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• How to Use XSLT to Replace Coordinate Separator With List of Tuples?

  - by kuloch

  I have a space-separated list of coordinate tuples. Each tuple consists of a space-separated list of 2-dimensional coordinates. E.g. "1.1 2.8 1.2 2.9" represents a line from POINT(1.1 2.8) to POINT(1.2 2.9). I need this to instead be "1.1,2.8 1.2,2.9". How would I use XSLT to perform the replacement of space-to-comma between pairs of numbers? I have the "string(gml:LinearRing/gml:posList)". This is being used on a Java Web Service that spits out GML 3.1.1 features with geometries. The service supports optional KML output, by using XSLT to transform the GML document into a KML document (at least, the chunks deemed "important"). I am locked into XSLT 1.0, so regex from XSLT 2.0 is not an option. I am aware that GML uses lat/lon while KML uses lon/lat. That's being handled before XSLT, though it would be nice to have that also done with XSLT.

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• How to implement web cache: internal fragmentation VS external fragmentation

  - by Summer_More_More_Tea

  Hi there: I come up with this question when play with Firefox web cache: in which approach does the browser cache a response in limited disk space(take my configuration as an example, 50MB is the upper bound)? I think two ways can be employed. One is cache the total response object one by one, but this is inefficient and will introduce external fragmentation, thus the total cache space may not be fully used. The second is take the total space(50MB) as a consecutive file, splitting it into fixed-length slots; incoming response objects will also be treated blocks of data with the same length as the slots. We can fill slots until the whole file is run out of, then some displacement algorithm can be used to swap out the old cached objects. The latter approach will of course bing in internal fragmentation, but in my opinion is easier to implement and maintain than the first strategy. But when I enter Firefox's Cache directory, I find it (maybe) use a different method: a lot of varied-length files reside in that directory and all those files are filled with undisplayable characters. I don't but really want to know what mechanism that a commercial browser, e.g. Firefoix, employed to implement web cache. Regards.

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• Fluent Nhibernate Mapping Single class on two database tables

  - by nabeelfarid

  Hi guys, I am having problems with Mapping. I have two tables in my database as follows: Employee and EmployeeManagers Employee EmployeeId int Name nvarchar EmployeeManagers EmployeeIdFk int ManagerIdFk int So the employee can have 0 or more Managers. A manager itself is also an Employee. I have the following class to represent the Employee and Managers public class Employee { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Employee> Managers { get; protected set; } public Employee() { Managers = new List<Employee>(); } } I don't have any class to represent Manager because I think there is no need for it, as Manager itself is an Employee. I am using autoMapping and I just can't figure out how to map this class to these two tables. I am implementing IAutoMappingOverride for overriding automappings for Employee but I am not sure what to do in it. public class NodeMap : IAutoMappingOverride { public void Override(AutoMapping<Node> mapping) { //mapping.HasMany(x => x.ValidParents).Cascade.All().Table("EmployeeManager"); //mapping.HasManyToMany(x => x.ValidParents).Cascade.All().Table("EmployeeManager"); } } I also want to make sure that an employee can not be assigned the same manager twice. This is something I can verify in my application but I would like to put constraint on the EmployeeManager table (e.g. a composite key) so a same manager can not be assigned to an employee more than once. Could anyone out there help me with this please? Awaiting Nabeel

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• How to Elegantly convert switch+enum with polymorphism

  - by Kyle

  I'm trying to replace simple enums with type classes.. that is, one class derived from a base for each type. So for example instead of: enum E_BASE { EB_ALPHA, EB_BRAVO }; E_BASE message = someMessage(); switch (message) { case EB_ALPHA: applyAlpha(); case EB_BRAVO: applyBravo(); } I want to do this: Base* message = someMessage(); message->apply(this); // use polymorphism to determine what function to call. I have seen many ways to do this which all seem less elegant even then the basic switch statement. Using dyanimc_pointer_cast, inheriting from a messageHandler class that needs to be updated every time a new message is added, using a container of function pointers, all seem to defeat the purpose of making code easier to maintain by replacing switches with polymorphism. This is as close as I can get: (I use templates to avoid inheriting from an all-knowing handler interface) class Base { public: template<typename T> virtual void apply(T* sandbox) = 0; }; class Alpha : public Base { public: template<typename T> virtual void apply(T* sandbox) { sandbox->applyAlpha(); } }; class Bravo : public Base { public: template<typename T> virtual void apply(T* sandbox) { sandbox->applyBravo(); } }; class Sandbox { public: void run() { Base* alpha = new Alpha; Base* bravo = new Bravo; alpha->apply(this); bravo->apply(this); delete alpha; delete bravo; } void applyAlpha() { // cout << "Applying alpha\n"; } void applyBravo() { // cout << "Applying bravo\n"; } }; Obviously, this doesn't compile but I'm hoping it gets my problem accross.

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• Fluent NHibernate Map to private/protected Field that has no exposing Property

  - by Jon Erickson

  I have the following Person and Gender classes (I don't really, but the example is simplified to get my point across), using NHibernate (Fluent NHibernate) I want to map the Database Column "GenderId" [INT] value to the protected int _genderId field in my Person class. How do I do this? FYI, the mappings and the domain objects are in separate assemblies. public class Person : Entity { protected int _genderId; public virtual int Id { get; private set; } public virtual string Name { get; private set; } public virtual Gender Gender { get { return Gender.FromId(_genderId); } } } public class Gender : EnumerationBase<Gender> { public static Gender Male = new Gender(1, "Male"); public static Gender Female = new Gender(2, "Female"); private static readonly Gender[] _genders = new[] { Male, Female }; private Gender(int id, string name) { Id = id; Name = name; } public int Id { get; private set; } public string Name { get; private set; } public static Gender FromId(int id) { return _genders.Where(x => x.Id == id).SingleOrDefault(); } }

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• Diamond problem in C++

  - by Jack

  I know the diamond problem. I am using gcc compiler. I have some scenarios I need explanation about. 1) class A{ public: virtual void eat(){cout<<"A eat\n";} }; class B:public A{ public: void eat(){ cout<<"B eat\n";}}; class C:public A{ public: void eat(){ cout<<"C eat\n";}}; class D:public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } Why doesn't this work? 2) class A{ public: void eat(){cout<<"A eat\n";} }; class B:virtual public A{ public: void eat(){ cout<<"B eat\n";}}; class C:virtual public A{ public: void eat(){ cout<<"C eat\n";}}; class D: public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } When I do this what happens in the background. How does the ambiguity get removed. Is the concept of vtables involved here?

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• How to write a Criteria Query when there's an <any> association

  - by Bevan

  I'm having some trouble constructing the correct Criteria to do a particular query - after an afternoon of consultation with Professor Google, I'm hoping that someone can point me in the right direction. I have two entities of interest: OutputTsDef and NamedAttribute What I'm trying to do is to find all OutputTsDef that have a particular NamedAttribute value. I can write a detached Criteria to find all NamedAttributes that have a given name and value: var attributesCriteria = DetachedCriteria.For<INamedAttribute>() .Add(Expression.Eq("Name", "some name")) .Add(Expression.Eq("Value", "some value")); How do I inject this in to a query for OutputTsDef to restrict the results? var criteria = nHibernateSession.CreateCriteria(typeof(IOutputTsDefEntity)); // What do I write here? var results = criteria.List(); NamedAttribute looks like this - note the use of [Any] as we can have NamedAttributes on many kinds of entity. [AttributeIdentifier("DbKey", Name = "Id.Column", Value = "NamedAttributeID")] [Class(Table = "NamedAttributes")] public class NamedAttribute : BusinessEntity, INamedAttribute { [Any(0, Name = "Entity", MetaType = "System.String", IdType = "System.Int32")] [MetaValue(1, Class = "Sample.OutputTsDef, Sample.Entities", Value = "OTD")] [MetaValue(2, Class = "Sample.OutputTimeSeriesAttributesEntity, Sample.Entities", Value = "OTA")] [Column(3, Name = "OwnerType")] [Column(4, Name = "OwnerKey")] public virtual IBusinessEntity Entity { get; set; } [Property(Column = "Name")] public virtual string Name { get; set; } [Property(Column = "Value")] public virtual string Value { get; set; } ... omitted ... } In regular SQL, I'd just include an extra "where" clause like this: where OutputTsDefId in ( select distinct OwnerKey from NamedAttributes where Name = ? and Value = ? and OwnerType = 'OTD' ) What am I missing? (Question also posted to the NHUsers mailing list - I'll copy any useful information from there, here.)

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• regular expression for indian vehicle number in javascript and php

  - by I Like PHP

  i need regular expression in java script as well as in PHP for Indian vehicle NUMBER here are conditions list let expression is (x)(y)(z)(m)(a)(b)(c) 1. (x) contains only alphabets of length 2. 2. (y) may be - or single space ' ' 3. (z) contains only numbers of length 2 4. (m) may be or , or single space ' ' 5. length of (a) can be 2 or 3. contains alphanumeric value with minimum one alphabetic character. 6. (b) may be - or single space ' ' ( similar to (y) ) 7. (c) contains only numbers of length 4 i show you the various examples of vehicle number valid number RJ-14,NL-1234 RJ-01,4M-5874 RJ-07,14M-2345 RJ 07,3M 2345 RJ-07,3M-8888 RJ 07 4M 2345 RJ 07,4M 2933 invalid number RJ-07 3M 1234 ( both (y) and (b) should be same). RJ-07 M3-1234 ((a) must ends with alphabat). rj-07 M3-123 ( length of (c) must be 4).

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• Mapping enum with fluent nhibernate

  - by Puneet

  I am following the http://wiki.fluentnhibernate.org/Getting%5Fstarted tutorial to create my first NHibernate project with Fluent NHibernate I have 2 tables 1) Account with fields Id AccountHolderName AccountTypeId 2) AccountType with fields Id AccountTypeName Right now the account types can be Savings or Current So the table AccountTypes stores 2 rows 1 - Savings 2 - Current For AccoutType table I have defined enum public enum AccountType { Savings=1, Current=2 } For Account table I define the entity class public class Account { public virtual int Id {get; private set;} public virtual string AccountHolderName {get; set;} public virtual string AccountType {get; set;} } The fluent nhibernate mappings are: public AgencyMap() { Id(o => o.Id); Map(o => o.AccountHolderName); Map(o => o.AccountType); } When I try to run the solution, it gives an exception - InnerException = {"(XmlDocument)(2,4): XML validation error: The element 'class' in namespace 'urn:nhibernate-mapping-2.2' has incomplete content. List of possible elements expected: 'meta, subselect, cache, synchronize, comment, tuplizer, id, composite-id' in namespace 'ur... I guess that is because I have not speciofied any mapping for AccountType. The questions are: How can I use AccountType enum instead of a AccountType class? Maybe I am going on wrong track. Is there a better way to do this? Thanks!

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• NHibernate mapping for subclasses and joined-subclasses

  - by Husain

  In a project that I am working on, I have the following entities: Analyst, Client and Contractor. Each inherit from a base class User. public abstract class User { public virtual int Id { get; set; } public virtual string Username { get; set; } public virtual string FullName { get; set; } } I then have the other classes inheriting from the base class as: public class Analyst : User { // Empty class. There are no additional properties for an analyst. } public class Client : User { // Empty class. There are no additional properties for a client. } public class Contractor : User { public int TotalJobs { get; set; } public int JobsInProgress { get; set; } } For the above classes, I have the following table structure: USER ---- UserId Username FullName UserType (1 = Analyst, 2 = Client, 3 = Contractor) CONTRACTOR ---------- UserId TotalJobs JobsInProgress There are no tables for Analyst and Client classes. I would like to know how I can write the NHibernate mapping file for the Contractor class. For the other classes, I have created a User mapping file and added Client and Analyst as sub-classes. How can I map the Contractor class?

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• How to get SimpleRpcClient.Call() to be a blocking call to achieve synchronous communication with RabbitMQ?

  - by Nick Josevski

  In the .NET version (2.4.1) of RabbitMQ the RabbitMQ.Client.MessagePatterns.SimpleRpcClient has a Call() method with these signatures: public virtual object[] Call(params object[] args); public virtual byte[] Call(byte[] body); public virtual byte[] Call(IBasicProperties requestProperties, byte[] body, out IBasicProperties replyProperties); The problem: With various attempts, the method still continues to not block where I expect it to, so it's unable ever handle the response. The Question: Am I missing something obvious in the setup of the SimpleRpcClient, or earlier with the IModel, IConnection, or even PublicationAddress? More Info: I've also tried various paramater configurations of the QueueDeclare() method too with no luck. string QueueDeclare(string queue, bool durable, bool exclusive, bool autoDelete, IDictionary arguments); Some more reference code of my setup of these: IConnection conn = new ConnectionFactory{Address = "127.0.0.1"}.CreateConnection()); using (IModel ch = conn.CreateModel()) { var client = new SimpleRpcClient(ch, queueName); var queueName = ch.QueueDeclare("t.qid", true, true, true, null); ch.QueueBind(queueName, "exch", "", null); //HERE: does not block? var replyMessageBytes = client.Call(prop, msgToSend, out replyProp); } Looking elsewhere: Or is it likely there's an issue in my "server side" code? With and without the use of BasicAck() it appears the client has already continued execution.

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• jquery post and get request different on local intranet and live server

  - by nccsbim071

  Hi, I have been developing an asp.net mvc application where i need to make large amounts of jquery post and get request to call controller methods and get back json result. Everything is working fine. The problem is i had to write different jquery post and get request url on local intranet(deployed by making virtual directory) and live server. the current jquery request url is given as below: $.post("/ProjectsChat/GetMessages", { roomId: 24 },.......... now this format of url for jquery request works fine for live server but not for local intranet. Since on local intranet i have made a virtual directory. It only works when i append the name of the virtual directory like this "$.post("MyProjectVirutalDirName/ProjectsChat..................." I am sure most of you must have come across same problem. now i have made a full project, there are large number of jquery requests made, i want to test the application by deploying on local intranet and fix the bugs. Changing all the jquery requests for local intranet doesn't seem feasible solution to me, i am really in a big problem, i can't deploy the same project on live server just like that and test it there, client will kill me. I need some expert advice. Please help Thanks

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• Constructor and Destructors in C++ [Not a question] [closed]

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• How to Specify Columntype in fluent nHibernate?

  - by Bipul

  I have a class CaptionItem public class CaptionItem { public virtual int SystemId { get; set; } public virtual int Version { get; set; } protected internal virtual IDictionary<string, string> CaptionValues {get; private set;} } I am using following code for nHibernate mapping Id(x => x.SystemId); Version(x => x.Version); Cache.ReadWrite().IncludeAll(); HasMany(x => x.CaptionValues) .KeyColumn("CaptionItem_Id") .AsMap<string>(idx => idx.Column("CaptionSet_Name"), elem => elem.Column("Text")) .Not.LazyLoad() .Cascade.Delete() .Table("CaptionValue") .Cache.ReadWrite().IncludeAll(); So in database two tables get created. One CaptionValue and other CaptionItem. In CaptionItem table has three columns 1. CaptionItem_Id int 2. Text nvarchar(255) 3. CaptionSet_Name nvarchar(255) Now, my question is how can I make the columnt type of Text to nvarchar(max)? Thanks in advance.

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• How to use Nhibernate Validator + NHib component + ddl

  - by mynkow

  I just configured my NHibValidator. My NHibernate creates the DB schema. When I set MaxLenght="20" to some property of a class then in the database the length appears in the database column. I am doing this in the NHibValidator xml file. But the problem is that I have components and cannot figure out how to achieve this behaviour. The component is configured correctly in the Customer.hbm.xml file. EDIT: Well, I found that Hibernate Validator users had the same problem two years ago. http://opensource.atlassian.com/projects/hibernate/browse/HV-25 Is this an issue for NHibernate Validator or it is fixed. If it is working tell me how please. ----------------------------------------------------- public class Customer { public virtual string Name{get;set;} public virtual Contact Contacts{ get; } } ----------------------------------------------------- public class Contact { public virtual string Address{get;set;} } ----------------------------------------------------- <?xml version="1.0" encoding="utf-8" ?> <nhv-mapping xmlns="urn:nhibernate-validator-1.0" namespace="MyNamespace" assembly="MyAssembly"> <class name="Customer"> <property name="Name"> <length max="20"/> </property> <property name="Contacts"> <notNull/> <valid/> </property> </class> </nhv-mapping> ----------------------------------------------------- <?xml version="1.0" encoding="utf-8" ?> <nhv-mapping xmlns="urn:nhibernate-validator-1.0" namespace="MyNamespace" assembly="MyAssembly"> <class name="Contact"> <property name="Address"> <length max="50"/> <valid/> </property> </class> </nhv-mapping> -----------------------------------------------------

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• C++: calling non-member functions with the same syntax of member ones

  - by peoro

  One thing I'd like to do in C++ is to call non-member functions with the same syntax you call member functions: class A { }; void f( A & this ) { /* ... */ } // ... A a; a.f(); // this is the same as f(a); Of course this could only work as long as f is not virtual (since it cannot appear in A's virtual table. f doesn't need to access A's non-public members. f doesn't conflict with a function declared in A (A::f). I'd like such a syntax because in my opinion it would be quite comfortable and would push good habits: calling str.strip() on a std::string (where strip is a function defined by the user) would sound a lot better than calling strip( str );. most of the times (always?) classes provide some member functions which don't require to be member (ie: are not virtual and don't use non-public members). This breaks encapsulation, but is the most practical thing to do (due to point 1). My question here is: what do you think of such feature? Do you think it would be something nice, or something that would introduce more issues than the ones it aims to solve? Could it make sense to propose such a feature to the next standard (the one after C++0x)? Of course this is just a brief description of this idea; it is not complete; we'd probably need to explicitly mark a function with a special keyword to let it work like this and many other stuff.

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• CRONTAB doesn't finish svndump

  - by Andrew

  I just discovered that the automated dumps I've been creating of my SVN repository have been getting cut off early and basically only half the dump is there. It's not an emergency, but I hate being in this situation. It defeats the purpose of making automated backups in the first place. The command I'm using is below. If I execute it manually in the terminal, it completes fine; the output.txt file is 16 megs in size with all 335 revisions. But if I leave it to crontab, it bails at the halfway mark, at around 8.1 megs and only the first 169 revisions. # m h dom mon dow command 18 00 * * * svnadmin dump /var/svn/repos/myproject > /home/andrew/output.txt I actually save to a dated gzipped file, and there's no shortage of space on the server, so this is not a disk space issue. It seems to bail after two seconds, so this could be a time issue, but the file size is the same every single time for the past month, so I don't think it's that either. Does crontab execute within a limited memory space?

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• Mapping an instance of IList in NHibernate

  - by Martin Kirsche

  I'm trying to map a parent-child relationship using NHibernate (2.1.2), MySql.Data (6.2.2) and MySQL Server (5.1). I figured out that this must be done using a <bag> in the mapping file. I build a test app which is running without yielding any errors and is doing an insert for each entry but somehow the foreign key inside the children table (ParentId) is always empty (null). Here are the important parts of my code... Parent public class Parent { public virtual int Id { get; set; } public virtual IList<Child> Children { get; set; } } <class name="Parent"> <id name="Id"> <generator class="native"/> </id> <bag name="Children" cascade="all"> <key column="ParentId"/> <one-to-many class="Child"/> </bag> </class> Child public class Child { public virtual int Id { get; set; } } <class name="Child"> <id name="Id"> <generator class="native"/> </id> </class> Program using (ISession session = sessionFactory.OpenSession()) { session.Save( new Parent() { Children = new List<Child>() { new Child(), new Child() } }); } Any ideas what I did wrong?

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• Keeping sync in multiplayer RTS game that uses floating point arithmetic

  - by Calmarius

  I'm writing a 2D space RTS game in C#. Single player works. Now I want to add some multiplayer functionality. I googled for it and it seems there is only one way to have thousands of units continuously moving without a powerful net connection: send only the commands through the network while running the same simulation at every player. And now there is a problem the entire engine uses doubles everywhere. And floating point calculations are depends heavily on compiler optimalizations and cpu architecture so it is very hard to keep things syncronized. And it is not grid based at all, and have a simple phisics engine to move the space-ships (space ships have impulse and angular-momentum...). So recoding the entire stuff to use fixed point would be quite cumbersome (but probably the only solution). So I have 2 options so far: Say bye to the current code and restart from scratch using integers Make the game LAN only where there is enough bandwidth to have 8 players with thousands of units and sending the positions and orientation etc in (almost) every frame... So I looking for better opinions, (or even tips on migrating the code to fixed-point without messing everything up...)

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• Mutual class instances in C++

  - by SepiDev

  Hi guys. What is the issue with this code? Here we have two files: classA.h and classB.h classA.h: #ifndef _class_a_h_ #define _class_a_h_ #include "classB.h" class B; //???? class A { public: A() { ptr_b = new B(); //???? } virtual ~A() { if(ptr_b) delete ptr_b; //???? num_a = 0; } int num_a; B* ptr_b; //???? }; #endif //_class_a_h_ classB.h: #ifndef _class_b_h_ #define _class_b_h_ #include "classA.h" class A; //???? class B { public: B() { ptr_a = new A(); //???? num_b = 0; } virtual ~B() { if(ptr_a) delete ptr_a; //???? } int num_b; A* ptr_a; //???? }; #endif //_class_b_h_ when I try to compile it, the compiler (g++) says: classB.h: In constructor ‘B::B()’: classB.h:12: error: invalid use of incomplete type ‘struct A’ classB.h:6: error: forward declaration of ‘struct A’ classB.h: In destructor ‘virtual B::~B()’: classB.h:16: warning: possible problem detected in invocation of delete operator: classB.h:16: warning: invalid use of incomplete type ‘struct A’ classB.h:6: warning: forward declaration of ‘struct A’ classB.h:16: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• why does setting stderr=subprocess.STDOUT fix a subprocess.check_output call?

  - by ShankarG

  I have a python script running on a small server that is called in three different ways - from within another python script, by cron, or by gammu-smsd (an SMS daemon with the wonderful mobile utility [gammu]). The script is for maintenance and contained the following kludge to measure used space on the system (presumably this is possible from within Python, but this was quick and dirty): reportdict['Used Space'] = subprocess.check_output(["df / | tail -1 | awk '{ print $5; }'"], shell=True)[0:-1] Oddly enough this line would only fail when the script was called by a shell script running from gammu-smsd. The line would fail with a CalledProcessError exception saying "returned exit status 2", even though the output attribute of the CalledProcessError object contained the correct output. The only command in the sequence of shell commands that would give such an error status would be awk, with status 2 indicating a fatal error. If the python script with this line was called by cron, by another python script, or from the command line, this line would work fine. I broke my head trying to fix the environment for the script, thinking this must be the problem. Finally though I put in stderr=subprocess.STDOUT, like so: reportdict['Used Space'] = subprocess.check_output(["df / | tail -1 | awk '{ print $5; }'"], stderr=subprocess.STDOUT, shell=True)[0:-1] This was a debug measure to help me figure out if some output was coming on stderr. But after this the script started working, even when called from gammu-smsd! Why might this be the case? I ask for future reference when using subprocess...

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• In Fluent NHibernate, how would I map the following domain models?

  - by Brandon

  I have a user class that looks something like this public class User { public virtual int Id { get; set; } public virtual long ValueA { get; set; } public virtual int? ValueB { get; set; } } ValueA is automatically assigned by the system. It is used in a lookup that would map to UserClass. However, if a value for ValueB exists, then it would do the lookup for UserClass in a different way. Right now the way I handle it is to get the User and then perform a separate lookup each time. return user.ValueB.HasValue ? Find(user.ValueB.Value) : Find(user.ValueA); Is there any way to make Fluent NHibernate do this for me so I can have UserClass as a property on the User class instead of having to do the lookup separately? I was thinking of the ComponentMap but I'm not sure how to make it account for the two possible lookup values.

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• Performance of C# method polymorphism with generics

  - by zildjohn01

  I noticed in C#, unlike C++, you can combine virtual and generic methods. For example: using System.Diagnostics; class Base { public virtual void Concrete() {Debug.WriteLine("base concrete");} public virtual void Generic<T>() {Debug.WriteLine("base generic");} } class Derived : Base { public override void Concrete() {Debug.WriteLine("derived concrete");} public override void Generic<T>() {Debug.WriteLine("derived generic");} } class App { static void Main() { Base x = new Derived(); x.Concrete(); x.Generic<PerformanceCounter>(); } } Given that any number of versions of Generic<T> could be instantiated, it doesn't look like the standard vtbl approach could be used to resolve method calls, and in fact it's not. Here's the generated code: x.Concrete(); mov ecx,dword ptr [ebp-8] mov eax,dword ptr [ecx] call dword ptr [eax+38h] x.Generic<PerformanceCounter>(); push 989A38h mov ecx,dword ptr [ebp-8] mov edx,989914h call 76A874F1 mov dword ptr [ebp-4],eax mov ecx,dword ptr [ebp-8] call dword ptr [ebp-4] The extra code appears to be looking up a dynamic vtbl according to the generic parameters, and then calling into it. Has anyone written about the specifics of this implementation? How well does it perform compared to the non-generic case?

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