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• Updating an image's ImageUrl within a Repeater

  - by Django Reinhardt

  I hope someone can help me. It's a pretty newbie question, I'm afraid. I have an image inside a repeater, and I would like to change its IMAGEURL based on parameter that's being passed to it. <asp:Repeater ID="Repeater" runat="server"> <HeaderTemplate> <asp:Image ID="imgType" runat="server" /> </HeaderTemplate> <ItemTemplate> <%# Eval("DisplayName")%> </ItemTemplate> <SeparatorTemplate> <hr /> </SeparatorTemplate> </asp:Repeater> There is a SWITCH statement in the code behind that is altering the IMAGEURL depending on what's being passed to it. Inevitably, however, the images ID ("imgType") is not visible to the SWITCH statement (presumably because it's inside a REPEATER). Any suggestions on the best way to implement this would be greatly appreciated. Sorry for such a newbie question.

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• using replace to produce javascript code, django

  - by durdenk

  I want to use highcharts with my django site but it requires a comlex javascript code such as below. So I wanted to get this script in my python code and replace apropriate portions then write it in my template, first question is, is this a dump way to do that for a person not knowing javascript. I can read it tough. Second question is, Why I cant replace this string. Lets say this string is a variable like this. lineChartsTemplate = """ ... ... """ if I try and do lineChartsTemplate .replace('dataCategory', dataCategory) it basically suppossed to change dataCategory text with my dataCategory variable, but no such luck. I need guidance here. thx. $(function () { var chart = new Highcharts.Chart({ chart: { renderTo: 'container', type: 'bar' }, xAxis: { categories: dataCategory }, yAxis: { }, legend: { layout: 'vertical', floating: true, backgroundColor: '#FFFFFF', align: 'right', verticalAlign: 'top', y: 60, x: -60 }, tooltip: { formatter: function() { return '<b>'+ this.series.name +'</b><br/>'+ this.x +': '+ this.y; } }, plotOptions: { }, series: [{ data: dataList , name : 'Satislar'}] }); });

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• Difference between MVC FilterAttribute and Filter

  - by zaaaaphod

  I'm trying to write my own custom AuthorizationAttribute that uses DI. I'm using the MUNQ IoC provider for it's speed and have decided to use constructor injection on all my classes as opposed to post instatiation property binding (because I prefer it). I'm trying to write a custom IFilterProvider that will use my IoC container to return requests for filters (so that I can map concrete classes using the container). I've come up with the following. public class FilterProvider : IFilterProvider { private readonly IocContainer _container; public FilterProvider(IocContainer container) { _container = container; } public IEnumerable<Filter> GetFilters(ControllerContext controllerContext, ActionDescriptor actionDescriptor) { var x = Enumerable.Union<Object>(_container.ResolveAll<IActionFilter>(), _container.ResolveAll<IAuthorizationFilter>()); foreach (Filter actionFilter in x) yield return new Filter(actionFilter, FilterScope.First, null); } } The above code will fail during the foreach because my objects that implement IAuthorizationFilter are based on FilterAttribute and not Filter My question is, what is the difference between Filter and FilterAttribute? I would have thought that there would have been a common link between them, unless I'm missing something. Another deeper question is, how come there is no IFilterAttributeProvider that would support IEnumerable GetFilters(...) Is there some other way that I should be using to resolve IAuthorizationFilter via my IoC container? Thank you very much for your help. Z

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• Partial class or "chained inheritance"

  - by Charlie boy

  Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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• How to run <script src= > tag from javascript

  - by Gleeb

  I am having some difficulties implementing Paypal buttons with backbone.js The problem is that the button is implemented in a script tag: <script src="paypal-button.min.js?merchant=YOUR_MERCHANT_ID" data-button="buynow" data-name="My product" data-amount="1.00"></script> which i cant run from Handlebars.js because the </script> tag is closing the handlebars <script> I cant use eval(), or i don't understand how i am supposed to do that with the . So there you have it. i am kind of stuck. I am out of ideas on how to implement this button with backbone.js the last resort is to ask the server to produce html pages with the script in them and then load them to the page. i am just refusing to believe that JavaScript has no way to take care of this. Please help. This question relates to another question i asked in this subject. Is it possible to use JavaScript inside handlebars.js template Thank you.

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• What exactly does this PHP code do?

  - by Rob

  Alright, my friend gave me this code for requesting headers and comparing them to what the header should be. It works perfectly, but I'm not sure why. Here is the code: $headers = apache_request_headers(); $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; foreach ($headers as $header => $value) { // 1 $custom .= "$header: $value"; // 2 } $mystring = $custom; // 3 $findme = $customheader; // 4 $pos = strpos($mystring, $findme); if ($pos !== false) { // Do something } else{ exit(); } //If it doesn't match, exit. I commented with some numbers relating to the following questions: 1: What exactly is happening here? Is it setting the $headers as $header AND $value? 2: Again, don't have any idea what is going on here. 3: Why set the variable to a different variable? This is the only area where the variable is getting used, so is there a reason to set it to something else? 4: Same question as 3. I'm sorry if this is a terrible question, but its been bothering me, and I really want to know WHY it works. Well, I understand why it works, I guess I just want to know more specifically. Thanks for any insight you can provide.

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• What are major differences between C# and Java?

  - by enba

  I just want to clarify one thing. This is not a question on which one is better, that part I leave to someone else to discuss. I don't care about it. I've been asked this question on my job interview and I thought it might be useful to learn a bit more. These are the ones I could come up with: Java is "platform independent". Well nowadays you could say there is the Mono project so C# could be considered too but I believe it is a bit exaggerating. Why? Well, when a new release of Java is done it is simultaneously available on all platforms it supports, on the other hand how many features of C# 3.0 are still missing in the Mono implementation? Or is it really CLR vs. JRE that we should compare here? Java doesn't support events and delegates. As far as I know. In Java all methods are virtual Development tools: I believe there isn't such a tool yet as Visual Studio. Especially if you've worked with team editions you'll know what I mean. Please add others you think are relevant. Update: Just popped up my mind, Java doesn't have something like custom attributes on classes, methods etc. Or does it?

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• GUID or int entity key with SQL Compact/EF4?

  - by David Veeneman

  This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension method that uses the Max operator with a selector expression to find the next available key: public static TResult NextId<TSource, TResult>(this ObjectSet<TSource> table, Expression<Func<TSource, TResult>> selector) where TSource : class { TResult lastId = table.Any() ? table.Max(selector) : default(TResult); if (lastId is int) { lastId = (TResult)(object)(((int)(object)lastId) + 1); } return lastId; } Here's my take on the extension method: It will work fine if the ObjectContext that I am working with has an unfiltered entity set. In that case, the ObjectContext will contain all rows from the data table, and I will get an accurate result. But if the entity set is the result of a query filter, the method will return the last entity key in the filtered entity set, which will not necessarily be the last key in the data table. So I think the extension method won't really work. At this point, the obvious solution seems to be to simply use a GUID as the entity key. That way, I only need to call Guid.NewGuid() method to set the ID property before I add a new entity to my ObjectContext. Here is my question: Is there a simple way of getting the last primary key in the data store from EF4 (without having to create a second ObjectContext for that purpose)? Any other reason not to take the easy way out and simply use a GUID? Thanks for your help.

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• iPhone -trouble with a loading data from webservice into a tableview

  - by medampudi

  I am using a Window based application and then loading up my initial navigationview based controller. After loading it if the user is not registered/ does not have a credentials present then it takes the user to a login view controller . loginViewController *sampleView = [[loginViewController alloc] initWithNibName:@"loginViewController" bundle:nil]; [self.navigationController presentModalViewController:sampleView animated:YES]; [sampleView release]; then right after that i try to load the table with data that i get from a webservice using asiHTTP .. for this question lets say it takes 3 seconds time to get the data and then deserialize it . now... my question is it works out okey in the later runs as I store the username and password in a seure location... but in the first instance.... i am not able to get the data to laod to the tableview... I have tried a lot of things... 1. Initially the data fetch methods was in a diffrent methods.. so i thought that might be the problem as then moved it the same place as the tbleviewController(navigationController) 2. I event put in the Reload data at the end of the functionality for the data parsing and deserialization... nothing happens. 3. i did not understand the concept of @property and alll.... 4. The screen is black screen with nothing displayed on it for a good 5 seconds in the consecutive launches of the app.... so could we have something like a MBPorgressHUD implemented for the same. could any one please help for these scenarios and guidance as to what paths to take from here...

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• I want a insert query for a temp table

  - by John Stephen

  Hi..I am using C#.Net and Sql Server ( Windows Application ). I had created a temporary table. When a button is clicked, temporary table (#tmp_emp_answer) is created. I am having another button called "insert Values" and also 5 textboxes. The values that are entered in the textbox are used and whenever com.ExecuteNonQuery(); line comes, it throws an error message Invalid object name '#tbl_emp_answer'.. Below is the set of code.. Please give me a solution. Code for insert (in insert value button): private void btninsertvalues_Click(object sender, EventArgs e) { username = txtusername.Text; examloginid = txtexamloginid.Text; question = txtquestion.Text; answer = txtanswer.Text; useranswer = txtanswer.Text; SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=tempdb;Integrated Security=True;"); SqlCommand com = new SqlCommand("Insert into #tbl_emp_answer values('"+username+"','"+examloginid+"','"+question+"','"+answer+"','"+useranswer+"')", con); con.Open(); com.ExecuteNonQuery(); con.Close(); }

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• Find the order among tasks in a company by using prolog?

  - by Cem

  First of all,I wish a happy new year for everyone.I searched more and worked a lot but I could not solve this question.I am quite a new in prolog and I must do this homework. In my homework,the question is like this: Write a prolog program that determines a valid order for the tasks to be carried out in a company. The prolog program will consist of a set of "before" predicates which denotes the order between task pairs. Here is an example; before(a,b). before(a,e). before(d,c). before(b,c). before(c,e). Here, task a should be carried before tasks b and e, d before c and so on. Hence a valid ordering of the tasks would be [a, b, d, c, e]. The order predicate in your program will be queried as follows. ?- order([a,b,c,d,e],X). X = [a, b, d, c, e] ; X = [a, d, b, c, e] ; X = [d, a, b, c, e] ; false. Hint: Try to generate different orders for the tasks (permutation) and then check if the order is consistent with the "before" relationships given. Even if you can generate a single valid order, you will get reasonable partial credits.

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• How can you change the font color of a theme-enabled control?

  - by Edouard Westphal

  Yes, this is again this question: How can I change the font color of a TCheckBox (or any handled control) with Delphi7-Delphi2007 on a themes enabled application? After reading a lot on the internet and on this site, I found 4 kinds of answer: and Most populare (even from QC): You can't, it's designed like that by Microsoft. Create a component that let you draw it like you want. Buy expensive component set that draws like you want. Do not use themes. OK, but I am still unhappy with that. Giving a user colored feedback for the status of a property/data he has on a form, seems legitimate to me. Then I just installed the MSVC# 2008 Express edition, and what a surprise, they can change the color of the font (property ForeColor of the check box) Then what? It does not seem to be a "it's designed like that, by Microsoft." then now the question again: How can I change the font color of a TCheckBox (or any handled control) with Delphi 7 through Delphi 2007 on a theme-enabled application?

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• How to get the set of beans that are to be created in Spring?

  - by cyborg

  So here's the scenario: I have a Spring XML configuration with some lazy-beans, some not lazy-beans and some beans that depend on other beans. Eventually Spring will resolve all this so that only the beans that are meant to be created are created. The question: how can I programmatically tell what this set is? When I use context.getBean(name) that initializes the bean. BeanDefinition.isLazyInit() will only tell me how I defined the bean. Any other ideas? ETA: In DefaultListableBeanFactory: public void preInstantiateSingletons() throws BeansException { if (this.logger.isInfoEnabled()) { this.logger.info("Pre-instantiating singletons in " + this); } synchronized (this.beanDefinitionMap) { for (Iterator it = this.beanDefinitionNames.iterator(); it.hasNext();) { String beanName = (String) it.next(); RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { if (isFactoryBean(beanName)) { FactoryBean factory = (FactoryBean) getBean(FACTORY_BEAN_PREFIX + beanName); if (factory instanceof SmartFactoryBean && ((SmartFactoryBean) factory).isEagerInit()) { getBean(beanName); } } else { getBean(beanName); } } } } } The set of instantiable beans is initialized. When initializing this set any beans not in this set referenced by this set will also be created. From looking through the source it does not look like there's going to be any easy way to answer my question.

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• how to handle empty selection in a jface bound combobox?

  - by guido

  I am developing a search dialog in my eclipse-rcp application. In the search dialog I have a combobox as follows: comboImp = new CCombo(grpColSpet, SWT.BORDER | SWT.READ_ONLY); comboImp.setBounds(556, 46, 184, 27); comboImpViewer = new ComboViewer(comboImp); comboImpViewer.setContentProvider(new ArrayContentProvider()); comboImpViewer.setInput(ImpContentProvider.getInstance().getImps()); comboImpViewer.setLabelProvider(new LabelProvider() { @Override public String getText(Object element) { return ((Imp)element).getImpName(); } }); Imp is a database entity, ManyToOne to the main entity which is searched, and ImpContentProvider is the model class which speaks to embedded sqlite database via jpa/hibernate. This combobox is supposed to contain all instances of Imp, but to also let empty selection; it's value is bound to a service bean as follows: IObservableValue comboImpSelectionObserveWidget = ViewersObservables.observeSingleSelection(comboImpViewer); IObservableValue filterByImpObserveValue = BeansObservables.observeValue(searchPrep, "imp"); bindingContext.bindValue(comboImpSelectionObserveWidget, filterByImpObserveValue , null, null); As soon as the user clicks on the combo, a selection (first element) is made: I can see the call to a selectionlistener i added on the viewer. My question is: after a selection has been made, how do I let the user change his mind and have an empty selection in the combobox? should I add a "fake" empty instance of Imp to the List returned by the ImpContentProvider? or should I implement an alternative to ArrayContentProvider? and one additional related question is: why calling deselectAll() and clearSelection() on the combo does NOT set a null value to the bound bean?

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• DDD: Enum like entities

  - by Chris

  Hi all, I have the following DB model: **Person table** ID | Name | StateId ------------------------------ 1 Joe 1 2 Peter 1 3 John 2 **State table** ID | Desc ------------------------------ 1 Working 2 Vacation and domain model would be (simplified): public class Person { public int Id { get; } public string Name { get; set; } public State State { get; set; } } public class State { private int id; public string Name { get; set; } } The state might be used in the domain logic e.g.: if(person.State == State.Working) // some logic So from my understanding, the State acts like a value object which is used for domain logic checks. But it also needs to be present in the DB model to represent a clean ERM. So state might be extended to: public class State { private int id; public string Name { get; set; } public static State New {get {return new State([hardCodedIdHere?], [hardCodeNameHere?]);}} } But using this approach the name of the state would be hardcoded into the domain. Do you know what I mean? Is there a standard approach for such a thing? From my point of view what I am trying to do is using an object (which is persisted from the ERM design perspective) as a sort of value object within my domain. What do you think? Question update: Probably my question wasn't clear enough. What I need to know is, how I would use an entity (like the State example) that is stored in a database within my domain logic. To avoid things like: if(person.State.Id == State.Working.Id) // some logic or if(person.State.Id == WORKING_ID) // some logic

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• Heroku: Postgres type operator error after migrating DB from MySQL

  - by sevennineteen

  This is a follow-up to a question I'd asked earlier which phrased this as more of a programming problem than a database problem. http://stackoverflow.com/questions/2935985/postgres-error-with-sinatra-haml-datamapper-on-heroku I believe the problem has been isolated to the storage of the ID column in Heroku's Postgres database after running db:push. In short, my app runs properly on my original MySQL database, but throws Postgres errors on Heroku when executing any query on the ID column, which seems to have been stored in Postgres as TEXT even though it is stored as INT in MySQL. My question is why the ID column is being created as INT in Postgres on the data transfer to Heroku, and whether there's any way for me to prevent this. Here's the output from a heroku console session which demonstrates the issue: Ruby console for myapp.heroku.com >> Post.first.title => "Welcome to First!" >> Post.first.title.class => String >> Post.first.id => 1 >> Post.first.id.class => Fixnum >> Post[1] PostgresError: ERROR: operator does not exist: text = integer LINE 1: ...", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Query: SELECT "id", "name", "email", "url", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER BY "id" LIMIT 1 Thanks!

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• fix needed for bug in TextField/Text

  - by Mark

  Sort of a complicated scenario - just curious if anyone else could come up with something: I have a Text control and when I scroll it and stop the scroll with the cursor over some text that has a url, the cursor doesn't revert to a hand, and also flash player starts acting as if a selection is being made from the last cursor position. So IOW a bonafide bug in flash as far as I can determine. The above probably wasn't completely clear so let me elaborate. If you grab a scrollbar thumb and start moving it up and down, you don't actually have to keep the mouse pointer on the thumb while doing so. When you stop the scroll, the mouse pointer could be outside the browser window, inside your flash application, but not currently on the scroll bar thumb, or wherever. The previously mentioned bug occurs when you stop the scroll with the mouse pointer positioned over text with an html anchor (a hyperlink). At that point the cursor enters into some state of limbo, and doesn't show the url hand pointer, and furthermore acts as if some text selection is taking place from the last cursor position prior to the scroll. So the question would be, what sort of event could I simulate in code to jolt flash out of this erroneous state it is in. And furthermore in what event could I perform this simulated event (given that for example there is no AS3 event to signal the end of a scroll.) To be clear, the Text control in question is on a canvas, and that canvas (call it A) is on another canvas which actually owns the scrollbar, and scrolling takes place by changing the scrollRect of canvas A.

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• Drupal module for complex hours of operation / office hours

  - by Eronarn

  Background: I am building a website in Drupal that links together a wide variety of social service providers for the purposes of discovery, collaboration, and all that good stuff. The goal is to make a website that is simple to browse for consumers of these services and simple to update for providers of these services. The beta has been very well received, but I want to switch to a different information schema before the site goes live. Specific question: I am looking for a module (or other solution) that... Stores this data in Drupal (i.e., no GCal) Supports a wide variety of repeats Is intuitive for people editing the node (no Cron-style interfaces, please!) I have looked into several modules on drupal.org and none seem to meet all of these criteria. I've also searched here, and while this question is similar: http://stackoverflow.com/questions/2794149/drupal-create-a-node-with-employee-working-hours my needs are too complex for the offered solution. Some of these providers have "hours" such as "the third Wednesday of every month", or "open during Winter months", or separate hotline & office hours. Likewise, the Date Repeat module doesn't cut it as stands currently. I'm comfortable hacking what I need into an existing module - I just don't want to duplicate effort! If you have a suggestion on what module might be a good starting point, I'd appreciate that input, too. Thanks. <3

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• how to get selected chracter position in JTextArea?

  - by Reddy

  Hi! Here is a challenging question! Let me first tell you my scenario how am i implementing a solution to a problem. I am reading a log file and displaying it on the JTextArea. Log file is cp037 character coded. I was reading each file as a byte stream or byte array from the log file & displaying it. Anyways, i managed to display the text properly in JTextArea by cp037 character coding. Now, User may select a set of characters in the JTextArea. All i want is the position of first character of the user's selected text, from a nearest special character '+'(its character code in cp037 is 4E), which is prior to the selected text. This character may occur at several places in the JTextArea. In simple sentence, i want the first character location(of user selected text) from nearset '+' which should be occuring prior to the user's selected text. PS: cp037 is a type of character encoding scheme which is created by IBM & used for IBM Mainframes. Please fell free to ask me if the question is not clear...:-

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• Java string to double conversion.

  - by wretrOvian

  Hi, I've been reading up on the net about the issues with handling float and double types in java. Unfortunately, the image is still not clear. Hence, i'm asking here direct. :( My MySQL table has various DECIMAL(m,d) columns. The m may range from 5 to 30. d stays a constant at 2. Question 1. What equivalent data-type should i be using in Java to work (i.e store, retrieve, and process) with the size of the values in my table? (I've settled with double - hence this post). Question 2. While trying to parse a double from a string, i'm getting errors Double dpu = new Double(dpuField.getText()); for example - "1" -> java.lang.NumberFormatException: empty String "10" -> 1.0 "101" -> 10.0 "101." -> 101.0 "101.1" -> 101.0 "101.19" -> 101.1 What am i doing wrong? What is the correct way to convert a string to a double value? And what measures should i take to perform operations on such values?

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• What OpenGL functions are not GPU accelerated?

  - by Xavier Ho

  I was shocked when I read this (from the OpenGL wiki): glTranslate, glRotate, glScale Are these hardware accelerated? No, there are no known GPUs that execute this. The driver computes the matrix on the CPU and uploads it to the GPU. All the other matrix operations are done on the CPU as well : glPushMatrix, glPopMatrix, glLoadIdentity, glFrustum, glOrtho. This is the reason why these functions are considered deprecated in GL 3.0. You should have your own math library, build your own matrix, upload your matrix to the shader. For a very, very long time I thought most of the OpenGL functions use the GPU to do computation. I'm not sure if this is a common misconception, but after a while of thinking, this makes sense. Old OpenGL functions (2.x and older) are really not suitable for real-world applications, due to too many state switches. This makes me realise that, possibly, many OpenGL functions do not use the GPU at all. So, the question is: Which OpenGL function calls don't use the GPU? I believe knowing the answer to the above question would help me become a better programmer with OpenGL. Please do share some of your insights.

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• How do I use an index in an array reference as a method reference in Perl?

  - by Robert P

  Similar to this question about iterating over subroutine references, and as a result of answering this question about a OO dispatch table, I was wondering how to call a method reference inside a reference, without removing it first, or if it was even possible. For example: package Class::Foo; use 5.012; #Yay autostrict! use warnings; # a basic constructor for illustration purposes.... sub new { my $class = shift; return bless {}, $class; } # some subroutines for flavor... sub sub1 { say 'in sub 1' } sub sub2 { say 'in sub 2' } sub sub3 { say 'in sub 3' } # and a way to dynamically load the tests we're running... sub sublist { my $self = shift; return [ $self->can('sub1'); $self->can('sub3'}; $self->can('sub2'); ]; } package main; my $instance = Class::Foo->new(a => 1, b => 2, c => 3); my $tests = $instance->sublist(); my $index = int(rand($#{$tests})); # <-- HERE So, at HERE, we could do: my $ref = $tests->{$index}; $instance->$ref(); but how would we do this, without removing the reference first?

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• There is a Default instance of form in VB.Net but not in C#, WHY?

  - by Shekhar_Pro

  I'm just curious to know that there is The (Name) property, which represents the name of the Form class.This property is used within the namespace to uniquely identify the class that the Form is an instance of and, in the case of Visual Basic, is used to access the default instance of the form. Now where this Default Instance come from, why can't C# have a equivalent method to this. Also for example to show a form in C# we do something like this: //Only method Form1 frm = new Form1(); frm.Show(); But in VB.Net we have both ways to do it: //'First common method (used slash because editor wouldn't format it properly) Form1.Show(); //'Second method Dim frm as New Form1(); frm.Show(); My question comes from this first method. What is this Form1, is it an instance of Form1 or the Form1 class itself. Now as i mentioned above the Form name is the Default instance in VB.Net. But we also know that Form1 is a class defined in Designer so how can the names be same for both the Instance and class name. If Form1 is Class then there is no (Static\Shared) method named Show(). So where does this method come from. And finally why C# can't have an equivalent of this. If there some mistake in my question Please let me know *I've checked this on stackoverflow, but couldn't find an answer to this.If you do find then please give a link to it.*

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• Appropriate uses of Monad `fail` vs. MonadPlus `mzero`

  - by jberryman

  This is a question that has come up several times for me in the design code, especially libraries. There seems to be some interest in it so I thought it might make a good community wiki. The fail method in Monad is considered by some to be a wart; a somewhat arbitrary addition to the class that does not come from the original category theory. But of course in the current state of things, many Monad types have logical and useful fail instances. The MonadPlus class is a sub-class of Monad that provides an mzero method which logically encapsulates the idea of failure in a monad. So a library designer who wants to write some monadic code that does some sort of failure handling can choose to make his code use the fail method in Monad or restrict his code to the MonadPlus class, just so that he can feel good about using mzero, even though he doesn't care about the monoidal combining mplus operation at all. Some discussions on this subject are in this wiki page about proposals to reform the MonadPlus class. So I guess I have one specific question: What monad instances, if any, have a natural fail method, but cannot be instances of MonadPlus because they have no logical implementation for mplus? But I'm mostly interested in a discussion about this subject. Thanks! EDIT: One final thought occured to me. I recently learned (even though it's right there in the docs for fail) that monadic "do" notation is desugared in such a way that pattern match failures, as in (x:xs) <- return [] call the monad's fail. It seems like the language designers must have been strongly influenced by the prospect of some automatic failure handling built in to haskell's syntax in their inclusion of fail in Monad.

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