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  • boost::python string-convertible properties

    - by Checkers
    I have a C++ class, which has the following methods: class Bar { ... const Foo& getFoo() const; void setFoo(const Foo&); }; where class Foo is convertible to std::string (it has an implicit constructor from std::string and an std::string cast operator). I define a Boost.Python wrapper class, which, among other things, defines a property based on previous two functions: class_<Bar>("Bar") ... .add_property( "foo", make_function( &Bar::getFoo, return_value_policy<return_by_value>()), &Bar::setFoo) ... I also mark the class as convertible to/from std::string. implicitly_convertible<std::string, Foo>(); implicitly_convertible<Foo, std::string>(); But at runtime I still get a conversion error trying to access this property: TypeError: No to_python (by-value) converter found for C++ type: Foo How to achieve the conversion without too much boilerplate of wrapper functions? (I already have all the conversion functions in class Foo, so duplication is undesirable.

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  • How to let the matcher to match the second invocation on mock?

    - by Alex Luya
    I have an interface like this public interface EventBus{ public void fireEvent(GwtEvent<?> event); } and test code(testng method) looks like this: @Test public void testFireEvent(){ EventBus mock=mock(EventBus.class); //when both Event1 and Event2 are subclasses of GwtEvent<?> mock.fireEvent(new Event1()); mock.fireEvent(new Event2()); //then verify(mock).fireEvent(argThat(new Event2Matcher())); } Event2Matcher looks like this: private class Event2Matcher extends ArgumentMatcher<Event2> { @Override public boolean matches(Object arg) { return ((Event2) arg).getSth==sth; } } But get an error indicating that: Event1 can't be cast to Event2 And obviously,the matcher matched the first invoking mock.fireEvent(new Event1()); So,the statement within matcher return ((Event2) arg).getSth==sth; Will throw out this exception.So the question is how to let verify(mock).fireEvent(argThat(new Event2Matcher())); to match the second invoking?

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  • RAII: Initializing data member in const method

    - by Thomas Matthews
    In RAII, resources are not initialized until they are accessed. However, many access methods are declared constant. I need to call a mutable (non-const) function to initialize a data member. Example: Loading from a data base struct MyClass { int get_value(void) const; private: void load_from_database(void); // Loads the data member from database. int m_value; }; int MyClass :: get_value(void) const { static bool value_initialized(false); if (!value_initialized) { // The compiler complains about this call because // the method is non-const and called from a const // method. load_from_database(); } return m_value; } My primitive solution is to declare the data member as mutable. I would rather not do this, because it suggests that other methods can change the member. How would I cast the load_from_database() statement to get rid of the compiler errors?

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  • Linux application that bundles multiple incoming audio and video streams into one container file?

    - by StackedCrooked
    I've been assigned to implement a video on-demand service for a local university. Different aspects of the lectures (video, audio, screen cast, white board) will be recorded. During a lecture all these data streams arrive at one Linux server. This server should transcode and bundle all these streams into one container (Matroska) file. My options seem to be: Write a GStreamer application do something with FFMPEG do something with VLC ...? Has anyone done something similar in the past? Can you recommend something? Edit For those interested, here are a few of my findings: Matroska is not a good format for streaming (it's possible, but it's not its primary intent) For Flash streaming you can use MPEG4 If you want to combine different videos into one video where each subvideo occupies a rectangular portion of the total screen, then this GStreamer script is useful (I found it on this blog post). Desktop capture works fine with VLC

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  • Problem at JUnit test with generics

    - by Tom Brito
    In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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  • C# Entity Framework Base Repository

    - by Andy
    I'm trying to create a base repository for use with Entity Framework 4.0 and having some trouble. In this code below, why is it not possible to do this in one line? public IEnumerable<T> GetAll<T>(Expression<Func<T, bool>> filter) { IEnumerable<T> allCustomers = this.GetAll<T>(); IEnumerable<T> result = allCustomers.Where(filter.Compile()); return result; } Won't this result in 2 SQL statements: one without a where clause that retrieves all rows, and one with a where clause that only retrieves the rows that match the predicate? How can this be done with a single SQL statement? I can't get it to compile if I try to cast the filter.Compile() to Func<Customer, bool>. Thanks, Andy

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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • How do I make a class whose interface matches double, but upon which templates can be specialized?

    - by Neil G
    How do I make a class whose interface matches double, but whose templated types do not dynamic cast to double? The reason is that I have a run-time type system, and I want to be able to have a type that works just like double: template<int min_value, int max_value> class BoundedDouble: public double {}; And then inherit use template specialization to get run-time information about that type: template<typename T> class Type { etc. } template<int min_value, int max_value> class Type<BoundedDouble<min_value, max_value>> { int min() const { return min_value; } etc. } But, you can't inherit from double...

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  • EF4: common interface for EF entities

    - by Feryt
    Hi. I have public interface: public interface IEntity { int ID { get; set; } string Name { get; set; } bool IsEnabled { get; set; } } ehich some EF entities implements(thanks to partial class) and extesion method: public static IEnumerable<SelectListItem> ToSelectListItems<T>(this IQueryable<T> entities, int? selectedID = null) where T : IEntity { return entities.Select(c => new { c.Name, c.ID }).ToList().Select(c => new SelectListItem { Text = c.Name, Value = c.ID.ToString(), Selected = (c.ID == selectedID) }); } Calling ToSelectListItems return exception: Unable to cast the type '<EF entity name>' to type 'IEntity'. LINQ to Entities only supports casting Entity Data Model primitive types. Why, any ideas? Thank you.

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  • best way to output a full precision double into a text file

    - by flevine100
    Hi, I need to use an existing text file to store some very precise values. When read back in, the numbers essentially need to be exactly equivalent to the ones that were originally written. Now, a normal person would use a binary file... for a number of reasons, that's not possible in this case. So... do any of you have a good way of encoding a double as a string of characters (aside from increasing the precision). My first thought was to cast the double to a char[] and write out the chars. I don't think that's going to work because some of the characters are not visible, produce sounds, and even terminate strings ('\0'... I'm talkin to you!) Thoughts?

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  • Converting between unsigned and signed int safely

    - by polemic
    I have an interface between a client and a server where a client sends (1) an unsigned value, and (2) a flag which indicates if value is signed/unsigned. Server would then static cast unsigned value to appropriate type. I later found out that this is implementation defined behavior and I've been reading about it but I couldn't seem to find an appropriate solution that's completely safe? I've read about type punning, pointer conversions, and memcpy. Would simply using a union type work? A UnionType containing signed and unsigned int, along with the signed/unsigned flag. For signed values, client sets the signed part of the union, and server reads the signed part. Same for the unsigned part. Or am I completely misunderstanding something? Side question: how do I know the specific behavior in this case for a specific scenario, e.g. windriver diab on PPC? I'm a bit lost on how to find such documentation.

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  • Storing object as a column in LINQ

    - by Alex
    Hello, i have some class which constructs itself from string, like this: CurrencyVector v = new CurrencyVector("10 WMR / 20 WMZ"); it's actually a class which holds multiple currency values, but it does not matter much. I need to change type of column in my LINQ table (in vs 2010 designer) from String to that class, CurrencyVector. If i do it - i get runtime error when LINQ runtime tries to cast String as CurrencyVector (when populating the table from database). Adding IConvertible did not help. I wrapped these columns in properties, but it's ugly and slow solution. Searching internet gave no results.

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  • Create Generic Class Instance from Static Method in a Derived Class

    - by user343547
    I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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  • Is there a Scala version of .irbrc or another way to define some default libraries for REPL use?

    - by Tom Morris
    I've written a little library that uses implicits to add functionality that one only needs when using the REPL in Scala. Ruby has libraries like this - for things like pretty printing, firing up text editors (like the interactive_editor gem which invokes Vim from irb - see this post), debuggers and the like. The library I am trying to write adds some methods to java.lang.Class and java.lang.reflect classes using the 'pimp my library' implicit conversion process to help you go and find documentation (initially, with Google, then later possibly with a JavaDoc/ScalaDoc viewer, and maybe the StackOverflow API eventually!). It's an itch-scratching library: I spend so much time copying and pasting classnames into Google that I figured I may as well automate the process. It is the sort of functionality that developers will want to add to their system for use only in the REPL - they shouldn't really be adding it to projects (partly because it may not be something that their fellow developers want, but also because if you are doing some exploratory development, it may be with just a Scala REPL that's not being invoked by an IDE or build tool). In my case, I want to include a few classes and set up some implicits - include a .jar on the CLASSPATH and import it, basically. In Ruby, this is the sort of thing that you'd add to your .irbrc file. Other REPLs have similar ways of setting options and importing libraries. Is there a similar file or way of doing this for the Scala REPL?

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  • Type or namespace name could not be found

    - by Pandiya Chendur
    I use this: public IQueryable<MaterialsView> FindAllMaterials() { var materials = from m in db.Materials join Mt in db.MeasurementTypes on m.MeasurementTypeId equals Mt.Id select new MaterialsView { MatId = m.Mat_Name, MesName = Mt.Name, MesType = m.Mat_Type }; return materials; } It gives me the following errors: The type or namespace name MaterialsView could not be found (are you missing a using directive or an assembly reference?) Cannot implicitly convert type System.Collections.Generic.IEnumerable<MaterialsView> to System.Linq.IQueryable<MaterialsView>. An explicit conversion exists (are you missing a cast?) The type arguments for method System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>) cannot be inferred from the usage. Try specifying the type arguments explicitly. I have googled it and found this SO question but it doesn't help. What's wrong?

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  • Using java class HttpsURLConnection

    - by KB22
    Hi all, I have a small piece of code which basically impements a HTTP-Client, i.e. it POSTS request and works with re RESPONSE. As long as HTTP is concenerned everthing work well. For some reason I now have to support HTTPS too. So here is briefly what I do in order to get a connection opened: URL url = new URL(serverAddress); HttpsURLConnection httpsConn = (HttpsURLConnection) url.openConnection(); This fails, stating: sun.net.www.protocol.https.HttpsURLConnectionImpl cannot be cast to com.sun.net.ssl.HttpsURLConnection I guess this is kinda trivial, but I just don't get what I'm doing wrong in this one... Googled it, and the code just looks right - not? any ideas are appreciated! thanks, K

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  • boost::shared_ptr<const T> to boost::shared_ptr<T>

    - by Flevine
    I want to cast the const-ness out of a boost::shared_ptr, but I boost::const_pointer_cast is not the answer. boost::const_pointer_cast wants a const boost::shared_ptr, not a boost::shared_ptr. Let's forego the obligitory 'you shouldn't be doing that'. I know... but I need to do it... so what's the best/easiest way to do it? For clarity sake: boost::shared_ptr<const T> orig_ptr( new T() ); boost::shared_ptr<T> new_ptr = magic_incantation(orig_ptr); I need to know the magic_incantation() Thanks!

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  • Problem with Clojure function

    - by Bozhidar Batsov
    Hi, everyone, I've started working yesterday on the Euler Project in Clojure and I have a problem with one of my solutions I cannot figure out. I have this function: (defn find-max-palindrom-in-range [beg end] (reduce max (loop [n beg result []] (if (>= n end) result (recur (inc n) (concat result (filter #(is-palindrom? %) (map #(* n %) (range beg end))))))))) I try to run it like this: (find-max-palindrom-in-range 100 1000) and I get this exception: java.lang.Integer cannot be cast to clojure.lang.IFn [Thrown class java.lang.ClassCastException] which I presume means that at some place I'm trying to evaluate an Integer as a function. I however cannot find this place and what puzzles me more is that everything works if I simply evaluate it like this: (reduce max (loop [n 100 result []] (if (>= n 1000) result (recur (inc n) (concat result (filter #(is-palindrom? %) (map #(* n %) (range 100 1000)))))))) (I've just stripped down the function definition and replaced the parameters with constants) Thanks in advance for your help and sorry that I probably bother you with idiotic mistake on my part. Btw I'm using Clojure 1.1 and the newest SLIME from ELPA.

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  • Java reflection for generics

    - by Vijay Bhore
    I am using Java Reflection to expose methods in custom eclipse tool. I am writing method getReturnType which accepts java.lang.reflect.Method as input and returns object of Class private static Class<?> getReturnType(Method method) { Type type = ((ParameterizedType)method.getGenericReturnType()).getRawType(); return getClass(type); } This code compiles well but at runtime i get the below exception while casting Type to ParameterizedType. java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType Please suggest. Thanks!

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  • Cannot implicitly convert type ... to ... problem

    - by Younes
    I have this code: public static IEnumerable<dcCustomer> searchCustomer(string Companyname) { TestdbDataContext db = new TestdbDataContext(); IEnumerable<dcCustomer> myCustomerList = (from Customer res in db.Customers where res.CompanyName == Companyname select res); return myCustomerList; } And whatever i try i keep getting the convert error. Error 1 Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<ConnectionWeb.Customer>' to 'System.Collections.Generic.IEnumerable<ConnectionWeb.DAL.dcCustomer>'. An explicit conversion exists (are you missing a cast?) \\srv01\home$\Z****\Visual Studio 2008\Projects\ConnectionWeb\ConnectionWeb\DAL\dcCustomer.cs 63 20 ConnectionWeb I want to try get myCustomerList to keep the values in an enumerator and return it.

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  • Custom Web Control - ParseChildren & Resource Objects

    - by Raybiez
    I hope someone can help me. I have the following custom server control: [ParseChildren(true)] public class MyControl : WebControl, INamingContainer { [PersistenceMode(PersistenceMode.InnerProperty)] public string MyProperty { get;set; } } It works perfectly with the following mark-up: <acme:MyControl runat="sever"> <MyProperty>Test String</MyProperty> </acme:MyControl> But if I try to localise the property string, I get a parse error: <acme:MyControl runat="sever"> <MyProperty><%=(string)GetLocalResourceObject("MyResourceKey") %></MyProperty> </acme:MyControl> Even if I cast the type, ASP.NET indicates that the property cannot accept controls as children. How should the expression look like if I want to localise it? I can make the property accessible as an attribute of the control's tag, but I prefer the mark-up above, it looks more elegant and clean. Thanks

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  • How can I use a custom configured RememberMeAuthenticationFilter in spring security?

    - by Sebastian
    I want to use a slightly customized rememberme functionality with spring security (3.1.0). I declare the rememberme tag like this: <security:remember-me key="JNJRMBM" user-service-ref="gymUserDetailService" /> As I have my own rememberme service I need to inject that into the RememberMeAuthenticationFilter which I define like this: <bean id="rememberMeFilter" class="org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter"> <property name="rememberMeServices" ref="gymRememberMeService"/> <property name="authenticationManager" ref="authenticationManager" /> </bean> I have spring security integrated in a standard way in my web.xml: <filter-name>springSecurityFilterChain</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> Everything works fine, except that the RememberMeAuthenticationFilter uses the standard RememberMeService, so I think that my defined RememberMeAuthenticationFilter is not being used. How can I make sure that my definition of the filter is being used? Do I need to create a custom filterchain? And if so, how can I see my current "implicit" filterchain and make sure I use the same one except my RememberMeAuthenticationFilter instead of the default one? Thanks for any advice and/or pointers!

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  • how to make shadows for transparent objects using ray tracing in C++/openGL

    - by happy face
    I'm trying to make a code that cast shadow from trasnparent objects(such as glass) for rendering in 3D I do not have a shadow map and photon mapping yet, and I wanted to know if there is a way to make shadows for transparent materials using ray tracing only. Caustics sounds very hard without photon mapping... I have implemented a simple code in C++ that only makes the shadows black (no matter if the objects are transparent or opaque) Pseudo code would be great, thnx. for(size_t i = 0;i < num; ++i) { if(state_list[i].hit && state_list[i].distance < dist_from_light[i]) { return[i] = BLACK; }

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  • Reading in 4 bytes at a time

    - by alphomega
    I have a big file full of integers that I'm loading in. I've just started using C++, and I'm trying out the filestream stuff. From everything I've read, it appears I can only read in bytes, So I've had to set up a char array, and then cast it as a int pointer. Is there a way I can read in 4 bytes at a time, and eliminate the need for the char array? const int HRSIZE = 129951336; //The size of the table char bhr[HRSIZE]; //The table int *dwhr; int main() { ifstream fstr; /* load the handranks.dat file */ std::cout << "Loading table.dat...\n"; fstr.open("table.dat"); fstr.read(bhr, HRSIZE); fstr.close(); dwhr = (int *) bhr; }

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  • casting a generic array in java

    - by liloboy
    The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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