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  • Why this friend function can't access a private member of the class?

    - by Alceu Costa
    I am getting the following error when I try to access bins private member of the GHistogram class from within the extractHistogram() implementation: error: 'QVector<double> MyNamespace::GHistogram::bins' is private error: within this context Where the 'within this context' error points to the extractHistogram() implementation. Does anyone knows what's wrong with my friend function declaration? Here's the code: namespace MyNamespace{ class GHistogram { public: GHistogram(qint32 numberOfBins); qint32 getNumberOfBins(); /** * Returns the frequency of the value i. */ double getValueAt(qint32 i); friend GHistogram * Gbdi::extractHistogram(GImage *image, qint32 numberOfBins); private: QVector<double> bins; }; GHistogram * extractHistogram(GImage * image, qint32 numberOfBins); }

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  • How do i change Object to String in a class which extends AsyncTask?

    - by Filip V.
    I'm learning from Google's Android developing tutorial and i came across a problem. On this link https://developer.android.com/training/basics/network-ops/connecting.html#AsyncTask it says to create a class that extends AsyncTask. So when i write the class it automatically implements the method as follows: private Object doInBackground(Object... args) {..} //it's fine but when i try writing just as it says in the tutorial: private String doInBackground(String... args) {..} //it gives an error and the error says: The method doInBackground(String...) of type MainActivity.DownloadWebpageText must override a superclass method. So how do i change Object to String without getting an error there?

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  • Java Interfaces Methodology: Should every class implement an interface?

    - by Amir Rachum
    I've been programming in Java for a few courses in the University and I have the following question: Is it methodologically accepted that every class should implement an interface? Is it considered bad practice not to do so? Can you describe a situation where it's not a good idea to use interfaces? Edit: Personally, I like the notion of using Interfaces for everything as a methodology and habit, even if it's not clearly beneficial. Eclipse automatically created a class file with all the methods, so it doesn't waste any time anyway.

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  • DropDownList always does full-page postback, the first time it fires.

    - by CodexArcanum
    I have an ASP.NET page using the AJAX library. There is a dropdownlist inside an UpdatePanel, which on index changing is supposed to update a different UpdatePanel to modify a grid control. But after the page first comes up, and you adjust the ddl, the entire page postbacks, followed by a (correct) partial postback. After this one time, every other usage of the ddl performs correctly, trigger partial postbacks. Both the panel and the ddl are being added from code. The UP is Conditional updates and ChildrenAsTriggers = true. The dropdownlist is AutoPostBack true and has an event set up on SelectedIndexChanged. So what is going on? I've tried adjusting every setting I can think of and still the page completely refreshes once, then works fine after that.

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  • C# ToolTip will not re-appear after first use.

    - by Roberto Sebestyen
    I have a Forms C# application where I would like to use a toolTip on one of the text boxes. I Initialize the tool-tip in the constructor of the Form class, and it works the first time. So when I hover over the text box with my mouse it works, but once the toolTip times out and it goes away, it does not re-appear when I move my mouse away and back onto the control. I would expect it to come back and I'm wondering what I'm doing wrong. Here is how I initialize the tooltip: myTip = new ToolTip(); myTip.ToolTipIcon = ToolTipIcon.Info; myTip.IsBalloon = true; myTip.ShowAlways = true; myTip.SetToolTip(txtMyTextBox,"My Tooltip Text");

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  • 2 compareTo method overriden in the same class definition, how could I force to use the second?

    - by jayjaypg22
    I want to sort a list List<Blabla> donnees by a criterion on one of its field. My problem is that compareTo is already overriden for this Class. So I've got something like : Blabla { public int compareTo(Object other) { ... } public int compareTo(Blabla other) { ... } } In a business layer class I call : Business { method (){ Collections.sort(List<Blabla > donnees); } } But this call N°1 compareTo method with object parameter. How could I sort my list with the N°2 method?

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  • How can I find out how much memory an object of a C++ class consumes?

    - by Shadow
    Hi, I am developing a Graph-class, based on boost-graph-library. A Graph-object contains a boost-graph, so to say an adjacency_list, and a map. When monitoring the total memory usage of my program, it consumes quite a lot (checked with pmap). Now, I would like to know, how much of the memory is exactly consumed by a filled object of this Graph-class? With filled I mean when the adjacency_list is full of vertices and edges. I found out, that using sizeof() doesn't bring me far. Using valgrind is also not an alternative as there is quite some memory allocation done previously and this makes the usage of valgrind impractical for this purpose. I'm also not interested in what other parts of the program cost in memory, I want to focus on one single object. Thank you.

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  • How do I delete an object from an Entity Framework model without first loading it?

    - by Tomas Lycken
    I am quite sure I've seen the answer to this question somewhere, but as I couldn't find it with a couple of searches on SO or google, I ask it again anyway... In Entity Framework, the only way to delete a data object seems to be MyEntityModel ent = new MyEntityModel(); ent.DeleteObject(theObjectToDelete); ent.SaveChanges(); However, this approach requires the object to be loaded to, in this case, the Controller first, just to delete it. Is there a way to delete a business object referencing only for instance its ID? If there is a smarter way using Linq or Lambda expressions, that is fine too. The main objective, though, is to avoid loading data just to delete it.

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  • Does a persons' first programming language affect their programming style and if so, how? [closed]

    - by Scott Walsh
    I was speaking to an experienced lecturer recently who told me he could usually tell which programming language a student had learnt to program in by looking at their coding style (more specifically, when programming in other languages to the one which they were most comfortable with). He said that there have been multiple times when he's witnessed students attempted to write C# in Prolog. So I began to wonder, what specific traits do people gain from their first (or favourite) language which are carried over into their overall programming style, and more interestingly what good or bad habits do you think people would benefit from or should be wary of when learning specific language?

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  • Adobe edge animation fails to load first time in Opera, Crome but works in Firefox and Safari

    - by user3721777
    I have quite a serous problem here since I work on this animation for a while, I have a Adobe Edge Animation (done in CC) that fails to load the first time in Opera and Crome but does work in Firefox and Safari. It fail to load every time coming from another page. Only work if you reload. The problem persist both locally and online. It does work in preview every single time. I you can push me in the right direction, that would be great. Thanks! Here you can see the animation: http://tierraburritos.com/test/laCarta.html

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  • How can I map UIDs to user names using Perl library functions?

    - by Mike
    I'm looking for a way of mapping a uid (unique number representing a system user) to a user name using Perl. Please don't suggest greping /etc/passwd :) Edit As a clarification, I wasn't looking for a solution that involved reading /etc/passwd explicitly. I realize that under the hood any solution would end up doing this, but I was searching for a library function to do it for me.

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  • Is possible to set generic type by another class?

    - by Soul_Master
    I use ASP.NET MVC for serving web application and I want to create something like the following code. <% using(HTML.Form(Model)) { %> <% HTML.CreateTextBox('txt1', x => x.Property1); <% } From the above code, Form extension method will receive object that represent type of current Model object in current View page. Next, CreateTextBox method will receive type from Form method and I can bind textbox to some property of this model. Update 1 The following code is code of CreateTextBox method that will create instance of TextBox class. public static CreateTextBox(string value, Expression<Func<object>> bindedProperty) { // T should be receive from HTML.Form method or class return new TextBox<T>(value); } Is it possible to creating some code that doing something like the above code? Thanks,

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  • how to call a php class function directly using ajax?

    - by payling
    Is it possible to call a php class function DIRECTLY using ajax? Something like below... except ajax... myclass::myfunction(); I've been using the jquery library to work with AJAX. $.get('control.php', {func: funcName, arg1: arg1}); The above is similar to what I'm trying to achieve MINUS the control.php; I'm not sure if this is even possible, but I just thought it would be nice to skip the landing page (control.php) that recieves the funcName. I have a bunch of conditional statements that sort out what class function to run based on the funcName recieved. It seems kind of silly to do this, to have a separate page just to handle function calls. Is there a better way?

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  • How can I find out how much memory an instance of a C++ class consumes?

    - by Shadow
    Hi, I am developing a Graph-class, based on boost-graph-library. A Graph-object contains a boost-graph, so to say an adjacency_list, and a map. When monitoring the total memory usage of my program, it consumes quite a lot (checked with pmap). Now, I would like to know, how much of the memory is exactly consumed by a filled object of this Graph-class? With filled I mean when the adjacency_list is full of vertices and edges. I found out, that using sizeof() doesn't bring me far. Using valgrind is also not an alternative as there is quite some memory allocation done previously and this makes the usage of valgrind impractical for this purpose. I'm also not interested in what other parts of the program cost in memory, I want to focus on one single object. Thank you.

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  • When did people first start thinking 'C is portable assembler' ?

    - by Jacques Carette
    It seems to be an 'accepted concept' in the popular culture of programming languages that 'C is portable assembler'. I have first heard this at least 15 years ago. But when did it really become part of the popular culture? Note: if you don't agree that 'C is portable assembler', please just skip this question. This question is about 'popular culture of programming'. I'll add a comment to this question which you can up-vote for those who disagree with that statement.

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  • String.split() - matching leading empty String prior to first delimiter?

    - by tehblanx
    I need to be able to split an input String by commas, semi-colons or white-space (or a mix of the three). I would also like to treat multiple consecutive delimiters in the input as a single delimiter. Here's what I have so far: String regex = "[,;\\s]+"; return input.split(regex); This works, except for when the input string starts with one of the delimiter characters, in which case the first element of the result array is an empty String. I do not want my result to have empty Strings, so that something like, ",,,,ZERO; , ;;ONE ,TWO;," returns just a three element array containing the capitalized Strings. Is there a better way to do this than stripping out any leading characters that match my reg-ex prior to invoking String.split? Thanks in advance!

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  • Overhead of calling tiny functions from a tight inner loop? [C++]

    - by John
    Say you see a loop like this one: for(int i=0; i<thing.getParent().getObjectModel().getElements(SOME_TYPE).count(); ++i) { thing.getData().insert( thing.GetData().Count(), thing.getParent().getObjectModel().getElements(SOME_TYPE)[i].getName() ); } if this was Java I'd probably not think twice. But in performance-critical sections of C++, it makes me want to tinker with it... however I don't know if the compiler is smart enough to make it futile. This is a made up example but all it's doing is inserting strings into a container. Please don't assume any of these are STL types, think in general terms about the following: Is having a messy condition in the for loop going to get evaluated each time, or only once? If those get methods are simply returning references to member variables on the objects, will they be inlined away? Would you expect custom [] operators to get optimized at all? In other words is it worth the time (in performance only, not readability) to convert it to something like: ElementContainer &source = thing.getParent().getObjectModel().getElements(SOME_TYPE); int num = source.count(); Store &destination = thing.getData(); for(int i=0;i<num;++i) { destination.insert(thing.GetData().Count(), source[i].getName(); } Remember, this is a tight loop, called millions of times a second. What I wonder is if all this will shave a couple of cycles per loop or something more substantial? Yes I know the quote about "premature optimisation". And I know that profiling is important. But this is a more general question about modern compilers, Visual Studio in particular.

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  • JavaScript: supposed to execute functions sequentially, not actually doing so?

    - by AP257
    I'm seeing a lot of answers on StackOverflow that say that JavaScript executes code sequentially, but I can actually see my own JavaScript not doing so. From the following code: function centre_map(lat, lng, zoom_level) { alert('centre_map'); map = new GMap2(document.getElementById('map_canvas')); var latlng = new GLatLng(lat, lng); map.setCenter(latlng, zoom_level); } function add_markers_within_bounds() { alert('add_markers_within_bounds'); // add numerous BLUE markers within map bounds using MarkerClusterer } function add_marker(lat, lng, place_name, grid, county) { alert('add_marker'); // add one ordinary RED Google Maps marker } centre_map('{{lat}}', '{{lng}}', 12); add_markers_within_bounds('{{grid}}', '{{place_name}}'); add_marker('{{lat}}', '{{lng}}', '{{place_name}}', '{{grid}}', '{{county}}'); I get the following sequence of events: 'centre_map' alert 'add_markers_within_bounds' alert 'add_marker' alert individual RED marker appears on map (i.e. add_marker renders) multiple BLUE markers appear on map (i.e. add_markers_within_bounds renders) Why doesn't add_markers_within_bounds complete before add_marker gets under way: and how can I make it do so? I know that one way might be to call add_marker from within add_markers_within_bounds, but for various reasons I'd rather keep it as a separate function.

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  • Constant time change first k elements of an array in C++?

    - by Johny 96
    Let's suppose I have an array: bool eleme[1000000] = {false}; and at some point in my code I change some of the first of the n elements of this array to true. Afterwards I want to be sure that all elements of the array are false. So I do: for (int i =0; i < n; ++i) eleme[i] = false; which costs T(n). Is there a way to do this in constant time? E.g. something like make_false(eleme, n);

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