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• Cannot initialize non-const reference from convertible type

  - by Julien L.

  Hi, I cannot initialize a non-const reference to type T1 from a convertible type T2. However, I can with a const reference. long l; const long long &const_ref = l; // fine long long &ref = l; // error: invalid initialization of reference of // type 'long long int&' from expression of type // 'long int' Most problems I encountered were related to r-values that cannot be assigned to a non-const reference. This is not the case here -- can someone explain? Thanks.

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• PropelBundle database:create for postgres

  - by Karol85

  I've installed propel bundle for symfony2. my database configuration is: propel: dbal: driver: pgsql user: postgres password: postgres dsn: pgsql:host=localhost;port=5432;dbname=test_database options: {} attributes: {} When i wan to create this database from console (console propel: database:create) i have got strange error : Unable to open PDO connection [wrapped: SQLSTATE[08006] [7] FATAL: database "pgsql" does not exist. i created pgsql database on my localhost and everything was good. Database "test_database" was succesfull created. Can somebody explain me why i got this previous error? On mysql i've created database without any problems.

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• c++ builder TClientWinSocket simbol substitution

  - by Vlad

  I have the following problem. I have to send a text telegram over tcp/ip to a host device. Telegram should be terminated using 0x1A (CTRL-Z) character. But when I send it, host told me that there is a wrong symbol in the telegram. When I terminate a telegram with 32 (0x20) everything is ok. I look the transfered data using WireShark and I see that when I send 0x1A it is substituted with 0x16, when I send 32 (0x20) as a terminator it is somehow substituted with 0x1A. Can you explain it please. P.S. I am working on windows 7, using c++builder xe2. Thanks, Vladimir

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• Objective C for Windows

  - by Luther Baker

  What would be the best way to write Objective-C on the Windows platform? Cygwin and gcc? Is there a way I can somehow integrate this into Visual Studio? Along those lines - are there any suggestions as to how to link in and use the Windows SDK for something like this. Its a different beast but I know I can write assembly and link in the Windows DLLs giving me accessibility to those calls but I don't know how to do this without googling and getting piecemeal directions. Is anyone aware of a good online or book resource to do or explain these kinds of things?

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• Neural Network Basics

  - by Stat Onetwothree

  I'm a computer science student and for this years project, I need to create and apply a Genetic Algorithm to something. I think Neural Networks would be a good thing to apply it to, but I'm having trouble understanding them. I fully understand the concepts but none of the websites out there really explain the following which is blocking my understanding: How the decision is made for how many nodes there are. What the nodes actually represent and do. What part the weights and bias actually play in classification. Could someone please shed some light on this for me? Also, I'd really appreciate it if you have any similar ideas for what I could apply a GA to. Thanks very much! :)

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• Visual C++/CLI "An unhandled exception of type 'System.StackOverflowException' occurred in"

  - by JennyWong

  Hi, I have a game I am making, it is giving me this message... "An unhandled exception of type 'System.StackOverflowException' occurred in game.exe" To explain...I have a 2D array with 9 different opening moves and I am getting a random number to use as the array reference to retrieve the details needed for a move... you may get the same move again - but that's illegal. the move may be illegal for other reasons too So to try and fix this, I am calling the function again from within the function. The error occurs very randomly Is this bad practise to call a function from within itself? What would be a better way to randomly row from a 2D array, AND if it isn't accept to get another one.... Or better still, how can I retrieve a random LEGAL move?

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• Looking for an algorithm in vb.net or c# but I don't know it's name!

  - by Jules

  I'll do my best to explain what the algorithm is supposed to do: There's a class 'Recipe'. Each Recipe can include other Recipes but cannot include itself or any other Recipe that includes it. So, a simple example is we have just two Recipes A & B. If A adds B first, then later on B cannot add A because it will cause a loop. A more complicated example is: A,B,C (1) Recipe C Adds B (2) Recipe B Adds A (3) Recipe A attempts to add C, but can't because of the relationship. C - B - A. I can do this myself, I just wondered if this was a standard named algorithm and I could grab the optimal solution. Thanks

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• nodejs response speed and nginx

  - by user1502440

  I'm just started testing nodejs, and wanted to get some help in understanding following behavior: Example #1: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.end('foo'); }).listen(1001, '0.0.0.0'); Example #2: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.write('foo'); res.end('bar'); }).listen(1001, '0.0.0.0'); When testing response time in Chrome: example #1 - 6-10ms example #2 - 200-220ms But, if test both examples through nginx proxy_pass server{ listen 1011; location / { proxy_pass http://127.0.0.1:1001; } } i get this: example #1 - 4-8ms example #2 - 4-8ms I am not an expert on either nodejs or nginx, and asking if someone can explain this? nodejs - v.0.8.1 nginx - v.1.2.2

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• Initializing structs in C++

  - by Neil Butterworth

  As an addendum to this question, what is going on here: #include <string> using namespace std; struct A { string s; }; int main() { A a = {0}; } Obviously, you can't set a std::string to zero. Can someone provide an explanation (backed with references to the C++ Standard, please) about what is actually supposed to happen here? And then explain for example): int main() { A a = {42}; } Are either of these well-defined? Once again an embarrassing question for me - I always give my structs constructors, so the issue has never arisen before.

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• When to use Version Control?

  - by user156814

  I am a lone developer, developing Web Sites/Apps in PHP. I dont work with anybody, I use a framework so I dont create libraries for my apps (most of the time). I have read a lot about Version Control and its benefits, but I dont understand how it would benefit somebody like me. The biggest benefit I can see it having is that if I posted the code on a remote server I could work from anywhere on any computer, but I carry my laptop like I carry my phone so again I dont see much of a reason there. Can somebody please explain to me in a simple manner the reasons for going with a VCS, and give me some good free ones I should try? Are there any hidden benefits/scenarios that you can think of that may sway me in any direction one way or the other. Thanks

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• MongoDB map/reduce counts

  - by ibz

  The output from MongoDB's map/reduce includes something like 'counts': {'input': I, 'emit': E, 'output': O}. I thought I clearly understand what those mean, until I hit a weird case which I can't explain. According to my understanding, counts.input is the number of rows that match the condition (as specified in query). If so, how is it possible that the following two queries have different results? db.mycollection.find({MY_CONDITION}).count() db.mycollection.mapReduce(SOME_MAP, SOME_REDUCE, {'query': {MY_CONDITION}}).counts.input I thought the two should always give the same result, independent of the map and reduce functions, as long as the same condition is used.

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• Delays in .net app when connecting to oracle db using Oracle.DataAccess

  - by chris

  I have a .net desktop app that connects to an oracle database. At times, there are very noticable delays. I ran a trace on the code, and it was always in the DataReader.Read(). I turned on sql tracing, and found the following, which corresponds to the delays I'm seeing: (2128) [23-MAR-2010 13:00:07:310] nsprecv: reading from transport... (2128) [23-MAR-2010 13:00:07:310] nttrd: entry (2128) [23-MAR-2010 13:00:24:655] nttrd: socket 676 had bytes read=2047 (2128) [23-MAR-2010 13:00:24:655] nttrd: exit (2128) [23-MAR-2010 13:00:24:655] nsprecv: 2047 bytes from transport There's about a 14 second pause in there. I'm pretty sure that there's not a problem in the code, but not sure where to look at next. Is there anyone out there with experience with oracle trace that can explain what's going on?

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• The pros and cons of use JSON for WCF service

  - by brz dot net

  What are the pros and cons of the following 2 cases: Case I: Traditional way: Add service reference in project. Create object and Get data from service on server side and bind to asp.net grid. Case II: Update Service for JSON behavior. Add service reference in project. Call service from javascript to get data. Bind data to jquery grid. Which one is the best approach and why?(Not developer point of view) If there is another approach which is more optimized, please explain it.

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• How to use Git properly with XCode?

  - by rickharrison

  I have been an iphone developer for a while, and I have recently been including git in my workflow. I have used git settings found on http://shanesbrain.net/2008/7/9/using-xcode-with-git for my workflow so far. Those settings tell git to exclude *.pbxproj from merges? Is there a real reason for doing this? For example, when I add a file to the project and push to origin, my fellow developers will not have that file added to their xcode project when they pull. Then if one of them builds a release this file may not be included. Shouldn't I just let git handle the merges for the project file? Could someone please explain why or why not this file should be in merges and how to properly handle the situation when files are added to the project. Thanks.

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• Why isn't my Ruby object deleted when the last reference goes out of scope?

  - by Andrew Clegg

  Hi gurus, I've found a weird effect when trying to track down a memory leak in a Rails app. Can anyone explain what's going on here? Save this script as a plain Ruby script (Rails not necessary): class Fnord def to_s 'fnord' end end def test f = Fnord.new end test GC.start sleep 2 ObjectSpace.each_object do |o| puts o if o.is_a? Fnord end When I run this via ruby 1.8.7 (2009-06-12 patchlevel 174) [i486-linux] I get the following: bash $ ruby var_test fnord Although the variable f is out of scope, there are no other references to the single Fnord object, and I've garbage collected, the object still seems to exist. Is this a nefarious memory leak of some sort, or am I completely missing something about Ruby? Further, if I change the test method to this: def test f = Fnord.new f = nil end I get no output. But surely this should not change the semantics here? Many thanks!

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• Confused by this PHP Exception try..catch nesting

  - by Domenic

  Hello. I'm confused by the following code: class MyException extends Exception {} class AnotherException extends MyException {} class Foo { public function something() { print "throwing AnotherException\n"; throw new AnotherException(); } public function somethingElse() { print "throwing MyException\n"; throw new MyException(); } } $a = new Foo(); try { try { $a->something(); } catch(AnotherException $e) { print "caught AnotherException\n"; $a->somethingElse(); } catch(MyException $e) { print "caught MyException\n"; } } catch(Exception $e) { print "caught Exception\n"; } I would expect this to output: throwing AnotherException caught AnotherException throwing MyException caught MyException But instead it outputs: throwing AnotherException caught AnotherException throwing MyException caught Exception Could anyone explain why it "skips over" catch(MyException $e) ? Thanks.

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• How to find scrollable elements in DOM using XPath?

  - by ak.

  Basically I need to find all elements on the page that have a scrollbar (vertical or horizontal) How to tell if an element has a scrollbar and can actually be scrolled? I found this code snippet on jsperf. Is it possible to capture the logic behind the code into and XPath expression? Or are there any other ways to check for scrollbars? Added: Just to explain what I'm trying to do: I'm developing extension for Firefox. Basically it introduces Vim-style mouseless shortcuts (I know there is Vimperator and Pentadactyl...). One of the features I'd like to implement is to allow the use to select the container that's scrolled with j/k keys. That's why I need to discover all scrollable elements on any given random page.

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• Jsp declaration element

  - by Stardust

  <%! class father { static int s = 0; } %> <% father f1 = new father(); father f2 = new father(); f1.s++; out.println(f2.s); // It must print "1" %> When I run the file, I got this error. Can anybody explain? "The field s cannot be declared static; static fields can only be declared in static or top level types"

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• How to get the "#" symbol in the :id into the redirect_to method in Rails

  - by Matthias Günther

  Hello, this is a silly questions but I don't understand, why rails isn't evaluating my string as expected. Here is my problem: I want to redirect to an url in the form ~/:controller/index/#_76 redirect_to :action => "index", :id => '#_76' But I'm getting the url in the form: ~/:controller/index/%25_76 and so my anchor for linking to a certain place in the website isn't working. Can someone please explain me, why rails makes this rendering? I think this hase something to do with url encoding. Again thanks for your help, I'm learning every day a little bit more about rails :).

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• urllib alternative for iPhone

  - by Pr301

  hi, I am trying to create an iPhone application which in some point connects to the internet, fills an on-line form, fetches the resulting website, parses it and returns a string to the user. I want all this process to happen in the background. I know how to do this kind of things with python and urllib but in objc I can't find an alternative, from on-line search I found either sites that explain how to use webkit to retrieve webpages (I suppose this is for displaying them to the user) or how to parse an existing HTML file or string. Since I want the file to be retrieved from the internet and the whole process should be running in the background, neither of these solutions covers my needs.

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• Create DataGridView columns from Table values

  - by fireBand

  Hi, I am using data grid view to display items as excel spread sheet in VB.NET. I got a table named CostTypes with column names [CostTypeID, CostType] and values [1,External] and [2,Internal] (These are constant but more values can be added to table). I want to create columns with names of the values[External , Internal] in DataGridView. If I use databiding directly I get columns [CostTypeID,CostType] which is not what I am looking for. If some one could explain how to create columns at runtime in datagridview or how to retrieve data from data base using LINQ so that [External , Internal] turn out to be columns that would be great. Thanks in advance.

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• Question About Abstract Classes?

  - by IbrarMumtaz

  URL: Link (1) According to this wesbite .. you cannot implement Abstract classes but derive from them. This makes sense and I have read this many times. Like an interface, you cannot implement an instance of an abstract class, however you can implement methods, fields, and properties in the abstract class that can be used by the child class. But on MSDN URL: TextWriter CLass on MSDN TextWriter is an abstract class but it has two constructors defined ... and according to the MS 70-536 book, the following statement is valid: TextWriter tw = new File.CreateText("myFile.Txt") The static file class and it's CreateText method is fine by me as I have studied it on MSDN but can somebody explain this little contradiction I have found? Surely I am not the first? Why is instantaion of base abstract classes possible????

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• Kernel thread exit in linux

  - by Raffo

  Hi guys, I'm here to ask you the difference between a process and a thread in linux. I know that a thread for linux is just a "task", which shares with the father process things that they need to have in common (the address space and other important informations). I also know that the two are creating calling the same function ('clone()'), but there's still something that I'm missing: what really happens when a thread exit? What function is called inside the linux kernel? I know that when a process exits calls the do_exit function, but here or somewhere else there should be a way to understand if it is just a thread exiting or a whole process. Can you explain me this thing or redirect to some textbook?? I tried 'Understanding the linux kernel' but I was not satisfied with it. I'm asking this thing because a need to add things to the task_struct struct, but I need to discriminate how to manage those informations for a process and its children. Thank you.

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• Javascript array length incorrect on array of objects

  - by Serenti

  Could someone explain this (strange) behavior? Why is the length in the first example 3 and not 2, and most importantly, why is the length in the second example 0? As long as the keys are numerical, length works. When they are not, length is 0. How can I get the correct length from the second example? Thank you. a = []; a["1"] = {"string1":"string","string2":"string"}; a["2"] = {"string1":"string","string2":"string"}; alert(a.length); // returns 3 b = []; b["key1"] = {"string1":"string","string2":"string"}; b["key2"] = {"string1":"string","string2":"string"}; alert(b.length); // returns 0

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• I have a problem with the following Java code

  - by Sanjeev

  public class b { public static void main(String[] args) { byte b = 1; long l = 127; // b = b + l; // 1 if I try this then it does not compile b += l; // 2 if I try this then it does compile System.out.println(b); } } I am using this code but I have problem: I don't understand why b=b+l; is not compiling but if I write b+=l; then it compiles and runs. Please explain why this happens.

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