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  • Write binary stream to browser using PHP

    - by Dave Jarvis
    Background Trying to stream a PDF report written using iReport through PHP to the browser. The general problem is: how do you write binary data to the browser using PHP? Working Code The following code does the job, but (for many reasons) it is not as efficient as it should be (the code writes a file then sends the file contents the browser). // Load the MySQL database driver. // java( 'java.lang.Class' )->forName( 'com.mysql.jdbc.Driver' ); // Attempt a database connection. // $conn = java( 'java.sql.DriverManager' )->getConnection( "jdbc:mysql://localhost:3306/climate?user=$user&password=$password" ); // Extract parameters. // $params = new java('java.util.HashMap'); $params->put('DistrictCode', '101'); $params->put('StationCode', '0066'); $params->put('CategoryCode', '010'); // Use the fill manager to produce the report. // $fm = java('net.sf.jasperreports.engine.JasperFillManager'); $pm = $fm->fillReport($report, $params, $conn); header('Cache-Control: no-cache private'); header('Content-Description: File Transfer'); header('Content-Disposition: attachment, filename=climate-report.pdf'); header('Content-Type: application/pdf'); header('Content-Transfer-Encoding: binary'); header('Content-Length: ' . strlen( $result ) ); $path = realpath( "." ) . "/output.pdf"; $em = java('net.sf.jasperreports.engine.JasperExportManager'); $result = $em->exportReportToPdfFile($pm,$path); readfile( $path ); $conn->close(); Non-working Code To remove the slight redundancy (i.e., write directly to the browser), the following code looks like it should work, but it does not: $em = java('net.sf.jasperreports.engine.JasperExportManager'); $result = $em->exportReportToPdf($pm); header('Content-Length: ' . strlen( $result ) ); echo $result; Content is sent to the browser, but the file is corrupt (it begins with the PDF header) and cannot be read by any PDF reader. Question How can I take out the middle step of writing to the file and write directly to the browser so that the PDF is not corrupted? Thank you!

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  • Using Hibernate to do a query involving two tables

    - by Nathan Spears
    I'm inexperienced with sql in general, so using Hibernate is like looking for an answer before I know exactly what the question is. Please feel free to correct any misunderstandings I have. I am on a project where I have to use Hibernate. Most of what I am doing is pretty basic and I could copy and modify. Now I would like to do something different and I'm not sure how configuration and syntax need to come together. Let's say I have two tables. Table A has two (relevant) columns, user GUID and manager GUID. Obviously managers can have more than one user under them, so queries on manager can return more than one row. Additionally, a manager can be managing the same user on multiple projects, so the same user can be returned multiple times for the same manager query. Table B has two columns, user GUID and user full name. One-to-one mapping there. I want to do a query on manager GUID from Table A, group them by unique User GUID (so the same User isn't in the results twice), then return those users' full names from Table B. I could do this in sql without too much trouble but I want to use Hibernate so I don't have to parse the sql results by hand. That's one of the points of using Hibernate, isn't it? Right now I have Hibernate mappings that map each column in Table A to a field (well the get/set methods I guess) in a DAO object that I wrote just to hold that Table's data. I could also use the Hibernate DAOs I have to access each table separately and do each of the things I mentioned above in separate steps, but that would be less efficient (I assume) that doing one query. I wrote a Service object to hold the data that gets returned from the query (my example is simplified - I'm going to keep some other data from Table A and get multiple columns from Table B) but I'm at a loss for how to write a DAO that can do the join, or use the DAOs I have to do the join. FYI, here is a sample of my hibernate config file (simplified to match my example): <hibernate-mapping package="com.my.dao"> <class name="TableA" table="table_a"> <id name="pkIndex" column="pk_index" /> <property name="userGuid" column="user_guid" /> <property name="managerGuid" column="manager_guid" /> </class> </hibernate-mapping> So then I have a DAOImplementation class that does queries and returns lists like public List<TableA> findByHQL(String hql, Map<String, String> params) etc. I'm not sure how "best practice" that is either.

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  • CSS selectors : should I make my CSS easier to read or optimise the speed

    - by Laurent Bourgault-Roy
    As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It make my .css file harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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  • Odd "Object reference not set to an instance of an object" involving xWinForms

    - by Kyle
    Hey, I've been trying to get the xWinForms 3.0 library (a library with forms support in xna) working with my C# XNA Game project but I keep getting the same problem. I add the reference to my project, put in the using statement, declare a formCollection variable and then I try to initialize it. whenever I run the project I get stopped on this line: formCollection = new FormCollection(this.Window, Services, ref graphics); it gives me the error: " System.NullReferenceException was unhandled Message="Object reference not set to an instance of an object." Source="Microsoft.Xna.Framework" StackTrace: at Microsoft.Xna.Framework.Graphics.VertexShader..ctor(GraphicsDevice graphicsDevice, Byte[] shaderCode) at Microsoft.Xna.Framework.Graphics.SpriteBatch.ConstructPlatformData() at Microsoft.Xna.Framework.Graphics.SpriteBatch..ctor(GraphicsDevice graphicsDevice) at xWinFormsLib.FormCollection..ctor(GameWindow window, IServiceProvider services, GraphicsDeviceManager& graphics) at GameSolution.Game2.LoadContent() in C:\Users\Owner\Documents\School\Year 3\Winter\Soen 390\TeamWTF_3\SourceCode\GameSolution\GameSolution\Game2.cs:line 45 at Microsoft.Xna.Framework.Game.Initialize() at GameSolution.Game2.Initialize() in C:\Users\Owner\Documents\School\Year 3\Winter\Soen 390\TeamWTF_3\SourceCode\GameSolution\GameSolution\Game2.cs:line 37 at Microsoft.Xna.Framework.Game.Run() at GameSolution.Program.Main(String[] args) in C:\Users\Owner\Documents\School\Year 3\Winter\Soen 390\TeamWTF_3\SourceCode\GameSolution\GameSolution\Program.cs:line 14 InnerException: " In a project I downloaded that used the xWinForms, I put the following code in and it compiled and ran no error. but when I put it in my project I get the error. Am I making some stupid mistake about including dlls or something? I've been at this for hours and I can't seem to find anything that would cause this. using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; using Microsoft.Xna.Framework.Net; using Microsoft.Xna.Framework.Storage; using xWinFormsLib; namespace GameSolution { public class Game2 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; FormCollection formCollection; public Game2() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); formCollection = new FormCollection(this.Window, Services, ref graphics); } protected override void Update(GameTime gameTime) { base.Update(gameTime); } protected override void Draw(GameTime gameTime) { base.Draw(gameTime); } } } Any help would be greatly appreciated ._.

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  • Would Like Multiple Checkboxes to Update World PNG Image Using Mogrify to FloodFill Countries With C

    - by socrtwo
    Hi. I'm seeing in another forum if the best way to do this is with Javascript or Ajax but I'm wondering if there is an even easier simpler way. I'm trying to create a web service where users can check which countries they have visited from a list of 175 or so and a World map image would then instantly update with a filled color. There are other similar services, but I'm envisioning mine to be both updating from checks in checkboxes and by clicking on the target country in the displayed image say with an imagemap. Additionally other solutions display all the visited countries in the same color. I would like different colors for different countries or at least for those countries that touch. Eventually I would like to include a feature that enables the choice of which colors to assign countries. I found a Sourceforge project called pwmfccd. It's simply an open source image of the world and the coordinates on the PNG image for all the countries. You can use mogrify from ImageMagick and floodfill to fill the countries with color. I have done this successfully, locally with batch files. My ISP has told me where mogrify is located, basically "/usr/bin/mogrify". I now have a horrendously complicated cgi script which if it worked is set to redraw the world map image with each checkbox. It's here. It also redraws the whole web page with each check. The web page starts here. Of course this is not at all efficient, and I think probably the real way to go is Ajax or Javascript, so that maybe just the image gets changed and redrawn, not the whole web page. Sorry I don't even know the difference between Javascript and Ajax and their relative merits at this point. I suppose you could make just one part of the image update with each check or click on the image instead of even just the image redrawing, but I have never even heard of a hint at being able to do that for irregularly shaped image elements like countries. So I guess an Image map and sister checkbox entries tied to mogrify events redrawing the user's personal copy of the image with an image refresh would be the only way to go. So how do you do this with something other than Javascript or Ajax or is that definitely the way to go and if so, how would you do it? Or can you after all cut up a web based image into irregular puzzle shaped piece which you can redraw individually at will. Thanks in advance for reading and considering answering this post.

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  • How can I get image data from QTKit without color or gamma correction in Snow Leopard?

    - by Nick Haddad
    Since Snow Leopard, QTKit is now returning color corrected image data from functions like QTMovies frameImageAtTime:withAttributes:error:. Given an uncompressed AVI file, the same image data is displayed with larger pixel values in Snow Leopard vs. Leopard. Currently I'm using frameImageAtTime to get an NSImage, then ask for the tiffRepresentation of that image. After doing this, pixel values are slightly higher in Snow Leopard. For example, a file with the following pixel value in Leopard: [0 180 0] Now has a pixel value like: [0 192 0] Is there any way to ask a QTMovie for video frames that are not color corrected? Should I be asking for a CGImageRef, CIImage, or CVPixelBufferRef instead? Is there a way to disable color correction altogether prior to reading in the video files? I've attempted to work around this issue by drawing into a NSBitmapImageRep with the NSCalibratedColroSpace, but that only gets my part of the way there: // Create a movie NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys : nsFileName, QTMovieFileNameAttribute, [NSNumber numberWithBool:NO], QTMovieOpenAsyncOKAttribute, [NSNumber numberWithBool:NO], QTMovieLoopsAttribute, [NSNumber numberWithBool:NO], QTMovieLoopsBackAndForthAttribute, (id)nil]; _theMovie = [[QTMovie alloc] initWithAttributes:dict error:&error]; // .... NSMutableDictionary *imageAttributes = [NSMutableDictionary dictionary]; [imageAttributes setObject:QTMovieFrameImageTypeNSImage forKey:QTMovieFrameImageType]; [imageAttributes setObject:[NSArray arrayWithObject:@"NSBitmapImageRep"] forKey: QTMovieFrameImageRepresentationsType]; [imageAttributes setObject:[NSNumber numberWithBool:YES] forKey:QTMovieFrameImageHighQuality]; NSError* err = nil; NSImage* image = (NSImage*)[_theMovie frameImageAtTime:frameTime withAttributes:imageAttributes error:&err]; // copy NSImage into an NSBitmapImageRep (Objective-C) NSBitmapImageRep* bitmap = [[image representations] objectAtIndex:0]; // Draw into a colorspace we know about NSBitmapImageRep *bitmapWhoseFormatIKnow = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:getWidth() pixelsHigh:getHeight() bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO colorSpaceName:NSCalibratedRGBColorSpace bitmapFormat:0 bytesPerRow:(getWidth() * 4) bitsPerPixel:32]; [NSGraphicsContext saveGraphicsState]; [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:bitmapWhoseFormatIKnow]]; [bitmap draw]; [NSGraphicsContext restoreGraphicsState]; This does convert back to a 'Non color corrected' colorspace, but the color values NOT are exactly the same as what is stored in the Uncompressed AVI files we are testing with. Also this is much less efficient because it is converting from RGB - "Device RGB" - RGB. Also, I am working in a 64-bit application, so dropping down to the Quicktime-C API is not an option. Thanks for your help.

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  • When is #include <new> library required in C++?

    - by Czarak
    Hi, According to this reference entry for operator new ( http://www.cplusplus.com/reference/std/new/operator%20new/ ) : Global dynamic storage operator functions are special in the standard library: All three versions of operator new are declared in the global namespace, not in the std namespace. The first and second versions are implicitly declared in every translation unit of a C++ program: The header does not need to be included for them to be present. This seems to me to imply that the third version of operator new (placement new) is not implicitly declared in every translation unit of a C++ program and the header <new> does need to be included for it to be present. Is that correct? If so, how is it that using both g++ and MS VC++ Express compilers it seems I can compile code using the third version of new without #include <new> in my source code? Also, the MSDN Standard C++ Library reference entry on operator new gives some example code for the three forms of operator new which contains the #include <new> statement, however the example seems to compile and run just the same for me without this include? // new_op_new.cpp // compile with: /EHsc #include<new> #include<iostream> using namespace std; class MyClass { public: MyClass( ) { cout << "Construction MyClass." << this << endl; }; ~MyClass( ) { imember = 0; cout << "Destructing MyClass." << this << endl; }; int imember; }; int main( ) { // The first form of new delete MyClass* fPtr = new MyClass; delete fPtr; // The second form of new delete char x[sizeof( MyClass )]; MyClass* fPtr2 = new( &x[0] ) MyClass; fPtr2 -> ~MyClass(); cout << "The address of x[0] is : " << ( void* )&x[0] << endl; // The third form of new delete MyClass* fPtr3 = new( nothrow ) MyClass; delete fPtr3; } Could anyone shed some light on this and when and why you might need to #include <new> - maybe some example code that will not compile without #include <new> ? Thanks.

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  • Help with storing/accessing user access roles C# Winforms

    - by user222453
    Hello, firstly I would like to thank you in advance for any assistance provided. I am new to software development and have designed several Client/Server applications over the last 12 months or so, I am currently working on a project that involves a user logging in to gain access to the application and I am looking at the most efficient and "simple" method of storing the users permissions once logged in to the application which can be used throughout restricting access to certain tabs on the main form. I have created a static class called "User" detailed below: static class User { public static int _userID; public static string _moduleName; public static string _userName; public static object[] UserData(object[] _dataRow) { _userID = (int)_dataRow[0]; _userName = (string)_dataRow[1]; _moduleName = (string)_dataRow[2]; return _moduleName; } } When the user logs in and they have been authenticated, I wish to store the _moduleName objects in memory so I can control which tabs on the main form tab control they can access, for example; if the user has been assigned the following roles in the database: "Sales Ledger", "Purchase Ledger" they can only see the relevant tabs on the form, by way of using a Switch - Case block once the login form is hidden and the main form is instantiated. I can store the userID and userName variables in the main form once it loads by means of say for example: Here we process the login data from the user: DataAccess _dal = new DataAccess(); switch (_dal.ValidateLogin(txtUserName.Text, txtPassword.Text)) { case DataAccess.ValidationCode.ConnectionFailed: MessageBox.Show("Database Server Connection Failed!"); break; case DataAccess.ValidationCode .LoginFailed: MessageBox.Show("Login Failed!"); _dal.RecordLogin(out errMsg, txtUserName.Text, workstationID, false); break; case DataAccess.ValidationCode .LoginSucceeded: frmMain frmMain = new frmMain(); _dal.GetUserPrivList(out errMsg,2); //< here I access my DB and get the user permissions based on the current login. frmMain.Show(); this.Hide(); break; default: break; } private void frmMain_Load(object sender, EventArgs e) { int UserID = User._userID; } That works fine, however the _modules object contains mutiple permissions/roles depending on what has been set in the database, how can I store the multiple values and access them via a Switch-Case block? Thank you again in advance.

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  • Making a Grid in an NSView

    - by Hooligancat
    I currently have an NSView that draws a grid pattern (essentially a guide of horizontal and vertical lines) with the idea being that a user can change the spacing of the grid and the color of the grid. The purpose of the grid is to act as a guideline for the user when lining up objects. Everything works just fine with one exception. When I resize the NSWindow by dragging the resize handle, if my grid spacing is particularly small (say 10 pixels). the drag resize becomes lethargic in nature. My drawRect code for the grid is as follows: -(void)drawRect:(NSRect)dirtyRect { NSRect thisViewSize = [self bounds]; // Set the line color [[NSColor colorWithDeviceRed:0 green:(255/255.0) blue:(255/255.0) alpha:1] set]; // Draw the vertical lines first NSBezierPath * verticalLinePath = [NSBezierPath bezierPath]; int gridWidth = thisViewSize.size.width; int gridHeight = thisViewSize.size.height; int i; while (i < gridWidth) { i = i + [self currentSpacing]; NSPoint startPoint = {i,0}; NSPoint endPoint = {i, gridHeight}; [verticalLinePath setLineWidth:1]; [verticalLinePath moveToPoint:startPoint]; [verticalLinePath lineToPoint:endPoint]; [verticalLinePath stroke]; } // Draw the horizontal lines NSBezierPath * horizontalLinePath = [NSBezierPath bezierPath]; i = 0; while (i < gridHeight) { i = i + [self currentSpacing]; NSPoint startPoint = {0,i}; NSPoint endPoint = {gridWidth, i}; [horizontalLinePath setLineWidth:1]; [horizontalLinePath moveToPoint:startPoint]; [horizontalLinePath lineToPoint:endPoint]; [horizontalLinePath stroke]; } } I suspect this is entirely to do with the way that I am drawing the grid and am open to suggestions on how I might better go about it. I can see where the inefficiency is coming in, drag-resizing the NSWindow is constantly calling the drawRect in this view as it resizes, and the closer the grid, the more calculations per pixel drag of the parent window. I was thinking of hiding the view on the resize of the window, but it doesn't feel as dynamic. I want the user experience to be very smooth without any perceived delay or flickering. Does anyone have any ideas on a better or more efficient method to drawing the grid? All help, as always, very much appreciated.

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  • Rendering javascript at the server side level. A good or bad idea?

    - by davidhong
    I want to make it clear first: This isn't a question in relation to server-side Javascript or running Javascript server side. This is a question regarding rendering of Javascript code (which will be executed on the client-side) from server-side code. Having said that, take a look at below ASP.net code for example: hlRemoveCategory.Attributes.Add("onclick", "return confirm('Are you sure you want to delete this?');") This is prescribing the client-side onclick event on the server-side. As oppose to: $('a[rel=remove]').bind('click', function(event) { return confirm('Are you sure you want to delete this?'); } Now the question I want to ask is: What is the benefit of rendering javascript from the server-side code? Or the vice-versa? I personally prefer the second way of hooking up client-side UI/behaviour to HTML elements for the following reasons: Server-side does what ever it needs to already, including data-validation, event delegation and etc; and What server-side sees as an event is not necessarily the same process on the client-side. i.e., there are plenty more events on client-side (just look at custom events); and What happens on client-side and on server-side, during an event, could be completely irrelevant and decoupled; and What ever happens on client-side happens on client-side, there is no need for the server to know. Server should process and run what is given to them, how the process comes to life is not really up to them to decide in the event of the client-side events; and so and so forth. These are my thoughts obviously. I want to know what others think and if there has been any discussions on this topic. Topics branching from this argument can reach: Code management: is it easier to render everything from server-side? Separation of concern: is it easier if client-side logic is separated to server-side logic? Efficiency: which is more efficient both in terms of coding and running? At the end of the day, I am trying to move my team to go towards the second approach. There are lot of old guys in this team who are afraid of this change. I just wish to convince them with the right facts and stats. Let me know your thoughts.

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  • WCF Duplex Interaction with Web Server

    - by Mark Struzinski
    Here is my scenario, and it is causing us a considerable amount of grief at the moment: We have a vendor web service which provides base level telephony functionality. This service has a SOAP api, which we are leveraging to build up a custom UI that is integrated into our in house web apps. The api functions on 2 levels. You make standard client calls into the service to initiate actions, such as Login, Place Call, Hang Up, etc. On a different thread, the service sends events back to the client to alert the user of things that are occurring on the system (agent successfully logged in, call was disconnected, etc). I implemented a WCF service to sit between the web server and the vendor service. This WCF service operates in duplex mode, establishing a 2 way connection with the web server. The web server makes outbound calls to the WCF service, which routes them to the vendor's web service. Events are received back to the WCF service, which passes them onto the web server via a callback channel on the WCF client. As events are received on the web server, they are placed into a hash table with the user's name as the key, and a .NET queue as the value to hold the event. Each event is enqueued to the agent who owns it. On a 2 second interval, the web page polls the web server via an ajax request to get new events for the logged in user. It hits the hash table for the user key, dequeues any events that are present, and serializes them back up to the web page. From there, they are processed in order and appropriate messages are displayed to the user. This implementation performs well in a single user scenario. The second I put more than 1 user on the system, I start getting frequent timeouts with the following CommunicationException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond We are running Windows Server 2008 R2 both servers. Both the web app and WCF service are running on .NET 3.5. The WCF service is running under the net.tcp protocol in duplex mode. The web app is ASP.NET MVC 2. Has anyone dealt with anything like this scenario? Is there a more efficient way (or a widely accepted pattern) to implement this?

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  • Program execution stop at scanf???

    - by Mohit Deshpande
    main.c (with all the headers like stdio, stdlib, etc): int main() { int input; while(1) { printf("\n"); printf("\n1. Add new node"); printf("\n2. Delete existing node"); printf("\n3. Print all data"); printf("\n4. Exit"); printf("Enter your option -> "); scanf("%d", &input); string key = ""; string tempKey = ""; string tempValue = ""; Node newNode; Node temp; switch (input) { case 1: printf("\nEnter a key: "); scanf("%s", tempKey); printf("\nEnter a value: "); scanf("%s", tempValue); //execution ternimates here newNode.key = tempKey; newNode.value = tempValue; AddNode(newNode); break; case 2: printf("\nEnter the key of the node: "); scanf("%s", key); temp = GetNode(key); DeleteNode(temp); break; case 3: printf("\n"); PrintAllNodes(); break; case 4: exit(0); break; default: printf("\nWrong option chosen!\n"); break; } } return 0; } storage.h: #ifndef DATABASEIO_H_ #define DATABASEIO_H_ //typedefs typedef char *string; /* * main struct with key, value, * and pointer to next struct * Also typedefs Node and NodePtr */ typedef struct Node { string key; string value; struct Node *next; } Node, *NodePtr; //Function Prototypes void AddNode(Node node); void DeleteNode(Node node); Node GetNode(string key); void PrintAllNodes(); #endif /* DATABASEIO_H_ */ I am using Eclipse CDT, and when I enter 1, then I enter a key. Then the console says . I used gdb and got this error: Program received signal SIGSEGV, Segmentation fault. 0x00177024 in _IO_vfscanf () from /lib/tls/i686/cmov/libc.so.6 Any ideas why?

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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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  • Help choosing authentication method

    - by Dima
    I need to choose an authentication method for an application installed and integrated in customers environment. There are two types of environments - windows and linux/unix. Application is user based, no web stuff, pure Java. The requirement is to authenticate users which will use my application against customer provided user base. Meaning, customer installs my app, but uses his own users to grant or deny access to my app. Typical, right? I have three options to consider and I need to pick up the one which would be a) the most flexible to cover most common modern environments and b) would take least effort while stay robust and standard. Option (1) - Authenticate locally managing user credentials in some local storage, e.g. file. Customer would then add his users to my application and it will then check the passwords. Simple, clumsy but would work. Customers would have to punch every user they want to grant access to my app using some UI we will have to provide. Lots of work for me, headache to the customer. Option (2) - Use LDAP authentication. Customers would tell my app where to look for users and I will walk their directory resolving names into user names and trying to bind with found password. This is better approach IMO, but more fragile because I will have to walk an unknown directory structure and who knows if this will be permitted everywhere. Would be harder to test since there are many LDAP implementation out there, last thing I want is drowning in this voodoo. Option(3) - Use plain Kerberos authentication. Customers would tell my app what realm (domain) and which KDC (key distribution center) to use. In ideal world these two parameters would be all I need to set while customers could use their own administration tools to configure domain and kdc. My application would simply delegate user credentials to this third party (using JAAS or Spring security) and consider success when third party is happy with them. I personally prefer #3, but not sure what surprises I might face. Would this cover windows and *nix systems entirely? Is there another option to consider?

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  • How to implement Xml Serialization with inherited classes in C#

    - by liorafar
    I have two classes : base class name Component and inheritd class named DBComponent [Serializable] public class Component { private string name = string.Empty; private string description = string.Empty; } [Serializable] public class DBComponent : Component { private List<string> spFiles = new List<string>(); // Storage Procedure Files [XmlArrayItem("SPFile", typeof(string))] [XmlArray("SPFiles")] public List<string> SPFiles { get { return spFiles; } set { spFiles = value; } } public DBComponent(string name, string description) : base(name, description) { } } [Serializable] public class ComponentsCollection { private static ComponentsCollection instance = null; private List<Component> components = new List<Component>(); public List<Component> Components { get { return components; } set { components = value; } } public static ComponentsCollection GetInstance() { if (ccuInstance == null) { lock (lockObject) { if (instance == null) PopulateComponents(); } } return instance; } private static void PopulateComponents() { instance = new CCUniverse(); XmlSerializer xs = new XmlSerializer(instance.GetType()); instance = xs.Deserialize(XmlReader.Create("Components.xml")) as ComponentsCollection; } } } I want read\write from a Xml file. I know that I need to implement the Serialization for DBComponent class otherwise it will not read it.But i cannot find any simple article for that. all the articles that I found were too complex for this simple scenario. The Xml file looks like this: <?xml version="1.0" encoding="utf-8" ?> <ComponentsCollection> <Components> <DBComponent Name="Tenant Historical Database" Description="Tenant Historical Database"> <SPFiles> <SPFile>Setup\TenantHistoricalSP.sql</SPFile> </SPFiles> </DBComponent> <Component Name="Agent" Description="Desktop Agent" /> </Components> </ComponentsCollection> Can someone please give me a simple example of how to read this kind of xml file and what should be implemented ? Thanks Lior

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  • What is the best algorithm for this problem?

    - by mark
    What is the most efficient algorithm to solve the following problem? Given 6 arrays, D1,D2,D3,D4,D5 and D6 each containing 6 numbers like: D1[0] = number D2[0] = number ...... D6[0] = number D1[1] = another number D2[1] = another number .... ..... .... ...... .... D1[5] = yet another number .... ...... .... Given a second array ST1, containing 1 number: ST1[0] = 6 Given a third array ans, containing 6 numbers: ans[0] = 3, ans[1] = 4, ans[2] = 5, ......ans[5] = 8 Using as index for the arrays D1,D2,D3,D4,D5 and D6, the number that goes from 0, to the number stored in ST1[0] minus one, in this example 6, so from 0 to 6-1, compare each res array against each D array My algorithm so far is: I tried to keep everything unlooped as much as possible. EML := ST1[0] //number contained in ST1[0] EML1 := 0 //start index for the arrays D While EML1 < EML if D1[ELM1] = ans[0] goto two if D2[ELM1] = ans[0] goto two if D3[ELM1] = ans[0] goto two if D4[ELM1] = ans[0] goto two if D5[ELM1] = ans[0] goto two if D6[ELM1] = ans[0] goto two ELM1 = ELM1 + 1 return 0 //bad row of numbers, if while ends two: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[1] goto two if D2[ELM1] = ans[1] goto two if D3[ELM1] = ans[1] goto two if D4[ELM1] = ans[1] goto two if D5[ELM1] = ans[1] goto two if D6[ELM1] = ans[1] goto two ELM1 = ELM1 + 1 return 0 three: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[2] goto two if D2[ELM1] = ans[2] goto two if D3[ELM1] = ans[2] goto two if D4[ELM1] = ans[2] goto two if D5[ELM1] = ans[2] goto two if D6[ELM1] = ans[2] goto two ELM1 = ELM1 + 1 return 0 four: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[3] goto two if D2[ELM1] = ans[3] goto two if D3[ELM1] = ans[3] goto two if D4[ELM1] = ans[3] goto two if D5[ELM1] = ans[3] goto two if D6[ELM1] = ans[3] goto two ELM1 = ELM1 + 1 return 0 five: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[4] goto two if D2[ELM1] = ans[4] goto two if D3[ELM1] = ans[4] goto two if D4[ELM1] = ans[4] goto two if D5[ELM1] = ans[4] goto two if D6[ELM1] = ans[4] goto two ELM1 = ELM1 + 1 return 0 six: EML1 := 0 start index for arrays Ds While EML1 < EML if D1[ELM1] = ans[0] return 1 //good row of numbers if D2[ELM1] = ans[0] return 1 if D3[ELM1] = ans[0] return 1 if D4[ELM1] = ans[0] return 1 if D5[ELM1] = ans[0] return 1 if D6[ELM1] = ans[0] return 1 ELM1 = ELM1 + 1 return 0 As language of choice, it would be pure c

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  • android zxing intentintegrator

    - by cristi _b
    I've written the following code that works fine if you decide to scan a QR code (using zxing) and store it in private storage but in case you decide to cancel scanning, it crashes and the file previously stored content disappears. I think it might be a design error, not sure why. Below is relevant code ... /** * menu generation */ @Override public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.menu, menu); return true; } /** * menu handling */ @Override public boolean onOptionsItemSelected(MenuItem item) { Context context = getApplicationContext(); Toast toast = Toast.makeText(context, "", Toast.LENGTH_LONG); toast.setGravity(Gravity.FILL_HORIZONTAL, 0, 0); switch (item.getItemId()) { case R.id.qrScan: IntentIntegrator integrator = new IntentIntegrator(this); integrator.initiateScan(); return true; case R.id.qrReset: File dir = getFilesDir(); File file = new File(dir, qrCodeFile); boolean deleted = file.delete(); return true; case R.id.appClose: this.finish(); return true; default: return super.onOptionsItemSelected(item); } } ... public void onActivityResult(int requestCode, int resultCode, Intent intent) { IntentResult scanResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, intent); Context context = getApplicationContext(); Toast toast = Toast.makeText(context, "", Toast.LENGTH_SHORT); if (scanResult != null) { FileOutputStream fos = null; CharSequence text = scanResult.getContents(); try { fos = openFileOutput(qrCodeFile, Context.MODE_PRIVATE); try { fos.write(text.toString().getBytes()); fos.close(); toast.setGravity(Gravity.FILL_HORIZONTAL, 0, 0); toast.setText("Code saved"); toast.show(); } catch (IOException ex) { toast.setGravity(Gravity.FILL_HORIZONTAL, 0, 0); toast.setText("Invalid code"); toast.show(); Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex); } } catch (FileNotFoundException ex) { toast.setGravity(Gravity.FILL_HORIZONTAL, 0, 0); toast.setText("Error while saving"); toast.show(); Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex); } } else { toast.setGravity(Gravity.FILL_HORIZONTAL, 0, 0); toast.setText("Invalid code"); toast.show(); } }

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  • Searches (and general querying) with HBase and/or Cassandra (best practices?)

    - by alexeypro
    I have User model object with quite few fields (properties, if you wish) in it. Say "firstname", "lastname", "city" and "year-of-birth". Each user also gets "unique id". I want to be able to search by them. How do I do that properly? How to do that at all? My understanding (will work for pretty much any key-value storage -- first goes key, then value) u:123456789 = serialized_json_object ("u" as a simple prefix for user's keys, 123456789 is "unique id"). Now, thinking that I want to be able to search by firstname and lastname, I can save in: f:Steve = u:384734807,u:2398248764,u:23276263 f:Alex = u:12324355,u:121324334 so key is "f" - which is prefix for firstnames, and "Steve" is actual firstname. For "u:Steve" we save as value all user id's who are "Steve's". That makes every search very-very easy. Querying by few fields (properties) -- say by firstname (i.e. "Steve") and lastname (i.e. "l:Anything") is still easy - first get list of user ids from "f:Steve", then list from "l:Anything", find crossing user ids, an here you go. Problems (and there are quite a few): Saving, updating, deleting user is a pain. It has to be atomic and consistent operation. Also, if we have size of value limited to some value - then we are in (potential) trouble. And really not of an answer here. Only zipping the list of user ids? Not too cool, though. What id we want to add new field to search by. Eventually. Say by "city". We certainly can do the same way "c:Los Angeles" = ..., "c:Chicago" = ..., but if we didn't foresee all those "search choices" from the very beginning, then we will have to be able to create some night job or something to go by all existing User records and update those "c:CITY" for them... Quite a big job! Problems with locking. User "u:123" updates his name "Alex", and user "u:456" updates his name "Alex". They both have to update "f:Alex" with their id's. That means either we get into overwriting problem, or one update will wait for another (and imaging if there are many of them?!). What's the best way of doing that? Keeping in mind that I want to search by many fields? P.S. Please, the question is about HBase/Cassandra/NoSQL/Key-Value storages. Please please - no advices to use MySQL and "read about" SELECTs; and worry about scaling problems "later". There is a reason why I asked MY question exactly the way I did. :-)

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  • use jquery to toggle disabled state with a radio button

    - by hbowman
    I want to toggle two radio buttons and select fields based on which radio button is selected. I have the jQuery working, but want to know if there is a way to make it more efficient. Seems like quite a few lines for the simple goal I am trying to achieve. Here are the requirements: when the page loads, #aircraftType should be checked and #aircraftModelSelect should be grayed out (right now, the "checked" is being ignored by Firefox). If the user clicks either #aircraftType or #aircraftModel, the opposite select field should become disabled (if #aircraftModel is checked, #aircraftTypeSelect should be disabled, and vise versa). Any help on optimizing this code is appreciated. Code is up on jsfiddle too: http://jsfiddle.net/JuRKn/ $("#aircraftType").attr("checked"); $("#aircraftModel").removeAttr("checked"); $("#aircraftModelSelect").attr("disabled","disabled").addClass("disabled"); $("#aircraftType").click(function(){ $("#aircraftModelSelect").attr("disabled","disabled").addClass("disabled"); $("#aircraftTypeSelect").removeAttr("disabled").removeClass("disabled"); }); $("#aircraftModel").click(function(){ $("#aircraftTypeSelect").attr("disabled","disabled").addClass("disabled"); $("#aircraftModelSelect").removeAttr("disabled").removeClass("disabled"); }); HTML <div class="aircraftType"> <input type="radio" id="aircraftType" name="aircraft" checked /> <label for="aircraftType">Aircraft Type</label> <select size="6" multiple="multiple" id="aircraftTypeSelect" name="aircraftType"> <option value="">Light Jet</option> <option value="">Mid-Size Jet</option> <option value="">Super-Mid Jet</option> <option value="">Heavy Jet</option> <option value="">Turbo-Prop</option> </select> </div> <div class="aircraftModel"> <input type="radio" id="aircraftModel" name="aircraft" /> <label for="aircraftModel">Aircraft Model</label> <select size="6" multiple="multiple" id="aircraftModelSelect" name="aircraftModel"> <option value="">Astra SP</option> <option value="">Beechjet 400</option> <option value="">Beechjet 400A</option> <option value="">Challenger 300</option> <option value="">Challenger 600</option> <option value="">Challenger 603</option> <option value="">Challenger 604</option> <option value="">Challenger 605</option> <option value="">Citation Bravo</option> </select> </div>

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  • Why is cell phone software still so primitive?

    - by Tomislav Nakic-Alfirevic
    I don't do mobile development, but it strikes me as odd that features like this aren't available by default on most phones: full text search: searches all address book contents, messages, anything else being a plus better call management: e.g. a rotating audio call log, meaning you always have the last N calls recorded for your listening pleasure later (your little girl just said her first "da-da" while you were on a business trip, you had a telephone job interview, you received complex instructions to do something etc.) bluetooth remote control (like e.g. anyRemote, but available by default on a bluetooth phone) no multitasking capabilities worth mentioning and in general no e.g. weekly software updates, making the phone much more usable (even if it had to be done over USB, rather than over the network). I'm sure I was dumbfounded by the lack or design of other features as well, but they don't come to mind right now. To clarify, I'm not talking about smartphones here: my plain, 2-year old phone has a CPU an order of magnitude faster than my first PC, about as much storage space and it's ridiculous how bad (slow, unwieldy) the software is and it's not one phone or one manufacturer. What keeps the (to me) obvious software functionality vacuum on a capable hardware platform from being filled up? Edit: I believe a clarification on the multitasking point might be beneficial. I'll use my phone as an example, although the point is much more general. The phone can multitask and in fact does: you can listen to music and do something else at the same time. On the other hand, the way the software has been designed makes multitasking next to useless. (Ditto with the external touch screen: it can take touch commands, but only one application makes use of it, and only with 3 commands.) To take the multitasking example to the extreme, if I plug my phone into my laptop and it registers as an external disk, it doesn't allow any kind of operation: messages, calling, calendar, everything out of reach, although I can receive a call. No "battery life" issue there: it's charging while connected. BTW, another example of design below the current state of the art: I don't see a phone on the horizon which will remember where in an audio or video file you were when you stopped listening/watching it last time (podcasts are a good use case). Simplistic rewind/fast forward functionality only aggravates the problem.

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  • Is Java assert broken?

    - by BlairHippo
    While poking around the questions, I recently discovered the assert keyword in Java. At first, I was excited. Something useful I didn't already know! A more efficient way for me to check the validity of input parameters! Yay learning! But then I took a closer look, and my enthusiasm was not so much "tempered" as "snuffed-out completely" by one simple fact: you can turn assertions off.* This sounds like a nightmare. If I'm asserting that I don't want the code to keep going if the input listOfStuff is null, why on earth would I want that assertion ignored? It sounds like if I'm debugging a piece of production code and suspect that listOfStuff may have been erroneously passed a null but don't see any logfile evidence of that assertion being triggered, I can't trust that listOfStuff actually got sent a valid value; I also have to account for the possibility that assertions may have been turned off entirely. And this assumes that I'm the one debugging the code. Somebody unfamiliar with assertions might see that and assume (quite reasonably) that if the assertion message doesn't appear in the log, listOfStuff couldn't be the problem. If your first encounter with assert was in the wild, would it even occur to you that it could be turned-off entirely? It's not like there's a command-line option that lets you disable try/catch blocks, after all. All of which brings me to my question (and this is a question, not an excuse for a rant! I promise!): What am I missing? Is there some nuance that renders Java's implementation of assert far more useful than I'm giving it credit for? Is the ability to enable/disable it from the command line actually incredibly valuable in some contexts? Am I misconceptualizing it somehow when I envision using it in production code in lieu of statements like if (listOfStuff == null) barf();? I just feel like there's something important here that I'm not getting. *Okay, technically speaking, they're actually off by default; you have to go out of your way to turn them on. But still, you can knock them out entirely.

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  • Select subsets of elements, and wrap them in a div

    - by scullytr
    Hello, I have a set of selected elements in jQuery: <div id="element1" class="element"></div> <div id="element2" class="element"></div> <div id="element3" class="element"></div> <div id="element4" class="element"></div> <div id="element5" class="element"></div> <div id="element6" class="element"></div> <div id="element7" class="element"></div> <div id="element8" class="element"></div> <div id="element9" class="element"></div> <div id="element10" class="element"></div> <div id="element11" class="element"></div> <div id="element12" class="element"></div> I would like to wrap these elements into groups of five like so: <div class="wrapper"> <div id="element1" class="element"></div> <div id="element2" class="element"></div> <div id="element3" class="element"></div> <div id="element4" class="element"></div> <div id="element5" class="element"></div> </div> <div class="wrapper"> <div id="element6" class="element"></div> <div id="element7" class="element"></div> <div id="element8" class="element"></div> <div id="element9" class="element"></div> <div id="element10" class="element"></div> </div> <div class="wrapper"> <div id="element11" class="element"></div> <div id="element12" class="element"></div> </div> Is there an efficient/easy way to do this? I imagine it would look something like this: $('.element').wrapAll('<div class="wrapper"></div>'); But with a selector that selects the elements in groups of five. Thanks!

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  • Recursive N-way merge/diff algorithm for directory trees?

    - by BobMcGee
    What algorithms or Java libraries are available to do N-way, recursive diff/merge of directories? I need to be able to generate a list of folder trees that have many identical files, and have subdirectories with many similar files. I want to be able to use 2-way merge operations to quickly remove as much redundancy as possible. Goals: Find pairs of directories that have many similar files between them. Generate short list of directory pairs that can be synchronized with 2-way merge to eliminate duplicates Should operate recursively (there may be nested duplicates of higher-level directories) Run time and storage should be O(n log n) in numbers of directories and files Should be able to use an embedded DB or page to disk for processing more files than fit in memory (100,000+). Optional: generate an ancestry and change-set between folders Optional: sort the merge operations by how many duplicates they can elliminate I know how to use hashes to find duplicate files in roughly O(n) space, but I'm at a loss for how to go from this to finding partially overlapping sets between folders and their children. EDIT: some clarification The tricky part is the difference between "exact same" contents (otherwise hashing file hashes would work) and "similar" (which will not). Basically, I want to feed this algorithm at a set of directories and have it return a set of 2-way merge operations I can perform in order to reduce duplicates as much as possible with as few conflicts possible. It's effectively constructing an ancestry tree showing which folders are derived from each other. The end goal is to let me incorporate a bunch of different folders into one common tree. For example, I may have a folder holding programming projects, and then copy some of its contents to another computer to work on it. Then I might back up and intermediate version to flash drive. Except I may have 8 or 10 different versions, with slightly different organizational structures or folder names. I need to be able to merge them one step at a time, so I can chose how to incorporate changes at each step of the way. This is actually more or less what I intend to do with my utility (bring together a bunch of scattered backups from different points in time). I figure if I can do it right I may as well release it as a small open source util. I think the same tricks might be useful for comparing XML trees though.

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  • [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

    - by fatai
    I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • Using multiple aggregate functions in an algebraic expression in (ANSI) SQL statement

    - by morpheous
    I have the following aggregate functions (AGG FUNCs): foo(), foobar(), fredstats(), barneystats(). I want to know if I can use multiple AGG FUNCs in an algebraic expression. This may seem a strange/simplistic question for seasoned SQL developers - however, the but the reason I ask is that so far, all AGG FUNCs examples I have seen are of the simplistic variety e.g. max(salary) < 100, rather than using the AGG FUNCs in an expression which involves using multiple AGG FUNCs in an expression (like agg_func1() agg_func2()). The information below should help clarify further. Given tables with the following schemas: CREATE TABLE item (id int, length float, weight float); CREATE TABLE item_info (item_id, name varchar(32)); # Is it legal (ANSI) SQL to write queries of this format ? SELECT id, name, foo, foobar, fredstats FROM A, B (SELECT id, foo(123) as foo, foobar('red') as foobar, fredstats('weight') as fredstats FROM item GROUP BY id HAVING [ALGEBRAIC EXPRESSION] ORDER BY id AS A), item_info AS B WHERE item.id = B.id Where: ALGEBRAIC EXPRESSION is the type of expression that can be used in a WHERE clause - for example: ((foo(x) < foobar(y)) AND foobar(y) IN (1,2,3)) OR (fredstats(x) <> 0)) I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible. Assuming it is legal to include AGG FUNCS in the way I have done above, I'd like to know: Is there a more efficient way to write the above query ? Is there any way I can speed up the query in terms of a judicious choice of indexes on the tables item and item_info ? Is there a performance hit of using AGG FUNCs in an algebraic expression like I am (i.e. an expression involving the output of aggregate functions rather than constants? Can the expression also include 'scaled' AGG FUNC? (for example: 2*foo(123) < -3*foobar(456) ) - will scaling (i.e. multiplying an AGG FUNC by a number have an effect on performance?) How can I write the query above using INNER JOINS instead?

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