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  • Is there a Design Pattern for preventing dangling references?

    - by iFreilicht
    I was thinking about a design for custom handles. The thought is to prevent clients from copying around large objects. Now a regular handle class would probably suffice for that, but it doesn't solve the "dangling reference problem"; If a client has multiple handles of the same object and deletes the object via one of them, all the others would be invalid, but not know it, so the client could write or read parts of the memory he shouldn't have access to. Is there a design pattern to prevent this from happening? Two ideas: An observer-like pattern where the destructor of an object would notify all handles. "Handle handles" (does such a thing even exist?). All the handles don't really point to the object, but to another handle. When the object gets destroyed, this "master-handle" invalidates itself and therefore all that point to it.

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  • I want to host clients' websites, but not their email. What's the easiest way to handle this?

    - by Phil
    My company lets non-technical users build their own niche industry websites on our server, which we host. they can currently point their nameservers at their registrar to us, which ends up with them no longer having access to their email if they've already set it up through said registrar. We don't want to interfere with their existing email, nor do we want to get into the business of setting up email for them through our service. Thus, having them point A records/cname to us would work, but is this too complex for a non-technie user? We thought of having them point nameservers to us but pointing the MX records back to them, but this is also beyond their scope. Is there an easy way to 'point records' at their initial state? Any other ideas/feedback?

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  • Handy Generic JQuery Functions

    - by Steve Wilkes
    I was a bit of a late-comer to the JQuery party, but now I've been using it for a while it's given me a host of options for adding extra flair to the client side of my applications. Here's a few generic JQuery functions I've written which can be used to add some neat little features to a page. Just call any of them from a document ready function. Apply JQuery Themeroller Styles to all Page Buttons   The JQuery Themeroller is a great tool for creating a theme for a site based on colours and styles for particular page elements. The JQuery.UI library then provides a set of functions which allow you to apply styles to page elements. This function applies a JQuery Themeroller style to all the buttons on a page - as well as any elements which have a button class applied to them - and then makes the mouse pointer turn into a cursor when you mouse over them: function addCursorPointerToButtons() {     $("button, input[type='submit'], input[type='button'], .button") .button().css("cursor", "pointer"); } Automatically Remove the Default Value from a Select Box   Required drop-down select boxes often have a default option which reads 'Please select...' (or something like that), but once someone has selected a value, there's no need to retain that. This function removes the default option from any select boxes on the page which have a data-val-remove-default attribute once one of the non-default options has been chosen: function removeDefaultSelectOptionOnSelect() {     $("select[data-val-remove-default='']").change(function () {         var sel = $(this);         if (sel.val() != "") { sel.children("option[value='']:first").remove(); }     }); } Automatically add a Required Label and Stars to a Form   It's pretty standard to have a little * next to required form field elements. This function adds the text * Required to the top of the first form on the page, and adds *s to any element within the form with the class editor-label and a data-val-required attribute: function addRequiredFieldLabels() {     var elements = $(".editor-label[data-val-required='']");     if (!elements.length) { return; }     var requiredString = "<div class='editor-required-key'>* Required</div>";     var prependString = "<span class='editor-required-label'> * </span>"; var firstFormOnThePage = $("form:first");     if (!firstFormOnThePage.children('div.editor-required-key').length) {         firstFormOnThePage.prepend(requiredString);     }     elements.each(function (index, value) { var formElement = $(this);         if (!formElement.children('span.editor-required-label').length) {             formElement.prepend(prependString);         }     }); } I hope those come in handy :)

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  • How do I keep co-worker from writing horrible code? [closed]

    - by Drew H
    Possible Duplicate: How do I approach a coworker about his or her code quality? I can handle the for in.. without the hasOwnProperty filtering. I can handle the blatant disregard for the libraries I've used in the past and just using something else. I can even handle the functions with 25 parameters. But I can't handle this. var trips = new Array(); var flights = new Array(); var passengers = new Array(); var persons = new Array(); var requests = new Array(); I've submitted documents on code style, had code reviews, gave him Douglas Crockford's book, shown him presentations, other peoples githubs, etc. He still show the same horrible Javascript style. How else could I approach this guy? Thanks for any help.

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  • Is there any difference between processor and core?

    - by Salvador
    The following two command seems to give me different information about the same hardware srs@ubuntu:~$ cat /proc/cpuinfo | grep -e processor -e cores processor : 0 cpu cores : 4 processor : 1 cpu cores : 4 processor : 2 cpu cores : 4 processor : 3 cpu cores : 4 srs@ubuntu:~$ sudo dmidecode -t processor # dmidecode 2.9 SMBIOS 2.6 present. Handle 0x0004, DMI type 4, 42 bytes Processor Information Socket Designation: LGA1155 Type: Central Processor Family: <OUT OF SPEC> Manufacturer: Intel ID: A7 06 02 00 FF FB EB BF Version: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz Voltage: 1.0 V External Clock: 100 MHz Max Speed: 3800 MHz Current Speed: 3300 MHz Status: Populated, Enabled Upgrade: Other L1 Cache Handle: 0x0005 L2 Cache Handle: 0x0006 L3 Cache Handle: 0x0007 Serial Number: To Be Filled By O.E.M. Asset Tag: To Be Filled By O.E.M. Part Number: To Be Filled By O.E.M. Core Count: 4 Core Enabled: 1 Characteristics: 64-bit capable Until today I thought I had a single processor with 4 independent cores. I also thought that within each core can be used different threads.

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  • How to know the number of pins on my laptop's ram?

    - by Rajat Saxena
    I am thinking about upgrading my laptop's ram.How can I get to know the number of pins on my ram without opening my laptop? I ran this command sudo dmidecode --type memory and got following info: Handle 0x0019, DMI type 17, 27 bytes Memory Device Array Handle: 0x0017 Error Information Handle: 0x001A Total Width: 64 bits Data Width: 64 bits Size: 1024 MB Form Factor: SODIMM Set: None Locator: DIMM0 Bank Locator: BANK 0 Type: DDR2 Type Detail: Synchronous Speed: 667 MHz Manufacturer: AD00000000000000 Serial Number: 04008104 Asset Tag: Unknown Part Number: 040404040404040404040404040404040404 Can anyone help?

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  • Troubleshooting Blocked Transaction in SQL Server

    - by ChrisD
    While troubleshooting a blocked transaction issue recently, I found this code online.  My apologies in not citing its source, but its lost in my browse history some where.   While the transaction is executing and blocked, open a connection to the database containing the transaction and run the following to return both the SQL statement blocked (the Victim), as well as the statement that’s causing the block (the Culprit)   -- prepare a table so that we can filter out sp_who2 results DECLARE @who TABLE(BlockedId INT, Status VARCHAR(MAX), LOGIN VARCHAR(MAX), HostName VARCHAR(MAX), BlockedById VARCHAR(MAX), DBName VARCHAR(MAX), Command VARCHAR(MAX), CPUTime INT, DiskIO INT, LastBatch VARCHAR(MAX), ProgramName VARCHAR(MAX), SPID_1 INT, REQUESTID INT) INSERT INTO @who EXEC sp_who2 --select the blocked and blocking queries (if any) as SQL text SELECT ( SELECT TEXT FROM sys.dm_exec_sql_text( (SELECT handle FROM ( SELECT CAST(sql_handle AS VARBINARY(128)) AS handle FROM sys.sysprocesses WHERE spid = BlockedId ) query) ) ) AS 'Blocked Query (Victim)', ( SELECT TEXT FROM sys.dm_exec_sql_text( (SELECT handle FROM ( SELECT CAST(sql_handle AS VARBINARY(128)) AS handle FROM sys.sysprocesses WHERE spid = BlockedById ) query) ) ) AS 'Blocking Query (Culprit)' FROM @who WHERE BlockedById != ' .'

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  • How to specialize a c++ variadic template?

    - by Serge
    I'm trying to understand c++ variadic templates. I'm not much aware of the correct language to use to explain what I'd like to achieve, so it might be simpler if I provide a bit of code which illustrate what I'd like to achieve. #include <iostream> #include <string> using namespace std; template<int ...A> class TestTemplate1 { public: string getString() { return "Normal"; } }; template<int T, int ...A> string TestTemplate1<2, A...>::getString() { return "Specialized"; } template<typename ...A> class TestTemplate2 { }; int main() { TestTemplate1<1, 2, 3, 4> t1_1; TestTemplate1<1, 2> t1_2; TestTemplate1<> t1_3; TestTemplate1<2> t1_4; TestTemplate2<> t2_1; TestTemplate2<int, double> t2_2; cout << t1_1.getString() << endl; cout << t1_2.getString() << endl; cout << t1_3.getString() << endl; cout << t1_4.getString() << endl; } This throws several errors. error C2333: 'TestTemplate1<::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2,3,4::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<2::getString' : error in function declaration; skipping function body error C2977: 'TestTemplate1' : too many template arguments error C2995: 'std::string TestTemplate1::getString(void)' : function template has already been defined error C3860: template argument list following class template name must list parameters in the order used in template parameter list How can I have a specialized behavior for every TestTemplate1<2, ...> instances like t1_4?

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  • How do I keep user input and rendering independent of the implementation environment?

    - by alex
    I'm writing a Tetris clone in JavaScript. I have a fair amount of experience in programming in general, but am rather new to game development. I want to separate the core game code from the code that would tie it to one environment, such as the browser. My quick thoughts led me to having the rendering and input functions external to my main game object. I could pass the current game state to the rendering method, which could render using canvas, elements, text, etc. I could also map input to certain game input events, such as move piece left, rotate piece clockwise, etc. I am having trouble designing how this should be implemented in my object. Should I pass references to functions that the main object will use to render and process user input? For example... var TetrisClone = function(renderer, inputUpdate) { this.renderer = renderer || function() {}; this.inputUpdate = input || function() {}; this.state = {}; }; TetrisClone.prototype = { update: function() { // Get user input via function passed to constructor. var inputEvents = this.inputUpdate(); // Update game state. // Render the current game state via function passed to constructor. this.renderer(this.state); } }; var renderer = function(state) { // Render blocks to browser page. } var inputEvents = {}; var charCodesToEvents = { 37: "move-piece-left" /* ... */ }; document.addEventListener("keypress", function(event) { inputEvents[event.which] = true; }); var inputUpdate = function() { var translatedEvents = [], event, translatedEvent; for (event in inputEvents) { if (inputEvents.hasOwnProperty(event)) { translatedEvent = charCodesToEvents[event]; translatedEvents.push(translatedEvent); } } inputEvents = {}; return translatedEvents; } var game = new TetrisClone(renderer, inputUpdate); Is this a good game design? How would you modify this to suit best practice in regard to making a game as platform/input independent as possible?

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  • Outlook hangs during startup by step &ldquo;loading profile&rdquo;

    - by Marko Apfel
    Problem Starting Outlook shows only the splash screen with comment “loading profile”. I could cancel the startup but restarting shows the same. I verified with Task Manager that no hidden outlook process is bother me. Solution Scanpst Normally with Outlook the tool “Microsoft Outlook Inbox Repair Tool” (scanpst.exe) is additionally installed. Some people could access it via Startmenu, but not me. My lovely Launchy found it under "C:\Program Files (x86)\Microsoft Office\Office14\SCANPST.EXE" Scanpst first ask you for the pst file which you would like to scan. I started with the first default offer: C:\Users\…\AppData\Local\Microsoft\Outlook\….ost And this brings up the information, that another application uses this file. Handle To investigate the causer Handle from Sysinternals is your friend in such cases. Start it from an administrative console and pipe the output to a file. handle > c:\temp\handle.txt Now you could open this file with the editor of your choose and search for the blocked file (your pst file). On top of the section you see the application which has a handle to this file opened (SfdcMsO1.exe). Task Manager Kill this application and start Outlook again. And voila – everything starts up fine … by me

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  • variable declaration in javascript [migrated]

    - by ShaggyInjun
    I have been doing something like this for a while and I have never seen any errors. But, unfortunately, I have never been able to explain why this works. The first line creates a variable which points to a function. The second line just adds func2 to func1 separated by a dot and defines a function. If I add a var in front of func1.func2 then I see a compilation error. func1.func2 = function(){}; Error SyntaxError: missing ; before statement var func1.func2 = function(){}; What type was func1 on first line 1 and what did it become on line 2. var func1 = function(){}; func1.func2 = function(){}; Thanks Venkat

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  • Attach my sprite with Box2d

    - by user919496
    I'm coding Javascript(HTML5) with Box2D. And I want to ask how to attach Sprite with Box2D. This is function My sprite: function My_Sprite() { this.m_Image = new Image(); this.m_Position = new Vector2D(0,0); this.m_CurFrame = 0; this.m_ColFrame = 0; this.m_Size = new Vector2D(0,0); this.m_Scale = new Vector2D(0,0); this.m_Rotation = 0; } My_Sprite.prototype.constructor = function (_Image_SRC) { this.m_Image.src = _Image_SRC; } My_Sprite.prototype.constructor = function (_Image_SRC,_Size,_Col) { this.m_Image.src = _Image_SRC; this.m_Size = _Size; this.m_ColFrame = _Col; this.m_Scale = new Vector2D(1, 1); } My_Sprite.prototype.Draw = function (context) { context.drawImage(this.m_Image, this.m_Size.X * (this.m_CurFrame % this.m_ColFrame), this.m_Size.Y * parseInt(this.m_CurFrame / this.m_ColFrame), this.m_Size.X, this.m_Size.Y, this.m_Position.X, this.m_Position.Y, this.m_Size.X * this.m_Scale.X, this.m_Size.Y * this.m_Scale.Y ); } and this is function Object : function Circle(type, angle, size) { // Circle.prototype = new My_Object(); // Circle.prototype.constructor = Circle; // Circle.prototype.parent = My_Object.prototype; this.m_den = 1.0; this.m_fri = 0.5; this.m_res = 0.2; fixDef.density = this.m_den; fixDef.friction = this.m_fri; fixDef.restitution = this.m_res; fixDef.shape = new b2PolygonShape; bodyDef.type = type; bodyDef.angle = angle; bodyDef.userData = m_spriteCircle; fixDef.shape = new b2CircleShape( Radius / SCALE //radius ); this.m_Body = world.CreateBody(bodyDef); this.m_Body.CreateFixture(fixDef); m_spriteCircle = new My_Sprite(); this.Init(); } Circle.prototype.Init = function () { m_spriteCircle.constructor("images/circle.png", new Vector2D(80, 80), 1); m_spriteCircle.m_CurFrame = 0; } Circle.prototype.Draw = function (context) { m_spriteCircle.Draw(context); } and I draw it : var m_Circle = new Circle(); m_Circle.Draw(context);

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  • jQuery event not working after load

    - by Shina
    $(document).ready(function(){ $(function() { $('a.ajaxload').live('click', function(e) { var url = $(this).attr('href'); $('#desktopcontainer').load(url); // load the html response into a DOM element e.preventDefault(); // stop the browser from following the link }); }); $(function() { $(".accordion .accordion-tabs .tab").each(function(){ $(this).click(function(){ if ($(this).hasClass('tab')){ $(this).removeClass('tab'); $(this).addClass('active'); }else{ $(this).removeClass('active'); $(this).addClass('tab'); } $(this).next().slideToggle('slow'); return false; }); }); }); }); My tab works fine but after I click the "a.ajaxload" to add a content to the page, then my tab doesn't respond anymore. Can anyone please tell me where the problem is? Thank you in advance.

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  • GSON on Google App Engine throws a Security Exception

    - by Legend
    I am trying to convert an object into JSON using the GSON library on Google App Engine. For some reason, it throws this exception and I don't understand how to solve this. Any suggestions? java.lang.SecurityException: java.lang.IllegalAccessException: Reflection is not allowed on private static final int java.util.BitSet.ADDRESS_BITS_PER_WORD at com.google.appengine.runtime.Request.process-8d5b435d6736643f(Request.java) at java.lang.reflect.AccessibleObject.setAccessible(AccessibleObject.java:29) at com.google.gson.ObjectNavigator.navigateClassFields(ObjectNavigator.java:141) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:123) at com.google.gson.JsonSerializationVisitor.getJsonElementForChild(JsonSerializationVisitor.java:148) at com.google.gson.JsonSerializationVisitor.addAsArrayElement(JsonSerializationVisitor.java:139) at com.google.gson.JsonSerializationVisitor.visitArray(JsonSerializationVisitor.java:83) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:109) at com.google.gson.JsonSerializationVisitor.getJsonElementForChild(JsonSerializationVisitor.java:148) at com.google.gson.JsonSerializationVisitor.addAsChildOfObject(JsonSerializationVisitor.java:126) at com.google.gson.JsonSerializationVisitor.visitArrayField(JsonSerializationVisitor.java:95) at com.google.gson.ObjectNavigator.navigateClassFields(ObjectNavigator.java:154) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:123) at com.google.gson.JsonSerializationContextDefault.serialize(JsonSerializationContextDefault.java:56) at com.google.gson.Gson.toJsonTree(Gson.java:230) at com.google.gson.Gson.toJson(Gson.java:315) at com.google.gson.Gson.toJson(Gson.java:270) at com.google.gson.Gson.toJson(Gson.java:250) at companionmodel.Sample_Model_PopulateServlet.printOutput(Sample_Model_PopulateServlet.java:59) at companionmodel.Sample_Model_PopulateServlet.doGet(Sample_Model_PopulateServlet.java:28) at javax.servlet.http.HttpServlet.service(HttpServlet.java:693) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166) at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923) at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135) at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:250) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5838) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5836) at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24) at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:398) at com.google.net.rpc.impl.Server$2.run(Server.java:852) at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56) at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:576) at com.google.net.rpc.impl.Server.startRpc(Server.java:807) at com.google.net.rpc.impl.Server.processRequest(Server.java:369) at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:442) at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319) at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290) at com.google.net.async.Connection.handleReadEvent(Connection.java:474) at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:831) at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:207) at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:103) at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251) at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:413) at java.lang.Thread.run(Unknown Source) Code I am using: Gson gson = new Gson(); String json = gson.toJson(modelObject);

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  • How do I convert some ugly inline javascript into a function?

    - by Taylor
    I've got a form with various inputs that by default have no value. When a user changes one or more of the inputs all values including the blank ones are used in the URL GET string when submitted. So to clean it up I've got some javascript that removes the inputs before submission. It works well enough but I was wondering how to put this in a js function or tidy it up. Seems a bit messy to have it all clumped in to an onclick. Plus i'm going to be adding more so there will be quite a few. Here's the relevant code. There are 3 seperate lines for 3 seperate inputs. The first part of the line has a value that refers to the inputs ID ("mf","cf","bf","pf") and the second part of the line refers to the parent div ("dmf","dcf", etc). The first part is an example of the input structure... echo "<div id='dmf'><select id='mf' name='mFilter'>"; This part is the submit and js... echo "<input type='submit' value='Apply' onclick='javascript: if (document.getElementById(\"mf\").value==\"\") { document.getElementById(\"dmf\").innerHTML=\"\"; } if (document.getElementById(\"cf\").value==\"\") { document.getElementById(\"dcf\").innerHTML=\"\"; } if (document.getElementById(\"bf\").value==\"\") { document.getElementById(\"dbf\").innerHTML=\"\"; } if (document.getElementById(\"pf\").value==\"\") { document.getElementById(\"dpf\").innerHTML=\"\"; } ' />"; I have pretty much zero javascript knowledge so help turning this in to a neater function or similar would be much appreciated.

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  • DFS function, can you guys tell me what is the wrong with this code?

    - by danielDhobbs
    can you guys tell me what is the wrong with this code? it is not working with 1 2 1 3 1 4 2 5 2 6 2 7 2 8 3 8 3 9 4 10 1 - 4 - 10 and stop DFS function void Is_Connected(graphType* g, int v){ //function to define the graph is connected or not int i=0; g_node* w; top = NULL; g -> visited[v] = TRUE; push(v); printf("%d", v); while (top != NULL) { w = g -> adjList[v]; while (w) { if (!g -> visited[w -> vertex]) { push(w -> vertex); g -> visited[w -> vertex] = TRUE; printf("->%d", w->vertex); v = w -> vertex; w = g -> adjList[v]; } else { w = w -> link; } } i++; v = pop(); } if (i == (g -> x)-1){ //number of vertices = number of vertetices pass through puts("\nIs_Connected() result : yes"); } else{ puts("\nIs_Connected() result : no"); } }

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  • In C# should I reuse a function / property parameter to compute temp result or create a temporary v

    - by Hamish Grubijan
    The example below may not be problematic as is, but it should be enough to illustrate a point. Imagine that there is a lot more work than trimming going on. public string Thingy { set { // I guess we can throw a null reference exception here on null. value = value.Trim(); // Well, imagine that there is so much processing to do this.thingy = value; // That this.thingy = value.Trim() would not fit on one line ... So, if the assignment has to take two lines, then I either have to abusereuse the parameter, or create a temporary variable. I am not a big fan of temporary variables. On the other hand, I am not a fan of convoluted code. I did not include an example where a function is involved, but I am sure you can imagine it. One concern I have is if a function accepted a string and the parameter was "abused", and then someone changed the signature to ref in both places - this ought to mess things up, but ... who would knowingly make such a change if it already worked without a ref? Seems like it is their responsibility in this case. If I mess with the value of value, am I doing something non-trivial under the hood? If you think that both approaches are acceptable, then which do you prefer and why? Thanks.

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  • How do I pass a callback function to sqlite3_exec on iOS 5.1?

    - by John Doh
    I am new to both xcode/iOS/Objective-C and sqlite. I am trying to teach myself the basics - and I would like to use the sqlite3 wrapper "sqlite3_exec" for a select query. For some reason, I can't find a simple example anywhere of someone doing this. Basically, the method has a parameter (the third one) for a callback function: int sqlite3_exec( sqlite3*, /* An open database */ const char *sql, /* SQL to be evaluated */ int (*callback)(void*,int,char**,char**), /* Callback function */ void *, /* 1st argument to callback */ char **errmsg /* Error msg written here */ ); That's fine. I'm no stranger to callbacks. However, I just can't seem to get the syntax down right. I took over one of the view controllers in my iPad (iOS 5.1) xcode (4.3) project, and made the changes shown below: #import "SecondViewController.h" #import "sqlite3.h" #import "AppState.h" @interface SecondViewController () @end @implementation SecondViewController - (int)myCallback:(void *)a_parm argc:(int)argc argv:(char **)argv column:(char **)column { return 0; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //grab questionnaire names char *sql = "select * from QST2Main order by [Name]"; char *err = nil; sqlite3 *db = [[AppState sharedManager] getgCn]; sqlite3_exec(db, sql, myCallback, nil, &err); } Essentially, I want to run a query when this view first loads, to store some data for later use. But, XCode doesn't like the "myCallback" usage at the bottom there. It says: Undeclared Use of Identifier 'myCallback.' That method is declared in the header file, and I've even tried making it static. Nothing seems to make this error go away. I know I must be doing something fundamentally wrong here, but for the life of me I can't figure out what - I can't even find other code samples in this area that could help me figure out what I'm missing. Many thanks!

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  • When does invoking a member function on a null instance result in undefined behavior?

    - by GMan
    This question arose in the comments of a now-deleted answer to this other question. Our question was asked in the comments by STingRaySC as: Where exactly do we invoke UB? Is it calling a member function through an invalid pointer? Or is it calling a member function that accesses member data through an invalid pointer? With the answer deleted I figured we might as well make it it's own question. Consider the following code: #include <iostream> struct foo { void bar(void) { std::cout << "gman was here" << std::endl; } void baz(void) { x = 5; } int x; }; int main(void) { foo* f = 0; f->bar(); // (a) f->baz(); // (b) } We expect (b) to crash, because there is no corresponding member x for the null pointer. In practice, (a) doesn't crash because the this pointer is never used. Because (b) dereferences the this pointer (this->x = 5;), and this is null, the program enters undefined behavior. Does (a) result in undefined behavior? What about if both functions are static?

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  • How to disable the drop down function of combo box on certain conditions?

    - by Angeline Aarthi
    Hi, I have a combo box in my application. I also have a variable called "Status". I want the combo box to be enabled only when the value of the Status variable is 5 or 6. Otherwise, I should not be able to change the value in the combo box. It should have the previous value only.. I had written a click event to disable the combo box. But even though the combo box is disabled, I get the drop down list of the combo box, and If I select some othe value in the drop down,it changes..Only after that it gets disabled.. How to avoid this? I want the drop down function itself to be disabled. This is the code I have written. Someone guide me. <mx:FormItem label="Review Status:" width="100%" horizontalAlign="right"> <mx:HBox> <mx:Label width="30"/> <mx:ComboBox id="reviewStatus" dataProvider="{Status}" width="150" click="onStatusChange(event)"/> </mx:HBox> Action Script part: private function onStatusChange(event:Event):void { var i:int; for(i=0;i<defectDetails.length;i++) { var defStatusId:String=defectDetails.getItemAt(i).DefectStatusId; if(defStatusId=="5"){ reviewStatus.enabled=true; } else if(defStatusId=="6"){ reviewStatus.enabled=true; } else{ reviewStatus.enabled=false; //reviewStatus.selectedItem.label="Review"; reviewStatus.toolTip="Status can be changed only if Defect Status is Verified or Deferred."; //Alert.show("Status can be changed only if defect status is verified or deferred"); } } } If I use Change event also, for the first time the value is changed. Only after that,the combo box is disabled. How to retain the same value and disable the combo box when the status is not 5 or 6?

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  • Reusing OAuth request token when user refresh page - Twitter4j on GAE

    - by Tahir Akram
    Hi I am using Twitter4J API on GAE/J. I want to use the request token when user came to my page. (called back URL). And press refresh button. I write following code for that. But When user press refresh button. I got Authentication credentials error. Please see the stacktrance. It works fine when user first time used that token. HomeServlet.java code: HttpSession session = request.getSession(); twitter.setOAuthConsumer(FFConstants.CONSUMER_KEY, FFConstants.CONSUMER_SECRET); String token = (String) session.getAttribute("token"); String authorizedToken = (String)session.getAttribute("authorizedToken"); User user = null; if (!token.equals(authorizedToken)){ AccessToken accessToken = twitter.getOAuthAccessToken( token, (String) session .getAttribute("tokenSecret")); twitter.setOAuthAccessToken(accessToken); user = twitter.verifyCredentials(); session.setAttribute("authorizedToken", token); session.setAttribute("user", user); }else{ user = (User)session.getAttribute("user"); } TwitterUser twitterUser = new TwitterUser(); twitterUser.setFollowersCount(user.getFollowersCount()); twitterUser.setFriendsCount(user.getFriendsCount()); twitterUser.setFullName(user.getName()); twitterUser.setScreenName(user.getScreenName()); twitterUser.setLocation(user.getLocation()); Please suggest how I can do that. I have seen on many website. They retain the user with the same token. Even if user press browser refresh buttion again and again. Please help. Exception stacktrace: Reason: twitter4j.TwitterException: 401:Authentication credentials were missing or incorrect. /friends/ids.xml This method requires authentication. at twitter4j.http.HttpClient.httpRequest(HttpClient.java:469) at twitter4j.http.HttpClient.get(HttpClient.java:412) at twitter4j.Twitter.get(Twitter.java:276) at twitter4j.Twitter.get(Twitter.java:228) at twitter4j.Twitter.getFriendsIDs(Twitter.java:1819) at com.tff.servlet.HomeServlet.doGet(HomeServlet.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:693) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093) at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:712) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139) at org.mortbay.jetty.Server.handle(Server.java:313) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:506) at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:830) at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381) at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135) at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:235) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5235) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5233) at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24) at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:363) at com.google.net.rpc.impl.Server$2.run(Server.java:838) at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56) at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:536) at com.google.net.rpc.impl.Server.startRpc(Server.java:793) at com.google.net.rpc.impl.Server.processRequest(Server.java:368) at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:448) at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319) at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290) at com.google.net.async.Connection.handleReadEvent(Connection.java:466) at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:759) at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:205) at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:101) at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251) at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:394) at java.lang.Thread.run(Unknown Source)

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