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• Can destructors be declared as pure virtual? [closed]

  - by skydoor

  Possible Duplicate: Why do we need a pure virtual destructor in C++? I know that the destructor can be virtual, how about pure virtual? If yes, what's the usage? If not, what's the error, compile error or runtime error?

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• simple Java "service provider frameworks"?

  - by Jason S

  I refer to "service provider framework" as discussed in Chapter 2 of Effective Java, which seems like exactly the right way to handle a problem I am having, where I need to instantiate one of several classes at runtime, based on a String to select which service, and an Configuration object (essentially an XML snippet): But how do I get the individual service providers (e.g. a bunch of default providers + some custom providers) to register themselves? interface FooAlgorithm { /* methods particular to this class of algorithms */ } interface FooAlgorithmProvider { public FooAlgorithm getAlgorithm(Configuration c); } class FooAlgorithmRegistry { private FooAlgorithmRegistry() {} static private final Map<String, FooAlgorithmProvider> directory = new HashMap<String, FooAlgorithmProvider>(); static public FooAlgorithmProvider getProvider(String name) { return directory.get(serviceName); } static public boolean registerProvider(String name, FooAlgorithmProvider provider) { if (directory.containsKey(name)) return false; directory.put(name, provider); return true; } } e.g. if I write custom classes MyFooAlgorithm and MyFooAlgorithmProvider to implement FooAlgorithm, and I distribute them in a jar, is there any way to get registerProvider to be called automatically, or will my client programs that use the algorithm have to explicitly call FooAlgorithmRegistry.registerProvider() for each class they want to use?

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• Cap deploy doesn't work all the sudden; something to do with FactoryGirl and assets

  - by Jason Swett

  I've been cap deploying my app all throughout it development, and this last time I tried to deploy it, it didn't work. Here's what happened: * executing `deploy:assets:precompile' * executing "cd /var/www/oneteam/releases/20121006153136 && bundle exec rake RAILS_ENV=production RAILS_GROUPS=assets assets:precompile" servers: ["electricsasquatch.com"] [electricsasquatch.com] executing command ** [out :: electricsasquatch.com] rake aborted! ** [out :: electricsasquatch.com] uninitialized constant OneTeam::Application::FactoryGirl ** [out :: electricsasquatch.com] ** [out :: electricsasquatch.com] (See full trace by running task with --trace) It looks like it failed on the deploy:assets:precompile command. I don't get why that command would have tried to do anything with FactoryGirl, though. Any ideas?

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• ASP.NET exception gives irrelevant stack trace on YSOD, very challenging!

  - by pootow

  Here is the YSOD: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.] System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +428 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 ECommerce.PMethod.Sql.SqlConns.Open() +78 ECommerce.PMethod.Sql.SqlConns..ctor() +120 ECommerce.login.DatasInfo.Proc.UserCenter.IsLogin(String UserGUID, Int32 UserID) +49 ECommerce.login.Rules.Users.UserLogin.isLogin() +44 Config.isUserLogined() +5 Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627 [TypeInitializationException: The type initializer for 'ECommerce.ERP.DAL.DBConn' threw an exception.] ECommerce.ERP.DAL.DBConn.get_ConnString() +0 [ObjectDefinitionStoreException: Factory method 'System.String get_ConnString()' threw an Exception.] Spring.Objects.Factory.Support.SimpleInstantiationStrategy.Instantiate(RootObjectDefinition definition, String name, IObjectFactory factory, MethodInfo factoryMethod, Object[] arguments) +257 Spring.Objects.Factory.Support.ConstructorResolver.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +624 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +60 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +56 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +436 [ObjectCreationException: Error thrown by a dependency of object 'styleService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 56' : Initialization of object failed : Factory method 'System.String get_ConnString()' threw an Exception. while resolving 'constructor argument with name promotionservice' to 'promotionService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 31' while resolving 'constructor argument with name domainservice' to 'promotionDomainService' defined in 'assembly [ECommerce.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Domain.AppContext.xml] line 20' while resolving 'constructor argument with name promotionrepos' to 'promotionRepos' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34' while resolving 'constructor argument with name connstr' to 'ECommerce.ERP.DAL.DBConn#389F399' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34'] Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveReference(IObjectDefinition definition, String name, String argumentName, RuntimeObjectReference reference) +394 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolvePropertyValue(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +312 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveValueIfNecessary(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +17 Spring.Objects.Factory.Support.ConstructorResolver.ResolveConstructorArguments(String objectName, RootObjectDefinition definition, ObjectWrapper wrapper, ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) +993 Spring.Objects.Factory.Support.ConstructorResolver.AutowireConstructor(String objectName, RootObjectDefinition rod, ConstructorInfo[] chosenCtors, Object[] explicitArgs) +171 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.AutowireConstructor(String name, RootObjectDefinition definition, ConstructorInfo[] ctors, Object[] explicitArgs) +65 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +161 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +636 Spring.Objects.Factory.Support.AbstractObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +174 Spring.Objects.Factory.Support.WebObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +150 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObjectInternal(String name, Type requiredType, Object[] arguments, Boolean suppressConfigure) +990 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObject(String name) +10 Spring.Context.Support.AbstractApplicationContext.GetObject(String name) +20 ECommerce.Common.ServiceLocator.GetService() +334 ECommerce.Mvc.Controllers.StylesController..ctor() +72 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) +86 System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) +230 System.Activator.CreateInstance(Type type, Boolean nonPublic) +67 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80 [InvalidOperationException: An error occurred when trying to create a controller of type 'ECommerce.Mvc.Controllers.StylesController'. Make sure that the controller has a parameterless public constructor.] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +190 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +68 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +118 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +46 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +63 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +13 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677954 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Question is: the first stack trace is irrelevant to others, what happened? Any ideas? Let me make this more clear: a MVC page uses the spring part trying to load a lazy-init service which constructor wants a connection string through a static property like this: <object id="promotionRepos" type="ECommerce.Data.AdoNet.Promotions.PromotionRepos, ECommerce.Data.AdoNet" lazy-init="true"> <constructor-arg name="provider"> <null /> </constructor-arg> <constructor-arg name="connStr"> <object type="ECommerce.ERP.DAL.DBConn, ECommerce.ERP.DAL" factory-method="get_ConnString" /> </constructor-arg> <property name="RefreshInterval" value="00:00:10" /> </object> the timeout part is some what irrelevent to all others. see this in the first exception: Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 it's another page at all. And also, ECommerce.PMethod.Sql.SqlConns.Open() uses its own connection string, not the one loaded by spring, it's different module from diffrent team. And I am sure the connection string is correct. And, this ysod cames up randomly. Sometimes nothing is wrong, and sometimes, it appears. I thought there could be something wrong with my database or the network/firewall, I will check it later, but now I want understand this tricky stack trace.

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• Examples of monoids/semigroups in programming

  - by jkff

  It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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• Why do pure virtual base classes get direct access to static data members while derived instances do

  - by Shamster

  I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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• Is this a right way to use NHibernate?

  - by Venemo

  I spent the rest of the evening reading StackOverflow questions and also some blog entries and links about the subject. All of them turned out to be very helpful, but I still feel that they don't really answer my question. So, I'm developing a simple web application. I'd like to create a reusable data access layer which I can later reuse in other solutions. 99% of these will be web applications. This seems to be a good excuse for me to learn NHibernate and some of the patterns around it. My goals are the following: I don't want the business logic layer to know ANYTHING about the inner workings of the database, nor NHibernate itself. I want the business logic layer to have the least possible number of assumptions about the data access layer. I want the data access layer as simplistic and easy-to-use as possible. This is going to be a simple project, so I don't want to overcomplicate anything. I want the data access layer to be as non-intrusive as possible. Will all this in mind, I decided to use the popular repository pattern. I read about this subject on this site and on various dev blogs, and I heard some stuff about the unit of work pattern. I also looked around and checked out various implementations. (Including FubuMVC contrib, and SharpArchitecture, and stuff on some blogs.) I found out that most of these operate with the same principle: They create a "unit of work" which is instantiated when a repository is instantiated, they start a transaction, do stuff, and commit, and then start all over again. So, only one ISession per Repository and that's it. Then the client code needs to instantiate a repository, do stuff with it, and then dispose. This usage pattern doesn't meet my need of being as simplistic as possible, so I began thinking about something else. I found out that NHibernate already has something which makes custom "unit of work" implementations unnecessary, and that is the CurrentSessionContext class. If I configure the session context correctly, and do the clean up when necessary, I'm good to go. So, I came up with this: I have a static class called NHibernateHelper. Firstly, it has a static property called CurrentSessionFactory, which upon first call, instantiates a session factory and stores it in a static field. (One ISessionFactory per one AppDomain is good enough.) Then, more importantly, it has a CurrentSession static property, which checks if there is an ISession bound to the current session context, and if not, creates one, and binds it, and it returns with the ISession bound to the current session context. Because it will be used mostly with WebSessionContext (so, one ISession per HttpRequest, although for the unit tests, I configured ThreadStaticSessionContext), it should work seamlessly. And after creating and binding an ISession, it hooks an event handler to the HttpContext.Current.ApplicationInstance.EndRequest event, which takes care of cleaning up the ISession after the request ends. (Of course, it only does this if it is really running in a web environment.) So, with all this set up, the NHibernateHelper will always be able to return a valid ISession, so there is no need to instantiate a Repository instance for the "unit of work" to operate properly. Instead, the Repository is a static class which operates with the ISession from the NHibernateHelper.CurrentSession property, and exposes some functionality through that. I'm curious, what do you think about this? Is it a valid way of thinking, or am I completely off track here?

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• Entity Framework RC1 DbContext query issue

  - by Steve

  I'm trying to implement the repository pattern using entity framework code first rc 1. The problem I am running into is with creating the DbContext. I have an ioc container resolving the IRepository and it has a contextprovider which just news up a new DbContext with a connection string in a windsor.config file. With linq2sql this part was no problem but EF seems to be choking. I'll describe the problem below with an example. I've pulled out the code to simplify things a bit so that is why you don't see any repository pattern stuff here. just sorta what is happening without all the extra code and classes. using (var context = new PlssContext()) { var x = context.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } using (var context2 = new DbContext(@"Data Source=.\SQLEXPRESS;Initial Catalog=PLSS.Models.PlssContext;Integrated Security=True;MultipleActiveResultSets=True")) { var x = context2.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } PlssContext is where I am creating my DbContext class. The repository pattern doesn't know anything about PlssContext. The best I thought I could do was create a DbContext with the connection string to the sqlexpress database and query the data that way. The connection string in the var context2 was grabbed from the context after newing up the PlssContext object. So they are pointing at the same sqlexpress database. The first query works. The second query fails miserably with this error: The model backing the 'DbContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data. on this line var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); Here is my DbContext namespace PLSS.Models { public class PlssContext : DbContext { public DbSet<User> Users { get; set; } public DbSet<Corner> Corners { get; set; } public DbSet<Lookup_County> Lookup_County { get; set; } public DbSet<Lookup_Accuracy> Lookup_Accuracy { get; set; } public DbSet<Lookup_MonumentStatus> Lookup_MonumentStatus { get; set; } public DbSet<Lookup_CoordinateSystem> Lookup_CoordinateSystem { get; set; } public class Initializer : DropCreateDatabaseAlways<PlssContext> { protected override void Seed(PlssContext context) { I've tried all of the Initializer strategies with the same errors. I don't think the database is changing. If I remove the modelBuilder.Conventions.Remove<IncludeMetadataConvention>(); Then the error returns is The entity type User is not part of the model for the current context. Which sort of makes sense. But how do you bring this all together?

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• Doubt about instance creation by using Spring framework ???

  - by Arthur Ronald F D Garcia

  Here goes a command object which needs to be populated from a Spring form public class Person { private String name; private Integer age; /** * on-demand initialized */ private Address address; // getter's and setter's } And Address public class Address { private String street; // getter's and setter's } Now suppose the following MultiActionController @Component public class PersonController extends MultiActionController { @Autowired @Qualifier("personRepository") private Repository<Person, Integer> personRepository; /** * mapped To /person/add */ public ModelAndView add(HttpServletRequest request, HttpServletResponse response, Person person) throws Exception { personRepository.add(person); return new ModelAndView("redirect:/home.htm"); } } Because Address attribute of Person needs to be initialized on-demand, i need to override newCommandObject to create an instance of Person to initiaze address property. Otherwise, i will get NullPointerException @Component public class PersonController extends MultiActionController { /** * code as shown above */ @Override public Object newCommandObject(Class clazz) thorws Exception { if(clazz.isAssignableFrom(Person.class)) { Person person = new Person(); person.setAddress(new Address()); return person; } } } Ok, Expert Spring MVC and Web Flow says Options for alternate object creation include pulling an instance from a BeanFactory or using method injection to transparently return a new instance. First option pulling an instance from a BeanFactory can be written as @Override public Object newCommandObject(Class clazz) thorws Exception { /** * Will retrieve a prototype instance from ApplicationContext whose name matchs its clazz.getSimpleName() */ getApplicationContext().getBean(clazz.getSimpleName()); } But what does he want to say by using method injection to transparently return a new instance ??? Can you show how i implement what he said ??? ATT: I know this funcionality can be filled by a SimpleFormController instead of MultiActionController. But it is shown just as an example, nothing else

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• I cannot understand the point of this simple code.

  - by M4design

  I am doing this assignment, and there are some stuff (from start-up materials) that I cannot comprehend. typedef enum { NORTH, EAST, SOUTH, WEST, NUM_POINTS } Point; typedef Point Course[NUM_POINTS] ; I don't get the idea behind the last line , and how can I use it in the code?

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• How do I pass values to the contractor on of a wcf service?

  - by Ian Ringrose

  I wish to pass values into the contractor on the class that implements my service. However ServiceHost only lets me pass in the name of the type to create, not what arguments to pass to it’s contractor. I would live to be able to pass in a “factor” that creates my service object.

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• Web.xml: Are url-pattern tags relative to each other?

  - by sixtyfootersdude

  <servlet-mapping> <servlet-name>myName</servlet-name> <url-pattern>/aName</url-pattern> </servlet-mapping> <security-constraint> <web-resource-collection> ... <url-pattern> /* </url-pattern> </web-resource-collection> ... </security-constraint> This is an excerpt from web.xml (using it to configure a jboss/tomcat webservice). Just wondering if the url-pattern in web-resource-collection is relative to the url-pattern in servlet-mapping.

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• What's the benefit of calling new on an object instance?

  - by Geo

  I'm reading [Programming Perl][1], and I found this code snippet: sub new { my $invocant = shift; my $class = ref($invocant) || $invocant; my $self = { color => "bay", legs => 4, owner => undef, @_, # Override previous attributes }; return bless $self, $class; } With constructors like this one, what's the benefit of calling new on an object instance? I assume that it's what it's for, right? My guess is that if anyone would want to write such a constructor, he would have to add some more code that copies the attributes of the first object to the one about to be created.

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• Permutations distinct under given symmetry (Mathematica 8 group theory)

  - by Yaroslav Bulatov

  Given a list of integers like {2,1,1,0} I'd like to list all permutations of that list that are not equivalent under given group. For instance, using symmetry of the square, the result would be {{2, 1, 1, 0}, {2, 1, 0, 1}}. Approach below (Mathematica 8) generates all permutations, then weeds out the equivalent ones. I can't use it because I can't afford to generate all permutations, is there a more efficient way? Update: actually, the bottleneck is in DeleteCases. The following list {2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 0, 0, 0} has about a million permutations and takes 0.1 seconds to compute. Apparently there are supposed to be 1292 orderings after removing symmetries, but my approach doesn't finish in 10 minutes removeEquivalent[{}] := {}; removeEquivalent[list_] := ( Sow[First[list]]; equivalents = Permute[First[list], #] & /@ GroupElements[group]; DeleteCases[list, Alternatives @@ equivalents] ); nonequivalentPermutations[list_] := ( reaped = Reap@FixedPoint[removeEquivalent, Permutations@list]; reaped[[2, 1]] ); group = DihedralGroup[4]; nonequivalentPermutations[{2, 1, 1, 0}]

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• Web.xml: Are url-pattern tags relitive to each other?

  - by sixtyfootersdude

  <servlet-mapping> <servlet-name>myName</servlet-name> <url-pattern>/aName</url-pattern> </servlet-mapping> <security-constraint> <web-resource-collection> ... <url-pattern> /* </url-pattern> </web-resource-collection> ... </security-constraint> This is an excerpt from web.xml (using it to configure a jboss/tomcat webservice). Just wondering if the url-pattern in web-resource-collection is relative to the url-pattern in servlet-mapping.

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• What's safe to assume about the NSMutableArray / NSArray class cluster?

  - by andyvn22

  I know you shouldn't use this to decide whether or not to change an array: if ([possiblyMutable isKindOfClass:[NSMutableArray class]]) But say I'm writing a method and need to return either an NSMutableArray or an NSArray, depending on the mutability of possiblyMutable. The class using my method already knows whether or not it's acceptable to change the returned array. Whether or not it's acceptable to change the returned array directly correlates with whether or not it's acceptable to change possiblyMutable. In that specific case, is this code safe? It seems to me that if it's not acceptable to change the array, but we accidentally get a mutable array, it's ok, because the class using my method won't try to change it. And if it is acceptable to change the array, then we will always get possiblyMutable as an NSMutableArray (though this is the part I'm not entirely clear on). So... safe or not? Alternatives?

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• Nested/Sub data types in haskell

  - by Tom Carstens

  So what would be nice is if you could do something like the following (not necessarily with this format, just the general idea): data Minor = MinorA | MinorB data Major = Minor | MajorB isMinor :: Major -> Bool isMinor Minor = True isMinor _ = False So isMinor MinorA would report True (instead of an error.) At the moment you might do something like: data Major = MinorA | MinorB | MajorB isMinor :: Major -> Bool isMinor MinorA = True isMinor MinorB = True isMinor _ = False It's not terrible or anything, but it doesn't expand nicely (as in if Minor when up to MinorZ this would be terribly clunky). To avoid that problem you can wrap Minor: data Minor = MinorA | MinorB data Major = MajorA Minor | MajorB isMinor :: Major -> Bool isMinor (MajorA _) = True isMinor _ = False But now you have to make sure to wrap your Minors to use them as a Major... again not terrible; just doesn't really express the semantics I'd like very well (i.e. Major can be any Minor or MajorB). The first (legal) example is "Major can be MinorA..." but doesn't have any knowledge of Minor and the second is "Major can be MajorA that takes a Minor..." p.s. No, this isn't really about anything concrete.

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• Microsoft Press Deal of the Day - 13/April/2012 - Building Enterprise Applications with Windows® Presentation Foundation and the MVVM Pattern

  - by TATWORTH

  Today's deal of the day from Microsoft Press at http://shop.oreilly.com/product/0790145309686.do is Building Enterprise Applications with Windows® Presentation Foundation and the MVVM Pattern"Simplify and improve business application development by applying the MVVM pattern to Windows Presentation Foundation (WPF) and Microsoft® Silverlight® 4. With this hands-on guide, you'll use MVVM with data binding, commands, and behaviors to create user interfaces loosely coupled to business logic. MVVM is ideal for .NET developers working with WPF and Silverlight—whether or not you have experience building enterprise applications."

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• Tests unitaires d'un DomainService WCF RIA : pattern Repository, un tutoriel de Kyle McClellan, traduit par Deepin Prayag

  Citation: Étant donné que WCF RIA Services emploie un « pipeline pattern » pour invoquer vos opérations DomainService, il n'est pas toujours évident de savoir comment les tester. Dans cette série d'articles nous allons voir un petit DomainService et comment le tester. Entre autres nous allons voir comment implémenter une IDomainServiceFactory personnalisée, comment implémenter le pattern Repository, et comment utiliser la DomainServiceTestHos...

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• What is the abstract name for Drive, Directory and file?

  - by Omkar panhalkar

  I want to give nice name to my function while returns drive, directory and file. Can you please suggest a good abstract name for this trio? This is the function. static IEnumerable<string> GetDriveDirectoriesAndFile(string path) { if (path.Contains('/')) { path = path.Replace('/', '\\'); } if (path.Contains('\\')) { return path.Split('\\'); } return null; } Thanks, Omkar

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• MVC - Cocoa interface - Cocoa Design pattern book

  - by Idan

  So I started reading this book: http://www.amazon.com/Cocoa-Design-Patterns-Erik-Buck/dp/0321535022 On chapter 2 it explains about the MVC design pattern and gives and example which I need some clarification to. The simple example shows a view with the following fields: hourlyRate, WorkHours, Standarthours , salary. The example is devided into 3 parts : View - contains some text fiels and a table (the table contains a list of employees' data). Controller - comprised of NSArrayController class (contains an array of MyEmployee) Model - MyEmployee class which describes an employee. MyEmployee class has one method which return the salary according to the calculation logic, and attributes in accordance with the view UI controls. MyEmployee inherits from NSManagedObject. Few things i'm not sure of : 1. Inside the MyEmplpyee class implemenation file, the calculation method gets the class attributes using sentence like " [[self valueForKey:@"hourlyRate"] floatValue];" Howevern, inside the header there is no data member named hourlyRate or any of the view fields. I'm not quite sure how does it work, and how it gets the value from the right view field. (does it have to be the same name as the field name in the view). maybe the conncetion is made somehow using the Interface builder and was not shown in the book ? and more important: 2. how does it seperate the view from the model ? let's say ,as the book implies might happen, I decide one day to remove one of the fields in the view. as far as I understand, that means changing the way the salary method works in MyEmplpyee (cause we have one field less) , and removing one attribute from the same calss. So how is that separate the View from the Model if changing one reflect on the other ? I guess I get something wrong... Any comments ? Thanks

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• Business Logic Layer Pattern on Rails? MVCL

  - by Fabiano PS

  That is a broad question, and I appreciate no short/dumb asnwers like: "Oh that is the model job, this quest is retarded (period)" PROBLEM Where I work at people created a system over 2 years for managing the manufacture process over demand in the most simplified still broad as possible, involving selling, buying, assemble, The system is coded over Ruby On Rails. The app has been changed lots of times and the result is a mess on callbacks (some are called several times), 200+ models, and fat controllers: Total bad. The QUESTION is, if there is a gem, or pattern designed to handle Rails large app logic? The logic whould be able to fully talk to models (whose only concern would be data format handling and validation) What I EXPECT is to reduce complexity from various controllers, and hard to track callbacks into files with the responsibility to handle a business operation logic. In some cases there is the need to wait for a response, in others, only validation of the input is enough and a bg process would take place. ie: -- Sell some products (need to wait the operation to finish) 1. Set a View able to get the products input 2. Controller gets the product list inputed by employee and call the logic Logic::ExecuteWithResponse('sell', 'products', :prods => @product_list_with_qtt, :when => @date, :employee => current_user() ) This Logic would handle buying order, assemble order, machine schedule, warehouse reservation, and others. Have in mind that a callback on SalesOrder is not enough, since it depends on where it is called (no field for that), depends on the class of the user, among other stuff not visible for the model, or in some cases it would take long for the model to process.

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• Maven/Spring/Java: ClassNotFoundException - but I know class is there...

  - by wuntee

  I have 2 maven projects set up like this: -com.wuntee.rsaAuthenticationManager (jar) -com.wuntee.taac (pom) --taac-backend-gui (jar) --taac-web (war) And 'com.wuntee.rsaAuthenticationManager' is a dep in 'taac-backend-gui'. When running a test case in taac-backend-gui, everything executes fine, but when trying to start the taac-web, I get the following ClassNotFoundException - the library that contains the class 'weblogic.security.SSL.TrustManager' is also in my local maven repository, and set as a dependency of com.wuntee.rsaAuthenticationManager. Does anyone know why I would be getting this error? I have also attempted to directly add the library containing TrustManager to the taac-web project, and still get the same Exception. Any ideas? ERROR[com.wuntee.taac.business.TaacWorkshop][main] - couldnt create rsa dao: com.rsa.common.SystemException: Command target (CommandAPIConnection) initialization failure java.lang.NoClassDefFoundError: weblogic/security/SSL/TrustManager at com.rsa.command.ConnectionFactory.getSpringBeanTarget(ConnectionFactory.java:212) at com.rsa.command.ConnectionFactory.getTarget(ConnectionFactory.java:170) at com.rsa.command.ConnectionFactory.getConnection(ConnectionFactory.java:246) at com.wuntee.rsaAuthenticationManager.RsaAuthenticationManagerDao.init(RsaAuthenticationManagerDao.java:60) at com.wuntee.taac.business.TaacWorkshop.<init>(TaacWorkshop.java:68) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:501) at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:126) at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:72) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:939) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:892) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:479) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:450) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:290) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:287) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:562) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:871) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:423) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:272) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:196) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3972) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4467) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardHost.start(StandardHost.java:722) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:593) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:592) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414) Caused by: com.rsa.ims.components.NoSuchComponentException: Unable to locate bean CommandAPIConnection at com.rsa.ims.components.spring.SpringComponentManagerImpl.getBean(SpringComponentManagerImpl.java:71) at com.rsa.command.ConnectionFactory.getSpringBeanTarget(ConnectionFactory.java:209) ... 39 more Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'CacheableCommandTargetBasicAuth': FactoryBean threw exception on object creation; nested exception is java.lang.reflect.InvocationTargetException at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:150) at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102) at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1387) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:301) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189) at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1044) at com.rsa.ims.components.spring.SpringComponentManagerImpl.getBean(SpringComponentManagerImpl.java:69) ... 40 more Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:501) at com.rsa.command.RemoteCommandTargetFactoryBean.getObject(RemoteCommandTargetFactoryBean.java:273) at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:143) ... 46 more Caused by: java.lang.NoClassDefFoundError: weblogic/security/SSL/TrustManager at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:164) at com.rsa.command.InitialContextFactoryLocator.getInitialContextFactory(InitialContextFactoryLocator.java:72) at com.rsa.command.EJBRemoteTarget.<init>(EJBRemoteTarget.java:189) ... 52 more

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• Java exception handling in non sequential tasks (pattern/good practice)

  - by Hernán Eche

  There are some task that should't be done in parallel, (for example opening a file, reading, writing, and closing, there is an order on that...) But... Some task are more like a shoping list, I mean they could have a desirable order but it's not a must..example in communication or loading independient drivers etc.. For that kind of tasks, I would like to know a java best practice or pattern for manage exceptions.. The java simple way is: getUFO { try { loadSoundDriver(); loadUsbDriver(); loadAlienDetectorDriver(); loadKeyboardDriver(); } catch (loadSoundDriverFailed) { doSomethingA; } catch (loadUsbDriverFailed) { doSomethingB; } catch (loadAlienDetectorDriverFailed) { doSomethingC; } catch (loadKeyboardDriverFailed) { doSomethingD; } } But what about having an exception in one of the actions but wanting to try with the next ones?? I've thought this approach, but don't seem to be a good use for exceptions I don't know if it works, doesn't matter, it's really awful!! getUFO { Exception ex=null; try { try{ loadSoundDriver(); }catch (Exception e) { ex=e; } try{ loadUsbDriver(); }catch (Exception e) { ex=e; } try{ loadAlienDetectorDriver(); }catch (Exception e) { ex=e; } try{ loadKeyboardDriver() }catch (Exception e) { ex=e; } close the file; if(ex!=null) { throw ex; } } catch (loadSoundDriverFailed) { doSomethingA; } catch (loadUsbDriverFailed) { doSomethingB; } catch (loadAlienDetectorDriverFailed) { doSomethingC; } catch (loadKeyboardDriverFailed) { doSomethingD; } } seems not complicated to find a better practice for doing that.. I still didn't thanks for any advice

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• Pattern for sharing data between views (MVP or MVVM)

  - by Dovix

  What is a good pattern for sharing data between related views?. I have an application where 1 form contains many small views, each views behaves independently from each other more or less (they communicate/interact via an event bus). Every so often I need to pass the same objects to the child views. Sometimes I need this same object to be passed to a child view and then the child passes it onto another child itself contains. What is a good approach to sharing this data between all the views contained within the parent form (view) ? I have looked into CAB and their approach and every "view" has a "root work item" this work item has dictionary that contains a shared "state" between the views that are contained. Is this the best approach? just a shared dictionary all the views under a root view can access? My current approach right now is to have a function on the view that allows one to set the object for that view. Something like view.SetCustomer(Customer c); then if the view contains a child view it knows to set it on the child view ala: this.childview1.SetCustomer(c); The application is written in C# 3.5, for winforms using MVP with structure map as a IoC/DI provider.

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