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• How do you attract programmers in rural areas?

  - by Reed Copsey

  I run a software development group for a very small, but stable and established company in a small town, somewhat outside of the "big city". Unfortunately, the "programmer" labor pool is much smaller due to the size of the city. There are many positives to working in this area, especially in terms of quality of life (particularly for people interested in outdoor activities), lower cost of living, great schools and neighborhoods, etc. However, I've always had difficulty attracting high-qualtiy, experienced developers. For those of you who hire developers outside of large cities: Where do you advertise to find good developers? Many of the large sites are very focused in certain metropolitan areas, and seem inappropriate places to advertise if you're outside of that main region. How do you attract quality developers to rural (or at least less metropolitan) locations? Do you find that you make more sacrifices in your hiring due to a smaller labor pool? Or do you just wait, and take extra time to attract people? What sacrifices do you expect to make if you are outside of the main developer-rich cities? For all of the developers out there... What would entice you to working in a smaller town? Are there things that would stand out and make you willing to relocate or at least apply to a position that was not nearby? What specific qualities would help you want to move outside of the city? In the past, I've had difficulty with finding good people. Most of the people who've applied and been willing to move out to a more rural location seem like the types that can't keep a quality job elsewhere. I'd like to know what advice people have to attracting quality technical staff. I don't believe its the work itself that's been the problem - The work is both interesting and challenging, and nearly 100% new development. The developers I have seem very happy with their situation - they love the work, the atmosphere, etc. It's more a matter of finding willing, able developers. Edit: More info after the first couple of answers: Right now, some of my best developers telecommute (some work from overseas); however, for this question, I'm trying to figure out how to get people who want to live and work full time locally. I need some people with whom I interact every day.

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• XPathNavigator in Silverlight

  - by vladimir

  I have a code library that makes heavy use of XPathNavigator to parse some specific xml document. The xml document is cross-referenced, meaning that an element can reference another which has not yet been encountered during parsing: <ElementA ...> <DependentElementX id="1234"> </ElementA> <ElementX id="1234" .../> The document doesn't really look like this, but the point is that 1) there is an xml schema that enforces the overall document structure, 2) elements inside the document can reference each other using some IDs, and 3) there is quite a few such cross references between different elements in the document. The document is parsed in two phases. In the first pass I walk through the document XPathDocument doc = ...; XPathNavigator nav = doc.CreateNavigator(); nav.MoveToRoot(); nav.MoveToFirstChild()... and occasionally 'bookmark' the current position (element) in the document using XPathNavigator.Clone() method. This gives me a lightweight instance of an XPathNavigator which I can store somewhere and use later to jump back to a particular place (element) in my document. Once I have enough information collected in the first pass (for example, I have made sure there is indeed an ElementX with an id='1234'), I jump back to saved bookmarks (using those saved XPathNavigators) and complete the parsing. Well, now I'm about to use this library in Silverlight 3.0 and to my horror the XPathNavigator is not in the System.Xml assembly. Questions: 1) Am I missing something obvious (i.e. XPathNavigator does exist in some shape or form, for example in a toolkit or a freeware library)? 2) If I do have to make modifications in the code, what would be the best way to go? Ideally, I would like to make minimal changes, not to rewrite 80% of the code just to be able to use something like XLinq. To resume, in case I have to give up XPathNavigator, all I need is a way to bookmark places in my document and to get back to them so that I can continue to iterate from where I left off. Thanks in advance for any help/ideas.

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• MySQL table organization and optimization (Rails)

  - by aguynamedloren

  I've been learning Ruby on Rails over the past few months with no prior programming experience. Lately, I've been thinking about database optimization and table organization. I know there are great books on the subject, but I typically learn by example / as I go. Here's a hypothetical situation: Let's say I am building a social network for a niche community with 250,000 members (users). The users have the ability to attend events. Let's say there are 50,000 past/present/future events. Much like Facebook events, a user can attend any number of events and an event can have any number of attendees. In the database, there would be a table for users and a table for events. Somehow I would have to create an association between the users and events. I could create an "events" column in the users table such that each user row would contain a hash of event IDs, or I could create an "attendees" column in the events table such that each event row would contain a hash of user IDs. Neither of these solutions seem ideal, however. On a users profile page, I want to display the list of events they are associated with, which would require scanning the 50,000 event rows for the user ID of said user if I include an "attendees" column in the events table. Likewise, on an event page, I want to display a list of attendees for the event, which would require scanning the 250,000 user rows for the event ID of said event if I include an "events" column in the users table. Option 3 would be to create a third table that contains the attendee information for each and every event - but I don't see how this would solve any problems. Are these non-issues? Rails makes accessing all of this information easy, but I guess I'm worried about scale. It is entirely possible that I am under-estimating the speed and processing power of modern databases / servers / etc. How long would it take to scan 250,000 user rows for specific event IDs - 10ms? 100ms? 1,000ms? I guess that's not that bad. Am I just over-thinking this?

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• WP7 silverlight custom control using popup

  - by Miloud B.

  Hi guys, I'm creating a custom datepicker, I have a textbox, once clicked it opens a calendar within a popup. What I want to do is change the size of the popup so it shows my whole calendar, but I can't manage to change it..., I've tried using Height, Width, MinHeight, MinWidth... but it doesn't work, the popup keep showing with a fixed size. The thing is that my popup's parent property isn't evaluated since it has expression issues (according to debugger), so I'm sure my popup's parent isn't the main screen( say layout grid). How can I for example make my popup open within a specific context ? This part of my code isn't XAML, it's C# code only and it looks like: using System; using System.Net; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes; using System.Windows.Controls.Primitives; namespace CalendarBranch.components { public class wpDatePicker:TextBox { private CalendarPopup calendar; private Popup popup; public wpDatePicker() { this.calendar = new CalendarPopup(); this.popup = new Popup(); this.popup.Child = this.calendar; this.popup.Margin = new Thickness(0); this.MouseLeftButtonUp += new MouseButtonEventHandler(wpDatePicker_MouseLeftButtonUp); this.calendar.onDateSelect += new EventHandler(onDateSelected); this.IsReadOnly = true; } protected void wpDatePicker_MouseLeftButtonUp(object sender, MouseButtonEventArgs e) { this.popup.Height = this.calendar.Height; this.popup.Width = this.calendar.Width; this.popup.HorizontalAlignment = HorizontalAlignment.Center; this.popup.VerticalAlignment = VerticalAlignment.Center; this.popup.HorizontalOffset = 0; this.popup.VerticalOffset = 0; this.popup.MinHeight = this.calendar.Height; this.popup.MinWidth = this.calendar.Width; this.popup.IsOpen = true; } private void onDateSelected(Object sender, EventArgs ea) { this.Text = this.calendar.SelectedValue.ToShortDateString(); this.popup.IsOpen = false; } } } PS: the class Calendar is simply a UserControl that contains a grid with multiple columns, HyperLinkButtons and TextBlocks, so nothing special. Thank you in advance guys ;) Cheers Miloud B.

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• Supplying a callback to Jeditable

  - by pjmorse

  Summary: When I try supplying a onsubmit or onreset callback to Jeditable, I get Object [function] has no method 'apply' errors. How I got here: I've been working on a rails plugin to supply Jeditable and jWYSIWYG for in-place WYSIWYG editing. Development is driven by a Rails project I'm working on which asks for specific functions. One of the options I added was the ability to trigger Jeditable's edit mode using a button instead of clicking on the editable text itself, following the pattern suggested in this answer. The next step, though, is to hide the button while in edit mode, and reveal it again when leaving edit mode. The hide is easy enough; I just added a line to the triggering function which sends .toggle() to the button. Reveal is trickier. I figure I need to .toggle() again on submit or cancel, and helpfully, Jeditable offers onsubmit and onreset callbacks. However, when I try using those callbacks, I get this Object [something] has no method 'apply' errors. What I'm trying: Because this is in the context of a Rails helper, the actual mechanics are a little more involved than this, but the upshot is that I'm trying to follow this pattern, handing Jeditable this in the args: "onsubmit":"showTrigger", and then including this script: function showTrigger(settings, original) { $(".edit_trigger[id='element_id']").toggle(); } However, on submitting changes or canceling an edit, I get the error Object showTrigger has no method 'apply' ...as described above. I also tried sending in a function directly as the "onsubmit" argument (i.e. "onsubmit": "function(settings, original){$(\".edit_trigger[id='element_id']\").toggle();}" and then I just get Object function(settings, original){$(\".edit_trigger[id='element_id']\").toggle();} has no method 'apply' instead. There must be something wrong with how I'm handing in this callback. Any ideas? ETA: This answer suggests to me that somehow I'm providing a string to Jeditable when it expects a function instead. However, because I'm working within the context of a Rails helper, I'm not at all sure how to fix that - the "showTrigger" bit is set as a Ruby variable in the helper, and although window.showTrigger() is defined when the window is loaded, I don't know how to designate that function within a Ruby variable such that it will be recognized as a function at page load time.

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• ASP.NET 2.0 files work in one folder, but NOT in another

  - by Steve

  I am about to leap of a building. I have created an app for a client and all the files are in a folder on their D drive. Now it is time to go production, so I copied all my files and folders to their excisting classic asp folder on the same drive. BUT NOTHING WORKS. The only difference I can see is that DEV does not require HTTPS like the production site. I also made sure all the permissions are the same on both folder. I made sure that the GAC has read rights using the aspnet_regiis tool. I am at the end of my debug knowlegde, could someone please help me out. Here are the error messages I get from the application event log. Failed to initialize the AppDomain:/LM/W3SVC/3/Root Exception: System.Configuration.ConfigurationErrorsException Message: Exception of type 'System.Configuration.ConfigurationErrorsException' was thrown. StackTrace: at System.Web.Configuration.ErrorRuntimeConfig.ErrorConfigRecord.System.Configuration.Internal.IInternalConfigRecord.GetLkgSection(String configKey) at System.Web.Configuration.RuntimeConfigLKG.GetSectionObject(String sectionName) at System.Web.Configuration.RuntimeConfig.GetSection(String sectionName, Type type, ResultsIndex index) at System.Web.Configuration.RuntimeConfig.get_HostingEnvironment() at System.Web.Hosting.HostingEnvironment.StartMonitoringForIdleTimeout() at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters) at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters) at System.Web.Hosting.ApplicationManager.CreateAppDomainWithHostingEnvironment(String appId, IApplicationHost appHost, HostingEnvironmentParameters hostingParameters) at System.Web.Hosting.ApplicationManager.CreateAppDomainWithHostingEnvironmentAndReportErrors(String appId, IApplicationHost appHost, HostingEnvironmentParameters hostingParameters) For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. ------------------------ Failed to execute the request because the ASP.NET process identity does not have read permissions to the global assembly cache. Error: 0x80131902 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. ------------------------- aspnet_wp.exe (PID: 4568) stopped unexpectedly. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Here is the web error message: Server Application Unavailable The web application you are attempting to access on this web server is currently unavailable. Please hit the "Refresh" button in your web browser to retry your request. Administrator Note: An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. Thank you for your help, Steve

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• Changing the itemsSource of a treeview makes it's children invisible, when they were already display

  - by Marnix Kraus

  I found some strange problem in WPF, using the itemsSource of a treeview. I hope I can make this specific problem clear for you. First; a story. There is a treeview. It has a list with treeviewitems as itemsSource. This list is called _roots. There is another list, called _leafs. For as in a treeview, the _roots contain the _leafs in some hierarchical way. For example: <TreeviewItem Header="Jungle"> <TreeviewItem> <SpecialTreeviewItem Header="Monkey"/> <SpecialTreeviewItem Header="Apple"/> </TreeviewItem> </TreeviewItem> Now I am trying to switch between these two lists as itemsSource. It seemed to work fine, but it doesn't: When the Jungle-item is un-expanded, and I change the itemsSource to _leafs, and change it back again to _roots, everything works fine and all items can be expanded and showed. But when the Jungle-item is expanded (and the special items are already visible) and I change it to the _leafs itemsSource, and then change the itemsSource back to _roots, all special items have disappeared!! Also, when I do the same as case 2, but first un-expand the Jungle-item again, the special items also disappear. I did a lot of debugging, before posting this question here and come to the following conclusion: Printing on the event: visibility changed, the visibility is set to false for all items that were already visible (that is, when _roots become visible, the special items become invisible (because they were already visible)) So, IsVisible is false for the items, but Visibility = Visible. Which is a bit strange. The problem seems to depend on the use of the _roots list, which in a certain way contain the _leafs. When I change the itemsSource to different lists with special items in it, everything works fine. The hierarchical structure of the _roots make this thing broken. I hope that this is a complete overview of my problem. Help would be appreciated.

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• ASP.NET MVC & EF4 Entity Framework - Are there any performance concerns in using the entities vs retrieving only the fields i need?

  - by Ant

  Lets say we have 3 tables, Users, Products, Purchases. There is a view that needs to display the purchases made by a user. I could lookup the data required by doing: from p in DBSet<Purchases>.Include("User").Include("Product") select p; However, I am concern that this may have a performance impact because it will retrieve the full objects. Alternatively, I could select only the fields i need: from p in DBSet<Purchases>.Include("User").Include("Product") select new SimplePurchaseInfo() { UserName = p.User.name, Userid = p.User.Id, ProductName = p.Product.Name ... etc }; So my question is: Whats the best practice in doing this? == EDIT Thanks for all the replies. [QUESTION 1]: I want to know whether all views should work with flat ViewModels with very specific data for that view, or should the ViewModels contain the entity objects. Real example: User reviews Products var query = from dr in productRepository.FindAllReviews() where dr.User.UserId = 'userid' select dr; string sql = ((ObjectQuery)query).ToTraceString(); SELECT [Extent1].[ProductId] AS [ProductId], [Extent1].[Comment] AS [Comment], [Extent1].[CreatedTime] AS [CreatedTime], [Extent1].[Id] AS [Id], [Extent1].[Rating] AS [Rating], [Extent1].[UserId] AS [UserId], [Extent3].[CreatedTime] AS [CreatedTime1], [Extent3].[CreatorId] AS [CreatorId], [Extent3].[Description] AS [Description], [Extent3].[Id] AS [Id1], [Extent3].[Name] AS [Name], [Extent3].[Price] AS [Price], [Extent3].[Rating] AS [Rating1], [Extent3].[ShopId] AS [ShopId], [Extent3].[Thumbnail] AS [Thumbnail], [Extent3].[Creator_UserId] AS [Creator_UserId], [Extent4].[Comment] AS [Comment1], [Extent4].[DateCreated] AS [DateCreated], [Extent4].[DateLastActivity] AS [DateLastActivity], [Extent4].[DateLastLogin] AS [DateLastLogin], [Extent4].[DateLastPasswordChange] AS [DateLastPasswordChange], [Extent4].[Email] AS [Email], [Extent4].[Enabled] AS [Enabled], [Extent4].[PasswordHash] AS [PasswordHash], [Extent4].[PasswordSalt] AS [PasswordSalt], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent4].[UserId] AS [UserId1], [Extent4].[UserName] AS [UserName] FROM [ProductReviews] AS [Extent1] INNER JOIN [Users] AS [Extent2] ON [Extent1].[UserId] = [Extent2].[UserId] LEFT OUTER JOIN [Products] AS [Extent3] ON [Extent1].[ProductId] = [Extent3].[Id] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent1].[UserId] = [Extent4].[UserId] WHERE N'615005822' = [Extent2].[UserId] or from d in productRepository.FindAllProducts() from dr in d.ProductReviews where dr.User.UserId == 'userid' orderby dr.CreatedTime select new ProductReviewInfo() { product = new SimpleProductInfo() { Id = d.Id, Name = d.Name, Thumbnail = d.Thumbnail, Rating = d.Rating }, Rating = dr.Rating, Comment = dr.Comment, UserId = dr.UserId, UserScreenName = dr.User.ScreenName, UserThumbnail = dr.User.Thumbnail, CreateTime = dr.CreatedTime }; SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[Thumbnail] AS [Thumbnail], [Extent1].[Rating] AS [Rating], [Extent2].[Rating] AS [Rating1], [Extent2].[Comment] AS [Comment], [Extent2].[UserId] AS [UserId], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent2].[CreatedTime] AS [CreatedTime] FROM [Products] AS [Extent1] INNER JOIN [ProductReviews] AS [Extent2] ON [Extent1].[Id] = [Extent2].[ProductId] INNER JOIN [Users] AS [Extent3] ON [Extent2].[UserId] = [Extent3].[UserId] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent2].[UserId] = [Extent4].[UserId] WHERE N'userid' = [Extent3].[UserId] ORDER BY [Extent2].[CreatedTime] ASC [QUESTION 2]: Whats with the ugly outer joins?

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• Storing simulation results in a persistent manner for Python?

  - by Az

  Background: I'm running multiple simuations on a set of data. For each session, I'm allocating projects to students. The difference between each session is that I'm randomising the order of the students such that all the students get a shot at being assigned a project they want. I was writing out some of the allocations in a spreadsheet (i.e. Excel) and it basically looked like this (tiny snapshot, actual table extends to a few thousand sessions, roughly 100 students). | | Session 1 | Session 2 | Session 3 | |----------|-----------|-----------|-----------| |Stu1 |Proj_AA |Proj_AB |Proj_AB | |----------|-----------|-----------|-----------| |Stu2 |Proj_AB |Proj_AA |Proj_AC | |----------|-----------|-----------|-----------| |Stu3 |Proj_AC |Proj_AC |Proj_AA | |----------|-----------|-----------|-----------| Now, the code that deals with the allocation currently stores a session in an object. The next time the allocation is run, the object is over-written. Thus what I'd really like to do is to store all the allocation results. This is important since I later need to derive from the data, information such as: which project Stu1 got assigned to the most or perhaps how popular Proj_AC was (how many times it was assigned / number of sessions). Question(s): What methods can I possibly use to basically store such session information persistently? Basically, each session output needs to add itself to the repository after ending and before beginning the next allocation cycle. One solution that was suggested by a friend was mapping these results to a relational database using SQLAlchemy. I kind of like the idea since this does give me an opportunity to delve into databases. Now the database structure I was recommended was: |----------|-----------|-----------| |Session |Student |Project | |----------|-----------|-----------| |1 |Stu1 |Proj_AA | |----------|-----------|-----------| |1 |Stu2 |Proj_AB | |----------|-----------|-----------| |1 |Stu3 |Proj_AC | |----------|-----------|-----------| |2 |Stu1 |Proj_AB | |----------|-----------|-----------| |2 |Stu2 |Proj_AA | |----------|-----------|-----------| |2 |Stu3 |Proj_AC | |----------|-----------|-----------| |3 |Stu1 |Proj_AB | |----------|-----------|-----------| |3 |Stu2 |Proj_AC | |----------|-----------|-----------| |3 |Stu3 |Proj_AA | |----------|-----------|-----------| Here, it was suggested that I make the Session and Student columns a composite key. That way I can access a specific record for a particular student for a particular session. Or I can merely get the entire allocation run for a particular session. Questions: Is the idea a good one? How does one implement and query a composite key using SQLAlchemy? What happens to the database if a particular student is not assigned a project (happens if all projects that he wants are taken)? In the code, if a student is not assigned a project, instead of a proj_id he simply gets None for that field/object. I apologise for asking multiple questions but since these are closely-related, I thought I'd ask them in the same space.

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• All embedded databases fail to open connections

  - by rsteckly

  Hi, I'm working on a winforms desktop application that needs to store data. I made the really bad decision to try and embed a database. I've tried: SQLite VistaDB SQL Server Compact In each case, I was able to generate a Entity Framework Model over the basic schema I've created. I have an event that adds data that I've been using to test these databases. Well, I kept adding a new record using EF and finding it didn't actually insert a record. In debugging, I checked the context object to see what was happening. It turns out that it is saying "the underlying provider failed to open," or something to that effect. It was not throwing an exception, just not inserting a record. The same thing has happened for all 3 embedded databases--prompting me to get it through my dense head that there has to be something wrong with my configuration. Well, I tried to write some basic sql using a sqlconnection and sqlcommand. This time it throws an exception. In the SQL Server Compact case, it now says: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) I thought perhaps a problem was the path in app.Config. So I changed the connection string to: Note that I simplified the path away from anything that might have spaces and avoided using the Data Directory nonsense that causes problem when the debugging directory does not match the preconfigured value for the data directory. I'm running Windows 7; I thought perhaps it might be an access issue--so I tried running VS 2010 in Administrator mode. No luck. I also installed Sql Server Compact SP2, thinking this might be a bug. No luck. Anyway, I'm ready to pull my hair out. I'm on a tight deadline for this thing and didn't expect to spend the day trying to figure out what is going on.

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• Purpose of Explicit Default Constructors

  - by Dennis Zickefoose

  I recently noticed a class in C++0x that calls for an explicit default constructor. However, I'm failing to come up with a scenario in which a default constructor can be called implicitly. It seems like a rather pointless specifier. I thought maybe it would disallow Class c; in favor of Class c = Class(); but that does not appear to be the case. Some relevant quotes from the C++0x FCD, since it is easier for me to navigate [similar text exists in C++03, if not in the same places] 12.3.1.3 [class.conv.ctor] A default constructor may be an explicit constructor; such a constructor will be used to perform default-initialization or value initialization (8.5). It goes on to provide an example of an explicit default constructor, but it simply mimics the example I provided above. 8.5.6 [decl.init] To default-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9), the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); 8.5.7 [decl.init] To value-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9) with a user-provided constructor (12.1), then the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); In both cases, the standard calls for the default constructor to be called. But that is what would happen if the default constructor were non-explicit. For completeness sake: 8.5.11 [decl.init] If no initializer is specified for an object, the object is default-initialized; From what I can tell, this just leaves conversion from no data. Which doesn't make sense. The best I can come up with would be the following: void function(Class c); int main() { function(); //implicitly convert from no parameter to a single parameter } But obviously that isn't the way C++ handles default arguments. What else is there that would make explicit Class(); behave differently from Class();? The specific example that generated this question was std::function [20.8.14.2 func.wrap.func]. It requires several converting constructors, none of which are marked explicit, but the default constructor is.

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• Design pattern question: encapsulation or inheritance

  - by Matt

  Hey all, I have a question I have been toiling over for quite a while. I am building a templating engine with two main classes Template.php and Tag.php, with a bunch of extension classes like Img.php and String.php. The program works like this: A Template object creates a Tag objects. Each tag object determines which extension class (img, string, etc.) to implement. The point of the Tag class is to provide helper functions for each extension class such as wrap('div'), addClass('slideshow'), etc. Each Img or String class is used to render code specific to what is required, so $Img->render() would give something like <img src='blah.jpg' /> My Question is: Should I encapsulate all extension functionality within the Tag object like so: Tag.php function __construct($namespace, $args) { // Sort out namespace to determine which extension to call $this->extension = new $namespace($this); // Pass in Tag object so it can be used within extension return $this; // Tag object } function render() { return $this->extension->render(); } Img.php function __construct(Tag $T) { $args = $T->getArgs(); $T->addClass('img'); } function render() { return '<img src="blah.jpg" />'; } Usage: $T = new Tag("img", array(...); $T->render(); .... or should I create more of an inheritance structure because "Img is a Tag" Tag.php public static create($namespace, $args) { // Sort out namespace to determine which extension to call return new $namespace($args); } Img.php class Img extends Tag { function __construct($args) { // Determine namespace then call create tag $T = parent::__construct($namespace, $args); } function render() { return '<img src="blah.jpg" />'; } } Usage: $Img = Tag::create('img', array(...)); $Img->render(); One thing I do need is a common interface for creating custom tags, ie I can instantiate Img(...) then instantiate String(...), I do need to instantiate each extension using Tag. I know this is somewhat vague of a question, I'm hoping some of you have dealt with this in the past and can foresee certain issues with choosing each design pattern. If you have any other suggestions I would love to hear them. Thanks! Matt Mueller

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• Data access pattern, combining push and pull?

  - by andlju

  I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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• architecture python question

  - by tom smith

  hi. creating a distributed crawling python app. it consists of a master server, and associated client apps that will run on client servers. the purpose of the client app is to run across a targeted site, to extract specific data. the clients need to go "deep" within the site, behind multiple levels of forms, so each client is specifically geared towards a given site. each client app looks something like main: parse initial url call function level1 (data1) function level1 (data) parse the url, for data1 use the required xpath to get the dom elements call the next function call level2 (data) function level2 (data2) parse the url, for data2 use the required xpath to get the dom elements call the next function call level3 function level3 (dat3) parse the url, for data3 use the required xpath to get the dom elements call the next function call level4 function level4 (data) parse the url, for data4 use the required xpath to get the dom elements at the final function.. --all the data output, and eventually returned to the server --at this point the data has elements from each function... my question: given that the number of calls that is made to the child function by the current function varies, i'm trying to figure out the best approach. each function essentialy fetches a page of content, and then parses the page using a number of different XPath expressions, combined with different regex expressions depending on the site/page. if i run a client on a single box, as a sequential process, it'll take awhile, but the load on the box is rather small. i've thought of attempting to implement the child functions as threads from the current function, but that could be a nightmare, as well as quickly bring the "box" to its knees! i've thought of breaking the app up in a manner that would allow the master to essentially pass packets to the client boxes, in a way to allow each client/function to be run directly from the master. this process requires a bit of rewrite, but it has a number of advantages. a bunch of redundancy, and speed. it would detect if a section of the process was crashing and restart from that point. but not sure if it would be any faster... i'm writing the parsing scripts in python.. so... any thoughts/comments would be appreciated... i can get into a great deal more detail, but didn't want to bore anyone!! thanks! tom

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• Mapscript queryByPoint return no results

  - by lucian.jp

  I have a dynamically generated mapfile made with c# mapscript that is defined like: MAP EXTENT 5.91828 45.63552 5.92346 45.65051 IMAGECOLOR 192 192 192 IMAGETYPE png SIZE 256 256 STATUS ON TRANSPARENT TRUE UNITS METERS NAME "GMAP_TILE" OUTPUTFORMAT NAME "png" MIMETYPE "image/png" DRIVER "GD/PNG" EXTENSION "png" IMAGEMODE "PC256" TRANSPARENT TRUE END SYMBOL NAME "circle" TYPE ELLIPSE FILLED TRUE POINTS 1 1 END END SYMBOL NAME ">" TYPE TRUETYPE ANTIALIAS TRUE CHARACTER ">" GAP -20 FONT "arial" POSITION CC END PROJECTION "proj=merc" "a=6378137" "b=6378137" "lat_ts=0.0" "lon_0=0.0" "x_0=0.0" "y_0=0" "units=m" "k=1.0" "nadgrids=@null" END LEGEND IMAGECOLOR 255 255 255 KEYSIZE 20 10 KEYSPACING 5 5 LABEL SIZE MEDIUM TYPE BITMAP BUFFER 0 COLOR 0 0 0 FORCE FALSE MINDISTANCE -1 MINFEATURESIZE -1 OFFSET 0 0 PARTIALS TRUE END POSITION LL STATUS OFF END QUERYMAP COLOR 255 255 0 SIZE -1 -1 STATUS ON STYLE HILITE END SCALEBAR ALIGN CENTER COLOR 0 0 0 IMAGECOLOR 255 255 255 INTERVALS 4 LABEL SIZE MEDIUM TYPE BITMAP BUFFER 0 COLOR 0 0 0 FORCE FALSE MINDISTANCE -1 MINFEATURESIZE -1 OFFSET 0 0 PARTIALS TRUE END POSITION LL SIZE 200 3 STATUS OFF STYLE 0 UNITS MILES END WEB IMAGEPATH "" IMAGEURL "" QUERYFORMAT text/html LEGENDFORMAT text/html BROWSEFORMAT text/html END LAYER NAME "Troncons" PROJECTION "proj=longlat" "ellps=WGS84" "datum=WGS84" END STATUS DEFAULT TEMPLATE "nofile.html" TOLERANCE 100 TOLERANCEUNITS METERS TYPE LINE UNITS METERS CLASS NAME "Troncons" STYLE ANGLE 360 COLOR 0 0 255 SIZE 5 SYMBOL "circle" WIDTH 5 END STYLE ANGLE 360 COLOR 0 0 0 SIZE 12 SYMBOL ">" WIDTH 1 END END FEATURE POINTS 5.91828 45.63552 5.91876 45.63611 5.91898 45.6364 5.91936 45.63701 5.91952 45.63731 5.91968 45.63762 5.91993 45.63825 5.92003 45.63856 5.92018 45.63919 5.92028 45.63983 5.92031 45.64014 5.92033 45.64046 5.92034 45.64077 5.92034 45.64108 5.92034 45.64171 5.92035 45.64234 5.92035 45.6428 5.92037 45.6433 5.9204 45.64394 5.92046 45.64458 5.92056 45.64522 5.92062 45.64554 5.92069 45.64586 5.92077 45.64617 5.92097 45.64679 5.92122 45.64739 5.92136 45.64769 5.92169 45.64828 5.92207 45.64886 5.92228 45.64914 5.92272 45.64969 5.92321 45.65023 5.92346 45.65051 END END END END I try to queryByPoint to retreive the index of the shape clciked near. In the code below I made a specific test function with fixed point instead of points passed by parameter so I am sure the point I use is actually part of a feature. In my case I use the first point of the only feature contained in mapfile. public string GetTronconId() { //_map is my dynamically created mapObj if (_map != null) for (int i = 0; i < _map.numlayers; i++) { layerObj layer = _map.getLayer(i); // Code never pass this point if (layer.queryByPoint(_map, new pointObj(5.91898, 45.6364, 0, 0), (int) MS_QUERY_MODE.MS_QUERY_MULTIPLE, 100) == (int) MS_RETURN_VALUE.MS_SUCCESS) { int numresults = layer.getNumResults(); if (numresults != 0) { layer.open(); for (int j = 0; j < numresults; j++) { resultCacheMemberObj resultat = layer.getResult(j); shapeObj shape = null; if (layer.getShape(shape, resultat.tileindex, resultat.shapeindex) == (int) MS_RETURN_VALUE.MS_SUCCESS) return shape.getValue(0); } } } } return null; } I have a dummy TEMPLATE set, I do not eveen have to use the tolerance since the point is derectly in a shape, but the queryByPoint keep returning me MS_FAILURE. From my searches on the web everything seem to be OK. Any idea?

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• Hibernate + Spring : cascade deletion ignoring non-nullable constraints

  - by E.Benoît

  Hello, I seem to be having one weird problem with some Hibernate data classes. In a very specific case, deleting an object should fail due to existing, non-nullable relations - however it does not. The strangest part is that a few other classes related to the same definition behave appropriately. I'm using HSQLDB 1.8.0.10, Hibernate 3.5.0 (final) and Spring 3.0.2. The Hibernate properties are set so that batch updates are disabled. The class whose instances are being deleted is: @Entity( name = "users.Credentials" ) @Table( name = "credentials" , schema = "users" ) public class Credentials extends ModelBase { private static final long serialVersionUID = 1L; /* Some basic fields here */ /** Administrator credentials, if any */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public AdminCredentials adminCredentials; /** Active account data */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public Account activeAccount; /* Some more reverse relations here */ } (ModelBase is a class that simply declares a Long field named "id" as being automatically generated) The Account class, which is one for which constraints work, looks like this: @Entity( name = "users.Account" ) @Table( name = "accounts" , schema = "users" ) public class Account extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials the account is linked to */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } And here is the AdminCredentials class, for which the constraints are ignored. @Entity( name = "admin.Credentials" ) @Table( name = "admin_credentials" , schema = "admin" ) public class AdminCredentials extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials linked with an administrative account */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } The code that attempts to delete the Credentials instances is: try { if ( account.validationKey != null ) { this.hTemplate.delete( account.validationKey ); } this.hTemplate.delete( account.languageSetting ); this.hTemplate.delete( account ); } catch ( DataIntegrityViolationException e ) { return false; } Where hTemplate is a HibernateTemplate instance provided by Spring, its flush mode having been set to EAGER. In the conditions shown above, the deletion will fail if there is an Account instance that refers to the Credentials instance being deleted, which is the expected behaviour. However, an AdminCredentials instance will be ignored, the deletion will succeed, leaving an invalid AdminCredentials instance behind (trying to refresh that instance causes an error because the Credentials instance no longer exists). I have tried moving the AdminCredentials table from the admin DB schema to the users DB schema. Strangely enough, a deletion-related error is then triggered, but not in the deletion code - it is triggered at the next query involving the table, seemingly ignoring the flush mode setting. I've been trying to understand this for hours and I must admit I'm just as clueless now as I was then.

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• FormView templates break when refactored to Master/Content

  - by ZaijiaN

  Let's say I have an abstract class IA, with subclasses A1, A2, A3. For each subclass, I had a page with a FormView to insert/edit/view, with code specific to that class. The templates for insert/edit/view are all very similar, so it was mostly cut & paste, and the compiler had no problem that there were controls with the same IDs in the different templates. Something like this: <asp:FormView> <InsertItemTemplate> <asp:Label id="Label1" /> </InsertItemTemplate> <EditItemTemplate> <asp:Label id="Label1" /> </EdittItemTemplate> </asp:FormView> Much of the code/markup ended up being redundant across the pages, so I refactored it to use a master/content format, with the master page having content placeholders for the insert/edit/view templates. Master page: <asp:FormView> <InsertItemTemplate> <asp:ContentPlaceHolder ID="InsertItemTemplate"></asp:ContentPlaceHolder> </InsertItemTemplate> <EditItemTemplate> <asp:ContentPlaceHolder ID="EditItemTemplate"></asp:ContentPlaceHolder> </EdittItemTemplate> </asp:FormView> And content page: <asp:Content ContentPlaceHolderID="InsertItemTemplate"> <asp:Label id="Label1" /> </asp:Content> <asp:Content ContentPlaceHolderID="EditItemTemplate"> <asp:Label id="Label1" /> </asp:Content> In the content page templates, I'm doing the exact same thing I was doing before I refactored, but now the compiler is blowing up with the error BC30260: 'Label1' is already declared as 'Protected WithEvents Label1 As System.Web.UI.WebControls.Label' in this class. For some reason, it's not separating the controls in the content blocks the same way it did when they were in the templates, even though the content placeholders are in the individual templates. Is there a way around this, other than to rename all my controls?

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• Help with iphone dev - beyond bounds error

  - by dusk

  I'm just learning iphone development, so please forgive me for what is probably a beginner error. I've searched around and haven't found anything specific to my problem, so hopefully it is an easy fix. The book has examples of building a table from data hard coded via an array. Unfortunately it never really tells you how to get data from a URL, so I've had to look that up and that is where my problems show up. When I debug in xcode, it seems like the count is correct, so I don't understand why it is going out of bounds? This is the error message: 2010-05-03 12:50:42.705 Simple Table[3310:20b] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray objectAtIndex:]: index (1) beyond bounds (0)' My URL returns the following string: first,second,third,fourth And here is the iphone code with the book's working example commented out #import "Simple_TableViewController.h" @implementation Simple_TableViewController @synthesize listData; - (void)viewDidLoad { /* //working code from book NSArray *array = [[NSArray alloc] initWithObjects:@"Sleepy", @"Sneezy", @"Bashful", @"Bashful", @"Happy", @"Doc", @"Grumpy", @"Thorin", @"Dorin", @"Norin", @"Ori", @"Balin", @"Dwalin", @"Fili", @"Kili", @"Oin", @"Gloin", @"Bifur", @"Bofur", @"Bombur", nil]; self.listData = array; [array release]; */ //code from interwebz that crashes NSString *urlstr = [[NSString alloc] initWithFormat:@"http://www.mysite.com/folder/iphone-test.php"]; NSURL *url = [[NSURL alloc] initWithString:urlstr]; NSString *ans = [NSString stringWithContentsOfURL:url]; NSArray *listItems = [ans componentsSeparatedByString:@","]; self.listData = listItems; [urlstr release]; [url release]; [ans release]; [listItems release]; [super viewDidLoad]; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; self.listData = nil; [super viewDidUnload]; } - (void)dealloc { [listData release]; [super dealloc]; } #pragma mark - #pragma mark Table View Data Source Methods - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.listData count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:SimpleTableIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:SimpleTableIdentifier] autorelease]; } NSUInteger row = [indexPath row]; cell.textLabel.text = [listData objectAtIndex:row]; return cell; } @end

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• Parsing line and selecting values corresponding to a key

  - by gagneet

  there is a set of data which is arranged in a specific manner (as a tree), as is given below. basically a key=value pair, with some additional values at the end, which informs how many children does the branch have and some junk value. 11=1 123 2 11=1>1=45 234 1 11=1>1=45>9=16 345 1 11=1>1=45>9=16>2=34 222 1 11=1>1=45>9=16>2=34>7=0 2234 1 11=1>1=45>9=16>2=34>7=0>8=0 22345 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138 22234 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0 5566 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0 664 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10 443 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10>3=11 445 0 11=1>1=47 4453 1 11=1>1=47>9=16 887 1 11=1>1=47>9=16>2=34 67 1 11=1>1=47>9=16>2=340>7=0 98 1 11=1>1=47>9=16>2=34>7=0>8=0 654 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138 5789 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0 9870 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0>4=0 3216 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10>3=11 66678 0 my problem is to get the appropriate branch from the above data, which satisfies exactly the values, which i give as the input. suppose, my input value to search in the above data stack are: 5=0 4=0 6=10 3=11 11=1 1=45 0=138 9=16 2=34 7=0 8=0 for the above given list of key-values, the function should return 11=11=459=162=347=08=00=1385=04=06=103=11 as the match. likewise, for another input file, in which another set of keys is given: 5=0 4=0 6=10 3=11 11=1 1=45 9=16 2=34 7=0 8=0 the function should return 11=11=459=162=347=08=0 1 as the match. not the last line; as that would also match all the values given in my input key, but, i want only the exact match. Also, I want to find out how many nodes were selected in the given array. (separated by ). What will be the best way to implement this kind of scenario?

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• How to find relation between change in latitudes at centre of map and top/bottom

  - by Imran

  Hi, Im having little trouble finding a relation between the movement at centre and edge of a circle, Im doing for panning world map,my map extent is 180,89:-180,-89, my map pans by adding change(dx,dY) to its extents and not its centre. Now a situation has arrrised where I have to move the map to a specific centre, to calculate the change in longitudes is very easy and simple, but its the change in lattitudes that has caused problem. It seems the change in centreY of map is more than the change at edge of the mapY, or simply if I have to move the map centre from 0long,0lat to 73long,33lat, for dX I simply get 73, but for dY apparently it looks 33 but if i add 33 to top of map that is 89 , it will be 122 which is incorrect since Latitudes are between 90 and -90 . It seems a case a projection of a circle on 2D plane where the edge of circle since is moving backward due to angle expereinces less change and the centre expereinces more change, now is there a relation between these two factors? I tried converting the difference between OriginY and destinationY into radians and then add to Top and Bottom of Map, but it did'nt really work for me. Please note that the map is project on a virtual canvas whose width starts from 256 and increases by 256*2^z , z=0 is default and whole world is visible at that extent of canvas code: public void moveMapTo(double destinationLongitude,double destinationLattitude) // moves map to the new centre { double dXLong=destinationLongitude-centreLongitude; double atanhsinO = atanh(Math.sin(destinationLattitude * Math.PI / 180.00)); double atanhsinD = atanh(Math.sin(centreLatitude * Math.PI / 180.00)); double atanhCentre = (atanhsinD + atanhsinO) / 2; double latitudeSpan =destinationLattitude - centreLatitude; double radianOfCentreLatitude = Math.atan(Math.sinh(atanhCentre)); double dXLat=latitudeSpan / Math.cos(radianOfCentreLatitude); dXLat*=getLattitudeSpan()*(Math.PI/180); <--- HERE IS THE PORBLEM System.out.println("dxLong:"+dXLong+"_dxLat:"+dXLat); mapLeft+=dXLong; mapRight+=dXLong; mapTop+=dXLat; mapBottom+=dXLat; } ////latitude span function private double getLattitudeSpan() { double latitudeSpan = mapTop - mapBottom; latitudeSpan = latitudeSpan / Math.cos(radianOfCentreLatitude); return Math.abs(latitudeSpan); } //ht

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• A python random function acts differently when assigned to a list or called directly...

  - by Dror Hilman

  I have a python function that randomize a dictionary representing a position specific scoring matrix. for example: mat = { 'A' : [ 0.53, 0.66, 0.67, 0.05, 0.01, 0.86, 0.03, 0.97, 0.33, 0.41, 0.26 ] 'C' : [ 0.14, 0.04, 0.13, 0.92, 0.99, 0.04, 0.94, 0.00, 0.07, 0.23, 0.35 ] 'T' : [ 0.25, 0.07, 0.01, 0.01, 0.00, 0.04, 0.00, 0.03, 0.06, 0.12, 0.14 ] 'G' : [ 0.08, 0.23, 0.20, 0.02, 0.00, 0.06, 0.04, 0.00, 0.54, 0.24, 0.25 ] } The scambling function: def scramble_matrix(matrix, iterations): mat_len = len(matrix["A"]) pos1 = pos2 = 0 for count in range(iterations): pos1,pos2 = random.sample(range(mat_len), 2) #suffle the matrix: for nuc in matrix.keys(): matrix[nuc][pos1],matrix[nuc][pos2] = matrix[nuc][pos2],matrix[nuc][pos1] return matrix def print_matrix(matrix): for nuc in matrix.keys(): print nuc+"[", for count in matrix[nuc]: print "%.2f"%count, print "]" now to the problem... When I try to scramble a matrix directly, It's works fine: print_matrix(mat) print "" print_matrix(scramble_matrix(mat,10)) gives: A[ 0.53 0.66 0.67 0.05 0.01 0.86 0.03 0.97 0.33 0.41 0.26 ] C[ 0.14 0.04 0.13 0.92 0.99 0.04 0.94 0.00 0.07 0.23 0.35 ] T[ 0.25 0.07 0.01 0.01 0.00 0.04 0.00 0.03 0.06 0.12 0.14 ] G[ 0.08 0.23 0.20 0.02 0.00 0.06 0.04 0.00 0.54 0.24 0.25 ] A[ 0.41 0.97 0.03 0.86 0.53 0.66 0.33.05 0.67 0.26 0.01 ] C[ 0.23 0.00 0.94 0.04 0.14 0.04 0.07 0.92 0.13 0.35 0.99 ] T[ 0.12 0.03 0.00 0.04 0.25 0.07 0.06 0.01 0.01 0.14 0.00 ] G[ 0.24 0.00 0.04 0.06 0.08 0.23 0.54 0.02 0.20 0.25 0.00 ] but when I try to assign this scrambling to a list , it does not work!!! ... print_matrix(mat) s=[] for x in range(3): s.append(scramble_matrix(mat,10)) for matrix in s: print "" print_matrix(matrix) result: A[ 0.53 0.66 0.67 0.05 0.01 0.86 0.03 0.97 0.33 0.41 0.26 ] C[ 0.14 0.04 0.13 0.92 0.99 0.04 0.94 0.00 0.07 0.23 0.35 ] T[ 0.25 0.07 0.01 0.01 0.00 0.04 0.00 0.03 0.06 0.12 0.14 ] G[ 0.08 0.23 0.20 0.02 0.00 0.06 0.04 0.00 0.54 0.24 0.25 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] What is the problem??? Why the scrambling do not work after the first time, and all the list filled with the same matrix?!

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• Boggling Direct3D9 dynamic vertex buffer Lock crash/post-lock failure on Intel GMA X3100.

  - by nj

  Hi, For starters I'm a fairly seasoned graphics programmer but as wel all know, everyone makes mistakes. Unfortunately the codebase is a bit too large to start throwing sensible snippets here and re-creating the whole situation in an isolated CPP/codebase is too tall an order -- for which I am sorry, do not have the time. I'll do my best to explain. B.t.w, I will of course supply specific pieces of code if someone wonders how I'm handling this-or-that! As with all resources in the D3DPOOL_DEFAULT pool, when the device context is taken away from you you'll sooner or later will have to reset your resources. I've built a mechanism to handle this for all relevant resources that's been working for years; but that fact nothingwithstanding I've of course checked, asserted and doubted any assumption since this bug came to light. What happens is as follows: I have a rather large dynamic vertex buffer, exact size 18874368 bytes. This buffer is locked (and discarded fully using the D3DLOCK_DISCARD flag) each frame prior to generating dynamic geometry (isosurface-related, f.y.i) to it. This works fine, until, of course, I start to reset. It might take 1 time, it might take 2 or it might take 5 resets to set off a bug that causes an access violation either on the pointer returned by the Lock() operation on the renewed resource or a plain crash -- regarding a somewhat similar address, but without the offset that it has tacked on to it in the first case because in that case we're somewhere halfway writing -- iside the D3D9 dll Lock() call. I've tested this on other hardware, upgraded my GMA X3100 drivers (using a MacBook with BootCamp) to the latest ones, but I can't reproduce it on any other machine and I'm at a loss about what's wrong here. I have tried to reproduce a similar situation with a similar buffer (I've got a large scratch pad of the same type I filled with quads) and beyond a certain amount of bytes it started to behave likewise. I'm not asking for a solution here but I'm very interested if there are other developers here who have battled with the same foe or maybe some who can point me in some insightful direction, maybe ask some questions that might shed a light on what I may or may not be overlooking. Another interesting artifact is that the vertex buffer starts to bug if I supply both D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE together which, even though not very logical (you're not going to overwrite if you've just discarded all), gives graphics glitches. Thanks and any corrections are more than welcome. Niels p.s - A friend of mine raised the valid point that it is a huge buffer for onboard video RAM and it's being at least double or triple buffered internally due to it's dynamic nature. On the other hand, the debug output (D3D9 debug DLL + max. warning output) remains silent. p.s 2 - Had it tested on more machines and still works -- it's probably a matter of circumstance: the huge dynamic, internally double/trippled buffered buffer, not a lot of memory and drivers that don't complain when they should.. Unless someone has a better suggestion; I'd still love to hear it :)

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• How to make this sub-sub-query work?

  - by Josh Weissbock

  I am trying to do this in one query. I asked a similar question a few days ago but my personal requirements have changed. I have a game type website where users can attend "classes". There are three tables in my DB. I am using MySQL. I have four tables: hl_classes (int id, int professor, varchar class, text description) hl_classes_lessons (int id, int class_id, varchar lessonTitle, varchar lexiconLink, text lessonData) hl_classes_answers (int id, int lesson_id, int student, text submit_answer, int percent) hl_classes stores all of the classes on the website. The lessons are the individual lessons for each class. A class can have infinite lessons. Each lesson is available in a specific term. hl_classes_terms stores a list of all the terms and the current term has the field active = '1'. When a user submits their answers to a lesson it is stored in hl_classes_answers. A user can only answer each lesson once. Lessons have to be answered sequentially. All users attend all "classes". What I am trying to do is grab the next lesson for each user to do in each class. When the users start they are in term 1. When they complete all 10 lessons in each class they move on to term 2. When they finish lesson 20 for each class they move on to term 3. Let's say we know the term the user is in by the PHP variable $term. So this is my query I am currently trying to massage out but it doesn't work. Specifically because of the hC.id is unknown in the WHERE clause SELECT hC.id, hC.class, (SELECT MIN(output.id) as nextLessonID FROM ( SELECT id, class_id FROM hl_classes_lessons hL WHERE hL.class_id = hC.id ORDER BY hL.id LIMIT $term,10 ) as output WHERE output.id NOT IN (SELECT lesson_id FROM hl_classes_answers WHERE student = $USER_ID)) as nextLessonID FROM hl_classes hC My logic behind this query is first to For each class; select all of the lessons in the term the current user is in. From this sort out the lessons the user has already done and grab the MINIMUM id of the lessons yet to be done. This will be the lesson the user has to do. I hope I have made my question clear enough.

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• Linux: How to find all serial devices (ttyS, ttyUSB, ..) without opening them?

  - by Thomas Tempelmann

  What is the proper way to get a list of all available serial ports/devices on a Linux system? In other words, when I iterate over all devices in /dev/, how do I tell which ones are serial ports in the classic way, i.e. those usually supporting baud rates and RTS/CTS flow control? The solution would be coded in C. I ask because I am using a 3rd party library that does this clearly wrong: It appears to only iterate over /dev/ttyS*. The problem is that there are, for instance, serial ports over USB (provided by USB-RS232 adapters), and those are listed under /dev/ttyUSB*. And reading the Serial-HOWTO at Linux.org, I get the idea that there'll be other name spaces as well, as time comes. So I need to find the official way to detect serial devices. Problem is that there appears none documented, or I can't find it. I imagine one way would be to open all files from /dev/tty* and call a specific ioctl() on them that is only available on serial devices. Would that be a good solution, though? Update hrickards suggested to look at the source for "setserial". Its code does exactly what I had in mind: First, it opens a device with: fd = open (path, O_RDWR | O_NONBLOCK) Then it invokes: ioctl (fd, TIOCGSERIAL, &serinfo) If that call returns no error, then it's a serial dev, apparently. I found similar code here, which suggested to also add the O_NOCTTY option. There is one problem with this approach, though: When I tested this code on BSD Unix (i.e. OSX), it worked as well, however serial devices that are provided thru Bluetooth cause the system (driver) to try to connect to the bluetooth device, which takes a while before it'll return with a timeout error. This is caused by just opening the device. And I can imagine that similar things can happen on Linux as well - ideally, I should not need to open the device to figure out its type. I wonder if there's also a way to invoke ioctl functions without an open, or open a device in a way that it does not cause connections to be made? Any ideas?

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• What's the best way to do base36 arithmetic in perl?

  - by DVK

  What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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