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• I would like to learn C++, what is the first step ?

  - by Cesar

  My actual experience comes from PHP and Delphi(Borland) and recently also from Obj-C (iPhone sdk). In the past I also used Java, Python, VB 6 and some other scripting language. I would like to learn C++ because i need a standard tool for write compiled applications with good performance but i have no idea about witch environment i have to choose (Ex: Borland, Microsoft, Eclipse+MinGW, ...). Based those parameters: Most useful more opensource project or work requests Most standard not a proprietary versions Biggest community documentation, manuals, tutorials, forums... Better IDE add-ons, highlight, debug, cross platform, autocomplete... Easy setup A simple setup, to focus on learning the basics Actually I'm on OSX but I can use a VM if needed. Advices about tutorial or books are welcome. I hope it's not too generic as question.

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• Qt and finding partial matches in a QList

  - by ExpatEgghead

  I have a struct viz: struct NameKey { std::string fullName; std::string probeName; std::string format; std::string source; } which are held in a QList: QList<NameKey> keyList; what I need to do is find an occurence in keyList of a partial match where the search is for a NameKey that only has two members filled. All the keyList entries are full NameKey's. My current implementation is , well, boring in the extreme with too many if's and conditions. So, If I have a DataKey with a fullName and a format I need to find all the occurences in keyList which match. Any useful Qt/boost things available?

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• How to analyse Dalvik GC behaviour?

  - by HRJ

  I am developing an application on Android. It is a long running application that continuously processes sensor data. While running the application I see a lot of GC messages in the logcat; about one every second. This is most probably because of objects being created and immediately de-referenced in a loop. How do I find which objects are being created and released immediately? All the java heap analysis tools that I have tried(*) are bothered with the counts and sizes of objects on the heap. While they are useful, I am more interested in finding out the site where temporary short-lived objects get created the most. (*) I tried jcat and Eclipse MAT. I couldn't get hat to work on the Android heap-dumps; it complained of an unsupported dump file version.

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• Java - understanding servlets

  - by Trup

  I am working on a homework project that should implement a board game between 2 clients over an HttpServlet. I have couple of questions: 1) I read that HttpServlets must be stateless, however, for the sake of the game, I have to keep a lot of state(whose turn it is, the state of the board, etc). Do I have to keep this in the clients? Does the HttpServlet indeed have to be stateless, i.e. have no fields that track state? 2) I know that the clients will talk to the servlet via the doGet/doPost methods, but how can the servlet talk to the clients(for example, if player 1 just made a move and sent it to the servlet, the servlet has to tell client 2 what the move was). Thank you Also, if you can point me to a useful, simple example of a similar code online, I would be very grateful

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• What are the things Java got right?

  - by hamletdarcy

  What are the things that Java (the language and platform) got categorically right? In other words, what things are more recent programming languages preserving and carrying forward? Some easy answer are: garbage collection, a VM, lack of pointers, classloaders, reflection(?) What about language based answers? Please don't list the things Java did wrong, just right. (note by Mark Harrison) This is an interesting and useful question, especially for those of us who don't use java regularly. I'm voting for reopening. Please don't close as argumentative, as it doesn't seem to be causing any arguments.

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• Why are C, C++, and LISP so prevalent in embedded devices and robots?

  - by David

  It seems that the software language skills most sought for embedded devices and robots are C, C++, and LISP. Why haven't more recent languages made inroads into these applications? For example, Erlang would seem particularly well-suited to robotic applications, since it makes concurrent programming easier and allows hot swapping of code. Python would seem to be useful, if for no other reason than its support of multiple programming paradigms. I'm even surprised that Java hasn't made a foray into general robotic programming. I'm sure one argument would be, "Some newer languages are interpreted, not compiled" - implying that compiled languages are quicker and use fewer computational resources. Is this still the case, in a time when we can put a Java Virtual Machine on a cell phone or a SunSpot? (and isn't LISP interpreted anyway?)

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• MySQL Full Text Search Boolean Mode Partial Match

  - by Rob

  I've found boolean mode of MySQL full text search useful, however there are a couple of things I can't seem to figure out how to achieve. For instance imagine I have a full text column containing the words "Steve's Javascript Tutorial - Part One". I would like to match this for each of the following searches: "tutorials", "javascript tutorials", "java", "java script", "script" Imagine that each of those searches is simply assigned to a variable in whatever language may be being used (I always use PHP). How could I modify this to make sure that Steve's article is returned on each of those searches? MATCH (article_title) AGAINST ('"+$variable+"*' IN BOOLEAN MODE)

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• What is the most under-valued part of .NET?

  - by Jan Bannister

  The .NET framework is massive. I've used it for years and I've still not used most of it. I'd like to expand my knowledge of the Framework's backwaters but just reading thought it seems daunting. So I thought I'd tap up the Stack Overflow community first. What part have you found to be the most surprisingly useful? What's your favourite obscure namespace? And conversely are there any shiny bits that are best avoided?

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• How to hash and check for equality of objects with circular references

  - by mfya

  I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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• SimpleDB direct client access

  - by AlexJReid

  One of the useful things about S3 for content storage is that a client can directly make a direct HTTP request to download the object. For instance, this is how Twitter serve up avatar images. SimpleDB provides an HTTP interface to data. Rather than having to write a proxy that sits inbetween SimpleDB and the client, is it possible for client software (i.e. desktop, mobile) to make calls to read values from a SimpleDB domain, without sharing credentials that shouldn't be shared? Or is a proxy in-between the only way to go?

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• Best approach to creating a database driven Java website?

  - by Craig Whitley

  I'm fairly new to programming and new to java, but I'd like to jump in the deep end with a little database driven website project. I've read quite a lot about requirements in the 'real world' requesting experience with Spring and Hibernate, so I have those installed on netbeans and a project created (if I hit run I get the default spring page). Now I just need a little guidance as to where to start designing my app (please tell me if I'm getting in a bit too over my head for a beginner!). Should I start off with my classes? - create all my classes as they map to my database tables and decide which attributes and methods each will require? Can anyone suggest any good books for maybe.. making a java based website from scratch (i.e. from design right through to deployment) that might be useful for a beginner? Any help appreciated thanks.

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• How to solve this Java type safety warning? (Struts2)

  - by Nicolas Raoul

  Map session = ActionContext.getContext().getSession(); session.put("user", user); This code generates a warning: Type safety: The method put(Object, Object) belongs to the raw type Map. References to generic type Map should be parameterized. Map<String, Serializable> session = (Map<String, Serializable>)ActionContext.getContext().getSession(); session.put("user", user); This code generates a warning: Type safety: Unchecked cast from Map to Map. The getSession method belongs to Struts2 so I can't modify it. I would like to avoid using @SuppressWarnings because other warnings can be useful. I guess all Struts2 users in the world faced the same problem... is there an elegant solution?

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• Check if NFS share is mounted in python script

  - by Fabian

  I wrote a python script that depends on a certain NFS share to be available. If the NFS share is not mounted it will happily copy the files to the local path where it should be mounted, but fail later when it tries to copy some files back that were created on the NFS server. I'd like to catch this error specifically so I can print a useful error message that will tell the users of this script what they have to do. My first idea would be to execute mount using subprocess and then check the output for this nfs share. But I'm wondering if there isn't a nicer and more robust method of doing it.

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• Which Java MVC frameworks integrate easily with StringTemplate?

  - by Daniel Jomphe

  It's hard to see how StringTemplate integrates easily (or not) with popular Java web MVC frameworks. Which Java MVC frameworks integrate easily with StringTemplate? A good answer: mentions one solution to integrate with a framework, includes a link to something useful and applicable, like: a tutorial, or documentation, or a reference to source code: free, and open source or public domain. Readers/Voters, please vote for a solution if you know it's true and great. In the scope of this question, I am not interested in any other templating engine than StringTemplate.

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• For anyone with free time: Trying to learn how to replace PHP with Python, failing terribly.

  - by MALON

  I want give web development using Python a shot, but I'm failing hard. I don't even know if I CAN run Python. The webpage for my web host says it supports all kinds of stuff, including Python. I've never touched anything CGI related and this does not appear to be a noob friendly area. Below is all the information I could think of that might be useful: Shared host: Yes Webhost: dibbsonhosting.com Server OS: linux Python installed: Yes (or so says the webhost) mod_python installed: Don't Know WSGI installed: Don't Know Access to http.conf: No Terminal access: No Cpanel: Yes FTP: Yes Django: downloaded latest stable release, not uploaded anywhere, not sure where to put it. DB: MySQL 5.x I really want to use Python for web development! Thanks!

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• How to unregister a specific hotkey using c#

  - by srk

  I am using the below code to register a HotKey : RegisterGlobalHotKey(Keys.F4, USE_ALT); private void RegisterGlobalHotKey(Keys hotkey, int modifiers) { try { // increment the hot key value - we are just identifying // them with a sequential number since we have multiples mHotKeyId++; if (mHotKeyId > 0) { // register the hot key combination if (RegisterHotKey(this.Handle, mHotKeyId, modifiers, Convert.ToInt16(hotkey)) == 0) { // tell the user which combination failed to register - // this is useful to you, not an end user; the end user // should never see this application run MessageBox.Show("Error: " + mHotKeyId.ToString() + " - " + Marshal.GetLastWin32Error().ToString(), "Hot Key Registration"); } } } catch { // clean up if hotkey registration failed - // nothing works if it fails UnregisterGlobalHotKey(); } } private void UnregisterGlobalHotKey() { // loop through each hotkey id and // disable it for (int i = 0; i < mHotKeyId; i++) { UnregisterHotKey(this.Handle, i); } } How can i unregister the Hot key and Make Alt+ F4 keep working again ?

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• Hidden Features of Google Guice

  - by Jon

  Google Guice provides some great dependency injection features. I came across the @Nullable feature recently which allows you to mark constructor arguments as optional (permitting null) since Guice does not permit these by default: e.g. public Person(String firstName, String lastName, @Nullable Phone phone) { this.firstName = checkNotNull(firstName, "firstName"); this.lastName = checkNotNull(lastName, "lastName"); this.phone = phone; } http://code.google.com/p/google-guice/wiki/UseNullable What are the other useful features of Guice (particularly the less obvious ones) that people use?

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• Given a document select a relevant snippet.

  - by BCS

  When I ask a question here, the tool tips for the question returned by the auto search given the first little bit of the question, but a decent percentage of them don't give any text that is any more useful for understanding the question than the title. Does anyone have an idea about how to make a filter to trim out useless bits of a question? My first idea is to trim any leading sentences that contain only words in some list (for instance, stop words, plus words from the title, plus words from the SO corpus that have very weak correlation with tags, that is that are equally likely to occur in any question regardless of it's tags)

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• Does any method exist quickly to detect valid range versions of used library

  - by daneel-yaitskov

  I'm a beginner Haskell programmer. I have written some useful code for the last six month. And I want to release a library from it. The code will use system installation cabal as any Haskell library. A library is released with cabal has a meta data file where there is a logical predicate from the libraries and their versions. A developer usually uses one set libraries. It tediously care a set of the sets libraries. How to know either my library is compiled successfully or not for some subset libraries?

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• Calculating the null space of a matrix

  - by Ainsworth

  I'm attempting to solve a set of equations of the form Ax = 0. A is known 6x6 matrix and I've written the below code using SVD to get the vector x which works to a certain extent. The answer is approximately correct but not good enough to be useful to me, how can I improve the precision of the calculation? Lowering eps below 1.e-4 causes the function to fail. from numpy.linalg import * from numpy import * A = matrix([[0.624010149127497 ,0.020915658603923 ,0.838082638087629 ,62.0778180312547 ,-0.336 ,0], [0.669649399820597 ,0.344105317421833 ,0.0543868015800246 ,49.0194290212841 ,-0.267 ,0], [0.473153758252885 ,0.366893577716959 ,0.924972565581684 ,186.071352614705 ,-1 ,0], [0.0759305208803158 ,0.356365401030535 ,0.126682113674883 ,175.292109352674 ,0 ,-5.201], [0.91160934274653 ,0.32447818779582 ,0.741382053883291 ,0.11536775372698 ,0 ,-0.034], [0.480860406786873 ,0.903499596111067 ,0.542581424762866 ,32.782593418975 ,0 ,-1]]) def null(A, eps=1e-3): u,s,vh = svd(A,full_matrices=1,compute_uv=1) null_space = compress(s <= eps, vh, axis=0) return null_space.T NS = null(A) print "Null space equals ",NS,"\n" print dot(A,NS)

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• Do you bother to write a pretty error page?

  - by Chacha102

  So, everyone is really used to the errors that PHP gives you. They look kind of like this: Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 2 bytes) in /path/to/file(437) on line 21 My question is, do you put in the time to make your error pages more useful? I find that I am able to debug a lot faster using my own error page: I find this to be a lot better than the PHP errors because it gives me a stack trace, the usual error message, along with the actual location of the error, and more. Also, are there any downsides from creating your own development error pages. Obviously you wouldn't want to have a user see this page, but what about during development?

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• Installing WindowBuilder on Eclipse 4.2

  - by WChargin

  I'm using Eclipse Juno 4.2, downloaded from here. On previous installs, I've been using 3.7, and I've been using WindowBuilder, which I find very useful. I noticed it wasn't included this time, so I used this update site provided on this page (the zip file download gives a "file unavailable" error). However, when I run the install, it rapidly climbs to 28%, then freezes. After half an hour, I get a very long error that start with this: An error occurred while collecting items to be installed session context was:(profile=epp.package.java, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=). Multiple problems occurred while downloading. Unable to read repository at http://download.eclipse.org/windowbuilder/WB/integration/4.2/plugins/org.eclipse.wb.core_1.5.0.r42x201205291332.jar.pack.gz. (full text) Does anyone know how I can go about installing it?

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• How will ASP.NET AJAX be licensed?

  - by hbb

  It would be very useful if somebody could indicate what the plans are for releasing and licensing the AJAX extensions. The EULA for Beta 2 states that the software may be used for development and for web site deployment only. Redistribution is explicitly forbidden. Does that imply that it is going to be released under terms different from the .NET framework and ASP.NET or is it just a precaution to prevent developers shipping the Beta? It seems too risky to include AJAX in new products before there is some indication what the model is going to be....

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• How to minimize the amount of place used by GPL copyright notice?

  - by Lukasz Lew

  Gnu GPL page advocates a following header in each file of GPL project: This file is part of Foobar. Foobar is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. Foobar is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Foobar. If not, see http://www.gnu.org/licenses/. I find this an over kill. Can't it be shorter and somehow refer to COPYING or LICENCE file?

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• Vim and clang_complete, how to explicitly compile my code

  - by puller

  I use Vim with clang_complete for omnicompletion. The plugin is automatically triggered when I need completion, e.g., after I type . or -> to access an object members or methods (see attached screenshot). The plugin works really nice, however I would need a way to trigger it manually (i.e. to compile my code for syntax checking). This is useful for two reasons: Static syntax checking Clear previous errors which have been fixed (which otherwise will remain in their buffer). See the two screenshots below for a better understanding. Any help is appreciated. Thanks. Screenshot 1 Screenshot 2

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