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  • C++ design question, container of instances and pointers

    - by Tom
    Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines, should return a pointer to a Polygon. Polygon* foo(Polygon& p){ std::vector<Line> lines = bar (p.begin(),p.end()); return new Polygon(lines); } Here's the question: I can always add a Polygon (vector Is there a better way that dereferencing each element of the vector and assigning it to the existing vector container? //for line in vector<Line*> v //vcopy is an instance of vector<Line> vcopy.push_back(*(v.at(i)) I think not, but I dont really like that approach. Hopefully, I will be able to convince the author of the class to change it, but I cant base my coding right now to that fact (and i'm scared of a performance hit). Thanks in advance.

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  • jQuery AJAX tabs + PHP

    - by ufw
    Hi, seems like I'm stuck with jQuery tabs. I'm trying to pass selected tab name to some php script but is seems like it doesn't get any data. This is how tabs normally work without any response from server side: http://pastebin.com/KBxj7p5k And this is how I try to pass the the current tab name to the server: $(document).ready(function() { $('ul.tabs li').css('cursor', 'pointer'); $('ul.tabs.tabs1 li').click(function(){ var thisClass = this.className.slice(0,2); $('div.t1').hide(); $('div.t2').hide(); $('div.t3').hide(); $('div.t4').hide(); $('div.' + thisClass).show('fast'); $('ul.tabs.tabs1 li').removeClass('tab-current'); $(this).addClass('tab-current'); var name = thisClass; var data = 'name='+name; $.ajax ({ type:"GET", url:"handler.php", data:data, success:function(html) { thisClass.html(html); } }); }); Thanks.

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  • Lite-Javascript Gallery - Can I position the img absolutely in relationship to the lis?

    - by blackessej
    I have a lite-javascript run image gallery. The javascript grabs each element in the list and places it as a background in the parent element. Then the CSS styles the thumbnails as small blocks with a defined height/width. A click-event for each object toggles it’s child’s element’s visibility and adds an “active” class name to the . Using CSS, I'm trying to place the absolutely to make it appear at the same position for each thumb, but it's moving in relation to the thumbs. Here's the CSS: #jgal li { background-position:50% 50%; background-repeat:no-repeat; border:solid #999 4px; cursor:pointer; display:block; float:left; height:60px; width:60px; margin-bottom:14px; margin-right:14px; opacity:0.5; } #jgal li img { position:absolute; top:0px; left:210px; display:none; } And the site: http://www.erisdesigns.net Thanks in advance for any help!

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  • What is the most efficient way of associating information with a Type in .Net?

    - by Miguel Angelo
    I want to associate custom data to a Type, and retrieve that data in run-time, blasingly fast. This is just my imagination, of my perfect world: var myInfo = typeof(MyClass).GetMyInformation(); this would be very fast... of course this does not exist! If it did I would not be asking. hehe ;) This is the way using custom attributes: var myInfo = typeof(MyClass).GetCustomAttribute("MyInformation"); this is slow because it requires a lookup of the string "MyInformation" This is a way using a Dictionary<Type, MyInformation: var myInfo = myInformationDictionary[typeof(MyClass)]; This is also slow because it is still a lookup of 'typeof(MyClass)'. I know that dictionary is very fast, but this is not enough... it is not as fast as calling a method. It is not even the same order of speed. I am not saying I want it to be as fast as a method call. I want to associate information with a type and access it as fast as possible. I am asking whether there is a better way, or event a best way of doing it. Any ideas?? Thanks!

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  • How to access the element of a list/vector that passed by reference in C++

    - by bsoundra
    Hi all, The problem is passing lists/vectors by reference int main(){ list<int> arr; //Adding few ints here to arr func1(&arr); return 0; } void func1(list<int> * arr){ // How Can I print the values here ? //I tried all the below , but it is erroring out. cout<<arr[0]; // error cout<<*arr[0];// error cout<<(*arr)[0];//error //How do I modify the value at the index 0 ? func2(arr);// Since it is already a pointer, I am passing just the address } void func2(list<int> *arr){ //How do I print and modify the values here ? I believe it should be the same as above but // just in case. } Is the vectors any different from the lists ? Thanks in advance. Any links where these things are explained elaborately will be of great help. Thanks again.

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  • Quickly accessing files in a 'project'

    - by bbbscarter
    Hi all. I'm looking for a way to quickly open files in my project's source tree. What I've been doing so far is adding files to the file-name-cache like so: (file-cache-add-directory-recursively (concat project-root "some/sub/folder") ".*\\.\\(py\\)$") after which I can use anything-for-files to access any file in the source tree with about 4 keystrokes. Unfortunately, this solution started falling over today. I've added another folder to the cache and emacs has started running out of memory. What's weird is that this folder contains less than 25% of files I'm adding, and yet emacs memory use goes up from 20mb to 400mb on adding just this folder. The total number of files is around 2000, so this memory use seems very high. Presumably I'm abusing the file cache. Anyway, what do other people do for this? I like this solution for its simplicity and speed; I've looked at some of the many, many project management packages for emacs and none of them really grabbed me... Thanks in advance! Simon

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  • simple image animation with the keyboard

    - by conorhiggins
    Hi the app I am currently working on requires a simple animation to be performed, which I am able to do but timing is an issue. The app uses the slightly opaque keyboard and I have set up a black background to make it more visually pleasing . The app is a utility app and as the user clicks on a settings button the app will flip which looks great. However there is a problem at the moment in that while the app is flipping the keyboard also closes which itself looks great also, however the background remains. I was wondering if there was a way of animating the background image to follow the keyboard's animation pattern and speed? If I set up a discrete animation time the chances are there will be some sort of overlap and either the image will show too long or the keyboard will show too long. Any suggestions? Another option is to make the keyboard show constantly if anyone knows how to do that? i would rather animate it though as it is quite a simple app and so I would like to make it as aesthetically pleasing as possible. /Conor

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  • Stil facing the problem in Orientation in iphone

    - by aman-gupta
    Hi, In my application I have 15 screens in that i m using UIViewController for all screens and in all screens i m using the below way to call other screen :- AppDelegate *appRefre = (AppDelegate *)[[UIApplication sharedApplication]delegate]; [self.navigationController pushViewController:appRefre.frmReferencesLink animated:YES]; And the below code is activated in all screen for orientation to control the user to switch from one orientation to other mode (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { if (interfaceOrientation == UIInterfaceOrientationPortrait) { return YES; } else { return NO; } } But when i run my application in iPhone device my application gets terminated when i physically rotate my iphone device from UIInterfaceOrientationPortrait to UIInterfaceOrientationPortraitUpsideDown or UIInterfaceOrientationLandscapeLeft,UIInterfaceOrientationLandscapeRight. And One more things is that when my application lauch i used following code for launching my appliaction :- 1) I made a pointer in mydelegate.h file: UINavigationController *navigationController; Then synthesize its property @property(nonatomic,retain)UINavigationController *navigationController 2) In mydelegat.m I Wrote @synthesize navigationController; (void)applicationDidFinishLaunching:(UIApplication *)application { navigationController = [[UINavigationController alloc] initWithRootViewController:DefaultViewLink]; [window addSubview:navigationController.view]; [window makeKeyAndVisible]; } 3) In above point DefaultView is launch first and gets remove from view and then actual my appliaction come into picture. So exactly what i want i want my appliaction to be in portrait mode for all screens i dont want my appliaction will switch to other mode.It remains the same as in portrait mode after rotation to any other mode. Please help me out its very urgent. Thanks in Advance and humble request to help me out

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  • PHP OO vs Procedure with AJAX

    - by vener
    I currently have a AJAX heavy(almost everything) intranet webapp for a business. It is highly modularized(components and modules ala Joomla), with plenty of folders and files. ~ 80-100 different viewing pages (each very unique in it's own sense) on last count and will likely to increase in the near future. I based around the design around commands and screens, the client request a command and sends the required data and receives the data that is displayed via javascript on the screen. That said, there are generally two types of files, a display files with html, javascript, and a little php for templating. And also a php backend file with a single switch statement with actions such as, save, update and delete and maybe other function. There is very little code reuse. Recently, I have been adding an server sided undo function that requires me to reuse some code. So, I took the chance to try out OOP but I notice that some functions are so simple, that creating a class, retrieving all the data then update all the related rows on the database seems like overkill for a simple action as speed is quite critical. Also I noticed there is only one class in an entire file. So, what if the entire php is a class. So, between creating a class and methods, and using global variables and functions. Which is faster?

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  • Fast find object by string property

    - by Andrew Kalashnikov
    Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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  • How can multiple variables be passed to a function cleanly in C?

    - by aquanar
    I am working on an embedded system that has different output capabilities (digital out, serial, analog, etc). I am trying to figure out a clean way to pass many of the variables that will control those functions. I don't need to pass ALL of them too often, but I was hoping to have a function that would read the input data (in this case from a TCP network), and then parse the data (IE, the 3rd byte contains the states of 8 of the digital outputs (according to which bit in that byte is high or low)), and put that into a variable where I can then use elsewhere in the program. I wanted that function to be separate from the main() function, but to do so would require passing pointers to some 20 or so variables that it would be writing to. I know I could make the variables global, but I am trying to make it easier to debug by making it obvious when a function is allowed to edit that variable, by passing it to the function. My best idea was a struct, and just pass a pointer to it, but wasn't sure if there was a more efficient way, especially since there is only really 1 function that would need to access all of them at once, while most others only require parts of the information that will be stored in this bunch of state variables. So anyway, is there a clean way to send many variables between functions at once that need to be edited?

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  • Deleting list items via ProcessBatchData()

    - by q-tuyen
    You can build a batch string to delete all of the items from a SharePoint list like this: 1: //create new StringBuilder 2: StringBuilder batchString= new StringBuilder(); 3: 4: //add the main text to the stringbuilder 5: batchString.Append(""); 6: 7: //add each item to the batch string and give it a command Delete 8: foreach (SPListItem item in itemCollection) 9: { 10: //create a new method section 11: batchString.Append(""); 12: //insert the listid to know where to delete from 13: batchString.Append("" + Convert.ToString(item.ParentList.ID) + ""); 14: //the item to delete 15: batchString.Append("" + Convert.ToString(item.ID) + ""); 16: //set the action you would like to preform 17: batchString.Append("Delete"); 18: //close the method section 19: batchString.Append(""); 20: } 21: 22: //close the batch section 23: batchString.Append(""); 24: 25: //preform the batch 26: SPContext.Current.Web.ProcessBatchData(batchString.ToString()); The only disadvantage that I can think of right know is that all the items you delete will be put in the recycle bin. How can I prevent that? I also found the solution like below: // web is a the SPWeb object your lists belong to // Before starting your deletion web.Site.WebApplication.RecycleBinEnabled = false; // When your are finished re-enable it web.Site.WebApplication.RecycleBinEnabled = true; Ref [Here](http://www.entwicklungsgedanken.de/2008/04/02/how-to-speed-up-the-deletion-of-large-amounts-of-list-items-within-sharepoint/) But the disadvantage of that solution is that only future deletion will not be sent to the Recycle Bins but it will delete all existing items as well which user do not want. Any idea to prevent not to delete existing items? Many thanks in advance, TQT

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  • How to identify multiple identical pairs in two vectors

    - by Sacha Epskamp
    In my graph-package (as in graph theory, nodes connected by edges) I have a vector indicating for each edge the node of origin from, a vector indicating for each edge the node of destination to and a vector indicating the curve of each edge curve. By default I want edges to have a curve of 0 if there is only one edge between two nodes and curve of 0.2 if there are two edges between two nodes. The code that I use now is a for-loop, and it is kinda slow: curve <- rep(0,5) from<-c(1,2,3,3,2) to<-c(2,3,4,2,1) for (i in 1:length(from)) { if (any(from==to[i] & to==from[i])) { curve[i]=0.2 } } So basically I look for each edge (one index in from and one in to) if there is any other pair in from and to that use the same nodes (numbers). What I am looking for are two things: A way to identify if there is any pair of nodes that have two edges between them (so I can omit the loop if not) A way to speed up this loop # EDIT: To make this abit clearer, another example: from <- c(4L, 6L, 7L, 8L, 1L, 9L, 5L, 1L, 2L, 1L, 10L, 2L, 6L, 7L, 10L, 4L, 9L) to <- c(1L, 1L, 1L, 2L, 3L, 3L, 4L, 5L, 6L, 7L, 7L, 8L, 8L, 8L, 8L, 10L, 10L) cbind(from,to) from to [1,] 4 1 [2,] 6 1 [3,] 7 1 [4,] 8 2 [5,] 1 3 [6,] 9 3 [7,] 5 4 [8,] 1 5 [9,] 2 6 [10,] 1 7 [11,] 10 7 [12,] 2 8 [13,] 6 8 [14,] 7 8 [15,] 10 8 [16,] 4 10 [17,] 9 10 In these two vectors, pair 3 is identical to pair 10 (both 1 and 7 in different orders) and pairs 4 and 12 are identical (both 2 and 8). So I would want curve to become: [1,] 0.0 [2,] 0.0 [3,] 0.2 [4,] 0.2 [5,] 0.0 [6,] 0.0 [7,] 0.0 [8,] 0.0 [9,] 0.0 [10,] 0.2 [11,] 0.0 [12,] 0.2 [13,] 0.0 [14,] 0.0 [15,] 0.0 [16,] 0.0 [17,] 0.0 (as I vector, I transposed twice to get row numbers).

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  • Is it possible to load an entire SQL Server CE database into RAM?

    - by DanM
    I'm using LinqToSql to query a small SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table via a foreign key, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of the appeal of LinqToSql. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view.

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  • How to convert a lambda to an std::function using templates

    - by retep998
    Basically, what I want to be able to do is take a lambda with any number of any type of parameters and convert it to an std::function. I've tried the following and neither method works. std::function([](){});//Complains that std::function is missing template parameters template <typename T> void foo(function<T> f){} foo([](){});//Complains that it cannot find a matching candidate The following code does work however, but it is not what I want because it requires explicitly stating the template parameters which does not work for generic code. std::function<void()>([](){}); I've been mucking around with functions and templates all evening and I just can't figure this out, so any help would be much appreciated. As mentioned in a comment, the reason I'm trying to do this is because I'm trying to implement currying in C++ using variadic templates. Unfortunately, this fails horribly when using lambdas. For example, I can pass a standard function using a function pointer. template <typename R, typename...A> void foo(R (*f)(A...)) {} void bar() {} int main() { foo(bar); } However, I can't figure out how to pass a lambda to such a variadic function. Why I'm interested in converting a generic lambda into an std::function is because I can do the following, but it ends up requiring that I explicitly state the template parameters to std::function which is what I am trying to avoid. template <typename R, typename...A> void foo(std::function<R(A...)>) {} int main() { foo(std::function<void()>([](){})); }

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  • Deleting from 2 arrays of dictionaries

    - by Matt Winters
    I have an array of dictionaries loaded from a plist (below) called arrayHistory. <plist version="1.0"> <array> <dict> <key>item</key> <string>1</string> <key>result</key> <string>8.1</string> <key>date</key> <date>2009-12-15T19:36:59Z</date> </dict> ... </array> </plist> I filter this array based on 'item' so that a second array, arrayHistoryDetail has the same structure as arrayHistory but only contains e.g. 'item's equal to '1'. These detail items are successfully displayed in a tableView. I then want to select an item from the tableView, and delete it from the tableView data source, arrayHistoryDetail (line 2 in the code below) - works, then I want to delete the item from the tableView itself (line 3 in the code below) - also works. My problem is that I also need to delete it from the original arrayHistory, so I tried the following: created a temporary dictionary as an ivar: NSMutableDictionary *tempDict; @property (nonatomic, retain) NSMutableDictionary *tempDict; Then my thinking was to make a copy in line 1 and remove it from the original array in line 4. 1 tempDict = [arrayHistoryDetail objectAtIndex: indexPath.row]; 2 [arrayHistoryDetail removeObjectAtIndex: indexPath.row]; 3 [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]; 4 [arrayHistory removeObject:tempDict]; Didn't work. Could someone please guide me in the right direction. I'm thinking that tempDict is a pointer and that removeObject needs a copy? I don't know. Thanks.

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  • Many users, many cpus, no delays. Good for cloud?

    - by Eric
    I wish to set up a CPU-intensive time-important query service for users on the internet. A usage scenario is described below. Is cloud computing the right way to go for such an implementation? If so, what cloud vendor(s) cater to this type of application? I ask specifically, in terms of: 1) pricing 2) latency resulting from: - slow CPUs, instance creations, JIT compiles, etc.. - internal management and communication of processes inside the cloud (e.g. a queuing process and a calculation process) - communication between cloud and end user 3) ease of deployment A usage scenario I am expecting is: - A typical user sends a query (XML of size around 1K) once every 30 seconds on average. - Each query requires a numerical computation of average time 0.2 sec and max time 1 sec on a 1 GHz Pentium. The computation requires no data other than the query itself and is performed by the same piece of code each time. - The delay a user experiences between sending a query and receiving a response should be on average no more than 2 seconds and in general no more than 5 seconds. - A background save to a DB of the response should occur (not time critical) - There can be up to 30000 simultaneous users - i.e., on average 1000 queries a second, each requiring an average 0.2 sec calculation, so that would necessitate around 200 CPUs. Currently I'm look at GAE Java (for quicker deployment and less IT hassle) and EC2 (Speed and price optimization) as options. Where can I learn more about the right way to set ups such a system? past threads, different blogs, books, etc.. BTW, if my terminology is wrong or confusing, please let me know. I'd greatly appreciate any help.

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  • Why doesn't this CompiledQuery give a performance improvement?

    - by Grammarian
    I am trying to speed up an often used query. Using a CompiledQuery seemed to be the answer. But when I tried the compiled version, there was no difference in performance between the compiled and non-compiled versions. Can someone please tell me why using Queries.FindTradeByTradeTagCompiled is not faster than using Queries.FindTradeByTradeTag? static class Queries { // Pre-compiled query, as per http://msdn.microsoft.com/en-us/library/bb896297 private static readonly Func<MyEntities, int, IQueryable<Trade>> mCompiledFindTradeQuery = CompiledQuery.Compile<MyEntities, int, IQueryable<Trade>>( (entities, tag) => from trade in entities.TradeSet where trade.trade_tag == tag select trade); public static Trade FindTradeByTradeTagCompiled(MyEntities entities, int tag) { IQueryable<Trade> tradeQuery = mCompiledFindTradeQuery(entities, tag); return tradeQuery.FirstOrDefault(); } public static Trade FindTradeByTradeTag(MyEntities entities, int tag) { IQueryable<Trade> tradeQuery = from trade in entities.TradeSet where trade.trade_tag == tag select trade; return tradeQuery.FirstOrDefault(); } }

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  • Should this work?

    - by Noah Roberts
    I am trying to specialize a metafunction upon a type that has a function pointer as one of its parameters. The code compiles just fine but it will simply not match the type. #include <iostream> #include <boost/mpl/bool.hpp> #include <boost/mpl/identity.hpp> template < typename CONT, typename NAME, typename TYPE, TYPE (CONT::*getter)() const, void (CONT::*setter)(TYPE const&) > struct metafield_fun {}; struct test_field {}; struct test { int testing() const { return 5; } void testing(int const&) {} }; template < typename T > struct field_writable : boost::mpl::identity<T> {}; template < typename CONT, typename NAME, typename TYPE, TYPE (CONT::*getter)() const > struct field_writable< metafield_fun<CONT,NAME,TYPE,getter,0> > : boost::mpl::false_ {}; typedef metafield_fun<test, test_field, int, &test::testing, 0> unwritable; int main() { std::cout << typeid(field_writable<unwritable>::type).name() << std::endl; std::cin.get(); } Output is always the type passed in, never bool_.

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  • Greasemonkey script, that creates Kineticjs drag and drop canvas over every website

    - by Michael Moeller
    I'd like to put a drag and drop canvas over every website I visit in Firefox. My Greasemonkey script puts a drag and drop canvas under every page: kinetic.user.js: // ==UserScript== // @name kineticjs_example // @description Canvas Drag and Drop // @include * // @require http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js // @require http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.7.2.min.js // ==/UserScript== var div = document.createElement( 'div' ); with( div ) { setAttribute( 'id', 'container' ); } // append at end document.getElementsByTagName( 'body' )[ 0 ].appendChild( div ); var stage = new Kinetic.Stage({ container: 'container', width: 1000, height: 1000 }); var layer = new Kinetic.Layer(); var rectX = stage.getWidth() / 2 - 50; var rectY = stage.getHeight() / 2 - 25; var box = new Kinetic.Rect({ x: rectX, y: rectY, width: 100, height: 50, fill: '#00D2FF', stroke: 'black', strokeWidth: 4, draggable: true }); // add cursor styling box.on('mouseover', function() { document.body.style.cursor = 'pointer'; }); box.on('mouseout', function() { document.body.style.cursor = 'default'; }); layer.add(box); stage.add(layer); How can I drag and drop this shape over the entire website?

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  • How can I modify the value of a string defined in a struct?

    - by Eric
    Hi, I have the following code in c++: #define TAM 4000 #define NUMPAGS 512 struct pagina { bitset<12> direccion; char operacion; char permiso; string *dato; int numero; }; void crearPagina(pagina* pag[], int pos, int dir) { pagina * paginas = (pagina*)malloc(sizeof(char) * TAM); paginas -> direccion = bitset<12> (dir); paginas -> operacion = 'n'; paginas -> permiso = 'n'; string **tempDato = &paginas -> dato; char *temp = " "; **tempDato = temp; paginas -> numero = 0; pag[pos] = paginas; } I want to modify the value of the variable called "string *dato" in the struct pagina but, everytime I want to assing a new value, the compiler throws a segmentation fault. In this case I'm using a pointer to string, but I have also tried with a string. In a few words I want to do the following: pagina - dato = "test"; Any idea? Thanks in advance!!!

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  • I have a bunch of template parameters that I want to hide from my users. How can I do this?

    - by Alex
    I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

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  • How to Check Authenticity of an AJAX Request

    - by Alex Reisner
    I am designing a web site in which users solve puzzles as quickly as they can. JavaScript is used to time each puzzle, and the number of milliseconds is sent to the server via AJAX when the puzzle is completed. How can I ensure that the time received by the server was not forged by the user? I don't think a session-based authenticity token (the kind used for forms in Rails) is sufficient because I need to authenticate the source of a value, not just the legitimacy of the request. Is there a way to cryptographically sign the request? I can't think of anything that couldn't be duplicated by a hacker. Is any JavaScript, by its exposed, client-side nature, subject to tampering? Am I going to have to use something that gets compiled, like Flash? (Yikes.) Or is there some way to hide a secret key? Or something else I haven't thought of? Update: To clarify, I don't want to penalize people with slow network connections (and network speed should be considered inconsistent), so the timing needs to be 100% client-side (the timer starts only when we know the user can see the puzzle). Also, there is money involved so no amount of "trusting the user" is acceptable.

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  • C struct written in file, open with Java

    - by DaunnC
    For example in C I have structure: typedef struct { int number; double x1; double y1; double x2; double y2; double x3; double y3; } CTRstruct;` Then I write it to file fwrite(&tr, 1, sizeof(tr), fp); (tr - its CTRstruct var, fp - File pointer); Then I need to read it with Java! I really don't know how to read struct from file... I tried to read it with ObjectInputStream(), last idea is to read with RandomAccessFile() but I also don't know how to... (readLong(), readDouble() also doesn't work, it works ofcource but doesn't read correct data). So, any idea how to read C struct from binary file with Java? If it's interesting, my version to read integer (but it's ugly, & I don't know what to do with double): public class MyDataInputStream extends DataInputStream{ public MyDataInputStream(InputStream AIs) { super(AIs); } public int readInt1() throws IOException{ int ch1 = in.read(); int ch2 = in.read(); int ch3 = in.read(); int ch4 = in.read(); if ((ch1 | ch2 | ch3 | ch4) < 0) throw new EOFException(); return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0)); } with double we can deal the same way (like with int or with long (8bytes) & then convert to double with native func).

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  • My java program seems to be skipping over the try{}, executing the catch{} and then throwing a NullPointerException. What should I do?

    - by Matt Bolopue
    I am writing a program that calculates the number of words, syllables, and sentences in any given text file. I don't need help finding those numbers, however my program (which currently should only find the number of words in the text file) will not import the text file even when I type in the name of the file correctly. The text file is in the same folder as the source code. Instead it tells me every time that what I typed in has the wrong file extension (see my catch{}) and then proceeds to throw a null pointer. I am at a loss for what could be causing it. Any suggestions? import java.io.*; import java.util.*; public class Reading_Lvl_Calc { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub int words = 0; String fileName; Scanner scan; Scanner keyread = new Scanner(System.in); System.out.println("Please enter a file name (or QUIT to exit)"); fileName = keyread.nextLine(); File doc = new File(fileName); //while(scan.equals(null)){ try { scan = new Scanner(doc); } catch(Exception e) { if(fileName.substring(fileName.indexOf(".")) != ".txt") System.out.println("I'm sorry, the file \"" + fileName + "\" has an invalid file extension."); else System.out.println("I am sorry, the file \"" + fileName + " \" cannot be found.\n The file must be in the same directory as this program"); scan = null; } // } while(scan.hasNext()){ words++; scan.next(); } System.out.println(words); } }

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