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• SPRING: How do you programmatically instantiate classes based on information passed from Flex UI

  - by babyangel86

  Imagine the UI passes back an XMl node as such: <properties> <type> Source </type> <name> Blooper </name> <delay> <type> Deterministic </type> <parameters> <param> 4 </param> </parameters> <delay> <batch> <type> Erlang </type> <parameters> <param> 4 </param> <param> 6 </param> </parameters> <batch> And behind the scene what it is asking that you instantiate a class as such: new Source("blooper", new Exp(4), new Erlang(4,6); The problem lies in the fact that you don't know what class you will need to processing, and you will be sent a list of these class definitions with instructions on how they can be linked to each other. I've heard that using a BeanFactoryPostProcessor might be helpful, or a property editor/convertor. However I am at a loss as to how best to use them to solve my problem. Any help you can provide will be much appreciated.

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• Visual Studio project remains "stuck" when stopped

  - by Traveling Tech Guy

  Hi, Currently developing a connector DLL to HP's Quality Center. I'm using their (insert expelative) COM API to connect to the server. An Interop wrapper gets created automatically by VStudio. My solution has 2 projects: the DLL and a tester application - essentially a form with buttons that call functions in the DLL. Everything works well - I can create defects, update them and delete them. When I close the main form, the application stops nicely. But when I call a function that returns a list of all available projects (to fill a combo box), if I close the main form, VStudio still shows the solution as running and I have to stop it. I've managed to pinpoint a single function in my code that when I call, the solution remains "hung" and if I don't, it closes well. It's a call to a property in the TDC object get_VisibleProjects that returns a List (not the .Net one, but a type in the COM library) - I just iterate over it and return a proper list (that I later use to fill the combo box): public List<string> GetAvailableProjects() { List<string> projects = new List<string>(); foreach (string project in this.tdc.get_VisibleProjects(qcDomain)) { projects.Add(project); } return projects; } My assumption is that something gets retained in memory. If I run the EXE outside of VStudio it closes - but who knows what gets left behind in memory? My question is - how do I get rid of whatever calling this property returns? Shouldn't the GC handle this? Do I need to delve into pointers? Things I've tried: getting the list into a variable and setting it to null at the end of the function Adding a destructor to the class and nulling the tdc object Stepping through the tester function application all the way out, whne the form closes and the Main function ends - it closes, but VStudio still shows I'm running. Thanks for your assistance!

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• How safe and reliable are C++ String Literals?

  - by DoctorT

  So, I'm wanting to get a better grasp on how string literals in C++ work. I'm mostly concerned with situations where you're assigning the address of a string literal to a pointer, and passing it around. For example: char* advice = "Don't stick your hands in the toaster."; Now lets say I just pass this string around by copying pointers for the duration of the program. Sure, it's probably not a good idea, but I'm curious what would actually be going on behind the scenes. For another example, let's say we make a function that returns a string literal: char* foo() { // function does does stuff return "Yikes!"; // somebody's feeble attempt at an error message } Now lets say this function is called very often, and the string literal is only used about half the time it's called: // situation #1: it's just randomly called without heed to the return value foo(); // situation #2: the returned string is kept and used for who knows how long char* retVal = foo(); In the first situation, what's actually happening? Is the string just created but not used, and never deallocated? In the second situation, is the string going to be maintained as long as the user finds need for it? What happens when it isn't needed anymore... will that memory be freed up then (assuming nothing points to that space anymore)? Don't get me wrong, I'm not planning on using string literals like this. I'm planning on using a container to keep my strings in check (probably std::string). I'm mostly just wanting to know if these situations could cause problems either for memory management or corrupted data.

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• Is the REST support in Spring 3's MVC Framework production quality yet?

  - by glenjohnson

  Hi all, Since Spring 3 was released in December last year, I have been trying out the new REST features in the MVC framework for a small commercial project involving implementing a few RESTful Web Services which consume XML and return XML views using JiBX. I plan to use either Hibernate or JDBC Templates for the data persistence. As a Spring 2.0 developer, I have found Spring 3's (and 2.5's) new annotations way of doing things quite a paradigm shift and have personally found some of the new MVC annotation features difficult to get up to speed with for non-trivial applications - as such, I am often having to dig for information in forums and blogs that is not apparent from going through the reference guide or from the various Spring 3 REST examples on the web. For deadline-driven production quality and mission critical applications implementing a RESTful architecture, should I be holding off from Spring 3 and rather be using mature JSR 311 (JAX-RS) compliant frameworks like RESTlet or Jersey for the REST layer of my code (together with Spring 2 / 2.5 to tie things together)? I had no problems using RESTlet 1.x in a previous project and it was quite easy to get up to speed with (no magic tricks behind the scenes), but when starting my current project it initially looked like the new REST stuff in Spring 3's MVC Framework would make life easier. Do any of you out there have any advice to give on this? Does anyone know of any commercial / production-quality projects using, or having successfully delivered with, the new REST stuff in Spring 3's MVC Framework. Many thanks Glen

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• JDBC call not executing

  - by dbyrne

  I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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• gluLookAt vectors and FPS-style camera

  - by Kevin Pamplona

  I am attempting to implemented an FPS-style camera by updating three vectors: EYE, DIR, UP. These vectors are the same that are used by gluLookAt (since gluLookAt is specified by the position of the camera, the direction it is looking at, and an up vector). I have already implemented the left-right and up-down strafing movements, but I'm having a lot of trouble understanding the math behind making the camera look-around while remaining stationary. In this case, the EYE vector remains the same, while I must update DIR and UP. Below is the code I tried, but it doesn't seem to work properly. Any suggestions? Thanks. void Transform::left(float degrees, vec3& dir, vec3& up) { vec3 axis; axis = glm::normalize(up); mat3 R = rotate(-degrees, axis); dir = R*dir; dir = R*up; }; void Transform::up(float degrees, vec3& dir, vec3& up) { vec3 axis; axis=glm::normalize(glm::cross(dir,up)); mat3 R = rotate(-degrees, axis); dir = R*dir-; up = R*up; };

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• How to implement a sharepoint lists webservice

  - by 1800 INFORMATION

  I want to implement a web-service that uses the same interface as the Lists web service in sharepoint. I do not want to run this through sharepoint. What is a good way to get started in this? I have tried to use the wsdl.exe tool to generate some wrapper classes but the generated wrappers seem to have punted on the structure parameters and just specified them as XML. For example below is the generated wrapper for GetList - it should return a structure which has the information in the list, but instead it is returning XML. What is going on? ... /// <remarks/> [System.CodeDom.Compiler.GeneratedCodeAttribute("wsdl", "2.0.50727.1432")] [System.Web.Services.WebServiceBindingAttribute(Name="ListsSoap", Namespace="http://schemas.microsoft.com/sharepoint/soap/")] public interface IListsSoap { /// <remarks/> [System.Web.Services.WebMethodAttribute()] [System.Web.Services.Protocols.SoapDocumentMethodAttribute("http://schemas.microsoft.com/sharepoint/soap/GetList", RequestNamespace="http://schemas.microsoft.com/sharepoint/soap/", ResponseNamespace="http://schemas.microsoft.com/sharepoint/soap/", Use=System.Web.Services.Description.SoapBindingUse.Literal, ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped)] System.Xml.XmlNode GetList(string listName); }

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• Boost Binary Endian parser not working?

  - by Hai

  I am studying how to use boost spirit Qi binary endian parser. I write a small test parser program according to here and basics examples, but it doesn't work proper. It gave me the msg:"Error:no match". Here is my code. #include "boost/spirit/include/qi.hpp" #include "boost/spirit/include/phoenix_core.hpp" #include "boost/spirit/include/phoenix_operator.hpp" #include "boost/spirit/include/qi_binary.hpp" // parsing binary data in various endianness template '<'typename P, typename T void binary_parser( char const* input, P const& endian_word_type, T& voxel, bool full_match = true) { using boost::spirit::qi::parse; char const* f(input); char const* l(f + strlen(f)); bool result1 = parse(f,l,endian_word_type,voxel); bool result2 =((!full_match) || (f ==l)); if ( result1 && result2) { //doing nothing, parsing data is pass to voxel alreay } else { std::cerr << "Error: not match!!" << std::endl; exit(1); } } typedef boost::uint16_t bs_int16; typedef boost::uint32_t bs_int32; int main ( int argc, char *argv[] ) { namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; using qi::big_word; using qi::big_dword; boost::uint32_t ui; float uf; binary_parser("\x01\x02\x03\x04",big_word,ui); assert(ui=0x01020304); binary_parser("\x01\x02\x03\x04",big_word,uf); assert(uf=0x01020304); return 0; }' I almost copy the example, but why this binary parser doesn't work. I use Mac OS 10.5.8 and gcc 4.01 compiler.

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• Install h5py in Mac OS X 10.6.3

  - by zyq524

  I'm trying to install h5py in Mac OS X 10.6.3. First I installed HDF5 1.8, which used the following commands: ./configure \ --prefix=/Library/Frameworks/Python.framework/Versions/Current \ --enable-shared \ --enable-production \ --enable-threadsafe \ CPPFLAGS=-I/Library/Frameworks/Python.framework/Versions/Current/include \ LDFLAGS=-L/Library/Frameworks/Python.framework/Versions/Current/lib make make check sudo make install Then install h5py: /Library/Frameworks/Python.framework/Versions/Current/bin/python \ setup.py \ build \ --api=18 \ --hdf5=/Library/Frameworks/Python.framework/Versions/Current Then I got the errors: Configure: Autodetecting HDF5 settings... Custom HDF5 dir: /Library/Frameworks/Python.framework/Versions/Current Custom API level: (1, 8) ld: warning: in detect/vers.o, file was built for unsupported file format which is not the architecture being linked (i386) ld: warning: in /Library/Frameworks/Python.framework/Versions/Current/lib/libhdf5.dylib, file was built for unsupported file format which is not the architecture being linked (i386) Undefined symbols: "_main", referenced from: start in crt1.10.5.o ld: symbol(s) not found collect2: ld returned 1 exit status Failed to compile HDF5 test program. Please check to make sure: * You have a C compiler installed * A development version of Python is installed (including header files) * A development version of HDF5 is installed (including header files) * If HDF5 is not in a default location, supply the argument --hdf5=<path> error: command 'cc' failed with exit status 1 I just updated my Xcode, I don't know whether this is because my gcc's default setting. If so, how can I get rid of this error? Thanks.

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• AssemblyResolve event is not firing during compilation of a dynamic assembly for an aspx page.

  - by John

  This one is really pissing me off. Here goes: My goal is to load assemblies at run-time that contain embedded aspx,ascx etc. What I would also like is to not lock the assembly file on disk so I can update it at run-time without having to restart the application (I know this will leave the previous version(s) loaded). To that end I have written a virtual path provider that does the trick. I have subscribed to the CurrentDomain.AssemblyResolve event so as to redirect the framework to my assemblies. The problem is that the when the framework tries to compile the dynamic assembly for the aspx page I get the following: Compiler Error Message: CS0400: The type or namespace name 'Pages' could not be found in the global namespace (are you missing an assembly reference?) Source Error: public class app_resource_pages__version_1_0_0_0__culture_neutral__publickeytoken_null_default_aspx : global::Pages._Default, System.Web.SessionState.IRequiresSessionState, System.Web.IHttpHandle I noticed that if I load the assembly with Assembly.Load(AssemblyName) or Assembly.LoadFrom(filename) I dont get the above error. If I load it with Assembly.Load(byte[]) (so as to not lock it), the exception is thrown but my AssemblyResolve handler, when called is returning the assembly correctly (it is called once). So I am guessing that it is called once when the framework parses the asp markup but not when it tries to create the dynamic assembly for the aspx page.

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• problem in working with thread

  - by Xaver

  Ihave the tree view in which i have file system of logical disk. When user select some files and folders and press button programm evaluate the size of selected files and folders. this function may takes a long time. i decide do thread which will run this function. This function works with array of TreeNode. but then i want to now was it node expaned or not compiler say: "attempt to access control "treeview1" not from the thread, in which it was created." Why it appeared? Next code is show how i create array of Nodes which i send to new thread: void frmMain::FillSelected(TreeNode^ a, array<TreeNode^>^ *Paths) { if (a->Parent == nullptr) { for(int j = 0;j < a->Nodes->Count;j++) { if ((a->Nodes[j]->ImageIndex == 1)&&(a->Nodes[j]->Checked==true)) { (*Paths)->Resize((*Paths), (*Paths)->Length + 1); (*Paths)[(*Paths)->Length-1] = a->Nodes[j]; } } } for(int i = 0;i < a->Nodes->Count;i++) { if (a->Parent == nullptr) { FillSelected(a->Nodes[i], Paths); } else { if(a->Nodes[i]->Checked == true) { (*Paths)->Resize((*Paths), (*Paths)->Length + 1); (*Paths)[(*Paths)->Length-1] = a->Nodes[i]; } if ((a->Nodes[i]->Nodes->Count > 0)&&(a->Nodes[i]->Nodes[0]->FullPath != (a->Nodes[i]->FullPath + "\\"))) { FillSelected(a->Nodes[i], Paths); } } } return; }

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• erlide, which eclipse/which packages?

  - by KevinDTimm

  I have downloaded eclipse 3.4 (java version) for MacOSX (carbon). I have tried to 'update' to the erlide, but see many (duplicated) options (many erlide, options that say 'only for erl SDK updates', etc.) Sometimes I get 403 errors when attempting to access http://erlide.org/update and http://erlide.sourceforge.net/update. Finally, when I get some set of options installed, I either get errors like : Loading of /Users/kevindtimm/Documents/eclipse-java-ganymede-SR2-macosx-carbon/eclipse/plugins/org.erlide.kernel.common_0.8.1.201005250801/ebin/erlide_kernel_common.beam failed: badfile (hello_world@ktmac)1> =ERROR REPORT==== 24-Nov-2010::19:17:32 === beam/beam_load.c(1768): Error loading function erlide_kernel_common:monitor/0: op put_string u u x: please re-compile this module with an R14B compiler or, when I've done different installations of erlide, I get no response in the console to : hello:hello(). Does anybody have a good reference for how to load this plug-in and which items I should install? -module(hello). -export([hello/0]). hello() -> io:write("Hello World\n"). [edit] I have installed eclipse 3.6 (c++) as requested below, and the following code still can't find hello:hello(). %%file_comment -module(hello). %% %% Include files %% %% %% Exported Functions %% -export([hello/0]). %% %% API Functions %% %% %% Local Functions %% hello() -> io:write("Hello World\n"). [/edit]

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• Problem with Boost::Asio for C++

  - by Martin Lauridsen

  Hi there, For my bachelors thesis, I am implementing a distributed version of an algorithm for factoring large integers (finding the prime factorisation). This has applications in e.g. security of the RSA cryptosystem. My vision is, that clients (linux or windows) will download an application and compute some numbers (these are independant, thus suited for parallelization). The numbers (not found very often), will be sent to a master server, to collect these numbers. Once enough numbers have been collected by the master server, it will do the rest of the computation, which cannot be easily parallelized. Anyhow, to the technicalities. I was thinking to use Boost::Asio to do a socket client/server implementation, for the clients communication with the master server. Since I want to compile for both linux and windows, I thought windows would be as good a place to start as any. So I downloaded the Boost library and compiled it, as it said on the Boost Getting Started page: bootstrap .\bjam It all compiled just fine. Then I try to compile one of the tutorial examples, client.cpp, from Asio, found (here.. edit: cant post link because of restrictions). I am using the Visual C++ compiler from Microsoft Visual Studio 2008, like this: cl /EHsc /I D:\Downloads\boost_1_42_0 client.cpp But I get this error: /out:client.exe client.obj LINK : fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-s-1_42.lib' Anyone have any idea what could be wrong, or how I could move forward? I have been trying pretty much all week, to get a simple client/server socket program for c++ working, but with no luck. Serious frustration kicking in. Thank you in advance.

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• Encapsulating user input of data for a class (C++)

  - by Dr. Monkey

  For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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• is using private shared objects/variables on class level harmful ?

  - by haansi

  Hello, Thanks for your attention and time. I need your opinion on an basic architectural issue please. In page behind classes I am using a private and shared object and variables (list or just client or simplay int id) to temporary hold data coming from database or class library. This object is used temporarily to catch data and than to return, pass to some function or binding a control. 1st: Can this approach harm any way ? I couldn't analyze it but a thought was using such shared variables may replace data in it when multiple users may be sending request at a time? 2nd: Please comment also on using such variables in BLL (to hold data coming from DAL/database). In this example every time new object of BLL class will be made. Here is sample code: public class ClientManager { Client objclient = new Client(); //Used in 1st and 2nd method List<Client> clientlist = new List<Client>();// used in 3rd and 4th method ClientRepository objclientRep = new ClientRepository(); public List<Client> GetClients() { return clientlist = objclientRep.GetClients(); } public List<Client> SearchClients(string Keyword) { return clientlist = objclientRep.SearchClients(Keyword); } public Client GetaClient(int ClientId) { return objclient = objclientRep.GetaClient(ClientId); } public Client GetClientDetailForConfirmOrder(int UserId) { return objclientRep.GetClientDetailForConfirmOrder(UserId); } } I am really thankful to you for sparing time and paying kind attention.

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• ASP Dot Net : How to repeat HTML parts with minor differences on a page?

  - by tinky05

  It's a really simple problem. I've got HTML code like this : <div> <img src="image1.jpg" alt="test1" /> </div> <div> <img src="image2.jpg" alt="test2" /> </div> <div> <img src="image3.jpg" alt="test3" /> </div> etc... The data is comming from a DB (image name, alt text). In JAVA, I would do something like : save the info in array in the back end. For the presentation I would loop through it with JSTL : <c:foeach items="${data}" var="${item}> <div> <img src="${item.image}" alt="${item.alt}" /> </div> </c:foreach> What's the best practice in ASP.net I just don't want to create a string with HTML code in it in the "code behind", it's ugly IMO.

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• VB.NET trying simple captcha

  - by Pride Grimm

  I'm trying to write a simple captcha program in vb.net. I'm just wanting to make an image from random numbers and display it, check the answer, and then proceed. I'm pretty new to vb.net, so I found some code to generate the information. I will cite the owner when I find it again (http://www.knowlegezone.com/80/article/Technology/Software/Asp-Net/Simple-ASP-NET-CAPTCHA-Tutorial) This is in the onload() of default2.aspx Public Sub returnNumer() Dim num1 As New Random Dim num2 As New Random Dim numQ1 As Integer Dim numQ2 As Integer Dim QString As String numQ1 = num1.Next(10, 15) numQ2 = num2.Next(17, 31) QString = numQ1.ToString + " + " + numQ2.ToString + " = " Session("answer") = numQ1 + numQ2 Dim bitmap As New Bitmap(85, 35) Dim Grfx As Graphics = Graphics.FromImage(bitmap) Dim font As New Font("Arial", 18, FontStyle.Bold, GraphicsUnit.Pixel) Dim Rect As New Rectangle(0, 0, 100, 50) Grfx.FillRectangle(Brushes.Brown, Rect) Grfx.DrawRectangle(Pens.PeachPuff, Rect) ' Border Grfx.DrawString(QString, font, Brushes.Azure, 0, 0) Response.ContentType = "Image/jpeg" bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg) bitmap.Dispose() Grfx.Dispose() End Sub So I put this in a separate page, like this This all works find and dandy, but when I get the answer from the session like this Dim literal As String = Convert.ToString(Session("answer")) It's always one behind. So if The images adds to 32, the answer in session isn't 32. But after a refresh (and a new image) the session("answer") will be 32. Is there a way to refresh the session on page 1, after the default2.aspx loads? Is there a better way to do this? I though about trying to run the code all on one page, and trying to set the src of and image to returnNumber(), but I need a bit of help on that one.

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• How do I make my ArrayList Thread-Safe? Another approach to problem in Java?

  - by thechiman

  I have an ArrayList that I want to use to hold RaceCar objects that extend the Thread class as soon as they are finished executing. A class, called Race, handles this ArrayList using a callback method that the RaceCar object calls when it is finished executing. The callback method, addFinisher(RaceCar finisher), adds the RaceCar object to the ArrayList. This is supposed to give the order in which the Threads finish executing. I know that ArrayList isn't synchronized and thus isn't thread-safe. I tried using the Collections.synchronizedCollection(c Collection) method by passing in a new ArrayList and assigning the returned Collection to an ArrayList. However, this gives me a compiler error: Race.java:41: incompatible types found : java.util.Collection required: java.util.ArrayList finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars)); Here is the relevant code: public class Race implements RaceListener { private Thread[] racers; private ArrayList finishingOrder; //Make an ArrayList to hold RaceCar objects to determine winners finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars)); //Fill array with RaceCar objects for(int i=0; i<numberOfRaceCars; i++) { racers[i] = new RaceCar(laps, inputs[i]); //Add this as a RaceListener to each RaceCar ((RaceCar) racers[i]).addRaceListener(this); } //Implement the one method in the RaceListener interface public void addFinisher(RaceCar finisher) { finishingOrder.add(finisher); } What I need to know is, am I using a correct approach and if not, what should I use to make my code thread-safe? Thanks for the help!

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• Abstract base class puzzle

  - by 0x80

  In my class design I ran into the following problem: class MyData { int foo; }; class AbstraktA { public: virtual void A() = 0; }; class AbstraktB : public AbstraktA { public: virtual void B() = 0; }; template<class T> class ImplA : public AbstraktA { public: void A(){ cout << "ImplA A()"; } }; class ImplB : public ImplA<MyData>, public AbstraktB { public: void B(){ cout << "ImplB B()"; } }; void TestAbstrakt() { AbstraktB *b = (AbstraktB *) new ImplB; b->A(); b->B(); }; The problem with the code above is that the compiler will complain that AbstraktA::A() is not defined. Interface A is shared by multiple objects. But the implementation of A is dependent on the template argument. Interface B is the seen by the outside world, and needs to be abstrakt. The reason I would like this is that it would allow me to define object C like this: Define the interface C inheriting from abstrakt A. Define the implementation of C using a different datatype for template A. I hope I'm clear. Is there any way to do this, or do I need to rethink my design?

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• C++ casted realloc causing memory leak

  - by wyatt

  I'm using a function I found here to save a webpage to memory with cURL: struct WebpageData { char *pageData; size_t size; }; size_t storePage(void *input, size_t size, size_t nmemb, void *output) { size_t realsize = size * nmemb; struct WebpageData *page = (struct WebpageData *)output; page->pageData = (char *)realloc(page->pageData, page->size + realsize + 1); if(page->pageData) { memcpy(&(page->pageData[page->size]), input, realsize); page->size += realsize; page->pageData[page->size] = 0; } return realsize; } and find the line: page->pageData = (char *)realloc(page->pageData, page->size + realsize + 1); is causing a memory leak of a few hundred bytes per call. The only real change I've made from the original source is casting the line in question to a (char *), which my compiler (gcc, g++ specifically if it's a c/c++ issue, but gcc also wouldn't compile with the uncast statement) insisted upon, but I assume this is the source of the leak. Can anyone elucidate? Thanks

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• Trying to make a plugin system in C++/Qt

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• What are the lengths/limits C preprocessor as a language creation tool? Where can I learn more about

  - by Weston C

  In his FAQ @ http://www2.research.att.com/~bs/bs_faq.html#bootstrapping, Bjarne Stroustrup says: To build [Cfront, the first C++ compiler], I first used C to write a "C with Classes"-to-C preprocessor. "C with Classes" was a C dialect that became the immediate ancestor to C++... I then wrote the first version of Cfront in "C with Classes". When I read this, it piqued my interest in the C preprocessor. I'd seen its macro capabilities as suitable for simplifying common expressions but hadn't thought about its ability to significantly add to syntax and semantics on the level that I imagine bringing classes to C took. So now I have a couple of questions on my mind: 1) Are there other examples of this approach to bootstrapping a language off of C? 2) Is the source to Stroustrup's original work available anywhere? 3) Where could I learn more about the specifics of utilizing this technique? 4) What are the lengths/limits of that approach? Could one, say, create a set of preprocessor macros that let someone write in something significantly Lisp/Scheme like?

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• How to increase PermGen memory for eclipselink StaticWeaveAntTask

  - by rayd09

  We are using Eclipselink and need to weave the code in order for lazy fetching to work property. During the weave process I'm getting the following error: weave: BUILD FAILED java.lang.OutOfMemoryError: PermGen space I have the following tasks within my ant build file: <target name="define_weave_task" description="task definition for EclipseLink static weaving"> <taskdef name="eclipse_weave" classname="org.eclipse.persistence.tools.weaving.jpa.StaticWeaveAntTask"/> </target> <target name="weave" depends="compile,define_weave_task" description="weave eclipselink code into compiled classes"> <eclipse_weave source="${path.classes}" target="${path.classes}"> <classpath refid="compile.classpath"/> </eclipse_weave> </target> It has been working great for a long time. Now that the amount of code to be woven has increased I'm getting the PermGen error. I would like to be able to up the amount of perm space. If I was doing a compile I would be able to up the perm space via a compiler argument such as <compilerarg value="-XX:MaxPermSize=256M"/> but this does not appear to be a valid argument for eclipselink weaving. How can I up the perm space for the weave?

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• Binding ComboBoxes to enums... in Silverlight!

  - by Domenic

  So, the web, and StackOverflow, have plenty of nice answers for how to bind a combobox to an enum property in WPF. But Silverlight is missing all of the features that make this possible :(. For example: You can't use a generic EnumDisplayer-style IValueConverter that accepts a type parameter, since Silverlight doesn't support x:Type. You can't use ObjectDataProvider, like in this approach, since it doesn't exist in Silverlight. You can't use a custom markup extension like in the comments on the link from #2, since markup extensions don't exist in Silverlight. You can't do a version of #1 using generics instead of Type properties of the object, since generics aren't supported in XAML (and the hacks to make them work all depend on markup extensions, not supported in Silverlight). Massive fail! As I see it, the only way to make this work is to either Cheat and bind to a string property in my ViewModel, whose setter/getter does the conversion, loading values into the ComboBox using code-behind in the View. Make a custom IValueConverter for every enum I want to bind to. Are there any alternatives that are more generic, i.e. don't involve writing the same code over and over for every enum I want? I suppose I could do solution #2 using a generic class accepting the enum as a type parameter, and then create new classes for every enum I want that are simply class MyEnumConverter : GenericEnumConverter<MyEnum> {} What are your thoughts, guys?

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• User defined literal arguments are not constexpr?

  - by Pubby

  I'm testing out user defined literals. I want to make _fac return the factorial of the number. Having it call a constexpr function works, however it doesn't let me do it with templates as the compiler complains that the arguments are not and cannot be constexpr. I'm confused by this - aren't literals constant expressions? The 5 in 5_fac is always a literal that can be evaluated during compile time, so why can't I use it as such? First method: constexpr int factorial_function(int x) { return (x > 0) ? x * factorial_function(x - 1) : 1; } constexpr int operator "" _fac(unsigned long long x) { return factorial_function(x); // this works } Second method: template <int N> struct factorial { static const unsigned int value = N * factorial<N - 1>::value; }; template <> struct factorial<0> { static const unsigned int value = 1; }; constexpr int operator "" _fac(unsigned long long x) { return factorial_template<x>::value; // doesn't work - x is not a constexpr }

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