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• Custom Silverlight Splash Screen causes White Screen of Death

  - by wickster05

  I'm developing a Silverlight 4 application and I've created a custom splash screen. At first glance, the custom splash screen worked well - really well. After a few days I started noticing that the splash screen would no longer show and the screen would remain blank. This seems to only occur when I open multiple IE tabs/windows all pointing to this same application. The first few will load fine, while the following tabs/windows will remain "white" - as if nothing has/is loaded. This doesn't appear to be an issue with other browsers that I've tested with (i.e., Firefox and Chrome). Unfortunately, this product requires multiple screens to be open (and I'm not going to require our users to use a non-Microsoft internet browser). Furthermore, we have another product that hosts this Silverlight application inside a WPF WebBrowser control (which is similar to IE - and experiences the same issues as delineated above). Does anyone have any ideas on how to get around this? This is becoming increasingly frustrating. I should also point out, that the default splash screen seems to avoid these issues. When I remove the custom splash screen, we no longer see these problems. ANY help would be appreciated greatly! -Tom

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• How to give points for each indices of list

  - by Eric Jung

  def voting_borda(rank_ballots): '''(list of list of str) -> tuple of (str, list of int) The parameter is a list of 4-element lists that represent rank ballots for a single riding. The Borda Count is determined by assigning points according to ranking. A party gets 3 points for each first-choice ranking, 2 points for each second-choice ranking and 1 point for each third-choice ranking. (No points are awarded for being ranked fourth.) For example, the rank ballot shown above would contribute 3 points to the Liberal count, 2 points to the Green count and 1 point to the CPC count. The party that receives the most points wins the seat. Return a tuple where the first element is the name of the winning party according to Borda Count and the second element is a four-element list that contains the total number of points for each party. The order of the list elements corresponds to the order of the parties in PARTY_INDICES.''' #>>> voting_borda([['GREEN','NDP', 'LIBERAL', 'CPC'], ['GREEN','CPC','LIBERAL','NDP'], ['LIBERAL','NDP', 'CPC', 'GREEN']]) #('GREEN',[4, 6, 5, 3]) list_of_party_order = [] for sublist in rank_ballots: for party in sublist[0]: if party == 'GREEN': GREEN_COUNT += 3 elif party == 'NDP': NDP_COUNT += 3 elif party == 'LIBERAL': LIBERAL_COUNT += 3 elif party == 'CPC': CPC_COUNT += 3 for party in sublist[1]: if party == 'GREEN': GREEN_COUNT += 2 elif party == 'NDP': NDP_COUNT += 2 elif party == 'LIBERAL': LIBERAL_COUNT += 2 elif party == 'CPC': CPC_COUNT += 2 for party in sublist[2]: if party == 'GREEN': GREEN_COUNT += 1 elif party == 'NDP': NDP_COUNT += 1 elif party == 'LIBERAL': LIBERAL_COUNT += 1 elif party == 'CPC': CPC_COUNT += 1 I don't know how I would give points for each indices of the list MORE SIMPLY. Can someone please help me? Without being too complicated. Thank you!

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• Implementing list position locator in C++?

  - by jfrazier

  I am writing a basic Graph API in C++ (I know libraries already exist, but I am doing it for the practice/experience). The structure is basically that of an adjacency list representation. So there are Vertex objects and Edge objects, and the Graph class contains: list<Vertex *> vertexList list<Edge *> edgeList Each Edge object has two Vertex* members representing its endpoints, and each Vertex object has a list of Edge* members representing the edges incident to the Vertex. All this is quite standard, but here is my problem. I want to be able to implement deletion of Edges and Vertices in constant time, so for example each Vertex object should have a Locator member that points to the position of its Vertex* in the vertexList. The way I first implemented this was by saving a list::iterator, as follows: vertexList.push_back(v); v->locator = --vertexList.end(); Then if I need to delete this vertex later, then rather than searching the whole vertexList for its pointer, I can call: vertexList.erase(v->locator); This works fine at first, but it seems that if enough changes (deletions) are made to the list, the iterators will become out-of-date and I get all sorts of iterator errors at runtime. This seems strange for a linked list, because it doesn't seem like you should ever need to re-allocate the remaining members of the list after deletions, but maybe the STL does this to optimize by keeping memory somewhat contiguous? In any case, I would appreciate it if anyone has any insight as to why this happens. Is there a standard way in C++ to implement a locator that will keep track of an element's position in a list without becoming obsolete? Much thanks, Jeff

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• CanCan polymorphic resource access problem

  - by Call 'naive' True

  Hi everybody, i don't quite understand how to restrict access to links in this particular case with CanCan. I always get "Edit" link displayed. So i believe the problem is in my incorrect definition of cancan methods(load_ and authorize_). I have CommentsController like that: class CommentsController < ApplicationController before_filter :authenticate_user! load_resource :instance_name => :commentable authorize_resource :article def index @commentable = find_commentable #loading our generic object end ...... private def find_commentable params.each { |name, value| if name =~ /(.+)_id$/ return $1.classify.constantize.includes(:comments => :karma).find(value) end } end end and i have in comments/index.html.erb following code that render file from other controller: <%= render :file => "#{get_commentable_partial_name(@commentable)}/show.html.erb", :collection => @commentable %> you can think about "#{get_commentable_partial_name(@commentable)}" like just "articles" in this case. Content of "articles/show.html.erb": <% if can? :update, @commentable %> <%= link_to 'Edit', edit_article_path(@commentable) %> | <% end %> my ability.rb: class Ability include CanCan::Ability def initialize(user) user ||= User.new # guest user if user.role? :admin can :manage, :all elsif user.role? :author can :read, [Article, Comment, Profile] can :update, Article, :user_id => user.id end end end relations with models is: class Comment < ActiveRecord::Base belongs_to :commentable, :polymorphic => true, :dependent => :destroy ... end class Article < ActiveRecord::Base has_many :comments, :as => :commentable, :dependent => :destroy ... end i have tried debug this issue like that user = User.first article = Article.first ability = Ability.new(user) ability.can?(:update, article) and i always get "= true" in ability check Note: user.role == author and article.user_id != user.id if you need more information please write thank's for your time && sorry for my english

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• Why is Request not available for my PDF request?

  - by Beska

  We're trying to create a .NET aspx page that will have a PDF within it. Doing this by hardcoding it is easy. <object height="1250px" width="100%" type="application/pdf" data="our.pdf"> <param value="our.pdf" name="src" /> <param value="transparent" name="wmode" /> </object> (don't worry too much about the transparent thing...we're doing that for other reasons...but I include it here "just in case".) The problem is when we want to generate the PDF dynamically. Our code to populate the literal on the front end looks like this: ltrPDF.Text = String.Format("<object height=\"1250px\" width=\"100%\" type=\"application/pdf\" data=\"ourPdfGenerator.aspx?var0={0}&var1={1}&var2={2}\">", var0, var1, var2); ltrPDF.Text += String.Format("<param value=\"ourPdfGenerator.aspx?var0={0}&var1={1}&var2={2}\">", var0, var1, var2); ltrPDF.Text += "<param value=\"transparent\" name=\"wmode\"/>"; ltrPDF.Text += "</object>"; Kind of ugly, but it seems like it should work. But it doesn't. When I debug, and put a breakpoint on the first line of ourPdfGenerator.aspx.cs Page_Load method, I reach the breakpoint without any difficulty. However, the first thing we do is try to use Request.QueryString: string var0 = Request.QueryString["var0"]; which immediately throws an HttpException: "Request is not available in this context." I'm not clear on: Why isn't it available? What can I do about it?

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• C++ How to read a string of text and create object of their class

  - by user1777711

  After reading a text file... The following information is available Point2D, [3, 2] Line3D, [7, 12, 3], [-9, 13, 68] Point3D, [1, 3, 8] Line2D, [5, 7], [3, 8] Point2D, [3, 2] Line3D, [7, -12, 3], [9, 13, 68] Point3D, [6, 9, 5] Point2D, [3, 2] Line3D, [70, -120, -3], [-29, 1, 268] Line3D, [25, -69, -33], [-2, -41, 58] Point3D, [6, 9, -50] The first data separate by the delimiter comma is the class name. for each of the 4 class Point2D,Line3D,Point3D,Line2D How do i like store them into relevant object base on their class means.. when it read first line Point2D, [3, 2] It will store it as Point2D object with the Data [3, 2] But the issue is what dataset should i pick, Vector, Set , Map or List I was thinking to actually create a data set then but i can't use new Point2D(); since Point2D is parent of Point3D Line2D is parent of Line3D and theres no parent class of Point2D and Line2D. how can i like create a object of them in a data set like e.g Vector so Vector[0] is of Point2D class with data [3,2] , then Vector[1] is of Line3D class with data [7, 12, 3], [-9, 13, 68] Thanks for helping.!

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• adding a token onto a webservice or wcf call

  - by duncanUK

  I have an httphandler which I am using to log the http soap request and response for each webservice that is called from my application as a comms log. i would like to inject a token ont he 1st call (possibly the 1st call to invoke the service that is being logged) and then be able to track all subsequent webservice calls run in the same context with this token so i can tie the subsequent calls back up to the original call. so for example. main webservice -> 2nd web service -> another web service [token] [token] [token] -> nth web service [token] I would like to inject the token on the first call to the main webservice (http handler checks if no token, add it), I would like to use the same http handler to intercept each call to the subsequent webservices and pass on the token if it exists already (the job of the httphandler is to log the in/out soap with the token to reference with. I have managed to inject the first token, but my problem is how do I add the token on the subsequent calls.. can I make it stick on the same context or session? My worry is that when we call a new webservice, we create a whole new proxy/http request which will not inhrit the token... or will it?! Ideally I would like it to persist on the http header as I am setting the token as a header at the moment? has anyone got any ideas or a better way of doing this? I would be most greatful for you comments!

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• [MySQL] Efficiently store last X records per item

  - by Saif Bechan

  I want to store the last X records in an MySQL database in an efficient way. So when the 4th record is stored the first should be deleted. The way I do this not is first run a query getting the items. Than check what I should do then insert/delete. There has to be a better way to do this. Any suggestions? Edit I think I should add that the records stored do not have a unique number. They have a mixed par. For example article_id and user_id. Then I want to make a table with the last X items for user_x. Just selecting the article from the table grouped by user and sorted by time is not an option for me. The table where I do the sort and group on has millions of records and gets hit a lot for no reason. So making a table in between with the last X records is way more effient. PS. I am not using this for articles and users.

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• Integrate OpenId into an existing site

  - by Andrea

  I have a working web application which already has a login and registration system. I'm looking for some advice on how to do it. Until now, users have a username, an email, a password and some optional fields. The registrartion is the usual process with email confirmation. Now I'd like to allow users to use OpenId. So I have added an openid field to the table. There are two different login forms, and users which are already registered can add their openid info and use either login form. The problem is with new users who come on the site for the first time and try to login with OpenId. I create a new user for them, and I don't need a password, but still I need at least a username, which is used on the site (I'm not sure if the email is needed). So my problems are: 1) How do I manage validation? Some fields are required for some users, (e.g. a password) but not for some others. I mean, I can do this, but it immediately gets messy. 2) Should I ask for a username and email on the first OpenId login? On the one hand I'd say yes, but I fear this vanishes the advantages of using OpenId, that is, not having to provide details. 3) I could get the details via SReg or AttributeExchange, but most providers have a bad support for those. For instance my Gmail OpenId account does not tell the email (!). Is there some place to learn more about the current support for these extensions?

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• Does anyone know of any good open source voting software?

  - by mezoid

  I'm looking for a voting system that we can implement at work amongst our developers. We need something that allows developers to submit ideas about what we can do to improve our development practices (amongst other things) and then have all the developers vote on the ideas to give everyone an idea of what ideas we should attempt to implement first. For example, our developers could list ideas for parts of our code base that should be improved/cleaned up and we'd be able to collectively vote on which parts to start on first. Something like www.uservoice.com might be one way of getting what we need but I'm still wanting to look at alternatives. Unfortunately, googling for voting and polling systems just doesn't seem to bring up any useful results because most of them seem geared towards elections and surveys rather than a way for people to make suggestions and vote on them. Does anyone here know of any sort of software system that might be able to do what I'm looking for? Better yet, does anyone have such a system set up for the developers at their work place? I'd be interested in knowing if it is useful at all.

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• Really Need a Facebook App to post to Facebook Page Wall?

  - by Lee Englestone

  Hi, I'm using the Facebook API Graph (C# & ASP.NET) to try to dynamically post to a Facebook page I created. Looking at the code samples floating around.. they suggest creating a Facebook App first (which I have done).. However.. I have 3 different pages I want to post to.. Do I need to create an app for each? (I want to post different things to the 3 pages, not the same posts to each) I just want messages & links to appear as Wall posts. I'm not bothered about having an 'app' that has 'canvas' that is placed in an IFrame. Question : So do I still need to write one or more Facebook Apps to post to my 3 different Facebook pages?? Where I am so far.. I can pass in my apps credentials and get back the access_token. But my posts don't appear to be going anywhere. I'd rather drop the 'facebook application /canvas' approach if possible If I can post directly to a wall (For the above reasons). Oh, and before you ask. I don't want to post to my Apps Wall page, I want to post to my other pages (Unless I have to post to my Apps Wall page first?). I'm sure loads of people have the same questions.. Thanks in advance. -- Lee

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• Can get members, but not count of NSMutableArray

  - by Curyous

  I'm filling an NSMutableArray from a CoreData call. I can get the first object, but when I try to get the count, the app crashes with Program received signal: “EXC_BAD_ACCESS”. How can I get the count? Here's the relevant code - I've put a comment on the line where it crashes. - (void)viewDidLoad { [super viewDidLoad]; managedObjectContext = [[MySingleton sharedInstance] managedObjectContext]; if (managedObjectContext != nil) { charactersRequest = [[NSFetchRequest alloc] init]; charactersEntity = [NSEntityDescription entityForName:@"Character" inManagedObjectContext:managedObjectContext]; [charactersEntity retain]; [charactersRequest setEntity:charactersEntity]; [charactersRequest retain]; NSError *error; characters = [[managedObjectContext executeFetchRequest:charactersRequest error:&error] mutableCopy]; if (characters == nil) { NSLog(@"Did not get results for characters: %@", error.localizedDescription); } else { [characters retain]; NSLog(@"Found some character(s)."); Character* character = (Character *)[characters objectAtIndex:0]; NSLog(@"Name of first one: %@", character.name); NSLog(@"Found %@ character(s).", characters.count); // Crashes on this line with - Program received signal: “EXC_BAD_ACCESS”. } } } And previous declarations from the header file: @interface CrowdViewController : UITableViewController { NSManagedObjectContext *managedObjectContext; NSFetchRequest *charactersRequest; NSEntityDescription *charactersEntity; NSMutableArray *characters; } I'm a bit perplexed and would really appreciate finding out what is going on.

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• Is it better to use a relational database or document-based database for an app like Wufoo?

  - by mboyle

  I'm working on an application that's similar to Wufoo in that it allows our users to create their own databases and collect/present records with auto generated forms and views. Since every user is creating a different schema (one user might have a database of their baseball card collection, another might have a database of their recipes) our current approach is using MySQL to create separate databases for every user with its own tables. So in other words, the databases our MySQL server contains look like: main-web-app-db (our web app containing tables for users account info, billing, etc) user_1_db (baseball_cards_table) user_2_db (recipes_table) .... And so on. If a user wants to set up a new database to keep track of their DVD collection, we'd do a "create database ..." with "create table ...". If they enter some data in and then decide they want to change a column we'd do an "alter table ....". Now, the further along I get with building this out the more it seems like MySQL is poorly suited to handling this. 1) My first concern is that switching databases every request, first to our main app's database for authentication etc, and then to the user's personal database, is going to be inefficient. 2) The second concern I have is that there's going to be a limit to the number of databases a single MySQL server can host. Pretending for a moment this application had 500,000 user databases, is MySQL designed to operate this way? What if it were a million, or more? 3) Lastly, is this method going to be a nightmare to support and scale? I've never heard of MySQL being used in this way so I do worry about how this affects things like replication and other methods of scaling. To me, it seems like MySQL wasn't built to be used in this way but what do I know. I've been looking at document-based databases like MongoDB, CouchDB, and Redis as alternatives because it seems like a schema-less approach to this particular problem makes a lot of sense. Can anyone offer some advice on this?

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• not able to run c/cpp execs in eclipse cdt

  - by user1658323

  i installed eclipse and then cdt on an ubuntu system recently and was trying to make the first runnable c/c++ proj.. i installed g++ also, and then created the first executable cpp 'Hello World' project some files are created... then some issues... 1) even though Build Automatically is selected, I have to goto the project n do a Build Project to build it manually, and this i have to do everytime i make a change 2) After Building manually, there are some new folders created with Binaries and Debug files and i can see g++ commands in the console being executed. The project binary is output both to debug n binaries folder. But i am not able to run these through the Green Play Button or any other way in eclipse. Even Run configuration is not showing any option for c/C++ proj.. though i can goto terminal and run the binary myself through ./ But i want to be able to run n debug this through eclipse. plz help in fixing me this problem as i really love eclipse n have some c/cpp assignments coming soon.. Console info on doing a manual project build - Build of configuration Debug for project qwe ** make all Building file: ../src/qwe.cpp Invoking: GCC C++ Compiler g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/qwe.d" -MT"src/qwe.d" -o "src/qwe.o" "../src/qwe.cpp" Finished building: ../src/qwe.cpp Building target: qwe Invoking: GCC C++ Linker g++ -o "qwe" ./src/qwe.o Finished building target: qwe Build Finished **

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• Why is this linq extension method hit the database twice?

  - by Pure.Krome

  Hi folks, I have an extension method called ToListIfNotNullOrEmpty(), which is hitting the DB twice, instead of once. The first time it returns one result, the second time it returns all the correct results. I'm pretty sure the first time it hits the database, is when the .Any() method is getting called. here's the code. public static IList<T> ToListIfNotNullOrEmpty<T>(this IEnumerable<T> value) { if (value.IsNullOrEmpty()) { return null; } if (value is IList<T>) { return (value as IList<T>); } return new List<T>(value); } public static bool IsNullOrEmpty<T>(this IEnumerable<T> value) { if (value != null) { return !value.Any(); } return true; } I'm hoping to refactor it so that, before the .Any() method is called, it actually enumerates through the entire list. If i do the following, only one DB call is made, because the list is already enumerated. var pewPew = (from x in whatever select x) .ToList() // This enumerates. .ToListIsNotNullOrEmpty(); // This checks the enumerated result. I sorta don't really want to call ToList() then my extension method. Any ideas, folks?

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• ASP.NET MVC 2 user input to SQL 2008 Database problems

  - by Rob

  After my publish in VS2010 the entire website loads and pulls data from the database perfectly. I can even create new users through the site with the correct key code, given out to who needs access. I have two connection strings in my web.config file The first: <add xdt:Transform="SetAttributes" xdt:Locator="Match(name)" name="EveModelContainer" connectionString="metadata=res://*/Models.EdmModel.EveModel.csdl|res://*/Models.EdmModel.EveModel.ssdl|res://*/Models.EdmModel.EveModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=localhost;Initial Catalog=fleet;Persist Security Info=True;User ID=fleet;Password=****&quot;" providerName="System.Data.EntityClient" /> The second: <add xdt:Transform="SetAttributes" xdt:Locator="Match(name)" name="ApplicationServices" connectionString="Data Source=localhost;Initial Catalog=fleet;Persist Security Info=True;User ID=fleet;Password=****;MultipleActiveResultSets=True" /> The first one is the one that is needed to post data with the main application, EveModelContainer. Everything else is pulled using the standard ApplicationServices connection. Do you see anything wrong with my connectionstring? I'm at a complete loss here. The site works perfectly on my friends server and not on mine... Could it be a provider issue? And if I go to iis 7's manager console, and click .net users I get a pop up message saying the custom provider isn't a trusted provider do I want to allow it to run at a higher trust level. I'm at the point where I think its either my string or this trusted provider error... but I have no clue how to add to the trusted provider list... Thank you in advance!!!

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• ControlCollection extension method optimization

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• Wrapping unmanaged C++ with C++/CLI - a proper approach.

  - by Jamie

  Hi there, as stated in the title, I want to have my old C++ library working in managed .NET. I think of two possibilities: 1) I might try to compile the library with /clr and try "It Just Works" approach. 2) I might write a managed wrapper to the unmanaged library. First of all, I want to have my library working FAST, as it was in unmanaged environment. Thus, I am not sure if the first approach will not cause a large decrease in performance. However, it seems to be faster to implement (not a right word :-)) (assuming it will work for me). On the other hand, I think of some problems that might appear while writing a wrapper (e.g. how to wrap some STL collection (vector for instance)?) I think of writing a wrapper residing in the same project as the unmanaged C++ resides - is that a reasonable approach (e.g. MyUnmanagedClass and MyManagedClass in the same project, the second wrapping the other)? What would you suggest in that problem? Which solution is going to give me better performance of the resulting code? Thank you in advance for any suggestions and clues! Cheers

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• Should uni provide "correct answer" after programming assignment is due?

  - by Michael Mao

  Hi all: This is my very first subjective question. And I think it is programming related - the assignment is to be written in a programming language. I am not for "getting the full marks out of a subject". I am actually not for a "correct answer", but for a "better solution", so that I can compare, and can improve. I reckon it is good that I practice programming first and check the solution later to pick up the things I've done wrong/bad. Without a "benchmark" to against, this would be much harder. Unfortunately as far as I know, not all programming subjects taught in uni would kindly provide the students with a "correct answer" in the end, after the assignment is due. One bad metaphor for this is like someone asks you a question which they don't have a clear answer themselves and hope to take advantage of your answer as the basis for their answer. Personally, I feel having a assignment solution provided by the academic staff is essential to students. I do appreciate this, and I feel I might not be the only one. I am a very proactive student in uni. I learn more, I practice more, an assignment for me is more like a challenge to achieve "the best solution I can come up with", not something "I have to pass"... The cause of this question is that for the past few days I have crafted 500+ lines of Perl code, for a tiny assignment. I feel pain when I look at my solution(not finished yet) and I feel like I am an idiot doing some crap code. I know there must be a much better solution. And I reckon it is better for the lecturer in this subject to get me one, rather than asking for an answer here, even I would shamelessly add the link to my solution apart from the assignment requirements. I know in SO, there are a lot of tutors/lecturers for programming subjects/courses. I'd like to hear your words on this question.

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• Static Variables somehow maintaining state?

  - by gfoley

  I am working on an existing project, setup by another coder. I'm having some trouble understanding how state is being maintained between pages. There is a Class library which has some helper objects. Mostly these objects are just used for there static methods and rarely instantiated or inherited. This is an example class I'm testing with. public sealed class Application { public static string Test; } Now when i run something like the following in the base class of my page, I would expect the result to be "1: 2:Test" all the time (note that "1" is empty), but strangly its only this way the first time it is run. Then every time afterwards its "1:Test 2:Test". Somehow its maintaining the state of the static variable between pages and being refreshed?? Response.Write("1:" + SharedLibrary.Application.Test); SharedLibrary.Application.Test = "Test"; Response.Write(" 2:" + SharedLibrary.Application.Test); I need to create more classes like this, but want to understand why this is occurring in the first place. Many Thanks

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• Still Confused About Identifying vs. Non-Identifying Relationships

  - by Jason

  So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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• Overloading generic implicit conversions

  - by raichoo

  Hi I'm having a little scala (version 2.8.0RC1) problem with implicit conversions. Whenever importing more than one implicit conversion the first one gets shadowed. Here is the code where the problem shows up: // containers class Maybe[T] case class Nothing[T]() extends Maybe[T] case class Just[T](value: T) extends Maybe[T] case class Value[T](value: T) trait Monad[C[_]] { def >>=[A, B](a: C[A], f: A => C[B]): C[B] def pure[A](a: A): C[A] } // implicit converter trait Extender[C[_]] { class Wrapper[A](c: C[A]) { def >>=[B](f: A => C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, f) } def >>[B](b: C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, { (x: A) => b } ) } } implicit def extendToMonad[A](c: C[A]) = new Wrapper[A](c) } // instance maybe object maybemonad extends Extender[Maybe] { implicit object MaybeMonad extends Monad[Maybe] { override def >>=[A, B](a: Maybe[A], f: A => Maybe[B]): Maybe[B] = { a match { case Just(x) => f(x) case Nothing() => Nothing() } } override def pure[A](a: A): Maybe[A] = Just(a) } } // instance value object identitymonad extends Extender[Value] { implicit object IdentityMonad extends Monad[Value] { override def >>=[A, B](a: Value[A], f: A => Value[B]): Value[B] = { a match { case Value(x) => f(x) } } override def pure[A](a: A): Value[A] = Value(a) } } import maybemonad._ //import identitymonad._ object Main { def main(args: Array[String]): Unit = { println(Just(1) >>= { (x: Int) => MaybeMonad.pure(x) }) } } When uncommenting the second import statement everything goes wrong since the first "extendToMonad" is shadowed. However, this one works: object Main { implicit def foo(a: Int) = new { def foobar(): Unit = { println("Foobar") } } implicit def foo(a: String) = new { def foobar(): Unit = { println(a) } } def main(args: Array[String]): Unit = { 1 foobar() "bla" foobar() } } So, where is the catch? What am I missing? Regards, raichoo

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• Supress output from Visual Studio output pane (C++)

  - by Ryan Ginstrom

  When I run my Win32 project in the Visual Studio debugger, I get this huge screed of output about which DLLs were loaded, first-chance exceptions, and so on. Is there a way that I can suppress this output? Some day, I might want to know when 'C:\Windows\SysWOW64\ntdll.dll' was loaded, but normally I don't care. This is especially true when I'm running unit tests, and just want to be told whether any of the tests failed. This stuff isn't output with console applications, but it is with windows applications. To give an example of what I mean, here are the first lines from the output of a recent unit-test run. 'MyProject.exe': Loaded 'C:\dev\MyProject\Testing\MyProject.exe', Symbols loaded. 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\ntdll.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\kernel32.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\KernelBase.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\dbghelp.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\msvcrt.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\user32.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\gdi32.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\lpk.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\usp10.dll' 'MyProject.exe': Loaded 'C:\Windows\SysWOW64\advapi32.dll' ... and on and on ...

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• Multidimensional array (parent and childs)

  - by Juan

  I have a category system in a MySQL database with parents and childs. The database only stores the id of it''s immediate parent (or 0 if on root). Since the system allows multiple subcategories there are cases of multiple childs. For example [98] Storage [1] External [3] Pendrives [4] Portable hhdds [2] Internal [5] Sata hhdd [6] IDE hhdd [...] [99] Clothing The database would be id parent_id name 1 98 External 2 98 Internal 3 1 Pendrives 4 1 Portable 5 2 Sata 6 2 IDE 98 0 Storage 99 0 Clothing I also have a products table with a category id and I need to get a list of all the products in the first level of categories. For example: Product Category A 3 B 4 C 5 D 6 E 74 Should return 98: A, B, C, D 99: X, Y, Z... I'm stuck and I can't think of the logic to retrieve it in that way. I started by getting the IDs of all the categories that aren't in the first level by: while ($row = mysql_fetch_assoc($result)) { if ($row['parent_id'] != 0) { $level1[$i]['name'] = utf8_encode($row['categories_name']); $level1[$i]['id'] = $row['categories_id']; } $i++; } but I'm having a burnout and can't think of a way that would nest them. I thought some kind of while but it's infinite :P Any ideas please?

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• Dynamic script addition should be ordered?

  - by hawkettc

  Hi, I'm adding some <script> tags dynamically to the head element after page load. I understand the scripts are loaded asynchronously, but can I expect them to be parsed in the order they are added? I'm seeing the expected behaviour in Firefox, but not in Safari or Chrome. Looking at the document in Chrome developer tools and Firebug, both show the following - <html> <head> ... <script type="text/javascript" src="A.js"></script> <script type="text/javascript" src="B.js"></script> </head> ... </html> However looking at the resource loading view, chrome seems to parse whichever is returned first from the server, while firebug always loads them in the order the script tags were added, even when B is returned first from the server. Should I expect Chrome/Safari to parse the files in the specified order? Using Chrome 5.0.375.29 beta on OS X 10.6.3

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