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  • Creating rapid function overloads in C++

    - by DeadMG
    template<typename Functor, typename Return, typename Arg1, typename Arg2, typename Arg3, typename Arg4, typename Arg5, typename Arg6, typename Arg7, typename Arg8, typename Arg9, typename Arg10> class LambdaCall : public Instruction { public: LambdaCall(Functor func ,unsigned char constructorarg1 ,unsigned char constructorarg2 ,unsigned char constructorarg3 ,unsigned char constructorarg4 ,unsigned char constructorarg5 ,unsigned char constructorarg6 ,unsigned char constructorarg7 ,unsigned char constructorarg8 ,unsigned char constructorarg9 ,unsigned char constructorarg10) : arg1(constructorarg1) , arg2(constructorarg2) , arg3(constructorarg3) , arg4(constructorarg4) , arg5(constructorarg5) , arg6(constructorarg6) , arg7(constructorarg7) , arg8(constructorarg8) , arg9(constructorarg9) , arg10(constructorarg10) , function(func) {} void Call(State& state) { state.Push<Return>(func(*state.GetRegisterValue<Arg1>(arg1) ,*state.GetRegisterValue<Arg1>(arg1) ,*state.GetRegisterValue<Arg2>(arg2) ,*state.GetRegisterValue<Arg3>(arg3) ,*state.GetRegisterValue<Arg4>(arg4) ,*state.GetRegisterValue<Arg5>(arg5) ,*state.GetRegisterValue<Arg6>(arg6) ,*state.GetRegisterValue<Arg7>(arg7) ,*state.GetRegisterValue<Arg8>(arg8) ,*state.GetRegisterValue<Arg9>(arg9) ,*state.GetRegisterValue<Arg10>(arg10) )); } Functor function; unsigned char arg1; unsigned char arg2; unsigned char arg3; unsigned char arg4; unsigned char arg5; unsigned char arg6; unsigned char arg7; unsigned char arg8; unsigned char arg9; unsigned char arg10; }; Then again for every possible number of arguments I want to support, and again for void returns. Any way to do this faster?

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  • LINQ to SQL: NOTing a prebuilt expression

    - by ck
    I'm building a library of functions for one of my core L2S classes, all of which return a bool to allow checking for certain situations. Example: Expression<Func<Account, bool>> IsSomethingX = a => a.AccountSupplementary != null && a.AccountSupplementary.SomethingXFlag != null && a.AccountSupplementary.SomethingXFlag.Value; Now to query where this is not true, I CAN'T do this: var myAccounts= context.Accounts .Where(!IsSomethingX); // does not compile However, using the syntax from the PredicateBuilder class, I've come up with this: public static IQueryable<T> WhereNot<T>(this IQueryable<T> items, Expression<Func<T, bool>> expr1) { var invokedExpr = Expression.Invoke(expr1, expr1.Parameters.Cast<Expression>()); return items.Where(Expression.Lambda<Func<T, bool>> (Expression.Not(invokedExpr), expr1.Parameters)); } var myAccounts= context.Accounts .WhereNot(IsSomethingX); // does compile which actually produces the correct SQL. Does this look like a good solution, and is there anything I need to be aware of that might cause me problems in future?

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  • JQuery to PHP function and back Ajaxed

    - by Xaris
    Hi all, i have a set of php function that i want to call on different events mostly onclick with jquery async (ajax). The first function is called on load $(document).ready(function() { $("#div2").hide('slow'); $("#div1").empty().html('<img src="ajax-loader.gif" />'); $.ajax( { type: "POST", url: "WebFunctions.php", data: {'func':'1'}, success: function(html) { $("#div1").show('slow').html(html) } }); The Data: {'func':'1'} -- is a switch statement on the php side switch($_POST['func']) { case '1': getParents(); break; case '2': getChilds(params); break; case '3': getChildObjects(params); break; default: } "This functions are calls to a soap server" <-- irrelevant. So when that function finishes i get an array which contains IDs and Names. I echo the names but i want the ID for reference so when i click on the echoed name i can call an other php function with parameter the ID of the name... How do i get rid of the switch statement?? How do i call properly php functions and pass params to it??? How can i save this IDs so when i click on an item with that id an other php function is called?? Plz feel free to ask any question, any answer is welcome :)

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  • How to differentiate between method and function in a decorator?

    - by defnull
    I want to write a decorator that acts differently depending on whether it is applied to a function or to a method. def some_decorator(func): if the_magic_happens_here(func): # <---- Point of interest print 'Yay, found a method ^_^ (unbound jet)' else: print 'Meh, just an ordinary function :/' return func class MyClass(object): @some_decorator def method(self): pass @some_decorator def function(): pass I tried inspect.ismethod(), inspect.ismethoddescriptor() and inspect.isfunction() but no luck. The problem is that a method actually is neither a bound nor an unbound method but an ordinary function as long as it is accessed from within the class body. What I really want to do is to delay the actions of the decorator to the point the class is actually instantiated because I need the methods to be callable in their instance scope. For this, I want to mark methods with an attribute and later search for these attributes when the .__new__() method of MyClass is called. The classes for which this decorator should work are required to inherit from a class that is under my control. You can use that fact for your solution. In the case of a normal function the delay is not necessary and the decorator should take action immediately. That is why I wand to differentiate these two cases.

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  • What is a good solution to log the deletion of a row in MySQL?

    - by hobodave
    Background I am currently logging deletion of rows from my tickets table at the application level. When a user deletes a ticket the following SQL is executed: INSERT INTO alert_log (user_id, priority, priorityName, timestamp, message) VALUES (9, 4, 'WARN', NOW(), "TICKET: David A. deleted ticket #6 from Foo"); Please do not offer schema suggestions for the alert_log table. Fields: user_id - User id of the logged in user performing the deletion priority - Always 4 priorityName - Always 'WARN' timestamp - Always NOW() message - Format: "[NAMESPACE]: [FullName] deleted ticket #[TicketId] from [CompanyName]" NAMESPACE - Always TICKET FullName - Full name of user identified by user_id above TicketId - Primary key ID of the ticket being deleted CompanyName - Ticket has a Company via tickets.company_id Situation/Questions Obviously this solution does not work if a ticket is deleted manually from the mysql command line client. However, now I need to. The issues I'm having are as follows: Should I use a PROCEDURE, FUNCTION, or TRIGGER? -- Analysis: TRIGGER - I don't think this will work because I can't pass parameters to it, and it would trigger when my application deleted the row too. PROCEDURE or FUNCTION - Not sure. Should I return the number of deleted rows? If so, that would require a FUNCTION right? How should I account for the absence of a logged in user? -- Possibilities: Using either a PROC or FUNC, require the invoker to pass in a valid user_id Require the user to pass in a string with the name Use the CURRENT_USER - meh Hard code the FullName to just be "Database Administrator" Could the name be an optional parameter? I'm rather green when it comes to sprocs. Assuming I went with the PROC/FUNC approach, is it possible to outright restrict regular DELETE calls to this table, yet still allow users to call this PROC/FUNC to do the deletion for them? Ideally the solution is usable by my application as well, so that my code is DRY.

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  • Skinny controller in ASP.NET MVC 4

    - by thangchung
    Rails community are always inspire a lot of best ideas. I really love this community by the time. One of these is "Fat models and skinny controllers". I have spent a lot of time on ASP.NET MVC, and really I did some miss-takes, because I made the controller so fat. That make controller is really dirty and very hard to maintain in the future. It is violate seriously SRP principle and KISS as well. But how can we achieve that in ASP.NET MVC? That question is really clear after I read "Manning ASP.NET MVC 4 in Action". It is simple that we can separate it into ActionResult, and try to implementing logic and persistence data inside this. In last 2 years, I have read this from Jimmy Bogard blog, but in that time I never had a consideration about it. That's enough for talking now. I just published a sample on ASP.NET MVC 4, implemented on Visual Studio 2012 RC at here. I used EF framework at here for implementing persistence layer, and also use 2 free templates from internet to make the UI for this sample. In this sample, I try to implementing the simple magazine website that managing all articles, categories and news. It is not finished at all in this time, but no problems, because I just show you about how can we make the controller skinny. And I wanna hear more about your ideas. The first thing, I am abstract the base ActionResult class like this:    public abstract class MyActionResult : ActionResult, IEnsureNotNull     {         public abstract void EnsureAllInjectInstanceNotNull();     }     public abstract class ActionResultBase<TController> : MyActionResult where TController : Controller     {         protected readonly Expression<Func<TController, ActionResult>> ViewNameExpression;         protected readonly IExConfigurationManager ConfigurationManager;         protected ActionResultBase (Expression<Func<TController, ActionResult>> expr)             : this(DependencyResolver.Current.GetService<IExConfigurationManager>(), expr)         {         }         protected ActionResultBase(             IExConfigurationManager configurationManager,             Expression<Func<TController, ActionResult>> expr)         {             Guard.ArgumentNotNull(expr, "ViewNameExpression");             Guard.ArgumentNotNull(configurationManager, "ConfigurationManager");             ViewNameExpression = expr;             ConfigurationManager = configurationManager;         }         protected ViewResult GetViewResult<TViewModel>(TViewModel viewModel)         {             var m = (MethodCallExpression)ViewNameExpression.Body;             if (m.Method.ReturnType != typeof(ActionResult))             {                 throw new ArgumentException("ControllerAction method '" + m.Method.Name + "' does not return type ActionResult");             }             var result = new ViewResult             {                 ViewName = m.Method.Name             };             result.ViewData.Model = viewModel;             return result;         }         public override void ExecuteResult(ControllerContext context)         {             EnsureAllInjectInstanceNotNull();         }     } I also have an interface for validation all inject objects. This interface make sure all inject objects that I inject using Autofac container are not null. The implementation of this as below public interface IEnsureNotNull     {         void EnsureAllInjectInstanceNotNull();     } Afterwards, I am just simple implementing the HomePageViewModelActionResult class like this public class HomePageViewModelActionResult<TController> : ActionResultBase<TController> where TController : Controller     {         #region variables & ctors         private readonly ICategoryRepository _categoryRepository;         private readonly IItemRepository _itemRepository;         private readonly int _numOfPage;         public HomePageViewModelActionResult(Expression<Func<TController, ActionResult>> viewNameExpression)             : this(viewNameExpression,                    DependencyResolver.Current.GetService<ICategoryRepository>(),                    DependencyResolver.Current.GetService<IItemRepository>())         {         }         public HomePageViewModelActionResult(             Expression<Func<TController, ActionResult>> viewNameExpression,             ICategoryRepository categoryRepository,             IItemRepository itemRepository)             : base(viewNameExpression)         {             _categoryRepository = categoryRepository;             _itemRepository = itemRepository;             _numOfPage = ConfigurationManager.GetAppConfigBy("NumOfPage").ToInteger();         }         #endregion         #region implementation         public override void ExecuteResult(ControllerContext context)         {             base.ExecuteResult(context);             var cats = _categoryRepository.GetCategories();             var mainViewModel = new HomePageViewModel();             var headerViewModel = new HeaderViewModel();             var footerViewModel = new FooterViewModel();             var mainPageViewModel = new MainPageViewModel();             headerViewModel.SiteTitle = "Magazine Website";             if (cats != null && cats.Any())             {                 headerViewModel.Categories = cats.ToList();                 footerViewModel.Categories = cats.ToList();             }             mainPageViewModel.LeftColumn = BindingDataForMainPageLeftColumnViewModel();             mainPageViewModel.RightColumn = BindingDataForMainPageRightColumnViewModel();             mainViewModel.Header = headerViewModel;             mainViewModel.DashBoard = new DashboardViewModel();             mainViewModel.Footer = footerViewModel;             mainViewModel.MainPage = mainPageViewModel;             GetViewResult(mainViewModel).ExecuteResult(context);         }         public override void EnsureAllInjectInstanceNotNull()         {             Guard.ArgumentNotNull(_categoryRepository, "CategoryRepository");             Guard.ArgumentNotNull(_itemRepository, "ItemRepository");             Guard.ArgumentMustMoreThanZero(_numOfPage, "NumOfPage");         }         #endregion         #region private functions         private MainPageRightColumnViewModel BindingDataForMainPageRightColumnViewModel()         {             var mainPageRightCol = new MainPageRightColumnViewModel();             mainPageRightCol.LatestNews = _itemRepository.GetNewestItem(_numOfPage).ToList();             mainPageRightCol.MostViews = _itemRepository.GetMostViews(_numOfPage).ToList();             return mainPageRightCol;         }         private MainPageLeftColumnViewModel BindingDataForMainPageLeftColumnViewModel()         {             var mainPageLeftCol = new MainPageLeftColumnViewModel();             var items = _itemRepository.GetNewestItem(_numOfPage);             if (items != null && items.Any())             {                 var firstItem = items.First();                 if (firstItem == null)                     throw new NoNullAllowedException("First Item".ToNotNullErrorMessage());                 if (firstItem.ItemContent == null)                     throw new NoNullAllowedException("First ItemContent".ToNotNullErrorMessage());                 mainPageLeftCol.FirstItem = firstItem;                 if (items.Count() > 1)                 {                     mainPageLeftCol.RemainItems = items.Where(x => x.ItemContent != null && x.Id != mainPageLeftCol.FirstItem.Id).ToList();                 }             }             return mainPageLeftCol;         }         #endregion     }  Final step, I get into HomeController and add some line of codes like this [Authorize]     public class HomeController : BaseController     {         [AllowAnonymous]         public ActionResult Index()         {             return new HomePageViewModelActionResult<HomeController>(x=>x.Index());         }         [AllowAnonymous]         public ActionResult Details(int id)         {             return new DetailsViewModelActionResult<HomeController>(x => x.Details(id), id);         }         [AllowAnonymous]         public ActionResult Category(int id)         {             return new CategoryViewModelActionResult<HomeController>(x => x.Category(id), id);         }     } As you see, the code in controller is really skinny, and all the logic I move to the custom ActionResult class. Some people said, it just move the code out of controller and put it to another class, so it is still hard to maintain. Look like it just move the complicate codes from one place to another place. But if you have a look and think it in details, you have to find out if you have code for processing all logic that related to HttpContext or something like this. You can do it on Controller, and try to delegating another logic  (such as processing business requirement, persistence data,...) to custom ActionResult class. Tell me more your thinking, I am really willing to hear all of its from you guys. All source codes can be find out at here. Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="http://weblogs.asp.net//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");

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  • mysql: Cannot load from mysql.proc. The table is probably corrupted

    - by Alex
    Mysql was started: /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 but when I'm trying to do something: ERROR 1548 (HY000) at line 1: Cannot load from mysql.proc. The table is probably corrupted How to fix it? $ mysql -V mysql Ver 14.14 Distrib 5.1.58, for debian-linux-gnu (x86_64) using readline 6.2 $ lsb_release -a Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric $ sudo mysql_upgrade -uroot -p<password> --force Looking for 'mysql' as: mysql Looking for 'mysqlcheck' as: mysqlcheck Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' mysql.columns_priv OK mysql.db OK mysql.event OK mysql.func OK mysql.general_log Error : You can't use locks with log tables. status : OK mysql.help_category OK mysql.help_keyword OK mysql.help_relation OK mysql.help_topic OK mysql.host OK mysql.ndb_binlog_index OK mysql.plugin OK mysql.proc OK mysql.procs_priv OK mysql.servers OK mysql.slow_log Error : You can't use locks with log tables. status : OK mysql.tables_priv OK mysql.time_zone OK mysql.time_zone_leap_second OK mysql.time_zone_name OK mysql.time_zone_transition OK mysql.time_zone_transition_type OK mysql.user OK Running 'mysql_fix_privilege_tables'... OK $ mysqlcheck --port=3700 --socket=/srv/mysql/sockets/mysql-my-env.sock -A -udata_owner -pdata_owner <all tables> OK UPD1: for example I'm trying to remove procedure: mysql> DROP PROCEDURE IF EXISTS mysql.myproc; ERROR 1548 (HY000): Cannot load from mysql.proc. The table is probably corrupted mysql> UPD2: mysql> REPAIR TABLE mysql.proc; +------------+--------+----------+-----------------------------------------------------------------------------------------+ | Table | Op | Msg_type | Msg_text | +------------+--------+----------+-----------------------------------------------------------------------------------------+ | mysql.proc | repair | error | 1 when fixing table | | mysql.proc | repair | Error | Can't change permissions of the file '/srv/mysql/myDB/mysql/proc.MYD' (Errcode: 1) | | mysql.proc | repair | status | Operation failed | +------------+--------+----------+-----------------------------------------------------------------------------------------+ 3 rows in set (0.04 sec) This is strange, because: $ ls -l /srv/mysql/myDB/mysql/proc.MYD -rwxrwxrwx 1 mysql root 3983252 2012-02-03 22:51 /srv/mysql/myDB/mysql/proc.MYD UPD3: $ ls -la /srv/mysql/myDB/mysql total 8930 drwxrwxrwx 2 mysql root 2480 2012-02-21 13:13 . drwxrwxrwx 13 mysql root 504 2012-02-21 19:01 .. -rwxrwxrwx 1 mysql root 8820 2012-02-20 15:50 columns_priv.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 columns_priv.MYD -rwxrwxrwx 1 mysql root 4096 2012-02-20 15:50 columns_priv.MYI -rwxrwxrwx 1 mysql root 9582 2012-02-20 15:50 db.frm -rwxrwxrwx 1 mysql root 8360 2011-12-08 02:14 db.MYD -rwxrwxrwx 1 mysql root 5120 2012-02-20 15:50 db.MYI -rwxrwxrwx 1 mysql root 54 2011-11-12 15:42 db.opt -rwxrwxrwx 1 mysql root 10223 2012-02-20 15:50 event.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 event.MYD -rwxrwxrwx 1 mysql root 2048 2012-02-20 15:50 event.MYI -rwxrwxrwx 1 mysql root 8665 2012-02-20 15:50 func.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 func.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 func.MYI -rwxrwxrwx 1 mysql root 8700 2012-02-20 15:50 help_category.frm -rwxrwxrwx 1 mysql root 21497 2011-11-12 15:42 help_category.MYD -rwxrwxrwx 1 mysql root 3072 2012-02-20 15:50 help_category.MYI -rwxrwxrwx 1 mysql root 8612 2012-02-20 15:50 help_keyword.frm -rwxrwxrwx 1 mysql root 88650 2011-11-12 15:42 help_keyword.MYD -rwxrwxrwx 1 mysql root 16384 2012-02-20 15:50 help_keyword.MYI -rwxrwxrwx 1 mysql root 8630 2012-02-20 15:50 help_relation.frm -rwxrwxrwx 1 mysql root 8874 2011-11-12 15:42 help_relation.MYD -rwxrwxrwx 1 mysql root 16384 2012-02-20 15:50 help_relation.MYI -rwxrwxrwx 1 mysql root 8770 2012-02-20 15:50 help_topic.frm -rwxrwxrwx 1 mysql root 414320 2011-11-12 15:42 help_topic.MYD -rwxrwxrwx 1 mysql root 20480 2012-02-20 15:50 help_topic.MYI -rwxrwxrwx 1 mysql root 9510 2012-02-20 15:50 host.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 host.MYD -rwxrwxrwx 1 mysql root 2048 2012-02-20 15:50 host.MYI -rwxrwxrwx 1 mysql root 8554 2011-11-12 15:42 innodb_monitor.frm -rwxrwxrwx 1 mysql root 98304 2011-11-12 15:55 innodb_monitor.ibd -rwxrwxrwx 1 mysql root 8592 2012-02-20 15:50 inventory.frm -rwxrwxrwx 1 mysql root 76 2011-11-12 15:42 inventory.MYD -rwxrwxrwx 1 mysql root 2048 2012-02-20 15:50 inventory.MYI -rwxrwxrwx 1 mysql root 8778 2012-02-20 15:50 ndb_binlog_index.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 ndb_binlog_index.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 ndb_binlog_index.MYI -rwxrwxrwx 1 mysql root 8586 2012-02-20 15:50 plugin.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 plugin.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 plugin.MYI -rwxrwxrwx 1 mysql root 9996 2012-02-20 15:50 proc.frm -rwxrwxrwx 1 mysql root 3983252 2012-02-03 22:51 proc.MYD -rwxrwxrwx 1 mysql root 36864 2012-02-21 13:23 proc.MYI -rwxrwxrwx 1 mysql root 8875 2012-02-20 15:50 procs_priv.frm -rwxrwxrwx 1 mysql root 1700 2011-11-12 15:42 procs_priv.MYD -rwxrwxrwx 1 mysql root 8192 2012-02-20 15:50 procs_priv.MYI -rwxrwxrwx 1 mysql root 3977704 2012-02-21 13:23 proc.TMD -rwxrwxrwx 1 mysql root 8800 2012-02-20 15:50 proxies_priv.frm -rwxrwxrwx 1 mysql root 693 2011-11-12 15:42 proxies_priv.MYD -rwxrwxrwx 1 mysql root 5120 2012-02-20 15:50 proxies_priv.MYI -rwxrwxrwx 1 mysql root 8838 2012-02-20 15:50 servers.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 servers.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 servers.MYI -rwxrwxrwx 1 mysql root 8955 2012-02-20 15:50 tables_priv.frm -rwxrwxrwx 1 mysql root 5957 2011-11-12 15:42 tables_priv.MYD -rwxrwxrwx 1 mysql root 8192 2012-02-20 15:50 tables_priv.MYI -rwxrwxrwx 1 mysql root 8636 2012-02-20 15:50 time_zone.frm -rwxrwxrwx 1 mysql root 8624 2012-02-20 15:50 time_zone_leap_second.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 time_zone_leap_second.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 time_zone_leap_second.MYI -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 time_zone.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 time_zone.MYI -rwxrwxrwx 1 mysql root 8606 2012-02-20 15:50 time_zone_name.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 time_zone_name.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 time_zone_name.MYI -rwxrwxrwx 1 mysql root 8686 2012-02-20 15:50 time_zone_transition.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 time_zone_transition.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 time_zone_transition.MYI -rwxrwxrwx 1 mysql root 8748 2012-02-20 15:50 time_zone_transition_type.frm -rwxrwxrwx 1 mysql root 0 2011-11-12 15:42 time_zone_transition_type.MYD -rwxrwxrwx 1 mysql root 1024 2012-02-20 15:50 time_zone_transition_type.MYI -rwxrwxrwx 1 mysql root 10630 2012-02-20 15:50 user.frm -rwxrwxrwx 1 mysql root 5456 2011-11-12 21:01 user.MYD -rwxrwxrwx 1 mysql root 4096 2012-02-20 15:50 user.MYI

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  • Performance of ClearCase servers on VMs?

    - by Garen
    Where I work, we are in need of upgrading our ClearCase servers and it's been proposed that we move them into a new (yet-to-be-deployed) VMmare system. In the past I've not noticed a significant problem with performance with most applications when running in VMs, but given that ClearCase "speed" (i.e. dynamic-view response times) is so latency sensitive I am concerned that this will not be a good idea. VMWare has numerous white-papers detailing performance related issues based on network traffic patterns that re-inforces my hypothesis, but nothing particularly concrete for this particular use case that I can see. What I can find are various forum posts online, but which are somewhat dated, e.g.: ClearCase clients are supported on VMWare, but not for performance issues. I would never put a production server on VM. It will work but will be slower. The more complex the slower it gets. accessing or building from a local snapshot view will be the fastest, building in a remote VM stored dynamic view using clearmake will be painful..... VMWare is best used for test environments (via http://www.cmcrossroads.com/forums?func=view&catid=31&id=44094&limit=10&start=10) and: VMware + ClearCase = works but SLUGGISH!!!!!! (windows)(not for production environment) My company tried to mandate that all new apps or app upgrades needed to be on/moved VMware instances. The VMware instance could not handle the demands of ClearCase. (come to find out that I was sharing a box with a database server) Will you know what else would be on that box besides ClearCase? Karl (via http://www.cmcrossroads.com/forums?func=view&id=44094&catid=31) and: ... are still finding we can't get the performance using dynamic views to below 2.5 times that of a physical machine. Interestingly, speaking to a few people with much VMWare experience and indeed from running builds, we are finding that typically, VMWare doesn't take that much longer for most applications and about 10-20% longer has been quoted. (via http://www.cmcrossroads.com/forums?func=view&catid=31&id=44094&limit=10&start=10) Which brings me to the more direct question: Does anyone have any more recent experience with ClearCase servers on VMware (if not any specific, relevant performance advice)?

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  • Useless Plesk Error?

    - by Josh Pennington
    I am trying to determine why Plesk on my server won't start and I have no idea where to even start (since my hosting company appears to not want to help me out). Anyways, the error in my Plesk error_log is as follows: 2010-12-25 21:30:28: (log.c.75) server started 2010-12-25 21:30:28: (network.c.336) SSL: error:00000000:lib(0):func(0):reason(0) 2010-12-25 21:30:28: (log.c.75) server started 2010-12-25 21:30:28: (network.c.336) SSL: error:00000000:lib(0):func(0):reason(0) It leads me to believe its a problem with the SSL on the server but I am not sure what to make of the error. Can someone lead me in the right direction? Thanks Josh Pennington

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  • Overriding the save() method of a model that uses django-mptt

    - by saturdayplace
    I've been using django-mptt in my project for a while now, it's fabulous. Recently, I've found a need to override a model's save() method that uses mptt, and I'm getting an error when I try to save a new instance of that model: Exception Type: ValueError at /admin/scrivener/page/add/ Exception Value: Cannot use None as a query value I'm assuming that this is a result of the fact that the instance hasn't been stuck into a tree yet, but I'm not sure how to go about fixing this. I added a comment about it onto a similar issue on the project's tracker, but I was hoping that someone here might be able to put me on the right track faster. Here's the traceback. Environment: Request Method: POST Request URL: http://localhost:8000/admin/scrivener/page/add/ Django Version: 1.2 rc 1 SVN-13117 Python Version: 2.6.4 Installed Applications: ['django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.sites', 'django.contrib.admin', 'django.contrib.sitemaps', 'mptt', 'filebrowser', 'south', 'haystack', 'django_static', 'etc', 'scrivener', 'gregor', 'annunciator'] Installed Middleware: ('django.middleware.common.CommonMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware') Traceback: File "B:\django-apps\3rd Party Source\django\core\handlers\base.py" in get_response 100. response = callback(request, *callback_args, **callback_kwargs) File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in wrapper 239. return self.admin_site.admin_view(view)(*args, **kwargs) File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapped_view 74. response = view_func(request, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\views\decorators\cache.py" in _wrapped_view_func 69. response = view_func(request, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\contrib\admin\sites.py" in inner 190. return view(request, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapper 21. return decorator(bound_func)(*args, **kwargs) File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapped_view 74. response = view_func(request, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in bound_func 17. return func(self, *args2, **kwargs2) File "B:\django-apps\3rd Party Source\django\db\transaction.py" in _commit_on_success 299. res = func(*args, **kw) File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in add_view 795. self.save_model(request, new_object, form, change=False) File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in save_model 597. obj.save() File "B:\django-apps\scrivener\models.py" in save 205. self.url = self.get_absolute_url() File "B:\django-apps\3rd Party Source\django\utils\functional.py" in _curried 55. return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs)) File "B:\django-apps\3rd Party Source\django\db\models\base.py" in get_absolute_url 940. return settings.ABSOLUTE_URL_OVERRIDES.get('%s.%s' % (opts.app_label, opts.module_name), func)(self, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\db\models\__init__.py" in inner 31. bits = func(*args, **kwargs) File "B:\django-apps\scrivener\models.py" in get_absolute_url 194. for ancestor in self.get_ancestors(): File "B:\django-apps\3rd Party Source\mptt\models.py" in get_ancestors 23. opts.tree_id_attr: getattr(self, opts.tree_id_attr), File "B:\django-apps\3rd Party Source\django\db\models\manager.py" in filter 141. return self.get_query_set().filter(*args, **kwargs) File "B:\django-apps\3rd Party Source\django\db\models\query.py" in filter 550. return self._filter_or_exclude(False, *args, **kwargs) File "B:\django-apps\3rd Party Source\django\db\models\query.py" in _filter_or_exclude 568. clone.query.add_q(Q(*args, **kwargs)) File "B:\django-apps\3rd Party Source\django\db\models\sql\query.py" in add_q 1131. can_reuse=used_aliases) File "B:\django-apps\3rd Party Source\django\db\models\sql\query.py" in add_filter 1000. raise ValueError("Cannot use None as a query value") Exception Type: ValueError at /admin/scrivener/page/add/ Exception Value: Cannot use None as a query value

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  • Throwing a C++ exception from inside a Linux Signal handler

    - by SoapBox
    As a thought experiment more than anything I am trying to get a C++ exception thrown "from" a linux signal handler for SIGSEGV. (I'm aware this is not a solution to any real world SIGSEGV and should never actually be done, but I thought I would try it out after being asked about it, and now I can't get it out of my head until I figure out how to do it.) Below is the closest I have come, but instead of the signal being caught properly, terminate() is being called as if no try/catch block is available. Anyone know why? Or know a way I can actually get a C++ exception from a signal handler? The code (beware, the self modifying asm limits this to running on x86_64 if you're trying to test it): #include <iostream> #include <stdexcept> #include <signal.h> #include <stdint.h> #include <errno.h> #include <string.h> #include <sys/mman.h> using namespace std; uint64_t oldaddr = 0; void thrower() { cout << "Inside thrower" << endl; throw std::runtime_error("SIGSEGV"); } void segv_handler(int sig, siginfo_t *info, void *pctx) { ucontext_t *context = (ucontext_t *)pctx; cout << "Inside SIGSEGV handler" << endl; oldaddr = context->uc_mcontext.gregs[REG_RIP]; uint32_t pageSize = (uint32_t)sysconf(_SC_PAGESIZE); uint64_t bottomOfOldPage = (oldaddr/pageSize) * pageSize; mprotect((void*)bottomOfOldPage, pageSize*2, PROT_READ|PROT_WRITE|PROT_EXEC); // 48 B8 xx xx xx xx xx xx xx xx = mov rax, xxxx *((uint8_t*)(oldaddr+0)) = 0x48; *((uint8_t*)(oldaddr+1)) = 0xB8; *((int64_t*)(oldaddr+2)) = (int64_t)thrower; // FF E0 = jmp rax *((uint8_t*)(oldaddr+10)) = 0xFF; *((uint8_t*)(oldaddr+11)) = 0xE0; } void func() { try { *(uint32_t*)0x1234 = 123456789; } catch (...) { cout << "caught inside func" << endl; throw; } } int main() { cout << "Top of main" << endl; struct sigaction action, old_action; action.sa_sigaction = segv_handler; sigemptyset(&action.sa_mask); action.sa_flags = SA_SIGINFO | SA_RESTART | SA_NODEFER; if (sigaction(SIGSEGV, &action, &old_action)<0) cerr << "Error setting handler : " << strerror(errno) << endl; try { func(); } catch (std::exception &e) { cout << "Caught : " << e.what() << endl; } cout << "Bottom of main" << endl << endl; } The actual output: Top of main Inside SIGSEGV handler Inside thrower terminate called after throwing an instance of 'std::runtime_error' what(): SIGSEGV Aborted Expected output: Top of main Inside thrower caught inside func Caught : SIGSEGV Bottom of main

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  • Issue with translating a delegate function from c# to vb.net for use with Google OAuth 2

    - by Jeremy
    I've been trying to translate a Google OAuth 2 example from C# to Vb.net for a co-worker's project. I'm having on end of issues translating the following methods: private OAuth2Authenticator<WebServerClient> CreateAuthenticator() { // Register the authenticator. var provider = new WebServerClient(GoogleAuthenticationServer.Description); provider.ClientIdentifier = ClientCredentials.ClientID; provider.ClientSecret = ClientCredentials.ClientSecret; var authenticator = new OAuth2Authenticator<WebServerClient>(provider, GetAuthorization) { NoCaching = true }; return authenticator; } private IAuthorizationState GetAuthorization(WebServerClient client) { // If this user is already authenticated, then just return the auth state. IAuthorizationState state = AuthState; if (state != null) { return state; } // Check if an authorization request already is in progress. state = client.ProcessUserAuthorization(new HttpRequestInfo(HttpContext.Current.Request)); if (state != null && (!string.IsNullOrEmpty(state.AccessToken) || !string.IsNullOrEmpty(state.RefreshToken))) { // Store and return the credentials. HttpContext.Current.Session["AUTH_STATE"] = _state = state; return state; } // Otherwise do a new authorization request. string scope = TasksService.Scopes.TasksReadonly.GetStringValue(); OutgoingWebResponse response = client.PrepareRequestUserAuthorization(new[] { scope }); response.Send(); // Will throw a ThreadAbortException to prevent sending another response. return null; } The main issue being this line: var authenticator = new OAuth2Authenticator<WebServerClient>(provider, GetAuthorization) { NoCaching = true }; The Method signature reads as for this particular line reads as follows: Public Sub New(tokenProvider As TClient, authProvider As System.Func(Of TClient, DotNetOpenAuth.OAuth2.IAuthorizationState)) My understanding of Delegate functions in VB.net isn't the greatest. However I have read over all of the MSDN documentation and other relevant resources on the web, but I'm still stuck as to how to translate this particular line. So far all of my attempts have resulted in either the a cast error (see below) or no call to GetAuthorization. The Code (vb.net on .net 3.5) Private Function CreateAuthenticator() As OAuth2Authenticator(Of WebServerClient) ' Register the authenticator. Dim client As New WebServerClient(GoogleAuthenticationServer.Description, oauth.ClientID, oauth.ClientSecret) Dim authDelegate As Func(Of WebServerClient, IAuthorizationState) = AddressOf GetAuthorization Dim authenticator = New OAuth2Authenticator(Of WebServerClient)(client, authDelegate) With {.NoCaching = True} 'Dim authenticator = New OAuth2Authenticator(Of WebServerClient)(client, GetAuthorization(client)) With {.NoCaching = True} 'Dim authenticator = New OAuth2Authenticator(Of WebServerClient)(client, New Func(Of WebServerClient, IAuthorizationState)(Function(c) GetAuthorization(c))) With {.NoCaching = True} 'Dim authenticator = New OAuth2Authenticator(Of WebServerClient)(client, New Func(Of WebServerClient, IAuthorizationState)(AddressOf GetAuthorization)) With {.NoCaching = True} Return authenticator End Function Private Function GetAuthorization(arg As WebServerClient) As IAuthorizationState ' If this user is already authenticated, then just return the auth state. Dim state As IAuthorizationState = AuthState If (Not state Is Nothing) Then Return state End If ' Check if an authorization request already is in progress. state = arg.ProcessUserAuthorization(New HttpRequestInfo(HttpContext.Current.Request)) If (state IsNot Nothing) Then If ((String.IsNullOrEmpty(state.AccessToken) = False Or String.IsNullOrEmpty(state.RefreshToken) = False)) Then ' Store Credentials HttpContext.Current.Session("AUTH_STATE") = state _state = state Return state End If End If ' Otherwise do a new authorization request. Dim scope As String = AnalyticsService.Scopes.AnalyticsReadonly.GetStringValue() Dim _response As OutgoingWebResponse = arg.PrepareRequestUserAuthorization(New String() {scope}) ' Add Offline Access and forced Approval _response.Headers("location") += "&access_type=offline&approval_prompt=force" _response.Send() ' Will throw a ThreadAbortException to prevent sending another response. Return Nothing End Function The Cast Error Server Error in '/' Application. Unable to cast object of type 'DotNetOpenAuth.OAuth2.AuthorizationState' to type 'System.Func`2[DotNetOpenAuth.OAuth2.WebServerClient,DotNetOpenAuth.OAuth2.IAuthorizationState]'. 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.InvalidCastException: Unable to cast object of type 'DotNetOpenAuth.OAuth2.AuthorizationState' to type 'System.Func`2[DotNetOpenAuth.OAuth2.WebServerClient,DotNetOpenAuth.OAuth2.IAuthorizationState]'. I've spent the better part of a day on this, and it's starting to drive me nuts. Help is much appreciated.

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  • Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

    - by Reed
    In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

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  • How I understood monads, part 1/2: sleepless and self-loathing in Seattle

    - by Bertrand Le Roy
    For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to understand a few interesting concepts about the universe, I had to check it out and try to understand monads so that I too can say “oh, yeah, that’s a monad”. Man, was I hit hard in the face with the limitations of my own abstract thinking abilities. All the articles I could find about the subject seemed to be vaguely understandable at first but very quickly overloaded the very few concept slots I have available in my brain. They also seemed to be consistently using arcane notation that I was entirely unfamiliar with. It finally all clicked together one Friday afternoon during the team’s beer symposium when Louis was patient enough to break it down for me in a language I could understand (C#). I don’t know if being intoxicated helped. Feel free to read this with or without a drink in hand. So here it is in a nutshell: a monad allows you to manipulate stuff in interesting ways. Oh, OK, you might say. Yeah. Exactly. Let’s start with a trivial case: public static class Trivial { public static TResult Execute<T, TResult>( this T argument, Func<T, TResult> operation) { return operation(argument); } } This is not a monad. I removed most concepts here to start with something very simple. There is only one concept here: the idea of executing an operation on an object. This is of course trivial and it would actually be simpler to just apply that operation directly on the object. But please bear with me, this is our first baby step. Here’s how you use that thing: "some string" .Execute(s => s + " processed by trivial proto-monad.") .Execute(s => s + " And it's chainable!"); What we’re doing here is analogous to having an assembly chain in a factory: you can feed it raw material (the string here) and a number of machines that each implement a step in the manufacturing process and you can start building stuff. The Trivial class here represents the empty assembly chain, the conveyor belt if you will, but it doesn’t care what kind of raw material gets in, what gets out or what each machine is doing. It is pure process. A real monad will need a couple of additional concepts. Let’s say the conveyor belt needs the material to be processed to be contained in standardized boxes, just so that it can safely and efficiently be transported from machine to machine or so that tracking information can be attached to it. Each machine knows how to treat raw material or partly processed material, but it doesn’t know how to treat the boxes so the conveyor belt will have to extract the material from the box before feeding it into each machine, and it will have to box it back afterwards. This conveyor belt with boxes is essentially what a monad is. It has one method to box stuff, one to extract stuff from its box and one to feed stuff into a machine. So let’s reformulate the previous example but this time with the boxes, which will do nothing for the moment except containing stuff. public class Identity<T> { public Identity(T value) { Value = value; } public T Value { get; private set;} public static Identity<T> Unit(T value) { return new Identity<T>(value); } public static Identity<U> Bind<U>( Identity<T> argument, Func<T, Identity<U>> operation) { return operation(argument.Value); } } Now this is a true to the definition Monad, including the weird naming of the methods. It is the simplest monad, called the identity monad and of course it does nothing useful. Here’s how you use it: Identity<string>.Bind( Identity<string>.Unit("some string"), s => Identity<string>.Unit( s + " was processed by identity monad.")).Value That of course is seriously ugly. Note that the operation is responsible for re-boxing its result. That is a part of strict monads that I don’t quite get and I’ll take the liberty to lift that strange constraint in the next examples. To make this more readable and easier to use, let’s build a few extension methods: public static class IdentityExtensions { public static Identity<T> ToIdentity<T>(this T value) { return new Identity<T>(value); } public static Identity<U> Bind<T, U>( this Identity<T> argument, Func<T, U> operation) { return operation(argument.Value).ToIdentity(); } } With those, we can rewrite our code as follows: "some string".ToIdentity() .Bind(s => s + " was processed by monad extensions.") .Bind(s => s + " And it's chainable...") .Value; This is considerably simpler but still retains the qualities of a monad. But it is still pointless. Let’s look at a more useful example, the state monad, which is basically a monad where the boxes have a label. It’s useful to perform operations on arbitrary objects that have been enriched with an attached state object. public class Stateful<TValue, TState> { public Stateful(TValue value, TState state) { Value = value; State = state; } public TValue Value { get; private set; } public TState State { get; set; } } public static class StateExtensions { public static Stateful<TValue, TState> ToStateful<TValue, TState>( this TValue value, TState state) { return new Stateful<TValue, TState>(value, state); } public static Stateful<TResult, TState> Execute<TValue, TState, TResult>( this Stateful<TValue, TState> argument, Func<TValue, TResult> operation) { return operation(argument.Value) .ToStateful(argument.State); } } You can get a stateful version of any object by calling the ToStateful extension method, passing the state object in. You can then execute ordinary operations on the values while retaining the state: var statefulInt = 3.ToStateful("This is the state"); var processedStatefulInt = statefulInt .Execute(i => ++i) .Execute(i => i * 10) .Execute(i => i + 2); Console.WriteLine("Value: {0}; state: {1}", processedStatefulInt.Value, processedStatefulInt.State); This monad differs from the identity by enriching the boxes. There is another way to give value to the monad, which is to enrich the processing. An example of that is the writer monad, which can be typically used to log the operations that are being performed by the monad. Of course, the richest monads enrich both the boxes and the processing. That’s all for today. I hope with this you won’t have to go through the same process that I did to understand monads and that you haven’t gone into concept overload like I did. Next time, we’ll examine some examples that you already know but we will shine the monadic light, hopefully illuminating them in a whole new way. Realizing that this pattern is actually in many places but mostly unnoticed is what will enable the truly casual “oh, yes, that’s a monad” comments. Here’s the code for this article: http://weblogs.asp.net/blogs/bleroy/Samples/Monads.zip The Wikipedia article on monads: http://en.wikipedia.org/wiki/Monads_in_functional_programming This article was invaluable for me in understanding how to express the canonical monads in C# (interesting Linq stuff in there): http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx

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  • C#/.NET Little Wonders: Skip() and Take()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. I’ve covered many valuable methods from System.Linq class library before, so you already know it’s packed with extension-method goodness.  Today I’d like to cover two small families I’ve neglected to mention before: Skip() and Take().  While these methods seem so simple, they are an easy way to create sub-sequences for IEnumerable<T>, much the way GetRange() creates sub-lists for List<T>. Skip() and SkipWhile() The Skip() family of methods is used to ignore items in a sequence until either a certain number are passed, or until a certain condition becomes false.  This makes the methods great for starting a sequence at a point possibly other than the first item of the original sequence.   The Skip() family of methods contains the following methods (shown below in extension method syntax): Skip(int count) Ignores the specified number of items and returns a sequence starting at the item after the last skipped item (if any).  SkipWhile(Func<T, bool> predicate) Ignores items as long as the predicate returns true and returns a sequence starting with the first item to invalidate the predicate (if any).  SkipWhile(Func<T, int, bool> predicate) Same as above, but passes not only the item itself to the predicate, but also the index of the item.  For example: 1: var list = new[] { 3.14, 2.72, 42.0, 9.9, 13.0, 101.0 }; 2:  3: // sequence contains { 2.72, 42.0, 9.9, 13.0, 101.0 } 4: var afterSecond = list.Skip(1); 5: Console.WriteLine(string.Join(", ", afterSecond)); 6:  7: // sequence contains { 42.0, 9.9, 13.0, 101.0 } 8: var afterFirstDoubleDigit = list.SkipWhile(v => v < 10.0); 9: Console.WriteLine(string.Join(", ", afterFirstDoubleDigit)); Note that the SkipWhile() stops skipping at the first item that returns false and returns from there to the rest of the sequence, even if further items in that sequence also would satisfy the predicate (otherwise, you’d probably be using Where() instead, of course). If you do use the form of SkipWhile() which also passes an index into the predicate, then you should keep in mind that this is the index of the item in the sequence you are calling SkipWhile() from, not the index in the original collection.  That is, consider the following: 1: var list = new[] { 1.0, 1.1, 1.2, 2.2, 2.3, 2.4 }; 2:  3: // Get all items < 10, then 4: var whatAmI = list 5: .Skip(2) 6: .SkipWhile((i, x) => i > x); For this example the result above is 2.4, and not 1.2, 2.2, 2.3, 2.4 as some might expect.  The key is knowing what the index is that’s passed to the predicate in SkipWhile().  In the code above, because Skip(2) skips 1.0 and 1.1, the sequence passed to SkipWhile() begins at 1.2 and thus it considers the “index” of 1.2 to be 0 and not 2.  This same logic applies when using any of the extension methods that have an overload that allows you to pass an index into the delegate, such as SkipWhile(), TakeWhile(), Select(), Where(), etc.  It should also be noted, that it’s fine to Skip() more items than exist in the sequence (an empty sequence is the result), or even to Skip(0) which results in the full sequence.  So why would it ever be useful to return Skip(0) deliberately?  One reason might be to return a List<T> as an immutable sequence.  Consider this class: 1: public class MyClass 2: { 3: private List<int> _myList = new List<int>(); 4:  5: // works on surface, but one can cast back to List<int> and mutate the original... 6: public IEnumerable<int> OneWay 7: { 8: get { return _myList; } 9: } 10:  11: // works, but still has Add() etc which throw at runtime if accidentally called 12: public ReadOnlyCollection<int> AnotherWay 13: { 14: get { return new ReadOnlyCollection<int>(_myList); } 15: } 16:  17: // immutable, can't be cast back to List<int>, doesn't have methods that throw at runtime 18: public IEnumerable<int> YetAnotherWay 19: { 20: get { return _myList.Skip(0); } 21: } 22: } This code snippet shows three (among many) ways to return an internal sequence in varying levels of immutability.  Obviously if you just try to return as IEnumerable<T> without doing anything more, there’s always the danger the caller could cast back to List<T> and mutate your internal structure.  You could also return a ReadOnlyCollection<T>, but this still has the mutating methods, they just throw at runtime when called instead of giving compiler errors.  Finally, you can return the internal list as a sequence using Skip(0) which skips no items and just runs an iterator through the list.  The result is an iterator, which cannot be cast back to List<T>.  Of course, there’s many ways to do this (including just cloning the list, etc.) but the point is it illustrates a potential use of using an explicit Skip(0). Take() and TakeWhile() The Take() and TakeWhile() methods can be though of as somewhat of the inverse of Skip() and SkipWhile().  That is, while Skip() ignores the first X items and returns the rest, Take() returns a sequence of the first X items and ignores the rest.  Since they are somewhat of an inverse of each other, it makes sense that their calling signatures are identical (beyond the method name obviously): Take(int count) Returns a sequence containing up to the specified number of items. Anything after the count is ignored. TakeWhile(Func<T, bool> predicate) Returns a sequence containing items as long as the predicate returns true.  Anything from the point the predicate returns false and beyond is ignored. TakeWhile(Func<T, int, bool> predicate) Same as above, but passes not only the item itself to the predicate, but also the index of the item. So, for example, we could do the following: 1: var list = new[] { 1.0, 1.1, 1.2, 2.2, 2.3, 2.4 }; 2:  3: // sequence contains 1.0 and 1.1 4: var firstTwo = list.Take(2); 5:  6: // sequence contains 1.0, 1.1, 1.2 7: var underTwo = list.TakeWhile(i => i < 2.0); The same considerations for SkipWhile() with index apply to TakeWhile() with index, of course.  Using Skip() and Take() for sub-sequences A few weeks back, I talked about The List<T> Range Methods and showed how they could be used to get a sub-list of a List<T>.  This works well if you’re dealing with List<T>, or don’t mind converting to List<T>.  But if you have a simple IEnumerable<T> sequence and want to get a sub-sequence, you can also use Skip() and Take() to much the same effect: 1: var list = new List<double> { 1.0, 1.1, 1.2, 2.2, 2.3, 2.4 }; 2:  3: // results in List<T> containing { 1.2, 2.2, 2.3 } 4: var subList = list.GetRange(2, 3); 5:  6: // results in sequence containing { 1.2, 2.2, 2.3 } 7: var subSequence = list.Skip(2).Take(3); I say “much the same effect” because there are some differences.  First of all GetRange() will throw if the starting index or the count are greater than the number of items in the list, but Skip() and Take() do not.  Also GetRange() is a method off of List<T>, thus it can use direct indexing to get to the items much more efficiently, whereas Skip() and Take() operate on sequences and may actually have to walk through the items they skip to create the resulting sequence.  So each has their pros and cons.  My general rule of thumb is if I’m already working with a List<T> I’ll use GetRange(), but for any plain IEnumerable<T> sequence I’ll tend to prefer Skip() and Take() instead. Summary The Skip() and Take() families of LINQ extension methods are handy for producing sub-sequences from any IEnumerable<T> sequence.  Skip() will ignore the specified number of items and return the rest of the sequence, whereas Take() will return the specified number of items and ignore the rest of the sequence.  Similarly, the SkipWhile() and TakeWhile() methods can be used to skip or take items, respectively, until a given predicate returns false.    Technorati Tags: C#, CSharp, .NET, LINQ, IEnumerable<T>, Skip, Take, SkipWhile, TakeWhile

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  • Make Your Menu Item Highlighted

    - by Shaun
    When I was working on the TalentOn project (Promotion in MSDN Chinese) I was asked to implement a functionality that makes the top menu items highlighted when the currently viewing page was in that section. This might be a common scenario in the web application development I think.   Simple Example When thinking about the solution of the highlighted menu items the biggest problem would be how to define the sections (menu item) and the pages it belongs to rather than making the menu highlighted. With the ASP.NET MVC framework we can use the controller – action infrastructure for us to achieve it. Each controllers would have a related menu item on the master page normally. The menu item would be highlighted if any of the views under this controller are being shown. Some specific menu items would be highlighted of that action was invoked, for example the home page, the about page, etc. The check rule can be specified on-demand. For example I can define the action LogOn and Register of Account controller should make the Account menu item highlighted while the ChangePassword should make the Profile menu item highlighted. I’m going to use the HtmlHelper to render the highlight-able menu item. The key point is that I need to pass the predication to check whether the current view belongs to this menu item which means this menu item should be highlighted or not. Hence I need a delegate as its parameter. The simplest code would be like this. 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Web; 5: using System.Web.Mvc; 6: using System.Web.Mvc.Html; 7:  8: namespace ShaunXu.Blogs.HighlighMenuItem 9: { 10: public static class HighlightMenuItemHelper 11: { 12: public static MvcHtmlString HighlightMenuItem(this HtmlHelper helper, 13: string text, string controllerName, string actionName, object routeData, object htmlAttributes, 14: string highlightText, object highlightHtmlAttributes, 15: Func<HtmlHelper, bool> highlightPredicate) 16: { 17: var shouldHighlight = highlightPredicate.Invoke(helper); 18: if (shouldHighlight) 19: { 20: return helper.ActionLink(string.IsNullOrWhiteSpace(highlightText) ? text : highlightText, 21: actionName, controllerName, routeData, highlightHtmlAttributes == null ? htmlAttributes : highlightHtmlAttributes); 22: } 23: else 24: { 25: return helper.ActionLink(text, actionName, controllerName, routeData, htmlAttributes); 26: } 27: } 28: } 29: } There are 3 groups of the parameters: the first group would be the same as the in-build ActionLink method parameters. It has the link text, controller name and action name, etc passed in so that I can render a valid linkage for the menu item. The second group would be more focus on the highlight link text and Html attributes. I will use them to render the highlight menu item. The third group, which contains one parameter, would be a predicate that tells me whether this menu item should be highlighted or not based on the user’s definition. And then I changed my master page of the sample MVC application. I let the Home and About menu highlighted only when the Index and About action are invoked. And I added a new menu named Account which should be highlighted for all actions/views under its Account controller. So my master would be like this. 1: <div id="menucontainer"> 2:  3: <ul id="menu"> 4: <li><% 1: : Html.HighlightMenuItem( 2: "Home", "Home", "Index", null, null, 3: "[Home]", null, 4: helper => helper.ViewContext.RouteData.Values["controller"].ToString() == "Home" 5: && helper.ViewContext.RouteData.Values["action"].ToString() == "Index")%></li> 5:  6: <li><% 1: : Html.HighlightMenuItem( 2: "About", "Home", "About", null, null, 3: "[About]", null, 4: helper => helper.ViewContext.RouteData.Values["controller"].ToString() == "Home" 5: && helper.ViewContext.RouteData.Values["action"].ToString() == "About")%></li> 7:  8: <li><% 1: : Html.HighlightMenuItem( 2: "Account", "Account", "LogOn", null, null, 3: "[Account]", null, 4: helper => helper.ViewContext.RouteData.Values["controller"].ToString() == "Account")%></li> 9: 10: </ul> 11:  12: </div> Note: You need to add the import section for the namespace “ShaunXu.Blogs.HighlighMenuItem” to make the extension method I created below available. So let’s see the result. When the home page was shown the Home menu was highlighted since at this moment it was controller = Home and action = Index. And if I clicked the About menu you can see it turned highlighted as now the action was About. And if I navigated to the register page the Account menu was highlighted since it should be like that when any actions under the Account controller was invoked.   Fluently Language Till now it’s a fully example for the highlight menu item but not perfect yet. Since the most common scenario would be: highlighted when the action invoked, or highlighted when any action was invoked under this controller, we can created 2 shortcut method so for them so that normally the developer will be no need to specify the delegation. Another place we can improve would be, to make the method more user-friendly, or I should say developer-friendly. As you can see when we want to add a highlight menu item we need to specify 8 parameters and we need to remember what they mean. In fact we can make the method more “fluently” so that the developer can have the hints when using it by the Visual Studio IntelliSense. Below is the full code for it. 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Web; 5: using System.Web.Mvc; 6: using System.Web.Mvc.Html; 7:  8: namespace Ethos.Xrm.HR 9: { 10: #region Helper 11:  12: public static class HighlightActionMenuHelper 13: { 14: public static IHighlightActionMenuProviderAfterCreated HighlightActionMenu(this HtmlHelper helper) 15: { 16: return new HighlightActionMenuProvider(helper); 17: } 18: } 19:  20: #endregion 21:  22: #region Interfaces 23:  24: public interface IHighlightActionMenuProviderAfterCreated 25: { 26: IHighlightActionMenuProviderAfterOn On(string actionName, string controllerName); 27: } 28:  29: public interface IHighlightActionMenuProviderAfterOn 30: { 31: IHighlightActionMenuProviderAfterWith With(string text, object routeData, object htmlAttributes); 32: } 33:  34: public interface IHighlightActionMenuProviderAfterWith 35: { 36: IHighlightActionMenuProviderAfterHighlightWhen HighlightWhen(Func<HtmlHelper, bool> predicate); 37: IHighlightActionMenuProviderAfterHighlightWhen HighlightWhenControllerMatch(); 38: IHighlightActionMenuProviderAfterHighlightWhen HighlightWhenControllerAndActionMatch(); 39: } 40:  41: public interface IHighlightActionMenuProviderAfterHighlightWhen 42: { 43: IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(object highlightHtmlAttributes, string highlightText); 44: IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(object highlightHtmlAttributes); 45: IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(string cssClass, string highlightText); 46: IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(string cssClass); 47: } 48:  49: public interface IHighlightActionMenuProviderAfterApplyHighlightStyle 50: { 51: MvcHtmlString ToActionLink(); 52: } 53:  54: #endregion 55:  56: public class HighlightActionMenuProvider : 57: IHighlightActionMenuProviderAfterCreated, 58: IHighlightActionMenuProviderAfterOn, IHighlightActionMenuProviderAfterWith, 59: IHighlightActionMenuProviderAfterHighlightWhen, IHighlightActionMenuProviderAfterApplyHighlightStyle 60: { 61: private HtmlHelper _helper; 62:  63: private string _controllerName; 64: private string _actionName; 65: private string _text; 66: private object _routeData; 67: private object _htmlAttributes; 68:  69: private Func<HtmlHelper, bool> _highlightPredicate; 70:  71: private string _highlightText; 72: private object _highlightHtmlAttributes; 73:  74: public HighlightActionMenuProvider(HtmlHelper helper) 75: { 76: _helper = helper; 77: } 78:  79: public IHighlightActionMenuProviderAfterOn On(string actionName, string controllerName) 80: { 81: _actionName = actionName; 82: _controllerName = controllerName; 83: return this; 84: } 85:  86: public IHighlightActionMenuProviderAfterWith With(string text, object routeData, object htmlAttributes) 87: { 88: _text = text; 89: _routeData = routeData; 90: _htmlAttributes = htmlAttributes; 91: return this; 92: } 93:  94: public IHighlightActionMenuProviderAfterHighlightWhen HighlightWhen(Func<HtmlHelper, bool> predicate) 95: { 96: _highlightPredicate = predicate; 97: return this; 98: } 99:  100: public IHighlightActionMenuProviderAfterHighlightWhen HighlightWhenControllerMatch() 101: { 102: return HighlightWhen((helper) => 103: { 104: return helper.ViewContext.RouteData.Values["controller"].ToString().ToLower() == _controllerName.ToLower(); 105: }); 106: } 107:  108: public IHighlightActionMenuProviderAfterHighlightWhen HighlightWhenControllerAndActionMatch() 109: { 110: return HighlightWhen((helper) => 111: { 112: return helper.ViewContext.RouteData.Values["controller"].ToString().ToLower() == _controllerName.ToLower() && 113: helper.ViewContext.RouteData.Values["action"].ToString().ToLower() == _actionName.ToLower(); 114: }); 115: } 116:  117: public IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(object highlightHtmlAttributes, string highlightText) 118: { 119: _highlightText = highlightText; 120: _highlightHtmlAttributes = highlightHtmlAttributes; 121: return this; 122: } 123:  124: public IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(object highlightHtmlAttributes) 125: { 126: return ApplyHighlighStyle(highlightHtmlAttributes, _text); 127: } 128:  129: public IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(string cssClass, string highlightText) 130: { 131: return ApplyHighlighStyle(new { @class = cssClass }, highlightText); 132: } 133:  134: public IHighlightActionMenuProviderAfterApplyHighlightStyle ApplyHighlighStyle(string cssClass) 135: { 136: return ApplyHighlighStyle(new { @class = cssClass }, _text); 137: } 138:  139: public MvcHtmlString ToActionLink() 140: { 141: if (_highlightPredicate.Invoke(_helper)) 142: { 143: // should be highlight 144: return _helper.ActionLink(_highlightText, _actionName, _controllerName, _routeData, _highlightHtmlAttributes); 145: } 146: else 147: { 148: // should not be highlight 149: return _helper.ActionLink(_text, _actionName, _controllerName, _routeData, _htmlAttributes); 150: } 151: } 152: } 153: } So in the master page when I need the highlight menu item I can “tell” the helper how it should be, just like this. 1: <li> 2: <% 1: : Html.HighlightActionMenu() 2: .On("Index", "Home") 3: .With(SiteMasterStrings.Home, null, null) 4: .HighlightWhenControllerMatch() 5: .ApplyHighlighStyle(new { style = "background:url(../../Content/Images/topmenu_bg.gif) repeat-x;text-decoration:none;color:#feffff;" }) 6: .ToActionLink() %> 3: </li> While I’m typing the code the IntelliSense will advise me that I need a highlight action menu, on the Index action of the Home controller, with the “Home” as its link text and no need the additional route data and Html attributes, and it should be highlighted when the controller was “Home”, and if it’s highlighted the style should be like this and finally render it to me. This is something we call “Fluently Language”. If you had been using Moq you will see that’s very development-friendly, document-ly and easy to read.   Summary In this post I demonstrated how to implement a highlight menu item in ASP.NET MVC by using its controller – action infrastructure. We can see the ASP.NET MVC helps us to organize our web application better. And then I also told a little bit more on the “Fluently Language” and showed how it will make our code better and easy to be used.   Hope this helps, Shaun   All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Arguments for a coding standard?

    - by acidzombie24
    A few friends and i are planning to work on a project together and we want a COMPLETELY DIFFERENT coding standard. We do NOT want to use the coding standard the libraries/language uses. Its our project and we want to mess around. So i came here to ask what you guys think are good standards and arguments for it (or what not to do and arguments against it). The styles i remember most are Upper casing the entire word Camel and Pascal casing Using '_' to separate each word pre or postfixing letters or words (i hate m for member but i think IsCond() is a good func name. SomethingException as a postfix example) Using '_' at the start or end of words Brace placement. On a new or same line? I know of libs that use Pascal casing on all public and protected members. But would you ever get confused if something is a func, var or even property if the lang supports it? What about if you decide a public member to be private (or vice versa) wouldnt that great a lot of fix up work or inconsistencies? Is prefixing C to every class a good idea? I ask what do you think and why?

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  • Switch or a Dictionary when assigning to new object

    - by KChaloux
    Recently, I've come to prefer mapping 1-1 relationships using Dictionaries instead of Switch statements. I find it to be a little faster to write and easier to mentally process. Unfortunately, when mapping to a new instance of an object, I don't want to define it like this: var fooDict = new Dictionary<int, IBigObject>() { { 0, new Foo() }, // Creates an instance of Foo { 1, new Bar() }, // Creates an instance of Bar { 2, new Baz() } // Creates an instance of Baz } var quux = fooDict[0]; // quux references Foo Given that construct, I've wasted CPU cycles and memory creating 3 objects, doing whatever their constructors might contain, and only ended up using one of them. I also believe that mapping other objects to fooDict[0] in this case will cause them to reference the same thing, rather than creating a new instance of Foo as intended. A solution would be to use a lambda instead: var fooDict = new Dictionary<int, Func<IBigObject>>() { { 0, () => new Foo() }, // Returns a new instance of Foo when invoked { 1, () => new Bar() }, // Ditto Bar { 2, () => new Baz() } // Ditto Baz } var quux = fooDict[0](); // equivalent to saying 'var quux = new Foo();' Is this getting to a point where it's too confusing? It's easy to miss that () on the end. Or is mapping to a function/expression a fairly common practice? The alternative would be to use a switch: IBigObject quux; switch(someInt) { case 0: quux = new Foo(); break; case 1: quux = new Bar(); break; case 2: quux = new Baz(); break; } Which invocation is more acceptable? Dictionary, for faster lookups and fewer keywords (case and break) Switch: More commonly found in code, doesn't require the use of a Func< object for indirection.

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  • How do you proactively guard against errors of omission?

    - by Gabriel
    I'll preface this with I don't know if anyone else who's been programming as long as I have actually has this problem, but at the very least, the answer might help someone with less xp. I just stared at this code for 5 minutes, thinking I was losing my mind that it didn't work: var usedNames = new HashSet<string>(); Func<string, string> l = (s) => { for (int i = 0; ; i++) { var next = (s + i).TrimEnd('0'); if (!usedNames.Contains(next)) { return next; } } }; Finally I noticed I forgot to add the used name to the hash set. Similarly, I've spent minutes upon minutes over omitting context.SaveChanges(). I think I get so distracted by the details that I'm thinking about that some really small details become invisible to me - it's almost at the level of mental block. Are there tactics to prevent this? update: a side effect of asking this was fixing the error it would have for i 9 (Thanks!) var usedNames = new HashSet<string>(); Func<string, string> name = (s) => { string result = s; if(usedNames.Contains(s)) for (int i = 1; ; result = s + i++) if (!usedNames.Contains(result)) break; usedNames.Add(result); return result; };

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  • Capturing and Transforming ASP.NET Output with Response.Filter

    - by Rick Strahl
    During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • How to maintain encapsulation with composition in C++?

    - by iFreilicht
    I am designing a class Master that is composed from multiple other classes, A, Base, C and D. These four classes have absolutely no use outside of Master and are meant to split up its functionality into manageable and logically divided packages. They also provide extensible functionality as in the case of Base, which can be inherited from by clients. But, how do I maintain encapsulation of Master with this design? So far, I've got two approaches, which are both far from perfect: 1. Replicate all accessors: Just write accessor-methods for all accessor-methods of all classes that Master is composed of. This leads to perfect encapsulation, because no implementation detail of Master is visible, but is extremely tedious and makes the class definition monstrous, which is exactly what the composition should prevent. Also, adding functionality to one of the composees (is that even a word?) would require to re-write all those methods in Master. An additional problem is that inheritors of Base could only alter, but not add functionality. 2. Use non-assignable, non-copyable member-accessors: Having a class accessor<T> that can not be copied, moved or assigned to, but overrides the operator-> to access an underlying shared_ptr, so that calls like Master->A()->niceFunction(); are made possible. My problem with this is that it kind of breaks encapsulation as I would now be unable to change my implementation of Master to use a different class for the functionality of niceFunction(). Still, it is the closest I've gotten without using the ugly first approach. It also fixes the inheritance issue quite nicely. A small side question would be if such a class already existed in std or boost. EDIT: Wall of code I will now post the code of the header files of the classes discussed. It may be a bit hard to understand, but I'll give my best in explaining all of it. 1. GameTree.h The foundation of it all. This basically is a doubly-linked tree, holding GameObject-instances, which we'll later get to. It also has it's own custom iterator GTIterator, but I left that out for brevity. WResult is an enum with the values SUCCESS and FAILED, but it's not really important. class GameTree { public: //Static methods for the root. Only one root is allowed to exist at a time! static void ConstructRoot(seed_type seed, unsigned int depth); inline static bool rootExists(){ return static_cast<bool>(rootObject_); } inline static weak_ptr<GameTree> root(){ return rootObject_; } //delta is in ms, this is used for velocity, collision and such void tick(unsigned int delta); //Interaction with the tree inline weak_ptr<GameTree> parent() const { return parent_; } inline unsigned int numChildren() const{ return static_cast<unsigned int>(children_.size()); } weak_ptr<GameTree> getChild(unsigned int index) const; template<typename GOType> weak_ptr<GameTree> addChild(seed_type seed, unsigned int depth = 9001){ GOType object{ new GOType(seed) }; return addChildObject(unique_ptr<GameTree>(new GameTree(std::move(object), depth))); } WResult moveTo(weak_ptr<GameTree> newParent); WResult erase(); //Iterators for for( : ) loop GTIterator& begin(){ return *(beginIter_ = std::move(make_unique<GTIterator>(children_.begin()))); } GTIterator& end(){ return *(endIter_ = std::move(make_unique<GTIterator>(children_.end()))); } //unloading should be used when objects are far away WResult unloadChildren(unsigned int newDepth = 0); WResult loadChildren(unsigned int newDepth = 1); inline const RenderObject& renderObject() const{ return gameObject_->renderObject(); } //Getter for the underlying GameObject (I have not tested the template version) weak_ptr<GameObject> gameObject(){ return gameObject_; } template<typename GOType> weak_ptr<GOType> gameObject(){ return dynamic_cast<weak_ptr<GOType>>(gameObject_); } weak_ptr<PhysicsObject> physicsObject() { return gameObject_->physicsObject(); } private: GameTree(const GameTree&); //copying is only allowed internally GameTree(shared_ptr<GameObject> object, unsigned int depth = 9001); //pointer to root static shared_ptr<GameTree> rootObject_; //internal management of a child weak_ptr<GameTree> addChildObject(shared_ptr<GameTree>); WResult removeChild(unsigned int index); //private members shared_ptr<GameObject> gameObject_; shared_ptr<GTIterator> beginIter_; shared_ptr<GTIterator> endIter_; //tree stuff vector<shared_ptr<GameTree>> children_; weak_ptr<GameTree> parent_; unsigned int selfIndex_; //used for deletion, this isn't necessary void initChildren(unsigned int depth); //constructs children }; 2. GameObject.h This is a bit hard to grasp, but GameObject basically works like this: When constructing a GameObject, you construct its basic attributes and a CResult-instance, which contains a vector<unique_ptr<Construction>>. The Construction-struct contains all information that is needed to construct a GameObject, which is a seed and a function-object that is applied at construction by a factory. This enables dynamic loading and unloading of GameObjects as done by GameTree. It also means that you have to define that factory if you inherit GameObject. This inheritance is also the reason why GameTree has a template-function gameObject<GOType>. GameObject can contain a RenderObject and a PhysicsObject, which we'll later get to. Anyway, here's the code. class GameObject; typedef unsigned long seed_type; //this declaration magic means that all GameObjectFactorys inherit from GameObjectFactory<GameObject> template<typename GOType> struct GameObjectFactory; template<> struct GameObjectFactory<GameObject>{ virtual unique_ptr<GameObject> construct(seed_type seed) const = 0; }; template<typename GOType> struct GameObjectFactory : GameObjectFactory<GameObject>{ GameObjectFactory() : GameObjectFactory<GameObject>(){} unique_ptr<GameObject> construct(seed_type seed) const{ return unique_ptr<GOType>(new GOType(seed)); } }; //same as with the factories. this is important for storing them in vectors template<typename GOType> struct Construction; template<> struct Construction<GameObject>{ virtual unique_ptr<GameObject> construct() const = 0; }; template<typename GOType> struct Construction : Construction<GameObject>{ Construction(seed_type seed, function<void(GOType*)> func = [](GOType* null){}) : Construction<GameObject>(), seed_(seed), func_(func) {} unique_ptr<GameObject> construct() const{ unique_ptr<GameObject> gameObject{ GOType::factory.construct(seed_) }; func_(dynamic_cast<GOType*>(gameObject.get())); return std::move(gameObject); } seed_type seed_; function<void(GOType*)> func_; }; typedef struct CResult { CResult() : constructions{} {} CResult(CResult && o) : constructions(std::move(o.constructions)) {} CResult& operator= (CResult& other){ if (this != &other){ for (unique_ptr<Construction<GameObject>>& child : other.constructions){ constructions.push_back(std::move(child)); } } return *this; } template<typename GOType> void push_back(seed_type seed, function<void(GOType*)> func = [](GOType* null){}){ constructions.push_back(make_unique<Construction<GOType>>(seed, func)); } vector<unique_ptr<Construction<GameObject>>> constructions; } CResult; //finally, the GameObject class GameObject { public: GameObject(seed_type seed); GameObject(const GameObject&); virtual void tick(unsigned int delta); inline Matrix4f trafoMatrix(){ return physicsObject_->transformationMatrix(); } //getter inline seed_type seed() const{ return seed_; } inline CResult& properties(){ return properties_; } inline const RenderObject& renderObject() const{ return *renderObject_; } inline weak_ptr<PhysicsObject> physicsObject() { return physicsObject_; } protected: virtual CResult construct_(seed_type seed) = 0; CResult properties_; shared_ptr<RenderObject> renderObject_; shared_ptr<PhysicsObject> physicsObject_; seed_type seed_; }; 3. PhysicsObject That's a bit easier. It is responsible for position, velocity and acceleration. It will also handle collisions in the future. It contains three Transformation objects, two of which are optional. I'm not going to include the accessors on the PhysicsObject class because I tried my first approach on it and it's just pure madness (way over 30 functions). Also missing: the named constructors that construct PhysicsObjects with different behaviour. class Transformation{ Vector3f translation_; Vector3f rotation_; Vector3f scaling_; public: Transformation() : translation_{ 0, 0, 0 }, rotation_{ 0, 0, 0 }, scaling_{ 1, 1, 1 } {}; Transformation(Vector3f translation, Vector3f rotation, Vector3f scaling); inline Vector3f translation(){ return translation_; } inline void translation(float x, float y, float z){ translation(Vector3f(x, y, z)); } inline void translation(Vector3f newTranslation){ translation_ = newTranslation; } inline void translate(float x, float y, float z){ translate(Vector3f(x, y, z)); } inline void translate(Vector3f summand){ translation_ += summand; } inline Vector3f rotation(){ return rotation_; } inline void rotation(float pitch, float yaw, float roll){ rotation(Vector3f(pitch, yaw, roll)); } inline void rotation(Vector3f newRotation){ rotation_ = newRotation; } inline void rotate(float pitch, float yaw, float roll){ rotate(Vector3f(pitch, yaw, roll)); } inline void rotate(Vector3f summand){ rotation_ += summand; } inline Vector3f scaling(){ return scaling_; } inline void scaling(float x, float y, float z){ scaling(Vector3f(x, y, z)); } inline void scaling(Vector3f newScaling){ scaling_ = newScaling; } inline void scale(float x, float y, float z){ scale(Vector3f(x, y, z)); } void scale(Vector3f factor){ scaling_(0) *= factor(0); scaling_(1) *= factor(1); scaling_(2) *= factor(2); } Matrix4f matrix(){ return WMatrix::Translation(translation_) * WMatrix::Rotation(rotation_) * WMatrix::Scale(scaling_); } }; class PhysicsObject; typedef void tickFunction(PhysicsObject& self, unsigned int delta); class PhysicsObject{ PhysicsObject(const Transformation& trafo) : transformation_(trafo), transformationVelocity_(nullptr), transformationAcceleration_(nullptr), tick_(nullptr) {} PhysicsObject(PhysicsObject&& other) : transformation_(other.transformation_), transformationVelocity_(std::move(other.transformationVelocity_)), transformationAcceleration_(std::move(other.transformationAcceleration_)), tick_(other.tick_) {} Transformation transformation_; unique_ptr<Transformation> transformationVelocity_; unique_ptr<Transformation> transformationAcceleration_; tickFunction* tick_; public: void tick(unsigned int delta){ tick_ ? tick_(*this, delta) : 0; } inline Matrix4f transformationMatrix(){ return transformation_.matrix(); } } 4. RenderObject RenderObject is a base class for different types of things that could be rendered, i.e. Meshes, Light Sources or Sprites. DISCLAIMER: I did not write this code, I'm working on this project with someone else. class RenderObject { public: RenderObject(float renderDistance); virtual ~RenderObject(); float renderDistance() const { return renderDistance_; } void setRenderDistance(float rD) { renderDistance_ = rD; } protected: float renderDistance_; }; struct NullRenderObject : public RenderObject{ NullRenderObject() : RenderObject(0.f){}; }; class Light : public RenderObject{ public: Light() : RenderObject(30.f){}; }; class Mesh : public RenderObject{ public: Mesh(unsigned int seed) : RenderObject(20.f) { meshID_ = 0; textureID_ = 0; if (seed == 1) meshID_ = Model::getMeshID("EM-208_heavy"); else meshID_ = Model::getMeshID("cube"); }; unsigned int getMeshID() const { return meshID_; } unsigned int getTextureID() const { return textureID_; } private: unsigned int meshID_; unsigned int textureID_; }; I guess this shows my issue quite nicely: You see a few accessors in GameObject which return weak_ptrs to access members of members, but that is not really what I want. Also please keep in mind that this is NOT, by any means, finished or production code! It is merely a prototype and there may be inconsistencies, unnecessary public parts of classes and such.

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  • C# convert an IOrderedEnumerable<KeyValuePair<string, int>> into a Dictionary<string, int>

    - by Kache4
    I was following the answer to another question, and I got: // itemCounter is a Dictionary<string, int>, and I only want to keep // key/value pairs with the top maxAllowed values if (itemCounter.Count > maxAllowed) { IEnumerable<KeyValuePair<string, int>> sortedDict = from entry in itemCounter orderby entry.Value descending select entry; sortedDict = sortedDict.Take(maxAllowed); itemCounter = sortedDict.ToDictionary<string, int>(/* what do I do here? */); } Visual Studio's asking for a parameter Func<string, int> keySelector. I tried following a few semi-relevant examples I've found online and put in k => k.Key, but that gives a compiler error: 'System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string,int>>' does not contain a definition for 'ToDictionary' and the best extension method overload 'System.Linq.Enumerable.ToDictionary<TSource,TKey>(System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,TKey>)' has some invalid arguments

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  • CS1685 Warning causes a CS0433 error when targeting 3.5 in VS2010

    - by Adam Driscoll
    I have a 2010 project that is targeting .NET v3.5. It was working fine until I started to mess with configurations a bit and now I cannot figure out what I'm doing wrong. The project doesn't have ANY references added. It won't even let me add a reference to System.Core as it is added by the 'build system'. warning CS1685: The predefined type 'System.Func' is defined in multiple assemblies in the global alias; using definition from 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll' IFilter.cs(82,49): error CS0433: The type 'System.Func' exists in both 'c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5\System.Core.dll' and 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll' Looks like something is grabbing onto 4.0 but I'm not quite sure how to fix it. Any one else run into this?

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  • Mixed-mode C++/CLI crashing: heap corruption in atexit (static destructor registration)

    - by thaimin
    I am working on deploying a program and the codebase is a mixture of C++/CLI and C#. The C++/CLI comes in all flavors: native, mixed (/clr), and safe (/clr:safe). In my development environment I create a DLL of all the C++/CLI code and reference that from the C# code (EXE). This method works flawlessly. For my releases that I want to release a single executable (simply stating that "why not just have a DLL and EXE separate?" is not acceptable). So far I have succeeded in compiling the EXE with all the different sources. However, when I run it I get the "XXXX has stopped working" dialog with options to Check online, Close and Debug. The problem details are as follows: Problem Event Name: APPCRASH Fault Module Name: StackHash_8d25 Fault Module Version: 6.1.7600.16559 Fault Module Timestamp: 4ba9b29c Exception Code: c0000374 Exception Offset: 000cdc9b OS Version: 6.1.7600.2.0.0.256.48 Locale ID: 1033 Additional Information 1: 8d25 Additional Information 2: 8d25552d834e8c143c43cf1d7f83abb8 Additional Information 3: 7450 Additional Information 4: 74509ce510cd821216ce477edd86119c If I debug and send it to Visual Studio, it reports: Unhandled exception at 0x77d2dc9b in XXX.exe: A heap has been corrupted Choosing break results in it stopping at ntdll.dll!77d2dc9b() with no additional information. If I tell Visual Studio to continue, the program starts up fine and seems to work without incident, probably since a debugger is now attached. What do you make of this? How do I avoid this heap corruption? The program seems to work fine except for this. My abridged compilation script is as follows (I have omitted my error checking for brevity): @set TARGET=x86 @set TARGETX=x86 @set OUT=%TARGETX% @call "%VS90COMNTOOLS%\..\..\VC\vcvarsall.bat" %TARGET% @set WIMGAPI=C:\Program Files\Windows AIK\SDKs\WIMGAPI\%TARGET% set CL=/Zi /nologo /W4 /O2 /GS /EHa /MD /MP /D NDEBUG /D _UNICODE /D UNICODE /D INTEGRATED /Fd%OUT%\ /Fo%OUT%\ set INCLUDE=%WIMGAPI%;%INCLUDE% set LINK=/nologo /LTCG /CLRIMAGETYPE:IJW /MANIFEST:NO /MACHINE:%TARGETX% /SUBSYSTEM:WINDOWS,6.0 /OPT:REF /OPT:ICF /DEFAULTLIB:msvcmrt.lib set LIB=%WIMGAPI%;%LIB% set CSC=/nologo /w:4 /d:INTEGRATED /o+ /target:module :: Compiling resources omitted @set CL_NATIVE=/c /FI"stdafx-native.h" @set CL_MIXED=/c /clr /LN /FI"stdafx-mixed.h" @set CL_PURE=/c /clr:safe /LN /GL /FI"stdafx-pure.h" @set NATIVE=... @set MIXED=... @set PURE=... cl %CL_NATIVE% %NATIVE% cl %CL_MIXED% %MIXED% cl %CL_PURE% %PURE% link /LTCG /NOASSEMBLY /DLL /OUT:%OUT%\core.netmodule %OUT%\*.obj csc %CSC% /addmodule:%OUT%\core.netmodule /out:%OUT%\GUI.netmodule /recurse:*.cs link /FIXED /ENTRY:GUI.Program.Main /OUT:%OUT%\XXX.exe ^ /ASSEMBLYRESOURCE:%OUT%\core.resources,XXX.resources,PRIVATE /ASSEMBLYRESOURCE:%OUT%\GUI.resources,GUI.resources,PRIVATE ^ /ASSEMBLYMODULE:%OUT%\core.netmodule %OUT%\gui.res %OUT%\*.obj %OUT%\GUI.netmodule Update 1 Upon compiling this with debug symbols and trying again, I do in fact get more information. The call stack is: msvcr90d.dll!_msize_dbg(void * pUserData, int nBlockUse) Line 1511 + 0x30 bytes msvcr90d.dll!_dllonexit_nolock(int (void)* func, void (void)* * * pbegin, void (void)* * * pend) Line 295 + 0xd bytes msvcr90d.dll!__dllonexit(int (void)* func, void (void)* * * pbegin, void (void)* * * pend) Line 273 + 0x11 bytes XXX.exe!_onexit(int (void)* func) Line 110 + 0x1b bytes XXX.exe!atexit(void (void)* func) Line 127 + 0x9 bytes XXX.exe!`dynamic initializer for 'Bytes::Null''() Line 7 + 0xa bytes mscorwks.dll!6cbd1b5c() [Frames below may be incorrect and/or missing, no symbols loaded for mscorwks.dll] ... The line of my code that 'causes' this (dynamic initializer for Bytes::Null) is: Bytes Bytes::Null; In the header that is declared as: class Bytes { public: static Bytes Null; } I also tried doing a global extern in the header like so: extern Bytes Null; // header Bytes Null; // cpp file Which failed in the same way. It seems that the CRT atexit function is responsible, being inadvertently required due to the static initializer. Fix As Ben Voigt pointed out the use of any CRT functions (including native static initializers) requires proper initialization of the CRT (which happens in mainCRTStartup, WinMainCRTStartup, or _DllMainCRTStartup). I have added a mixed C++/CLI file that has a C++ main or WinMain: using namespace System; [STAThread] // required if using an STA COM objects (such as drag-n-drop or file dialogs) int main() { // or "int __stdcall WinMain(void*, void*, wchar_t**, int)" for GUI applications array<String^> ^args_orig = Environment::GetCommandLineArgs(); int l = args_orig->Length - 1; // required to remove first argument (program name) array<String^> ^args = gcnew array<String^>(l); if (l > 0) Array::Copy(args_orig, 1, args, 0, l); return XXX::CUI::Program::Main(args); // return XXX::GUI::Program::Main(args); } After doing this, the program now gets a little further, but still has issues (which will be addressed elsewhere): When the program is solely in C# it works fine, along with whenever it is just calling C++/CLI methods, getting C++/CLI properties, and creating managed C++/CLI objects Events added by C# into the C++/CLI code never fire (even though they should) One other weird error is that an exception happens is a InvalidCastException saying can't cast from X to X (where X is the same as X...) However since the heap corruption is fixed (by getting the CRT initialized) the question is done.

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  • Ambiguous call between methods ASP.NET MVC

    - by GuiPereira
    I'm pretty new in ASP.NET MVC (about 3 months) and i've the followin issue: I have a Entity Class called 'Usuario' in a ClassLibrary referenced as 'Core' and, when i create a strongly-typed view and add a html.textboxfor< like: <%= Html.TextBoxFor(u => u.Login) %> it raises the following error: Error 3 The call is ambiguous between the following methods or properties: 'Microsoft.Web.Mvc.ExpressionInputExtensions.TextBoxFor<Core.Usuario,string>(System.Web.Mvc .HtmlHelper<Core.Usuario>, System.Linq.Expressions.Expression<System.Func<Core.Usuario,string>>)' and 'System.Web.Mvc.Html.InputExtensions.TextBoxFor<Core.Usuario,string>(System.Web.Mvc.HtmlHel per<Core.Usuario>, System.Linq.Expressions.Expression<System.Func<Core.Usuario,string>>)' d:\Documents\Visual Studio 2008\Projects\GuiPereiraMVC2\GuiPereiraMVC2\Views\Gestao\Index.aspx 20 25 GuiPereiraMVC2 anyone knows why?

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