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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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• Enumeration trouble: redeclared as different kind of symbol

  - by Matt

  Hello all. I am writing a program that is supposed to help me learn about enumeration data types in C++. The current trouble is that the compiler doesn't like my enum usage when trying to use the new data type as I would other data types. I am getting the error "redeclared as different kind of symbol" when compiling my trangleShape function. Take a look at the relevant code. Any insight is appreciated! Thanks! (All functions are their own .cpp files.) header file #ifndef HEADER_H_INCLUDED #define HEADER_H_INCLUDED #include <iostream> #include <iomanip> using namespace std; enum triangleType {noTriangle, scalene, isoceles, equilateral}; //prototypes void extern input(float&, float&, float&); triangleType extern triangleShape(float, float, float); /*void extern output (float, float, float);*/ void extern myLabel(const char *, const char *); #endif // HEADER_H_INCLUDED main function //8.1 main // this progam... #include "header.h" int main() { float sideLength1, sideLength2, sideLength3; char response; do //main loop { input (sideLength1, sideLength2, sideLength3); triangleShape (sideLength1, sideLength2, sideLength3); //output (sideLength1, sideLength2, sideLength3); cout << "\nAny more triangles to analyze? (y,n) "; cin >> response; } while (response == 'Y' || response == 'y'); myLabel ("8.1", "2/11/2011"); return 0; } triangleShape shape # include "header.h" triangleType triangleShape(sideLenght1, sideLength2, sideLength3) { triangleType triangle; return triangle; }

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• Cross-platform general purpose C++ RPC library

  - by iUm

  Here's the task: Imagine, we have an applications and a plug-in for it (dynamic library). Interface between the application and the plug-in is completely defined. Now I need to run the application and the plug-in on different computers. I wrote a stub for the plug-in on a computer where the real applications is running. And the application loads it and calls its functions like if it were a native plug-in. On the other computer there's a stub instead of the real application, which loads the native plug-in. Now I need to organize RPCs between my stubs over the network, regardless the very transport. Usually, it's not difficult. But there're some restrictions: Application-plug-in interaction can be reenterable (e.g. application calls f1() from plug-in, in f1() plug-in calls g1() from application, in g1() application calls f2() from plug-in and so on...) Any such reenteration should be executed exactly by the same thread, which started the sequence Where can I find a cross-platform C++ RPC library with such features?

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• Django Aggregation Across Reverse Relationship

  - by Tom

  Given these two models: class Profile(models.Model): user = models.ForeignKey(User, unique=True, verbose_name=_('user')) about = models.TextField(_('about'), blank=True) zip = models.CharField(max_length=10, verbose_name='zip code', blank=True) website = models.URLField(_('website'), blank=True, verify_exists=False) class ProfileView(models.Model): profile = models.ForeignKey(Profile) viewer = models.ForeignKey(User, blank=True, null=True) created = models.DateTimeField(auto_now_add=True) I want to get all profiles sorted by total views. I can get a list of profile ids sorted by total views with: ProfileView.objects.values('profile').annotate(Count('profile')).order_by('-profile__count') But that's just a dictionary of profile ids, which means I then have to loop over it and put together a list of profile objects. Which is a number of additional queries and still doesn't result in a QuerySet. At that point, I might as well drop to raw SQL. Before I do, is there a way to do this from the Profile model? ProfileViews are related via a ForeignKey field, but it's not as though the Profile model knows that, so I'm not sure how to tie the two together. As an aside, I realize I could just store views as a property on the Profile model and that may turn out to be what I do here, but I'm still interested in learning how to better use the Aggregation functions.

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• Backbone.js routes not firing

  - by drale2k

  I have a Base Router where i define some functions that need to be run everywhere. Every Router extends this Router. Now my problem is, that none of my routes defined in this Base router, actually fire. Every other route in other Routers work fine. I have created a test route called 'a' which calls method 'b', which should fire an alert but nothing happens. Here is the code: (This is Coffeescript, don't pay attention to the indentation, it's fine in my file) class Etaxi.Routers.Base extends Backbone.Router routes: 'register' : 'registerDevice' 'a' : 'b' b: -> alert "a" initialize: -> @registerDevice() unless localStorage.device_id? @getGeolocation() registerDevice: -> @collection = new Etaxi.Collections.Devices() @collection.fetch() view = new Etaxi.Views.RegisterDevice(collection: @collection) $('#wrapper').append(view.render().el) getGeolocation: -> navigator.geolocation.getCurrentPosition (position) -> lat = position.coords.latitude lng = position.coords.longitude #$('#apphead').tap -> # alert 'Position: ' + lat + " ," + lng So when i visit '/register' or '/a' it should fire the appropriate method but it does not. I wonder if it has something to do with the fact that other Router extend from this Router? Would be wired but it is the only thing i can think of because every other Router works fine.

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• Get XML-RPC (Andorid - PHP) web service different params type

  - by Jovan

  Hi, I want to create XML-RPC web service for Andorid (client) - PHP (Server) communication I create XML-RPC PHP web service server using this tutorial: http://articles.sitepoint.com/article/own-web-service-php-xml-rpc/5 For andorid client web service I use this project: http://code.google.com/p/android-xmlrpc/ server and client communication is OK, but I have problem with getting params from andorid client to php server. From andorid client I send two params (first integer and second float number) Object[] params = { 3, 3.6f, }; method.call(params); , but I don't know how to handle this parameters in php server?? in php server there is some function , but with only one param ($news_id): function news_viewNewsItem ( $news_id ) { /* Define the query to fetch the news item */ $query = "SELECT * FROM kd_xmlrpc_news WHERE news_id = '" . $news_id . "'"; $sql = mysql_query ( $query ); if ( $result = mysql_fetch_array ( $sql ) ) { /* Extract the variables for sending in our server response */ $news_item['news_id'] = $result['news_id']; $news_item['date'] = XMLRPC_convert_timestamp_to_iso8601( mysql_datetime_to_timestamp( $result['date'] ) ); $news_item['title'] = $result['title']; $news_item['full_desc'] = $result['full_desc']; $news_item['author'] = $result['author']; /* Respond to the client with the news item */ XMLRPC_response(XMLRPC_prepare($news_item), KD_XMLRPC_USERAGENT); } else { /* If there was an error, respond with a fault code instead */ XMLRPC_error("1", "news_viewNewsItem() error: Unable to read news:" . mysql_error(), KD_XMLRPC_USERAGENT); } } In server.py file there is functions for every method but I dont know how to write in php server: def add(self, x, y): print print "input x=%s, y=%s" % (str(x), str(y)) sum = x + y print "output", sum print return sum Can some one help me with code , and tell me how to handle various types from client to server?? Thanks and Happy New Year

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• Model class for NSDictionary information with Lazy Loading

  - by samfu_1

  My application utilizes approx. 50+ .plists that are used as NSDictionaries. Several of my view controllers need access to the properties of the dictionaries, so instead of writing duplicate code to retrieve the .plist, convert the values to a dictionary, etc, each time I need the info, I thought a model class to hold the data and supply information would be appropriate. The application isn't very large, but it does handle a good deal of data. I'm not as skilled in writing model classes that conform to the MVC paradigm, and I'm looking for some strategies for this implementation that also supports lazy loading.. This model class should serve to supply data to any view controller that needs it and perform operations on the data (such as adding entries to dictionaries) when requested by the controller functions currently planned: returning the count on any dictionary adding one or more dictionaries together Currently, I have this method for supporting the count lookup for any dictionary. Would this be an example of lazy loading? -(NSInteger)countForDictionary: (NSString *)nameOfDictionary { NSBundle *bundle = [NSBundle mainBundle]; NSString *plistPath = [bundle pathForResource: nameOfDictionary ofType: @"plist"]; //load plist into dictionary NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile: plistPath]; NSInteger count = [dictionary count] [dictionary release]; [return count] }

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• C++ compiler unable to find function (namespace related)

  - by CS student

  I'm working in Visual Studio 2008 on a C++ programming assignment. We were supplied with files that define the following namespace hierarchy (the names are just for the sake of this post, I know "namespace XYZ-NAMESPACE" is redundant): (MAIN-NAMESPACE){ a bunch of functions/classes I need to implement... (EXCEPTIONS-NAMESPACE){ a bunch of exceptions } (POINTER-COLLECTIONS-NAMESPACE){ Set and LinkedList classes, plus iterators } } The MAIN-NAMESPACE contents are split between a bunch of files, and for some reason which I don't understand the operator<< for both Set and LinkedList is entirely outside of the MAIN-NAMESPACE (but within Set and LinkedList's header file). Here's the Set version: template<typename T> std::ostream& operator<<(std::ostream& os, const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set<T>& set) Now here's the problem: I have the following data structure: Set A Set B Set C double num It's defined to be in a class within MAIN-NAMESPACE. When I create an instance of the class, and try to print one of the sets, it tells me that: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set' (or there is no acceptable conversion) However, if I just write a main() function, and create Set A, fill it up, and use the operator- it works. Any idea what is the problem? (note: I tried any combination of using and include I could think of).

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• How to fetch particular element from string after splitting it, using XSLT split() ?

  - by Vijay

  Hi All, I have one query regarding XSLT functions. I am using split function to fetch values from a string. I am using separator as "*". e.g. String : {"item1*item2*item3*item4"} split function I am using is as; <xsl:template name="SplitItemsCollection"> <xsl:param name="list" select="''"/> <xsl:param name="separator" select="'*'"/> <xsl:if test="not($list = '' or $separator = '')"> <xsl:variable name="head" select="substring-before(concat($list, $separator), $separator)"/> <xsl:variable name="tail" select="substring-after($list, $separator)"/> <xsl:value-of select="$head"/> <xsl:call-template name="split"> <xsl:with-param name="list" select="$tail"/> <xsl:with-param name="separator" select="$separator"/> </xsl:call-template> </xsl:if> </xsl:template> This function returns me all the items. Is there any way to fetch particular item from these separated items ? Say I want to fetch item3. Can we do it directly ? Thanks in advance.

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• QObject::connect not connecting signal to slot

  - by user1662800

  I am using C++ and Qt in my project and my problem is QObject::connect function doesn't connect signal to a slot. I have the following classes: class AddCommentDialog : public QDialog { Q_OBJECT public: ...some functions signals: void snippetAdded(); private slots: void on_buttonEkle_clicked(); private: Ui::AddCommentDialog *ui; QString snippet; }; A part of my Main window: class MainWindow : public QMainWindow { Q_OBJECT public: explicit MainWindow(QWidget *parent = 0); ~MainWindow(); private slots: void commentAddedSlot(); void variableAddedSlot(); ... private: AddCommentDialog *addCommentDialog; ... }; Ant the last dialog; class AddDegiskenDialog : public QDialog { Q_OBJECT public: ... signals: void variableAdded(); private slots: void on_buttonEkle_clicked(); private: Ui::AddDegiskenDialog *ui; ... }; In the main window constructor i connect signals and slots: addCommentDialog=new AddCommentDialog(); addDegiskenDialog=new AddDegiskenDialog(); connect(addDegiskenDialog, SIGNAL(variableAdded()), this, SLOT(variableAddedSlot())); connect(addCommentDialog, SIGNAL(snippetAdded()), this, SLOT(commentAddedSlot())); The point is my commentAddedSlot is connected to it's signal successfully, but commentAddedSlot is failed. There is the Q_OBJECT macros, no warning such as about no x slot. In addition to this, receivers(SIGNAL(snippetAdded())) gives me 1 but receivers(SIGNAL(variableAdded())) gives me 0 and i used commands qmake -project; qmake and make to fully compile. What am i missing?

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• ERROR 2019 Linker Error Visual Studio

  - by Corrie Duck

  Hey I hope someone can tell me know to fix this issue I am having i keep getting an error 2019 from Visual studio for the following file. Now most of the functions have been removed so excuse the empty varriables etc. Error error LNK2019: unresolved external symbol "void * __cdecl OpenOneDevice(void *,struct _SP_DEVICE_INTERFACE_DATA *,char *)" (?OpenOneDevice@@YAPAXPAXPAU_SP_DEVICE_INTERFACE_DATA@@PAD@Z) referenced in function _wmain c:\Users\K\documents\visual studio 2010\Projects\test2\test2\test2.obj test2 #include "stdafx.h" #include <windows.h> #include <setupapi.h> SP_DEVICE_INTERFACE_DATA deviceInfoData; HDEVINFO hwDeviceInfo; HANDLE hOut; char *devName; // HANDLE OpenOneDevice(IN HDEVINFO hwDeviceInfo,IN PSP_DEVICE_INTERFACE_DATA DeviceInfoData,IN char *devName); // HANDLE OpenOneDevice(IN HDEVINFO HardwareDeviceInfo,IN PSP_DEVICE_INTERFACE_DATA DeviceInfoData,IN char *devName) { PSP_DEVICE_INTERFACE_DETAIL_DATA functionClassDeviceData = NULL; ULONG predictedLength = 0, requiredLength = 0; HANDLE hOut = INVALID_HANDLE_VALUE; SetupDiGetDeviceInterfaceDetail(HardwareDeviceInfo, DeviceInfoData, NULL, 0, &requiredLength, NULL); predictedLength = requiredLength; functionClassDeviceData = (PSP_DEVICE_INTERFACE_DETAIL_DATA)malloc(predictedLength); if(NULL == functionClassDeviceData) { return hOut; } functionClassDeviceData->cbSize = sizeof (SP_DEVICE_INTERFACE_DETAIL_DATA); if (!SetupDiGetDeviceInterfaceDetail(HardwareDeviceInfo, DeviceInfoData, functionClassDeviceData, predictedLength, &requiredLength, NULL)) { free( functionClassDeviceData ); return hOut; } //strcpy(devName,functionClassDeviceData->DevicePath) ; hOut = CreateFile(functionClassDeviceData->DevicePath, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL); free(functionClassDeviceData); return hOut; } // int _tmain(int argc, _TCHAR* argv[]) { hOut = OpenOneDevice (hwDeviceInfo, &deviceInfoData, devName); if(hOut != INVALID_HANDLE_VALUE) { // error report } return 0; } Been driving me mad for hours. Any help appreciated. SOLVED THANKS TO CHRIS :-) Add #pragma comment (lib, "Setupapi.lib") Thanks

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• Compromising design & code quality to integrate with existing modules

  - by filip-fku

  Greetings! I inherited a C#.NET application I have been extending and improving for a while now. Overall it was obviously a rush-job (or whoever wrote it was seemingly less competent than myself). The app pulls some data from an embedded device & displays and manipulates it. At the core is a communications thread in the main application form which executes a 600+ lines of code method which calls functions all over the place, implementing a state machine - lots of if-state-then-do type code. Interaction with the device is done by setting the state/mode globally and letting the thread do it's thing. (This is just one example of the badness of the code - overall it is not very OO-like, it reminds of the style of embedded C code the device firmware is written in). My problem is that this piece of code is central to the application. The software, communications protocol or device firmware are not documented at all. Obviously to carry on with my work I have to interact with this code. What I would like some guidance on, is whether it is worth scrapping this code & trying to piece together something more reasonable from the information I can reverse engineer? I can't decide! The reason I don't want to refactor is because the code already works, and changing it will surely be a long, laborious and unpleasant task. On the flip side, not refactoring means I have to sometimes compromise the design of other modules so that I may call my code from this state machine! I've heard of "If it ain't broke don't fix it!", so I am wondering if it should apply when "it" is influencing the design of future code! Any advice would be appreciated! Thanks!

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• overwrite parameters passed by querystring

  - by opensas

  I have the following problem I have a web framework built with classic asp that saves the page state in hidden textboxes, and then issues a submit to itself. Before submitting, we have a javascript functions that saves the action in a hidden "action" input, and then performs the submit. The page loads the state from those hidden texts, reads the action issued, reads extra parameters, like the id of the record to edit, and then builds the page accordingly. I'd like to make a url link to automatically start the page with "edit" action on a "x" id. So I was thinking about building the following url, for example http://myapp/user?action=edit&id=23 the problem is that when the page auto-submits, que url string keeps the parameters. I'd like to achieve the following: when the user clicks on http://myapp/user?action=edit&id=23 my page should receive the posted values action=edit and id=23 but the url should be just http://myapp/user and both parameters should be kept in the hidden texts... (I wonder if I make myself clear...) thanks a lot saludos sas ps: I have a couple of ideas about how to solve it, but I'll post them as answers...

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• How do I select dynamic ids in this format?

  - by sjsc

  I'm trying to select dynamic ids when a user types something into the input fields. My app spits out the input fields in the following format: <input id="student_1_first_name" /> <input id="student_1_last_name" /> <input id="student_2_first_name" /> <input id="student_2_last_name" /> <input id="student_3_first_name" /> <input id="student_3_last_name" /> etc. For example, I tried doing this to select the end of the id string: <script type="text/javascript"> $(document).ready( function (){ $("input[id$=_first_name]").bind("keyup", run_some_function_here); run_some_function_here(); $("input[id$=_last_name]").bind("keyup", run_some_function_here); run_some_function_here(); } ); </script> When I do that, Jquery can't seem to select the input ids, so the functions don't run. Do you have any ideas on how I can select the ids correctly?

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• friend declaration in C++

  - by Happy Mittal

  In Thinking in C++ by Bruce eckel, there is an example given regarding friend functions as // Declaration (incomplete type specification): struct X; struct Y { void f(X*); }; struct X { // Definition private: int i; public: friend void Y::f(X*); // Struct member friend }; void Y::f(X* x) { x->i = 47; } Now he explained this: Notice that Y::f(X*) takes the address of an X object. This is critical because the compiler always knows how to pass an address, which is of a fixed size regardless of the object being passed, even if it doesn’t have full information about the size of the type. If you try to pass the whole object, however, the compiler must see the entire structure definition of X, to know the size and how to pass it, before it allows you to declare a function such as Y::g(X). But when I tried void f(X); as declaration in struct Y, it shows no error. Please explain why?

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• Toggle image based on cookie value

  - by danit

  Im using a couple of JS functions to set a cookie named 'visible' with the value of either yes or no. Essentially Im using these values to decide if a <div> is visible or hidden. I've only just added the cookie, previously I had been using two images 1. Show 2. Hide as a button to hide and show the <div> like this: HTML: <img class="show" title="Show" alt="Show" src="images/show.png" /> <img class="hide" title="Hide" alt="Hide" src="images/hide.png" /> JQUERY: $("#tool").click(function() { $(".help").slideToggle(); $("#wrapper").animate({ opacity: 1.0 },200).slideToggle(200, function() { $("#tool img").toggle(); }); }); However I have now added the Cookie into the mix: $("#tool").click(function() { if(get_cookie('visible')== null) { set_cookie('visible','no'); } else { delete_cookie('visible'); } $(".help").slideToggle(); $("#wrapper").animate({ opacity: 1.0 },200).slideToggle(200, function() { $("#slider img").toggle(); }); }); So the .toggle() no longer matches the state of the <div> When the cookie value = no the show.png should be visible When the cookie value = yes then the hide.png should be visible Can anyone suggest how i can ammend this?

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• Is there any class in the .NET Framework to represent a holding container for objects?

  - by Charles Prakash Dasari

  I am looking for a class that defines a holding structure for an object. The value for this object could be set at a later time than when this container is created. It is useful to pass such a structure in lambdas or in callback functions etc. Say: class HoldObject<T> { public T Value { get; set; } public bool IsValueSet(); public void WaitUntilHasValue(); } // and then we could use it like so ... HoldObject<byte[]> downloadedBytes = new HoldObject<byte[]>(); DownloadBytes("http://www.stackoverflow.com", sender => downloadedBytes.Value = sender.GetBytes()); It is rather easy to define this structure, but I am trying to see if one is available in FCL. I also want this to be an efficient structure that has all needed features like thread safety, efficient waiting etc. Any help is greatly appreciated.

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• C++ polymorphism, function calls

  - by moai

  Okay, I'm pretty inexperienced as a programmer, let alone in C++, so bear with me here. What I wanted to do was to have a container class hold a parent class pointer and then use polymorphism to store a child class object. The thing is that I want to call one of the child class's functions through the parent class pointer. Here's a sort of example of what I mean in code: class SuperClass { public: int x; } class SubClass : public SuperClass { public: void function1() { x += 1; } } class Container { public: SuperClass * alpha; Container(SuperClass& beta) { alpha = beta; } } int main() { Container cont = new Container(new SubClass); } (I'm not sure that's right, I'm still really shaky on pointers. I hope it gets the point across, at least.) So, I'm not entirely sure whether I can do this or not. I have a sneaking suspicion the answer is no, but I want to be sure. If someone has another way to accomplish this sort of thing, I'd be glad to hear it.

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• How to make a program not show up in Alt-Tab or on the taskbar.

  - by Scott Chamberlain

  I have a program that needs to sit in the background and when a user connects to a RDP session it will do some stuff then launch a program. when the program is closed it will do some housekeeping and logoff the session. The current way I am doing it is like this I have the terminal server launch this application. I have it set as a windows forms application and my code is this public static void Main() { //Do some setup work Process proc = new Process(); //setup the process proc.Start(); proc.WaitForExit(); //Do some housecleaning NativeMethods.ExitWindowsEx(0, 0); } I really like this because there is no item in the taskbar and there is nothing showing up in alt-tab. However to do this I gave up access to functions like void WndProc(ref Message m) So Now I can't listen to windows messages (Like WTS_REMOTE_DISCONNECT or WTS_SESSION_LOGOFF) and do not have a handle to use for for bool WTSRegisterSessionNotification(IntPtr hWnd, int dwFlags); I would like my code to be more robust so it will do the housecleaning if the user logs off or disconnects from the session before he closes the program. Any reccomendations on how I can have my cake and eat it too?

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• QListWidget drag and drop items disappearing from list

  - by ppalasek

  Hello, I'm having trouble implementing a QListWidget with custom items that can be reordered by dragging and dropping. The problem is when I make a fast double click (a very short drag&drop) on an item, the item sometimes disappears from the QListWidget. This is the constructor for my Widget: ListPopisiDragDrop::ListPopisiDragDrop(QWidget *parent) : QListWidget(parent) { setSelectionMode(QAbstractItemView::SingleSelection); setDragEnabled(true); viewport()->setAcceptDrops(true); setDefaultDropAction(Qt::MoveAction); setDropIndicatorShown(true); setDragDropMode(QAbstractItemView::InternalMove); } also the drop event: void ListPopisiDragDrop::dropEvent(QDropEvent *event){ int startRow=currentIndex().row(); QListWidget::dropEvent(event); int endRow=currentIndex().row(); //more code... } Custom items are made by implementing paint() and sizeHint() functions from QAbstractItemDelegate. When the problem with disappearing items happens, the dropEvent isn't even called. I really don't know what is happening and if I'm doing something wrong. Any help is appreciated. Thanks! Edit: I'm running the application on a Symbian S60 5th edition phone. Edit2: If I add this line to the constructor: setDragDropOverwriteMode(true); the item in the list still disappears, but an empty row stays in it's place.

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• Should I use a binary or a text file for storing protobuf messages?

  - by nbolton

  Using Google protobuf, I am saving my serialized messaged data to a file - in each file there are several messages. We have both C++ and Python versions of the code, so I need to use protobuf functions that are available in both languages. I have experimented with using SerializeToArray and SerializeAsString and there seems to be the following unfortunate conditions: SerializeToArray: As suggested in one answer, the best way to use this is to prefix each message with it's data size. This would work great for C++, but in Python it doesn't look like this is possible - am I wrong? SerializeAsString: This generates a serialized string equivalent to it's binary counterpart - which I can save to a file, but what happens if one of the characters in the serialization result is \n - how do we find line endings, or the ending of messages for that matter? Update: Please allow me to rephrase slightly. As I understand it, I cannot write binary data in C++ because then our Python application cannot read the data, since it can only parse string serialized messages. Should I then instead use SerializeAsString in both C++ and Python? If yes, then is it best practice to store such data in a text file rather than a binary file? My gut feeling is binary, but as you can see this doesn't look like an option.

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• How to mimic polymorphism in classes with template methods (c++)?

  - by davide

  in the problem i am facing i need something which works more or less like a polymorphic class, but which would allow for virtual template methods. the point is, i would like to create an array of subproblems, each one being solved by a different technique implemented in a different class, but holding the same interface, then pass a set of parameters (which are functions/functors - this is where templates jump up) to all the subproblems and get back a solution. if the parameters would be, e.g., ints, this would be something like: struct subproblem { ... virtual void solve (double& solution, double parameter)=0; } struct subproblem0: public subproblem { ... virtual void solve (double& solution, double parameter){...}; } struct subproblem1: public subproblem { ... virtual void solve (double* solution, double parameter){...}; } int main{ subproblem problem[2]; subproblem[0] = new subproblem0(); subproblem[1] = new subproblem1(); double argument0(0), argument1(1), sol0[2], sol1[2]; for(unsigned int i(0);i<2;++i) { problem[i]->solve( &(sol0[i]) , argument0); problem[i]->solve( &(sol1[i]) , argument1); } return 0; } but the problem is, i need the arguments to be something like Arg<T1,T2> argument0(f1,f2) and thus the solve method to be something of the likes of template<T1,T2> solve (double* solution, Arg<T1,T2> parameter) which cant obviously be declared virtual ( so cant be called from a pointer to the base class)... now i'm pretty stuck and don't know how to procede...

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