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• Can I join two tables whereby the joined table is sorted by a certain column?

  - by Ferdy

  I'm not much of a database guru so I need some help on a query I'm working on. In my photo community project I want to richly visualize tags by not only showing the tag name and counter (# of images inside them), I also want to show a thumb of the most popular image inside the tag (most karma). The table setup is as follow: Image table holds basic image metadata, important is the karma field Imagefile table holds multiple entries per image, one for each format Tag table holds tag definitions Tag_map table maps tags to images In my usual trial and error query authoring I have come this far: SELECT * FROM (SELECT tag.name, tag.id, COUNT(tag_map.tag_id) as cnt FROM tag INNER JOIN tag_map ON (tag.id = tag_map.tag_id) INNER JOIN image ON tag_map.image_id = image.id INNER JOIN imagefile on image.id = imagefile.image_id WHERE imagefile.type = 'smallthumb' GROUP BY tag.name ORDER BY cnt DESC) as T1 WHERE cnt > 0 ORDER BY cnt DESC [column clause of inner query snipped for the sake of simplicity] This query gives me somewhat what I need. The outer query makes sure that only tags are returned for which there is at least 1 image. The inner query returns the tag details, such as its name, count (# of images) and the thumb. In addition, I can sort the inner query as I want (by most images, alphabetically, most recent, etc) So far so good. The problem however is that this query does not match the most popular image (most karma) of the tag, it seems to always take the most recent one in the tag. How can I make sure that the most popular image is matched with the tag?

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• Persistant Http client connections in java

  - by Akusete

  I am trying to write a simple Http client application in Java and am a bit confused by the seemingly different ways to establish Http client connections, and efficiently re-use the objects. Current I am using the following steps (I have left out exception handling for simplicity) Iterator<URI> uriIterator = someURIs(); HttpClient client = new DefaultHttpClient(); while (uriIterator.hasNext()) { URI uri = uriIterator.next(); HttpGet request = new HttpGet(uri); HttpResponse response = client.execute(request); HttpEntity entity = response.getEntity(); InputStream s = entity.getContent(); processStream (); s.close(); } In regard to the code above, my questions is: Assuming all URI's are pointing to the same host (but different resources on that host). What is the recommended way to use a single http connection for all requests? And how do you close the connection after the last request? --edit: Also what is the difference between using uri.openConnection(), versus HttpClient? Which is preferable, and what other methods exist?

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• R selecting duplicate rows

  - by Matt

  Okay, I'm fairly new to R and I've tried to search the documentation for what I need to do but here is the problem. I have a data.frame called heeds.data in the following form (some columns omitted for simplicity) eval.num, eval.count, ... fitness, fitness.mean, green.h.0, green.v.0, offset.0, green.h.1, green.v.1,...green.h.7, green.v.7, offset.7... And I have selected a row meeting the following criteria: best.fitness <- min(heeds.data$fitness.mean[heeds.data$eval.count = 10]) best.row <- heeds.data[heeds.data$fitness.mean == best.fitness] Now, what I want are all of the other rows with that have columns green.h.0 to offset.7 (a contiguous section of columns) equal to the best.row Basically I'm looking for rows that have some of the conditions the same as the "best" row. I thought I could just do this, heeds.best <- heeds.data$fitness[ heeds.data$green.h.0 == best.row$green.h.0 & ... ] But with 24 columns it seems like a stupid method. Looking for something a bit simpler with less manual typing. Thanks!

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• How to Inject code in c# method calls from a separate app

  - by Fusspawn

  I was curious if anyone knew of a way of monitoring a .Net application's runtime info (what method is being called and such) and injecting extra code to be run on certain methods from a separate running process. say i have two applications: app1.exe that for simplicity's sake could be class Program { static void Main(string[] args) { while(true){ Somefunc(); } } static void Somefunc() { Console.WriteLine("Hello World"); } } and I have a second application that I wish to be able to detect when Somefunc() from application 1 is running and inject its own code, class Program { static void Main(string[] args) { while(true){ if(App1.SomeFuncIsCalled) InjectCode(); } } static void InjectCode() { App1.Console.WriteLine("Hello World Injected"); } } So The result would be Application one would show Hello World Hello World Injected I understand its not going to be this simple ( By a long shot ) but I have no idea if it's even possible and if it is where to even start. Any suggestions ? I've seen similar done in java, But never in c#. EDIT: To clarify, the usage of this would be to add a plugin system to a .Net based game that I do not have access to the source code of.

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• What are the advantages of using J2EE over ASP.net?

  - by m_oLogin

  We are currently planning to launch a couple of internal web projects in the future. Our company's dev teams are mostly experienced in J2EE and have worked with it for years. Today, we have the choice of launching a couple of our projects on .net. I have checked out a couple of sources on the net, and it seems like the "J2EE vs ASP.net" combat brings out as much discord as the overseen "Apple vs Microsoft" or "Free Eclipse vs Visual Studio"... Nevertheless, I have been somewhat quite impressed with ASP.net's abilities to create great things with huge simplicity (for ex. asp.net ajax's demos). No more tons of xmls to play with, no more tons of frameworks to configure (we usually use the famous combo struts/spring/hibernate)... It just seemed to me that ASP.net had some good advantages over J2EE, but then again, I may speak by ignorance. What I want to know is this : What are the real advantages of using J2EE over ASP.net? Is there anything that cannot be done in ASP.net that can be done in J2EE? Once the frameworks are all in place and configured, is it faster to develop apps in J2EE than it is in .net? Are the applications generally easier to maintain in J2EE than in ASP.net? Is it worth it for some developpers to leave their J2EE knowledge on the side and move on to ASP.net if it does exactly the same thing?

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• Creating a method for wrapping a loaded image in a UIImageView

  - by eco_bach

  I have the following un my applicationDidFinishLaunching method UIImage *image2 = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"image2.jpg" ofType:nil]]; view2 = [[UIImageView alloc] initWithImage:image2]; view2.hidden = YES; [containerView addSubview:view2]; I'm simply adding an image to a view. But because I need to add 30-40 images I need to wrap the above in a function (which returns a UIImageView) and then call it from a loop. This is my first attempt at creating the function -(UIImageView)wrapImageInView:(NSString *)imagePath { UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:imagePath ofType:nil]]; UIImageView *view = [[UIImageView alloc] initWithImage:image]; view.hidden = YES; } And then to invoke it I have the following so far, for simplicity I am only wrapping 3 images //Create an array and add elements to it NSMutableArray *anArray = [[NSMutableArray alloc] init]; [anArray addObject:@"image1.jpg"]; [anArray addObject:@"image2.jpg"]; [anArray addObject:@"image3.jpg"]; //Use a for each loop to iterate through the array for (NSString *s in anArray) { UIImageView *wrappedImgInView=[self wrapImage:s]; [containerView addSubview:wrappedImgInView]; NSLog(s); } //Release the array [anArray release]; I have 2 general questions 1-Is my approach correct?, ie following best practices, for what I am trying to do (load a multiple number of images(jpgs, pngs, etc.) and adding them to a container view) 2-For this to work properly with a large number of images, do I need to keep my array creation separate from my method invocation? Any other suggestions welcome!

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• Componentizing complex functionality in an MVC web app

  - by NXT

  Hi Everyone, This is question about MVC web-app architecture, and how it can be extended to handle componentizing moderately complex units of functionality. I have an MVC style web-app with a customer facing credit card charge page. I've been asked to allow the admins to enter credit card payments as well, for times when credit cards are taken over the phone. The customer facing credit card charge section of the website is currently it's own controller, with approximately 3 pages and a login. That controller is responsible for: Customer login credential authentication Credit card data collection Calling a library to do the actual charge. reporting the results to the user. I would like to extract the card data collection pages into a component of some kind so that I can easily reuse the code on the admin side of the app. Right now my components are limited to single "view" pages with PHP style embedded Perl code. This is a simple, custom MVC framework written in Perl. Right now, controllers are called directly from the framework to service web requests. My idea is to allow controllers to be called from other controllers, so that I can componentize more complex functionality. For simplicity I think I prefer composition over inheritance, even though it will require writing a bunch of pass-through methods (actions). Being Perl, I could in theory do multiple inheritance. I'm wondering if anyone with experience in other MVC web frameworks can comment on how this sort of thing is usually done. Thank you.

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• Converting to a column oriented array in Java

  - by halfwarp

  Although I have Java in the title, this could be for any OO language. I'd like to know a few new ideas to improve the performance of something I'm trying to do. I have a method that is constantly receiving an Object[] array. I need to split the Objects in this array through multiple arrays (List or something), so that I have an independent list for each column of all arrays the method receives. Example: List<List<Object>> column-oriented = new ArrayList<ArrayList<Object>>(); public void newObject(Object[] obj) { for(int i = 0; i < obj.length; i++) { column-oriented.get(i).add(obj[i]); } } Note: For simplicity I've omitted the initialization of objects and stuff. The code I've shown above is slow of course. I've already tried a few other things, but would like to hear some new ideas. How would you do this knowing it's very performance sensitive?

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• What is an efficient strategy for multiple threads posting jobs and waiting for response from a single thread?

  - by jakewins

  In java, what is an efficient solution to the following problem: I have multiple threads (10-20 or so) generating jobs ("Job Creators"), and a single thread capable of performing them ("The worker"). Once a job creator has posted a job, it should wait for the job to finish, yielding no result other than "it's done", before it keeps going. For sending the jobs to the worker thread, I think a ring buffer or similar standard fan-in setup would perhaps be a good approach? But for a Job Creator to find out that her job has been done, I'm not so sure.. The job creators could sleep, and the worker interrupt them when done.. Or each job creator could have an atomic boolean that it checks, and that the worker sets. I dunno, neither of those feel very nice. I'd like to do it with as few (none, if possible) locks as absolutely possible. So to be clear: What I'm looking for is speed, not necessarily simplicity. Does anyone have any suggestions? Links to reading about concurrency strategies would also be very welcome!

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• How to format individual DropDownlist Items (color, etc.) during onDataBinding event

  - by LesterDove

  Hi, I have a basic DropDownList bound to a ObjectDataSource: <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="objDataSource1" DataTextField="FieldName" DataValueField="FieldID" /> The DataTable from which it receives the DataTextField and DataValueField values also returns some other interesting information about the records. Say Active = Y/N for simplicity's sake. What I'd like to do is to set the background-color property of the DropDownList Item based on that Active field in the DataSource results. Further, I'd like to do this "in the same pass" as when the DropDownList is bound to the data. So my guess is that it has to happen during OnDataBinding. Things I already know/tried: I could go back and loop through the DropDownList items later. But it would involve embedding loops and re-visiting the DataTable rows and it just seems inefficient int row; for (row = 0; row < DropDownList1.Items.Count - 1; row++) { [[if this row = that data row]] DropDownList1.Items[row].[[DoStuffHere, etc.]] } We already do stuff like this with the GridView OnRowDataBound event, by accessing the GridViewRowEventArgs e. What I seem to be missing is an "OnDropDownListItemBound" event, so to speak. Hope I've been clear and concise. Seems as though it should be easy...

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• Trait, FunctionN, or trait-inheriting-FunctionN in Scala?

  - by Willis Blackburn

  I have a trait in Scala that has a single method. Call it Computable and the single method is compute(input: Int): Int. I can't figure out whether I should Leave it as a standalone trait with a single method. Inherit from (Int = Int) and rename "compute" to "apply." Just get rid of Computable and use (Int = Int). A factor in favor of it being a trait is that I could usefully add some additional methods. But of course if they were all implemented in terms of the compute method then I could just break them out into a separate object. A factor in favor of just using the function type is simplicity and the fact that the syntax for an anonymous function is more concise than that for an anonymous Computable instance. But then I've no way to distinguish objects that are actually Computable instances from other functions that map Int to Int but aren't meant to be used in the same context as Computable. How do other people approach this type of problem? No right or wrong answers here; I'm just looking for advice.

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• ASP.NET SqlDataSource update and create FK reference

  - by William

  The short version: I have a grid view bound to a data source which has a SelectCommand with a left join in it because the FK can be null. On Update I want to create a record in the FK table if the FK is null and then update the parent table with the new records ID. Is this possible to do with just SqlDataSources? The detailed version: I have two tables: Company and Address. The column Company.AddressId can be null. On my ascx page I am using a SqlDataSource to select a left join of company and address and a GridView to display the results. By having my UpdateCommand and DeleteCommand of the SqlDataSource execute two statements separated by a semi-colon I am able to use the GridView's Edit and Delete functionality to update both table simultaneously. The problem I have is when the Company.AddressId is null. What I need to have happen is have the data source create a record in the Address table and then update the Company table with the new Address.ID then proceed with the update as usual. I would like to do this with just data sources if possible for consistency/simplicity sake. Is it possible to have my data source do this, or perhaps add a second data source to the page to handle some of this? Once I have that working I can probably figure out how to make it work with the InsertCommand as well but if you are on a roll and have an answer for how to make that fly as well feel free to provide it. Thanks.

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• Sequential access to asynchronous sockets

  - by Lars A. Brekken

  I have a server that has several clients C1...Cn to each of which there is a TCP connection established. There are less than 10,000 clients. The message protocol is request/response based, where the server sends a request to a client and then the client sends a response. The server has several threads, T1...Tm, and each of these may send requests to any of the clients. I want to make sure that only one of these threads can send a request to a specific client at any one time, while the other threads wanting to send a request to the same client will have to wait. I do not want to block threads from sending requests to different clients at the same time. E.g. If T1 is sending a request to C3, another thread T2 should not be able to send anything to C3 until T1 has received its response. I was thinking of using a simple lock statement on the socket: lock (c3Socket) { // Send request to C3 // Get response from C3 } I am using asynchronous sockets, so I may have to use Monitor instead: Monitor.Enter(c3Socket); // Before calling .BeginReceive() And Monitor.Exit(c3Socket); // In .EndReceive I am worried about stuff going wrong and not letting go of the monitor and therefore blocking all access to a client. I'm thinking that my heartbeat thread could use Monitor.TryEnter() with a timeout and throw out sockets that it cannot get the monitor for. Would it make sense for me to make the Begin and End calls synchronous in order to be able to use the lock() statement? I know that I would be sacrificing concurrency for simplicity in this case, but it may be worth it. Am I overlooking anything here? Any input appreciated.

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• Is it possible to parameterize a MEF import?

  - by Josh Einstein

  I am relatively new to MEF so I don't fully understand the capabilities. I'm trying to achieve something similar to Unity's InjectionMember. Let's say I have a class that imports MEF parts. For the sake of simplicity, let's take the following class as an example of the exported part. [Export] [PartCreationPolicy(CreationPolicy.NonShared)] public class Logger { public string Category { get; set; } public void Write(string text) { } } public class MyViewModel { [Import] public Logger Log { get; set; } } Now what I'm trying to figure out is if it's possible to specify a value for the Category property at the import. Something like: public class MyViewModel { [MyImportAttribute(Category="MyCategory")] public Logger Log { get; set; } } public class MyOtherViewModel { [MyImportAttribute(Category="MyOtherCategory")] public Logger Log { get; set; } } For the time being, what I'm doing is implementing IPartImportsSatisfiedNotification and setting the Category in code. But obviously I would rather keep everything neatly in one place.

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• Creating a RESTful API - HELP!

  - by Martin Cox

  Hi Chaps Over the last few weeks I've been learning about iOS development, which has naturally led me into the world of APIs. Now, searching around on the Internet, I've come to the conclusion that using the REST architecture is very much recommended - due to it's supposed simplicity and ease of implementation. However, I'm really struggling with the implementation side of REST. I understand the concept; using HTTP methods as verbs to describe the action of a request and responding with suitable response codes, and so on. It's just, I don't understand how to code it. I don't get how I map a URI to an object. I understand that a GET request for domain.com/api/user/address?user_id=999 would return the address of user 999 - but I don't understand where or how that mapping from /user/address to some method that queries a database has taken place. Is this all coded in one php script? Would I just have a method that grabs the URI like so: $array = explode("/", ltrim(rtrim($_SERVER['REQUEST_URI'], "/"), "/")) And then cycle through that array, first I would have a request for a "user", so the PHP script would direct my request to the user object and then invoke the address method. Is that what actually happens? I've probably not explained my thought process very well there. The main thing I'm not getting is how that URI /user/address?id=999 somehow is broken down and executed - does it actually resolve to code? class user(id) { address() { //get user address } } I doubt I'm making sense now, so I'll call it a day trying to explain further. I hope someone out there can understand what I'm trying to say! Thanks Chaps, look forward to your responses. Martin p.s - I'm not a developer yet, I'm learning :)

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• Dealing with array of IntPtr

  - by Padu Merloti

  I think I'm close and I bet the solution is something stupid. I have a C++ native DLL where I define the following function: DllExport bool __stdcall Open(const char* filePath, int *numFrames, void** data); { //creates the list of arrays here... don't worry, lifetime is managed somewhere else //foreach item of the list: { BYTE* pByte = GetArray(i); //here's where my problem lives *(data + i * sizeofarray) = pByte; } *numFrames = total number of items in the list return true; } Basically, given a file path, this function creates a list of byte arrays (BYTE*) and should return a list of pointers via the data param. Each pointing to a different byte array. I want to pass an array of IntPtr from C# and be able to marshal each individual array in order. Here's the code I'm using: [DllImport("mydll.dll",EntryPoint = "Open")] private static extern bool MyOpen( string filePath, out int numFrames, out IntPtr[] ptr); internal static bool Open( string filePath, out int numFrames, out Bitmap[] images) { var ptrList = new IntPtr[512]; MyOpen(filePath, out numFrames, out ptrList); images = new Bitmap[numFrames]; var len = 100; //for sake of simplicity for (int i=0; i<numFrames;i++) { var buffer = new byte[len]; Marshal.Copy(ptrList[i], buffer, 0, len); images[i] = CreateBitmapFromBuffer(buffer, height, width); } return true; } Problem is in my C++ code. When I assign *(data + i * sizeofarray) = pByte; it corrupts the array of pointers... what am I doing wrong?

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• A good data model for finding a user's favorite stories

  - by wings

  Original Design Here's how I originally had my Models set up: class UserData(db.Model): user = db.UserProperty() favorites = db.ListProperty(db.Key) # list of story keys # ... class Story(db.Model): title = db.StringProperty() # ... On every page that displayed a story I would query UserData for the current user: user_data = UserData.all().filter('user =' users.get_current_user()).get() story_is_favorited = (story in user_data.favorites) New Design After watching this talk: Google I/O 2009 - Scalable, Complex Apps on App Engine, I wondered if I could set things up more efficiently. class FavoriteIndex(db.Model): favorited_by = db.StringListProperty() The Story Model is the same, but I got rid of the UserData Model. Each instance of the new FavoriteIndex Model has a Story instance as a parent. And each FavoriteIndex stores a list of user id's in it's favorited_by property. If I want to find all of the stories that have been favorited by a certain user: index_keys = FavoriteIndex.all(keys_only=True).filter('favorited_by =', users.get_current_user().user_id()) story_keys = [k.parent() for k in index_keys] stories = db.get(story_keys) This approach avoids the serialization/deserialization that's otherwise associated with the ListProperty. Efficiency vs Simplicity I'm not sure how efficient the new design is, especially after a user decides to favorite 300 stories, but here's why I like it: A favorited story is associated with a user, not with her user data On a page where I display a story, it's pretty easy to ask the story if it's been favorited (without calling up a separate entity filled with user data). fav_index = FavoriteIndex.all().ancestor(story).get() fav_of_current_user = users.get_current_user().user_id() in fav_index.favorited_by It's also easy to get a list of all the users who have favorited a story (using the method in #2) Is there an easier way? Please help. How is this kind of thing normally done?

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• Partitioning data set in r based on multiple classes of observations

  - by Danny

  I'm trying to partition a data set that I have in R, 2/3 for training and 1/3 for testing. I have one classification variable, and seven numerical variables. Each observation is classified as either A, B, C, or D. For simplicity's sake, let's say that the classification variable, cl, is A for the first 100 observations, B for observations 101 to 200, C till 300, and D till 400. I'm trying to get a partition that has 2/3 of the observations for each of A, B, C, and D (as opposed to simply getting 2/3 of the observations for the entire data set since it will likely not have equal amounts of each classification). When I try to sample from a subset of the data, such as sample(subset(data, cl=='A')), the columns are reordered instead of the rows. To summarize, my goal is to have 67 random observations from each of A, B, C, and D as my training data, and store the remaining 33 observations for each of A, B, C, and D as testing data. I have found a very similar question to mine, but it did not factor in multiple variables. I feel silly asking this question because it seems so simple, but I'm stumped. Also, this is my first question on this site, so I apologize in advance for any faux pas on my part.

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• C++: Reference and Pointer question (example regarding OpenGL)

  - by Jay

  I would like to load textures, and then have them be used by multiple objects. Would this work? class Sprite { GLuint* mTextures; // do I need this to also be a reference? Sprite( GLuint* textures ) // do I need this to also be a reference? { mTextures = textures; } void Draw( textureNumber ) { glBindTexture( GL_TEXTURE_2D, mTextures[ textureNumber ] ); // drawing code } }; // normally these variables would be inputed, but I did this for simplicity. const int NUMBER_OF_TEXTURES = 40; const int WHICH_TEXTURE = 10; void main() { std::vector<GLuint> the_textures; the_textures.resize( NUMBER_OF_TEXTURES ); glGenTextures( NUMBER_OF_TEXTURES, &the_textures[0] ); // texture loading code Sprite the_sprite( &the_textures[0] ); the_sprite.Draw( WHICH_TEXTURE ); } And is there a different way I should do this, even if it would work? Thanks.

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• Merge computed data from two tables back into one of them

  - by Tyler McHenry

  I have the following situation (as a reduced example). Two tables, Measures1 and Measures2, each of which store an ID, a Weight in grams, and optionally a Volume in fluid onces. (In reality, Measures1 has a good deal of other data that is irrelevant here) Contents of Measures1: +----+----------+--------+ | ID | Weight | Volume | +----+----------+--------+ | 1 | 100.0000 | NULL | | 2 | 200.0000 | NULL | | 3 | 150.0000 | NULL | | 4 | 325.0000 | NULL | +----+----------+--------+ Contents of Measures2: +----+----------+----------+ | ID | Weight | Volume | +----+----------+----------+ | 1 | 75.0000 | 10.0000 | | 2 | 400.0000 | 64.0000 | | 3 | 100.0000 | 22.0000 | | 4 | 500.0000 | 100.0000 | +----+----------+----------+ These tables describe equivalent weights and volumes of a substance. E.g. 10 fluid ounces of substance 1 weighs 75 grams. The IDs are related: ID 1 in Measures1 is the same substance as ID 1 in Measures2. What I want to do is fill in the NULL volumes in Measures1 using the information in Measures2, but keeping the weights from Measures1 (then, ultimately, I can drop the Measures2 table, as it will be redundant). For the sake of simplicity, assume that all volumes in Measures1 are NULL and all volumes in Measures2 are not. I can compute the volumes I want to fill in with the following query: SELECT Measures1.ID, Measures1.Weight, (Measures2.Volume * (Measures1.Weight / Measures2.Weight)) AS DesiredVolume FROM Measures1 JOIN Measures2 ON Measures1.ID = Measures2.ID; Producing: +----+----------+-----------------+ | ID | Weight | DesiredVolume | +----+----------+-----------------+ | 4 | 325.0000 | 65.000000000000 | | 3 | 150.0000 | 33.000000000000 | | 2 | 200.0000 | 32.000000000000 | | 1 | 100.0000 | 13.333333333333 | +----+----------+-----------------+ But I am at a loss for how to actually insert these computed values into the Measures1 table. Preferably, I would like to be able to do it with a single query, rather than writing a script or stored procedure that iterates through every ID in Measures1. But even then I am worried that this might not be possible because the MySQL documentation says that you can't use a table in an UPDATE query and a SELECT subquery at the same time, and I think any solution would need to do that. I know that one workaround might be to create a new table with the results of the above query (also selecting all of the other non-Volume fields in Measures1) and then drop both tables and replace Measures1 with the newly-created table, but I was wondering if there was any better way to do it that I am missing.

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• What programming technique not done by you, was ahead of its time?

  - by Ferds

  There are developers who understand a technology and produce a solution months or years ahead of its time. I worked with a guy who designed an system using C# beta which would monitor different system components on several servers. He used SQL Server that would pick up these system monitoring components (via reflection) and would instantiate them via an NT Service. The simplicity in this design, was that another developer (me), who understood part of a system, would produce a component that could monitor it, as he had the specialized knowledge of that part of the system. I would derive from the monitor base class (to start, stop and log info), install on the monitoring server GAC and then add an entry to the components table in sql server. Then the main engine would pick up this component and do its magic. I understood parts of it, but couldn't work out by derive from a base class, why add to the GAC etc. This was 6 years ago and it took me months to realize what he achieved. What programming technique not done by you was ahead of its time? EDIT : Techniques that you have seen at work or journals/blogs - I don't mean historically over years.

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• What is the nicest way to parse this in C++ ?

  - by ereOn

  Hi, In my program, I have a list of "server address" in the following format: host[:port] The brackets here, indicate that the port is optional. host can be a hostname, an IPv4 or IPv6 address. port, if present can be a numeric port number or a service string (like: "http" or "ssh"). If port is present and host is an IPv6 address, host must be in "bracket-enclosed" notation (Example: [::1]) Here are some valid examples: localhost localhost:11211 127.0.0.1:http [::1]:11211 ::1 [::1] And an invalid example: ::1:80 // Invalid: Is this the IPv6 address ::1:80 and a default port, or the IPv6 address ::1 and the port 80 ? ::1:http // This is not ambigous, but for simplicity sake, let's consider this is forbidden as well. My goal is to separate such entries in two parts (obviously host and port). I don't care if either the host or port are invalid as long as they don't contain a : (290.234.34.34.5 is ok for host, it will be rejected in the next process); I just want to separate the two parts, or if there is no port part, to know it somehow. I tried to do something with std::stringstream but everything I come up to seems hacky and not really elegant. How would you do this in C++ ? I don't mind answers in C but C++ is prefered. Any boost solution is welcome as well. Thank you.

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• DataGridView update datasource directly after changed Checkbox value

  - by SchlaWiener

  I have a System.Windows.Forms DataGridView that is bound to a List<MyObject>. The class MyObject contains a boolean property that is bound to DataGridViewCheckboxCell within the DataGridView. public class MyObject { public decimal DefaultValue {get; set; } public bool HasCustomValue {get;set; } public decimal CustomValue {get;set; } public decimal CurrentValue { get { return HasCustomValue ? CustomValue : DefaultValue; } } If I change the value of HasCustomValue another (readonly) property CurrentValue changes it's value, too. That is done by implementing the INotifyPropertyChanged event (I left that part in the source example for simplicity) If I changed HasCustomValue from outside the DataGridView, the column bound to CurrentValue gets updated immediately. Howevery, If the users enables/disables the checkbox, HasCustomValue is not changed in the underlying datasource unless he leaves the column by clicking with the mouse or pressing the TAB key. Is there a way to force the grid to update the datasource directly after changing a checkbox value? If I bind a Control Property I have the ability to set the DataSourceUpdateMode to Windows.Forms.DataSourceUpdateMode.OnPropertyChanged but I haven't found anything like that in a DataGridView

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• Classical task-scheduling assignment

  - by Bruno

  I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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