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• Any ideas for developing a Risc Processor friendly string allocator?

  - by Richard Fabian

  I'm working on some tools to enable high throughput data-oriented development, and one thing that I've not got an immediate answer for is how you go about allocating strings quickly. On risc processors you've got another problem of implementation that the CPU doesn't like branching, which is what I'm trying to minimise or avoid. Also, cache coherence is important on most CPUs, so that's gotta be influential in the design too. So, how would you go about reducing the overhead for a generic string allocator? Sometimes it's easier to solve a more explicit problem, so any ideas for string sizes of 5-30?

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• dynamic lib can't find static lib

  - by renyufei

  env: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) app: Bin(main) calls dynamic lib(testb.so), and testb.so contains a static lib(libtesta.a). file list: main.c test.h a.c b.c then compile as: gcc -o testa.o -c a.c ar -r libtesta.a testa.o gcc -shared -fPIC -o testb.so b.c gcc -o main main.c -L. -ltesta -ldl then compile success, but runs an error: ./main: symbol lookup error: ./testb.so: undefined symbol: print code as follows: test.h #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <dlfcn.h> int printa(const char *msg); int printb(const char *msg); a.c #include "test.h" int printa(const char *msg) { printf("\tin printa\n"); printf("\t%s\n", msg); } b.c #include "test.h" int printb(const char *msg) { printf("in printb\n"); printa("called by printb\n"); printf("%s\n", msg); } main.c #include "test.h" int main(int argc, char **argv) { void *handle; int (*dfn)(const char *); printf("before dlopen\n"); handle = dlopen("./testb.so", RTLD_LOCAL | RTLD_LAZY); printf("after dlopen\n"); if (handle == NULL) { printf("dlopen fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dlsym\n"); dfn = dlsym(handle, "printb"); printf("after dlsym\n"); if (dfn == NULL) { printf("dlsym fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dfn\n"); dfn("printb func\n"); printf("after dfn\n"); exit(EXIT_SUCCESS); }

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• Are there faster XML parsers in Java than Xalan/Xerces

  - by jm04469

  I haven't found many ways to increase the performance of a Java application that does intensive XML processing other than to leverage hardware such as Tarari or Datapower. Does anyone know of any open source ways to accelerate XML parsing?

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• File encyption with Python

  - by Pinkie

  Is there a way to encrypt files (.zip, .doc, .exe, ... any type of file) with Python? I've looked at a bunch of crypto libraries for Python including pycrypto and ezpycrypto but as far as I see they only offer string encryption.

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• Top tips for designing GUIs?

  - by oxbow_lakes

  A while back I read (before I lost it) a great book called GUI Bloopers which was full of examples of bad GUI design but also full of useful tidbits like Don't call something a Dialog one minute and a Popup the next. What top tips would you give for designing/documenting a GUI? It would be particularly useful to hear about widgets you designed to cram readable information into as little screen real-estate as possible. I'm going to roll this off with one of my own: avoid trees (e.g. Swing's JTree) unless you really can't avoid it, or have a unbounded hierarchy of stuff. I have found that users don't find them intuitive and they are hard to navigate and filter. PS. I think this question differs from this one as I'm asking for generalist tips

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• Merging code with dependencies? - Javascript

  - by RadiantHex

  Hi folks, this might be quite simple, but I must say I'm a bit confused on this topic. I'm writing code based on two popular libraries: jQuery underscore.js I am just wondering what would be the best way to isolate the code and prevent conflicts and how to merge it with its dependencies. By merging I mean putting them within the same file. :) I hope I'm not asking something which is too basic. ...and a last thing MERRY CHRISTMAS EVERYONE! =D

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• What do you do before starting on a project?

  - by hahuang65

  I'm still a pretty new project, and I haven't really worked on any large projects yet. However a few projects for school has shown me something I have never really thought of before. Pre-Project planning. One project we ran into a huge problem at the very last minute, and the other project was not divided up between partners very evenly, such that all the work was actually done at the end. So my question to everyone here is: How do you plan out the project beforehand? Please try to cover the following: Design (draw out UI by hand, UMLs, etc.) Division of Labor Timeline (especially how you estimate how much time is needed for certain things) and anything else you can think of. Thanks for all the help!

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• Parallel.For Batching

  - by chibacity

  Is there built-in support in the TPL for batching operations? I was recently playing with a routine to carry out character replacement on a character array which required a lookup table i.e. transliteration: for (int i = 0; i < chars.Length; i++) { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } } I could see that this could be trivially parallelized, so jumped in with a first stab which I knew would perform worse as the tasks were too fine-grained: Parallel.For(0, chars.Length, i => { char replaceChar; if (lookup.TryGetValue(chars[i], out replaceChar)) { chars[i] = replaceChar; } }); I then reworked the algorithm to use batching so that the work could be chunked onto different threads in less fine-grained batches. This made use of threads as expected and I got some near linear speed up. I'm sure that there must be built-in support for batching in the TPL. What is the syntax, and how do I use it? const int CharBatch = 100; int charLen = chars.Length; Parallel.For(0, ((charLen / CharBatch) + 1), i => { int batchUpper = ((i + 1) * CharBatch); for (int j = i * CharBatch; j < batchUpper && j < charLen; j++) { char replaceChar; if (lookup.TryGetValue(chars[j], out replaceChar)) { chars[j] = replaceChar; } } });

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• Read whole ASCII file into C++ std::string

  - by Arrieta

  Hello, I need to read a whole file into memory and place it in a C++ std::string. If I were to read it into a char, the answer would be very simple: std::ifstream t; int lenght; t.open("file.txt", "r"); // open input file t.seekg(0, std::ios::end); // go to the end length = t.tellg(); // report location (this is the lenght) t.seekg(0, std::ios::beg); // go back to the beginning buffer = new char[length]; // allocate memory for a buffer of appropriate dimension t.read(buffer, length); // read the whole file into the buffer t.close(); // close file handle // ... do stuff with buffer here ... Now, I want to do the exact same thing, but using a std::string instead of a char. I want to avoid loops, i. e., I don't want to: std::ifstream t; t.open("file.txt", "r"); std::string buffer; std::string line; while(t){ std::getline(t, line); // ... append line to buffer and go on } t.close() any ideas?

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• Problems installing PIL after OSX 10.9

  - by user2632417

  I installed Mac OSX 10.9 the day it came out. Afterwards I decided I needed to install PIL. I'd installed it before, but it appeared the update had broken that. When I try to use pip to install PIL, it fails when building _imaging. It appears the root cause is this. /usr/include/sys/cdefs.h:655:2: error: Unsupported architecture Theres also a similar error here: /usr/include/machine/limits.h:8:2: error: architecture not supported and here: /usr/include/machine/_types.h:34:2: error: architecture not supported Then there's a whole list of missing types. /usr/include/sys/_types.h:94:9: error: unknown type name '__int64_t' typedef __int64_t __darwin_blkcnt_t; /* total blocks */ ^ /usr/include/sys/_types.h:95:9: error: unknown type name '__int32_t' typedef __int32_t __darwin_blksize_t; /* preferred block size */ ^ /usr/include/sys/_types.h:96:9: error: unknown type name '__int32_t' typedef __int32_t __darwin_dev_t; /* dev_t */ ^ /usr/include/sys/_types.h:99:9: error: unknown type name '__uint32_t' typedef __uint32_t __darwin_gid_t; /* [???] process and group IDs */ ^ /usr/include/sys/_types.h:100:9: error: unknown type name '__uint32_t' typedef __uint32_t __darwin_id_t; /* [XSI] pid_t, uid_t, or gid_t*/ ^ /usr/include/sys/_types.h:101:9: error: unknown type name '__uint64_t' typedef __uint64_t __darwin_ino64_t; /* [???] Used for 64 bit inodes */ Needless to say I don't know where to go from here. I've got a couple of guesses, but I don't even know how to check. Wrong include probably as a result of a badly configured environment variable Problem with Xcode's installation/ missing command line tools Messed up header files If anyone has any suggestions either to check one of those possibilities or for one of their own I'm all ears.

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• Validation of textarea

  - by Hulk

  How to validate a textarea in a form.i.e, it should not be empty or have any new lines and if so raise an alert <script> function val() { //ifnewline found or blank raise an alert } </script> <form> <textarea name = "pt_text" rows = "8" cols = "8" class = "input" WRAP ></textarea> <input type=""button" onclick="val();" </form> Thanks

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• OOP App Architecture: Which layer does a lazy loader sit in?

  - by JW

  I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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• Which Hadoop API version should I use?

  - by Niels Basjes

  In the latest Hadoop Studio the 0.18 API of Hadoop is called "Stable" and the 0.20 API of Hadoop is called "Unstable". The distribution that comes from Yahoo is a 0.20 (with yahoo patches), which is apparently "the way to go". From cloudera they state the 0.20 (with cloudera patches) is also stable. Now given the fact that we'll start coding a new Hadoop project in the next few weeks; which API should we use and which Hadoop distribution (Apache, Cloudera, Yahoo, ...) should we use? Thanks for your insights.

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• Fitts Law, applying it to touch screens

  - by Caylem

  Been reading a lot into UI design lately and Fitts Law keeps popping up. Now from what i gather its basically the larger an item is, and the closer it is to your cursor, the easier it is to click on. So what about touch screen devices where the input comes from multiple touches or just single touches. What are the fundamentals to take into account considering this? Should it be something like, the hands of the user are on the sides of the device so the buttons should be close to the left and right hand sides of the device? Thanks

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• what is the event to handle row scrolling in EXTJS Gridpanel?

  - by user1480705

  I am displaying data in a GridPanel. My requirement is to hide some menu items based on the row selections. I have this perfectly working when a user clicks or rightclicks - i am handling the event for rowclick and rowcontextmenu respecitvely. But i am facing issue to locate the event - If the user first clicks on the row and them use up and down arrows to move on to other rows. Thanks in Advance

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• jQuery Drawing Plugin

  - by Ph.E

  Camarades, You'd know me identify good libraries (preferably in jQuery) to work with "Canvas" and drawings in javascript / html. I want to make my page more interesting, especially in some registries (registry of cars) and would like to draw a car and be able to go changing the number of wheels for example. Many thanks for any help. Success

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• Improve heavy work in a loop in multithreading

  - by xjaphx

  I have a little problem with my data processing. public void ParseDetails() { for (int i = 0; i < mListAppInfo.Count; ++i) { ParseOneDetail(i); } } For 300 records, it usually takes around 13-15 minutes. I've tried to improve by using Parallel.For() but it always stop at some point. public void ParseDetails() { Parallel.For(0, mListAppInfo.Count, i => ParseOneDetail(i)); } In method ParseOneDetail(int index), I set an output log for tracking the record id which is under processing. Always hang at some point, I don't know why.. ParseOneDetail(): 89 ... ParseOneDetail(): 90 ... ParseOneDetail(): 243 ... ParseOneDetail(): 92 ... ParseOneDetail(): 244 ... ParseOneDetail(): 93 ... ParseOneDetail(): 245 ... ParseOneDetail(): 247 ... ParseOneDetail(): 94 ... ParseOneDetail(): 248 ... ParseOneDetail(): 95 ... ParseOneDetail(): 99 ... ParseOneDetail(): 249 ... ParseOneDetail(): 100 ... _ <hang at this point> Appreciate your help and suggestions to improve this. Thank you! Edit 1: update for method: private void ParseOneDetail(int index) { Console.WriteLine("ParseOneDetail(): " + index + " ... "); ApplicationInfo appInfo = mListAppInfo[index]; var htmlWeb = new HtmlWeb(); var document = htmlWeb.Load(appInfo.AppAnnieURL); // get first one only HtmlNode nodeStoreURL = document.DocumentNode.SelectSingleNode(Constants.XPATH_FIRST); appInfo.StoreURL = nodeStoreURL.Attributes[Constants.HREF].Value; } Edit 2: This is the error output after a while running as Enigmativity suggest, ParseOneDetail(): 234 ... ParseOneDetail(): 87 ... ParseOneDetail(): 235 ... ParseOneDetail(): 236 ... ParseOneDetail(): 88 ... ParseOneDetail(): 238 ... ParseOneDetail(): 89 ... ParseOneDetail(): 90 ... ParseOneDetail(): 239 ... ParseOneDetail(): 92 ... Unhandled Exception: System.AggregateException: One or more errors occurred. --- > System.Net.WebException: The operation has timed out at System.Net.HttpWebRequest.GetResponse() at HtmlAgilityPack.HtmlWeb.Get(Uri uri, String method, String path, HtmlDocum ent doc, IWebProxy proxy, ICredentials creds) in D:\Source\htmlagilitypack.new\T runk\HtmlAgilityPack\HtmlWeb.cs:line 1355 at HtmlAgilityPack.HtmlWeb.LoadUrl(Uri uri, String method, WebProxy proxy, Ne tworkCredential creds) in D:\Source\htmlagilitypack.new\Trunk\HtmlAgilityPack\Ht mlWeb.cs:line 1479 at HtmlAgilityPack.HtmlWeb.Load(String url, String method) in D:\Source\htmla gilitypack.new\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1103 at HtmlAgilityPack.HtmlWeb.Load(String url) in D:\Source\htmlagilitypack.new\ Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1061 at SimpleChartParser.AppAnnieParser.ParseOneDetail(ApplicationInfo appInfo) i n c:\users\nhn60\documents\visual studio 2010\Projects\FunToolPack\SimpleChartPa rser\AppAnnieParser.cs:line 90 at SimpleChartParser.AppAnnieParser.<ParseDetails>b__0(ApplicationInfo ai) in c:\users\nhn60\documents\visual studio 2010\Projects\FunToolPack\SimpleChartPar ser\AppAnnieParser.cs:line 80 at System.Threading.Tasks.Parallel.<>c__DisplayClass21`2.<ForEachWorker>b__17 (Int32 i) at System.Threading.Tasks.Parallel.<>c__DisplayClassf`1.<ForWorker>b__c() at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.InnerInvokeWithArg(Task childTask) at System.Threading.Tasks.Task.<>c__DisplayClass7.<ExecuteSelfReplicating>b__ 6(Object ) --- End of inner exception stack trace --- at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceled Exceptions) at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationTo ken cancellationToken) at System.Threading.Tasks.Parallel.ForWorker[TLocal](Int32 fromInclusive, Int 32 toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWit hState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](TSource[] ar ray, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Act ion`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithEveryt hing, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable` 1 source, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState , Action`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithE verything, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable`1 source, Act ion`1 body) at SimpleChartParser.AppAnnieParser.ParseDetails() in c:\users\nhn60\document s\visual studio 2010\Projects\FunToolPack\SimpleChartParser\AppAnnieParser.cs:li ne 80 at SimpleChartParser.Program.Main(String[] args) in c:\users\nhn60\documents\ visual studio 2010\Projects\FunToolPack\SimpleChartParser\Program.cs:line 15

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• What are some best practices for making sure your .NET code will scale well?

  - by billmaya

  Last week I interviewed for a position at a TripleA MMORPG game company here in NE. I didn't get the job but one of the areas that came up during the interview was the about the scalability of the code that you write and how it should be considered early on in the design of your architecture and classes. Sadly to say I've never thought very much about the scalability of the .NET code that I've written (I work with single user desktop and mobile applications and our major concerns are usually with device memory and rates of data transmission). I'm interested in learning more about writing code that scales up well so it can handle a wide range of remote users in a client server environment, specifically MMORPGs. Are there any books, web sites, best practices, etc. that could get me started researching this topic?

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• Designing constructors around type erasure in Java

  - by Internet Friend

  Yesterday, I was designing a Java class which I wanted to be initalized with Lists of various generic types: TheClass(List<String> list) { ... } TheClass(List<OtherType> list) { ... } This will not compile, as the constructors have the same erasure. I just went with factory methods differentiated by their names instead: public static TheClass createWithStrings(List<String> list) public static TheClass createWithOtherTypes(List<OtherType> list) This is less than optimal, as there isn't a single obvious location where all the different options for creating instances are available. I tried to search for better design ideas, but found surprisingly few results. What other patterns exist for designing around this problem?

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• DBTransactions between stateless calls using GUIDs

  - by Marty Trenouth

  I'm looking to add transactional support to my DB engine and providing to Abstract Transaction Handling down to passing in Guids with the DB Action Command. The DB engine would run similar to: private static Database DB; public static Dictionary<Guid,DBTransaction> Transactions = new ...() public static void DoDBAction(string cmdstring,List<Parameter> parameters,Guid TransactionGuid) { DBCommand cmd = BuildCommand(cmdstring,parameters); if(Transactions.ContainsKey(TransactionGuid)) cmd.Transaction = Transactions[TransactionGuid]; DB.ExecuteScalar(cmd); } public static BuildCommand(string cmd, List<Parameter> parameters) { // Create DB command from EntLib Database and assign parameters } public static Guid BeginTransaction() { // creates new Transaction adding it to "Transactions" and opens a new connection } public static Guid Commit(Guid g) { // Commits Transaction and removes it from "Transactions" and closes connection } public static Guid Rollback(Guid g) { // Rolls back Transaction and removes it from "Transactions" and closes connection } The Calling system would run similar to: Guid g try { g = DBEngine.BeginTransaction() DBEngine.DoDBAction(cmdstring1, parameters,g) // do some other stuff DBEngine.DoDBAction(cmdstring2, parameters2,g) // sit here and wait for a response from other item DBEngine.DoDBAction(cmdstring3, parameters3,g) DBEngine.Commit(g) } catch(Exception){ DBEngine.Rollback(g);} Does this interfere with .NET connection pooling (other than a connection be accidently left open)? Will EntLib keep the connection open until the commit or rollback?

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• Problem when use compiled .A with simulator mode

  - by Paska

  Hi all, i have a lib .a that run only in device mode. My sdk vers is 4.2 with xcode 3.2.x. In simulator, compile correctle with no warning and no errors, but in run mode (simulator) it crash with this error: Detected an attempt to call a symbol in system libraries that is not present on the iPhone: strtod$UNIX2003 called from function pj_init in image MyAPP. If you are encountering this problem running a simulator binary within gdb, make sure you 'set start-with-shell off' first Program received signal: “SIGABRT”. I try to clean, rebuild and set "set start-with-shell off" from terminal in this way: cd ~ echo '' >> .gdbinit echo 'set start-with-shell 0' >> .gdbinit Restarted all, but nothing. The problem don't wont to resolve! Is there any tag or property that i forgotted to set in the options? In other linker flag is there only "-ObjC". It's very important to solve this issue... any idea please? thanks, A EDIT: It's my lib, compiled in simulator mode! EDIT: It run only with Simulator 4.1. Don't work with iphone 4.0, 4.2 and ipad 3.2 (all simulator).

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• Is this class + constructor definition pattern overly redundant?

  - by Protector one

  I often come across a pattern similar to this: class Person { public string firstName, lastName; public Person(string firstName, string lastName) { this.firstName = firstName; this.lastName = lastName; } } This feels overly redundant (I imagine typing "firstName" once, instead of thrice could be enough…), but I can't think of a proper alternative. Any ideas? Maybe I just don't know about a certain design pattern I should be using here? Edit - I think I need to elaborate a little. I'm not asking how to make the example code "better", but rather, "shorter". In its current state, all member names appear 3 times (declaration, initialization, constructor arguments), and it feels rather redundant. So I'm wondering if there is a pattern (or semantic sugar) to get (roughly) the same behavior, but with less bloat. I apologize for being unclear initially.

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• How to reference SMF libraries when deploying on phone 7 (Release)

  - by aHaH

  Initially, at Visual Studio, I clicked debug instead of release to deploy my app on phone 7 device. No errors, works perfectly fine! Received multitude of errors that mention that some of the libraries don't seem to exist on the mobile phone. For example, extract from the entire list of errors include Warning 10 The referenced component 'Microsoft.SilverlightMediaFramework.Utilities' could not be found. Warning 3 Could not resolve this reference. Could not locate the assembly "Microsoft.SilverlightMediaFramework.Plugins". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. SLARToolKitWinPhoneSample In addition, im also using Slartookit to power up the AR capabilities. Deploying (Release) on the mobile prompts the following errors too. Error 11 The type or namespace name 'SLARToolKit' could not be found (are you missing a using directive or an assembly reference?) What should I do? Will updating the mobile solve this? Do I have to manually install? Or? Thanks

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• C++: Platform independent game lib?

  - by Martijn Courteaux

  Hi, I want to write a serious 2D game, and it would be nice if I have a version for Linux and one for Windows (and eventually OSX). Java is fantastic because it is platform independent. But Java is too slow to write a serious game. So, I thought to write it in C++. But C++ isn't very cross-platform friendly. I can find game libraries for Windows and libraries for Linux, but I'm searching one that I can use for both, by recompiling the source on a Windows platform and on a Linux platform. Are there engines for this or is this idea irrelevant? Isn't it that easy (recompiling)? Any advice and information about C++ libraries would be very very very appreciated!

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• Ubiquitous framework to target multiple smartphone OS?

  - by Fabian

  Is there already a ubiquitous/general framework to target multiple smartphone OS, i.e. like a QT for Android/iPhone/Symbian? Or would be technically too hard to write such a framework?

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