributions to some small projects. Most of my time has been spent just reading over other people's code and trying to understand how it works. Often times I find myself frustrated by a lack of documentation and unit tests. There are also times where I think I can see a more intuitive solution to a problem, but implementing it would require large restructuring of code. I see all this and wonder to myself why I don't just start clean on the whole thing by myself and do things "the right way"? I'd also enjoy the experience of building it from scratch, as it would force me to learn skills that I might not learn by working on other people's code. On the other hand, working on other people's code is also a great experience because it requires me to understand and work with other people's code and collaborate with them. It's just harder, IMO. Thoughts?

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• I need an approach to the problem of preventing inserting duplicate records into the database

  - by Maurice

  Apologies is this question is asked on the incorrect "stack" A webservice that I call returns a list of data. The data from the webservice is updated periodically, so a call to the webservice done in one hour could return the same data as a call done in an hour. Also, the data is returned based on a start and end date. We have multiple users that can run the webservice search, and duplicate data is most likely to be returned (especially for historical data). However I don't want to insert this duplicate data in the database. I've created a db table in which the data is stored (most important columns are) Id int autoincrement PK Date date not null --The date to which the data set belongs. LastUpdate date not null --The date the data set was last updated. UserName varchar(50) --The name of the user doing the search. I use sql server 2008 express with c# 4.0 and visual studio 2010. Entity Framework is used as the ORM. If stored procedures could be avoided in the proposed solution, then that will be a plus. Another way of looking interpreting what I'm asking a solution for is as follows: I have a million unique records in my table. A user does a new search. The search results from the user contains around 300k of the data that is already in the db. An efficient solution to finding an inserting only the unique records is needed.

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• Real Time Monitoring System using .net [closed]

  - by sameer

  I need to develop the application which display the dashboard where data from various SQL DB is fetched from different servers and displayed. Now this need to happen real time we can have refresh time say 5 min. Here is my thought, suggest if anything is wrong. 1) To Develop the Windows Service to accumulate the data from various SQL Server Instance. 2) Then Persist those details into SQL DB from which Dashboard will displayed on the web page. 3) Fetch of data from Windows service will be trigger every x minutes. 4) SQL Server Instance details will be stored in SQL DB which Windows Service will be referring. Thus this approach make sense. Thanks..

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• Music player with a few specific requirements

  - by Jordan Uggla

  I am looking for a music player with a few specific requirements: Must have a search function that whittles down results as you type, searching the entire library. Must start playing a song when double clicked, and not continue to another song when that song finishes. Must be approachable and immediately usable by people completely unfamiliar with the program. I think this is mostly covered by the first two requirements being met. I've tried many players but unfortunately every one has failed to meet at least one of the requirements. Rhythmbox meets 1 and 3, but continues to the next search result after the song which was double clicked ends. Banshee is basically the same as Rhythmbox. While it has an option to "Stop when finished" this cannot (as far as I can tell) be made the default when double clicking a song. Audacious (as far as I can tell) fails at 1. Muine meets requirements 1 and 2, but unfortunately I couldn't make the search dialog always shown like it is with Rhythmbox / Banshee which, despite its very simple interface, made Muine incomprehensible to people trying to use it for the first time. Amarok I could not configure to meet requirement 1, but I think it's likely I was just missing something, and with its configurability I'm confident that I can set it up to meet requirements 2 and 3.

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• Any command line calculator for Ubuntu?

  - by AgentCool

  I am looking for a Calculator which can do calculations in the terminal itself without any other extra prefixes and suffixes. For example: If I typed something like 10000-9000 in the terminal, the answer should come out as 1000. Once again I am saying, I just need a quick calculator in terminal, without any characters added. I know if I switch to Python, it can do that but I don't want it in such a way.

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• Web designer help needed [closed]

  - by Felipe Caiado

  I have a ongoing problem, not knowing where to start to learn how to program websites, and which languages I should learn first, I have already taken a good look on the web, and I havn't found a clear awnser yet. Help would be much apreciated, in the cents of finding some good languages to start to program; and a good learning source such as a book or a website that covers from the basiscs to the most advanced of those languages.

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• I want to learn to program in SDL C++where do i start? I want to learn only what i need to to start making 2d games [on hold]

  - by user2644399

  Lazyfoo of Lazyfoo.net of the SDL 2d tutorial wrote that in order for me to start game programming in SDL, I need to know these concepts well; Operators, Controls, Loops, Functions, Structures, Arrays, References, Pointers, Classes, Objects how to use a template and Bitwise and/or. I want to know the fastest way to learn as much as I need of basic c++ that would allow me to make 2d games. Thanks in advance.

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• What is the general definition of something that can be included or excluded?

  - by gutch

  When an application presents a user with a list of items, it's pretty common that it permits the user to filter the items. Often a 'filter' feature is implemented as a set of include or exclude rules. For example: include all emails from [email protected], and exclude those emails without attachments I've seen this include/exclude pattern often; for example Maven and Google Analytics filter things this way. But now that I'm implementing something like this myself, I don't know what to call something that could be either included or excluded. In specific terms: If I have a database table of filter rules, each of which either includes or excludes matching items, what is an appropriate name of the field that stores include or exclude? When displaying a list of filters to a user, what is a good way to label the include or exclude value? (as a bonus, can anyone recommend a good implementation of this kind of filtering for inspiration?)

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• Concurrency pattern of logger in multithreaded application

  - by Dipan Mehta

  The context: We are working on a multi-threaded (Linux-C) application that follows a pipeline model. Each module has a private thread and encapsulated objects which do processing of data; and each stage has a standard form of exchanging data with next unit. The application is free from memory leak and is threadsafe using locks at the point where they exchange data. Total number of threads is about 15- and each thread can have from 1 to 4 objects. Making about 25 - 30 odd objects which all have some critical logging to do. Most discussion I have seen about different levels as in Log4J and it's other translations. The real big questions is about how the overall logging should really happen? One approach is all local logging does fprintf to stderr. The stderr is redirected to some file. This approach is very bad when logs become too big. If all object instantiate their individual loggers - (about 30-40 of them) there will be too many files. And unlike above, one won't have the idea of true order of events. Timestamping is one possibility - but it is still a mess to collate. If there is a single global logger (singleton) pattern - it indirectly blocks so many threads while one is busy putting up logs. This is unacceptable when processing of the threads are heavy. So what should be the ideal way to structure the logging objects? What are some of the best practices in actual large scale applications? I would also love to learn from some of the real designs of large scale applications to get inspirations from!

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• Expiring timed actions a good idea?

  - by Bart van Heukelom

  We have an online game where players sometimes have to wait a while (say 30 minutes) before a process they intiated completes. This encourages them to come back later. An example of this is growing crops in Farmville or basically any action in the Sims Play4Free. Now, however, there is the idea to let these processes expire, so if the player doesn't 'reap' them in time (e.g. within 4 hours) they are aborted. I'm a bit sceptical about this. How will this make players come back more often? Is not the reward of reaping the process enough for that? Can we expect players to fit their daily schedule around our game, maybe even set the alarm clock at night? Won't this just cause players to give up on starting these processes in the first place? I realise this may be too subjective for this site, so I'll end with a concrete question: Do (m)any other online free-to-play games employ this technique?

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• Which office suite is the ideal alternative to MSOffice?

  - by user64720

  Let's say I want to drop MSOffice permanently and switch to a free alternative, not having the need of opening the documents on other PC's except my own (I can also carry a portable version on a pendrive and edit the docs anywhere). I know 3 free office suites - LibreOffice, Abiword and Calligra. Which one of these is the most complete and provides the best features to be a viable alternative to MSOffice, without compromising the quality of the work I can produce on Office apps? Notice that I'm not focusing the question on compatibility between MSOffice and other suites but instead I am comparing their quality, taking in comparison MSOffice.

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• Java word scramble game [closed]

  - by Dan

  I'm working on code for a word scramble game in Java. I know the code itself is full of bugs right now, but my main focus is getting a vector of strings broken into two separate vectors containing hints and words. The text file that the strings are taken from has a colon separating them. So here is what I have so far. public WordApp() { inputRow = new TextInputBox(); inputRow.setLocation(200,100); phrases = new Vector <String>(FileUtilities.getStrings()); v_hints = new Vector<String>(); v_words = new Vector<String>(); textBox = new TextBox(200,100); textBox.setLocation(200,200); textBox.setText(scrambled + "\n\n Time Left: \t" + seconds/10 + "\n Score: \t" + score); hintBox = new TextBox(200,200); hintBox.setLocation(300,400); hintBox.hide(); Iterator <String> categorize = phrases.iterator(); while(categorize.hasNext()) { int index = phrases.indexOf(":"); String element = categorize.next(); v_words.add(element.substring(0,index)); v_hints.add(element.substring(index +1)); phrases.remove(index); System.out.print(index); } The FileUtilities file was given to us by the pofessor, here it is. import java.util.*; import java.io.*; public class FileUtilities { private static final String FILE_NAME = "javawords.txt"; //------------------ getStrings ------------------------- // // returns a Vector of Strings // Each string is of the form: word:hint // where word contains no spaces. // The words and hints are read from FILE_NAME // // public static Vector<String> getStrings ( ) { Vector<String> words = new Vector<String>(); File file = new File( FILE_NAME ); Scanner scanFile; try { scanFile = new Scanner( file); } catch ( IOException e) { System.err.println( "LineInput Error: " + e.getMessage() ); return null; } while ( scanFile.hasNextLine() ) { // read the word and follow it by a colon String s = scanFile.nextLine().trim().toUpperCase() + ":"; if( s.length()>1 && scanFile.hasNextLine() ) { // append the hint and add to collection s+= scanFile.nextLine().trim(); words.add(s); } } // shuffle Collections.shuffle(words); return words; } }

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• Service Layer - how broad should it be, and should it also be on the local application?

  - by BornToCode

  Background: I need to build a desktop application with some operations (CRUD and more) (=winforms), I need to make another application which will re-use some of the functions of the main application (=webforms). I understood that using service layer is the best approach here. If I understood correctly the service should be calling the function on the BL layer (correct me if I'm wrong) The dilemma: In my main winform UI - should I call the functions from the BL, or from the service? (please explain why) Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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• State Pattern - should a state know about its context?

  - by Extrakun

  I am referring to the state pattern as described in this link. In the example class diagram, a context has numerous states. However, it does not show how does a state communicates with a context (perhaps an input in a state has impact on a setting in the context). The two examples on the page shows either passing the context to the state via a function, or storing a reference to the context. Are those advisable? Are there other ways for a state to communicate with a context? Update to an edit: For instance, I am doing a remote control which can have several states. Say, the context has a setting for Volume, and I am in one of the states which allow me to tweak the volume. How should the state communicates with the context that the volume is being changed?

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• Trying to make a universe [on hold]

  - by caters

  I am wanting to program a universe so that it starts with a big bang and atoms form and then molecules form and stars start to form and planets start to form and then moons around those planets. I have a few questions. If 400 IPMUs(In Program Mass Units) = 1 solar mass than how would I calculate the number of IPMUs for a spectral class of star given the range of solar masses for a main sequence star in that spectral class? How can I have planets not look like stars? Since whether it is a subdwarf, main sequence star, subgiant, giant, bright giant, supergiant, or hypergiant is mainly dependent on the radius and luminosity how can I have the radius and luminosity independent of the mass?

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• two-part dice pool mechanic

  - by bythenumbers

  I'm working on a dice mechanic/resolution system based off of the Ghost/Echo (hereafter shortened to G/E) tabletop RPG. Specifically, since G/E can be a little harsh with dealing out consequences and failure, I was hoping to soften the system and add a little more player control, as well as offer the chance for players to evolve their characters into something unique, right from creation. So, here's the mechanic: Players roll 2d12 against the two statistics for their character (each is a number from 2-11, and may be rolled above or below depending on the nature of the action attempted, rolling your stat exactly always fails). Depending on the success for that roll, they add dice to the pool rolled for a modified G/E style action. The acting player gets two dice anyhow, and I am debating offering a bonus die for each success, or a single bonus die for succeeding on both of the statistic-compared rolls. One the size of the dice pool is set, the entire pool is rolled, and the players are allowed to assign rolled dice to a goal and a danger. Assigned results are judged as follows: 1-4 means the attempted goal fails, or the danger comes true. 5-8 is a partial success at the goal, or partially avoiding the danger. 9-12 means the goal is achieved, or the danger avoided. My concerns are twofold: Firstly, that the two-stage action is too complicated, with two rolls to judge separately before anything can happen. Secondly, that the statistics involved go too far in softening the game. I've run some basic simulations, and the approximate statistics follow: 2 dice (up to) 3 dice (up to) 4 dice failure ~33% ~25% ~20% partial ~33% ~35% ~35% success ~33% ~40% ~45% I'd appreciate any advice that addresses my concerns or offers to refine my simulation (right now the first roll is statistically modeled as sign(1d12-1d12), where 0 is a success).

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• Visually and audibly unambiguous subset of the Latin alphabet?

  - by elliot42

  Imagine you give someone a card with the code "5SBDO0" on it. In some fonts, the letter "S" is difficult to visually distinguish from the number five, (as with number zero and letter "O"). Reading the code out loud, it might be difficult to distinguish "B" from "D", necessitating saying "B as in boy," "D as in dog," or using a "phonetic alphabet" instead. What's the biggest subset of letters and numbers that will, in most cases, both look unambiguous visually and sound unambiguous when read aloud? Background: We want to generate a short string that can encode as many values as possible while still being easy to communicate. Imagine you have a 6-character string, "123456". In base 10 this can encode 10^6 values. In hex "1B23DF" you can encode 16^6 values in the same number of characters, but this can sound ambiguous when read aloud. ("B" vs. "D") Likewise for any string of N characters, you get (size of alphabet)^N values. The string is limited to a length of about six characters, due to wanting to fit easily within the capacity of human working memory capacity. Thus to find the max number of values we can encode, we need to find that largest unambiguous set of letters/numbers. There's no reason we can't consider the letters G-Z, and some common punctuation, but I don't want to have to go manually pairwise compare "does G sound like A?", "does G sound like B?", "does G sound like C" myself. As we know this would be O(n^2) linguistic work to do =)...

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• C++: calling non-member functions with the same syntax of member ones

  - by peoro

  One thing I'd like to do in C++ is to call non-member functions with the same syntax you call member functions: class A { }; void f( A & this ) { /* ... */ } // ... A a; a.f(); // this is the same as f(a); Of course this could only work as long as f is not virtual (since it cannot appear in A's virtual table. f doesn't need to access A's non-public members. f doesn't conflict with a function declared in A (A::f). I'd like such a syntax because in my opinion it would be quite comfortable and would push good habits: calling str.strip() on a std::string (where strip is a function defined by the user) would sound a lot better than calling strip( str );. most of the times (always?) classes provide some member functions which don't require to be member (ie: are not virtual and don't use non-public members). This breaks encapsulation, but is the most practical thing to do (due to point 1). My question here is: what do you think of such feature? Do you think it would be something nice, or something that would introduce more issues than the ones it aims to solve? Could it make sense to propose such a feature to the next standard (the one after C++0x)? Of course this is just a brief description of this idea; it is not complete; we'd probably need to explicitly mark a function with a special keyword to let it work like this and many other stuff.

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