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• Cone-Line Segment Intersection 2D

  - by nophnoph

  Hi everyone, I would like to know is there any way to determine if a cone is intersecting with a (finite)line segment. The cone actually a circle located at P(x,y) with theta degree field of view and radius r. The simple visualization can be found here (sorry i can't post the picture here) I'm trying to do it in C# but I don't have any idea how to that, so for now this is what I'm doing : Check if the line segment is intersecting with the circle If the line segment is intersecting with the circle then I check every single point in the line segment using a function I found here. But I don't think this is the best way to do it. Does anyone have an idea? For additional info, I need this function to make some kind of simple vision simulator. Thanks in advance :)

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• Can't update rows in my database using Entity Framework...?

  - by Dissonant

  Okay, this is really weird. I made a simple database with a single table, Customer, which has a single column, Name. From the database I auto-generated an ADO.NET Entity Data Model, and I'm trying to add a new Customer to it like so: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Test { class Program { static void Main() { Database1Entities db = new Database1Entities(); Customer c = new Customer(); c.Name = "Harry"; db.AddToCustomer(c); db.SaveChanges(); } } } But it doesn't persist Customer "Harry" to the database! I've been scratching my head for a while now wondering why such a simple operation doesn't work. What on earth could be the problem!?

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• Undefined Variable? But I defined it...

  - by Rob

  Well before anyone claims that theres a duplicate question... (I've noticed that people who can't answer the question tend to run and look for a duplicate, and then report it.) Here is the duplicate you are looking for: http://stackoverflow.com/questions/2481382/php-claims-my-defined-variable-is-undefined However, this isn't quite a duplicate. It gives me a solution, but I'm not really looking for this particular solution. Here is my problem: Notice: Undefined variable: custom Now here is my code: $headers = apache_request_headers(); // Request the visitor's headers. $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; //This is what the header should be. foreach ($headers as $header => $value) { $custom .= "$header: $value"; } Clearly, $custom is defined. According to the other question, it's a global and should be marked as one. But how is it a global? And how can I make it a (non-global)? The script works fine, it still displays what its supposed to and acts correctly, but when I turn on error messages, it simply outputs that notice as well. I suppose its not currently necessary to fix it, but I'd like to anyway, as well as know why its doing this.

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• Running Services.msc as a different User C#

  - by Simon Mark Smith

  Hi, I have a requirement to create a simple windows forms application that allows an admin user to manage the Services on remote servers. We don't want to give the admins the usernames and passwords to the servers so these will be encrypted and stored in a database. My question is whether or not it is possible to spawn a Services.msc window when impersonating one of the users stored within the database? I have looked at the ProcessStartInfo class but because Services.msc is not an executable it does not seem to like executing this. Any ideas on a simple way of doing the actual impersonation and loading of Services.msc - say off a button click? Thanks

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• WPF: Bind DataGrid to List<String>

  - by Sam

  Funny, how sometimes the simple things bite me in the behind. I can bind a DataGrid nicely to a Collection of some arbitrary class, using a DataGridTextColumn like this: <DataGridTextColumn Header="Name" Binding="{Binding Name}"/> Now I want to bind a DataGrid to a simple Collection. So since there is no property "Name" or something like that to bind to, how do I write the binding: <DataGridTextColumn Header="Name" Binding="{Binding ???}"/> String has no Property "Value" or something like that. And if I just write {Binding } I'll end up with a one-way-binding, unable to write changes back to the Collection. Thinking about it, I think it is not possible to bind to a collection, so I do need to wrap my string into a class? Or is there a way?

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• efficient thread-safe singleton in C++

  - by user168715

  The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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• Images not shown when publishing MVC application to virtual directory inside default web-site

  - by Michael Sagalovich

  Hi! I am developing an application using ASP.NET MVC 1 and VS2008. When I deploy it to the default web-site in my IIS6 on WinXP, all images are shown correctly, path to any given image is localhost/Content/ImagesUI/[image].[ext] When I deploy it to the virtual directory, created inside the same site, any image request returns IIS standard 404 error page, while the path is localhost/[DirectoryName]/Content/ImagesUI/[image].[ext] - that seems to be correct, true? I am mapping .* to c:\windows\microsoft.net\framework\v2.0.50727\aspnet_isapi.dll in both site and directory configurations. When this mapping is removed, images are shown correctly. However, all other URLs do not work, of course. When I am trying to open an image in browser using the URL to it, aspnet_wp.exe process is not even started (I restarted IIS to test it) - I merely get 404 or the image, depending on the presence of * mapping. Thus, I suppose it has nothing to do neither with routes registered for MVC, nor with ASP. The solution that I found is to make Content folder a virtual directory and remove * mapping from its configuration. While that's OK to some extent, I want a better solution, which will explain and eliminate the cause of the problem, not just workaround it. Thanks for your help!

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• I have a bunch of template parameters that I want to hide from my users. How can I do this?

  - by Alex

  I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• 2 (or more) ComboBoxes dependent on each other

  - by Mcad001

  Hi, I have an Organisation entity and a Region entity. An object of type Organisation can have one or more Region objects connected to it, thus I have a foreign key in my Region entity to the Organisation Entity. The Organisation and Region objects are pulled from my database using WCF RIA and entity framework. I want to put the Organisation objects in one ComboBox and the Region objects in another ComboBox, and when selecting an organsation having the ComboBox for Region objects automatically only showing regions that are connected to the selected organisation. Should be pretty basic, but the way I've designed it right now it doesnt work at all. So, any hint to how I can achive this? A simple simple codeexample is much appreciated! (I'm using SL4,WCF RIA MVVM)

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• Calculating collission for a moving circle, without overlapping the boundaries

  - by Robert Vella

  Let's say I have circle bouncing around inside a rectangular area. At some point this circle will collide with one of the surfaces of the rectangle and reflect back. The usual way I'd do this would be to let the circle overlap that boundary and then reflect the velocity vector. The fact that the circle actually overlaps the boundary isn't usually a problem, nor really noticeable at low velocity. At high velocity it becomes quite clear that the circle is doing something it shouldn't. What I'd like to do is to programmitically take reflection into account and place the circle at it's proper position before displaying it on the screen. This means that I have to calculate the point where it hits the boundary between it's current position and it's future position -- rather than calculating it's new position and then checking if it has hit the boundary. This is a little bit more complicated than the usual circle/rectangle collission problem. I have a vague idea of how I should do it -- basically create a bounding rectangle between the current position and the new position, which brings up a slew of problems of it's own (Since the rectangle is rotated according to the direction of the circle's velocity). However, I'm thinking that this is a common problem, and that a common solution already exists. Is there a common solution to this kind of problem? Perhaps some basic theories which I should look into?

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• Create a link to delete membership in web2py

  - by user1741325

  I'm trying to do something really simple but it's taking me ages to figure out how to do it properly. I want to have a button that simply deletes a member from a group. So in my view I have <div id="del-role">{{=A('Delete Role',_class="btn btn-danger", callback=URL('test'),delete='#del-role')}}</div> However, when I click the button, the only thing I get is a Javascript prompt asking whether I'm sure I want to delete the specified object, yes/no. That's fine but, what I'd really like to do is just auth.del_membership('role') What needs to go in my controller? I do not want any page redirection, I just want to auth.del_membership(role) This seemingly simple thing is taking me forever to understand. Thanks!

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• Does "Value Restriction" practically mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• Rails Model has_many with multiple foreign_keys

  - by Kenzie

  Relatively new to rails and trying to model a very simple family "tree" with a single Person model that has a name, gender, father_id and mother_id (2 parents). Below is basically what I want to do, but obviously I can't repeat the :children in a has_many (the first gets overwritten). class Person < ActiveRecord::Base belongs_to :father, :class_name => 'Person' belongs_to :mother, :class_name => 'Person' has_many :children, :class_name => 'Person', :foreign_key => 'mother_id' has_many :children, :class_name => 'Person', :foreign_key => 'father_id' end Is there a simple way to use has_many with 2 foreign keys, or maybe change the foreign key based on the object's gender? Or is there another/better way altogether? Thanks!

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• Attributes passed to .build() dont show up in the query

  - by Sebastian

  Hi there guys! Hope your all enjoying your hollydays. Ive run into a pretty funny problem when trying to insert rows into a really really simple database table. The basic idea is pretty simple. The user selects one/multiple users in a multiselect which are supposed to be added to a group. This piece of code will insert a row into the user_group_relationships table, but the users id always @group = Group.find(params[:group_id]) params[:newMember][:users].each do |uid| # For debugging purposes. puts 'Uid:'+uid @rel = @group.user_group_relationships.build( :user_id => uid.to_i ) @rel.save end The user id always gets inserted as null even though it is clearly there. You can see the uid in this example is 5, so it should work. Uid:5 ... SQL (0.3ms) INSERT INTO "user_group_relationships" ("created_at", "group_id", "updated_at", "user_id") VALUES ('2010-12-27 14:03:24.331303', 2, '2010-12-27 14:03:24.331303', NULL) Any ideas why this fails?

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• Looking for .NET library capable of reading HDF4 file format

  - by Gart

  Does anybody know a simple library to read data from HDF files in .NET framework?

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• iPhone RSS Reader -- parseXML won't Load some XML feeds

  - by JBMJBM

  I am using the SIMPLE RSS reading example found at http://theappleblog.com/2008/08/04/tutorial-build-a-simple-rss-reader-for-iphone/ It uses parseXML to load the RSS feeds. Here is the problem I am having. For the following RSS feed example, I am having trouble getting it to load the feed. Comes up with an error that it cannot connect. However on my Mac RSS Reader it works fine, so I know the link is good. Any ideas on why it cannot load this particular feed but it can load others fine? http://www.okstate.com/rss.dbml?db_oem_id=200&media=news Thanks.

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• Click at specified client area

  - by VixinG

  Click doesn't work - I don't know why and can't find a solution :( ie. Click(150,215) should move mouse to the client area and click there. [DllImport("user32.dll")] private static extern bool ScreenToClient(IntPtr hWnd, ref Point lpPoint); [DllImport("user32", SetLastError = true)] private static extern int SetCursorPos(int x, int y); static void MouseMove(int x, int y) { Point p = new Point(x * -1, y * -1); ScreenToClient(hWnd, ref p); p = new Point(p.X * -1, p.Y * -1); SetCursorPos(p.X, p.Y); } static void Click(int x, int y) { MouseMove(x, y); SendMessage(hWnd, WM_LBUTTONDOWN, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); SendMessage(hWnd, WM_LBUTTONUP, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); } Edit: Of course I can use mouse_event for that, but I would like to see a solution for SendMessage()... [DllImport("user32.dll")] static extern void mouse_event(int dwFlags, int dx, int dy, int dwData, int dwExtraInfo); const int LEFTDOWN = 0x00000002; const int LEFTUP = 0x00000004; static void Click(int x, int y) { MouseMove(x, y); mouse_event((int)(LEFTDOWN), 0, 0, 0, 0); mouse_event((int)(LEFTUP), 0, 0, 0, 0); }

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• In the generic programming/TMP world what exactly is a model / a policy and a "concept" ?

  - by Hassan Syed

  I'd like to know the precise yet succinct definitions of these three concepts in one place. The quality of the answer should depend on the following two points. Show a simple code snippet to show how and what the concept/technique is used for. Be simple enough to understand so that a programmer without any exposure to this area can grasp it. Note: There are probably many correct answers since each concept has many different facets. If there are a lot of good answers I will eventually turn the question into CW and aggregate the answers. -- Post Accept Edit -- Boost has a nice article on generic programming concepts

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• c++: use a #define in printf?

  - by John

  I was wanting to use a constant of some kind for the application ID (so I can use it in printf). I had this: #define _APPID_ "Hello World!" And then the simple printf, calling it into %s (string). It put this out: simple.cpp:32: error: cannot convert ‘_IO_FILE*’ to ‘const char*’ for argument ‘1’ to ‘int printf(const char*, ...)’ What would I use to define the application ID to use in printf? I tried: static const char _APPID_[] = "Hello World"` but it didn't work, same error I think.

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• SQL return ORDER BY result as an array

  - by EarthMind

  Is it possible to return groups as an associative array? I'd like to know if a pure SQL solution is possible. Note that I release that I could be making things more complex unnecessarily but this is mainly to give me an idea of the power of SQL. My problem: I have a list of words in the database that should be sorted alphabetically and grouped into separate groups according to the first letter of the word. For example: ape broom coconut banana apple should be returned as array( 'a' => 'ape', 'apple', 'b' => 'banana', 'broom', 'c' => 'coconut' ) so I can easily created sorted lists by first letter (i.e. clicking "A" only shows words starting with a, "B" with b, etc. This should make it easier for me to load everything in one query and make the sorted list JavaScript based, i.e. without having to reload the page (or use AJAX). Side notes: I'm using PostgreSQL but a solution for MySQL would be fine too so I can try to port it to PostgreSQL. Scripting language is PHP.

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• MySQL: Limit rows linked to each joined row

  - by SolidSnakeGTI

  Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

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• What object called a method in Obj-C

  - by Loz

  Hi, I am looking to write a plugin controller in Cocoa that loads bundles, and exposes a specific set of methods for the plugins to call. My question is this: is it possible to know (any) info about the object that called a method in the controller. When an instantiated plugin calls a method in my plugin controller, I would like to know which of the plugin instances called the method, without having to rely on the plugin sending a pointer to itself as a parameter (I could always validate the pointer they send, but I want to keep the API methods as simple as possible). There may be no perfect solution (and there are simple workarounds), but it's always good to learn some new tricks if possible (or the reasons why it's impossible). Thanks in advance.

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• How to close and open access to SQL Server 2008 in Windows application?

  - by hgulyan

  Hi, I have a MS Access 97 application (but the question is general) working directly with SQL Server 2008 (without application server or anything). Numbers of users can be up to 1000. Windows Authentication is used. The question is: How to handle modes, so some users will be allowed to work in read-only mode some users won't have access to db for some time My versions: Using a table with a mode id for every group of users, that will work the same way. On Form Load application will query that table for mode id. Using trigger on the tables, that must work according to that mode. The trigger will query mode value and doesn't work if access is closed or it's in read-only mode I know these are not the best solutions, that's why I'm asking for your advice. There's one more point. If the mode is changed to "access-is-closed" for a group of users, that group must not be able to query to DB starting that moment. With first solution I wrote it won't work, because user can be in application at that moment and no form load event will work. How can I do this? Is there any optimal solution? Thank you. Any help would be appreciated.

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• Packaging Java apps for the Windows/Linux desktop.

  - by alexmcchessers

  I am writing an application in Java for the desktop using the Eclipse SWT library for GUI rendering. I think SWT helps Java get over the biggest hurdle for acceptance on the desktop: namely providing a Java application with a consistent, responsive interface that looks like that belonging to any other app on your desktop. However, I feel that packaging an application is still an issue. OS X natively provides an easy mechanism for wrapping Java apps in native application bundles, but producing an app for Windows/Linux that doesn't require the user to run an ugly batch file or click on a .jar is still a hassle. Possibly that's not such an issue on Linux, where the user is likely to be a little more tech-savvy, but on Windows I'd like to have a regular .exe for him/her to run. Has anyone had any experience with any of the .exe generation tools for Java that are out there? I've tried JSmooth but had various issues with it. Is there a better solution before I crack out Visual Studio and roll my own? Edit: I should perhaps mention that I am unable to spend a lot of money on a commercial solution.

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