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  • C++: Binding to a base class

    - by Helltone
    The following code works, but I'm not sure it is correct/portable. #include <iostream> #include <tr1/functional> class base { public: base(int v) : x(v) {} protected: int x; }; class derived : public base { public: bool test() { return (x == 42); } }; int main(int argc, char* argv[]) { base b(42); if(std::tr1::bind((bool (base::*)()) &derived::test, b)()) { std::cout << "ok\n"; } return 0; }

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  • Modifying bundled properties from visitor

    - by ravenspoint
    How should I modify the bundled properties of a vertex from inside a visitor? I would like to use the simple method of sub-scripting the graph, but the graph parameter passed into the visitor is const, so compiler disallows changes. I can store a reference to the graph in the visitor, but this seems weird. /** A visitor which identifies vertices as leafs or trees */ class bfs_vis_leaf_finder:public default_bfs_visitor { public: /** Constructor @param[in] total reference to int variable to store total number of leaves @param[in] g reference to graph ( used to modify bundled properties ) */ bfs_vis_leaf_finder( int& total, graph_t& g ) : myTotal( total ), myGraph( g ) { myTotal = 0; } /** Called when the search finds a new vertex If the vertex has no children, it is a leaf and the total leaf count is incremented */ template <typename Vertex, typename Graph> void discover_vertex( Vertex u, Graph& g) { if( out_edges( u, g ).first == out_edges( u, g ).second ) { myTotal++; //g[u].myLevel = s3d::cV::leaf; myGraph[u].myLevel = s3d::cV::leaf; } else { //g[u].myLevel = s3d::cV::tree; myGraph[u].myLevel = s3d::cV::tree; } } int& myTotal; graph_t& myGraph; };

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  • shared_ptr as class member

    - by idimba
    It's common to declared contained objects as a pointers to that class, while "forward declarating" them in header file. This in order to reduce physical dependencies in code. For example class B; // forward declaration class A { private: B* pB; }; Would it be good idea to declare such a member as shared_ptr, instead of naked pointer? I would prefer scoped_ptr, but AFAIKit it won't be in standard.

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  • C++ associative array with arbitrary types for values

    - by Gerald Kaszuba
    What is the best way to have an associative array with arbitrary value types for each key in C++? Currently my plan is to create a "value" class with member variables of the types I will be expecting. For example: class Value { int iValue; Value(int v) { iValue = v; } std::string sValue; Value(std::string v) { sValue = v; } SomeClass *cValue; Value(SomeClass *v) { cValue = c; } }; std::map<std::string, Value> table; A downside with this is you have to know the type when accessing the "Value". i.e.: table["something"] = Value(5); SomeClass *s = table["something"].cValue; // broken pointer Also the more types that are put in Value, the more bloated the array will be. Any better suggestions?

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  • Why timed lock doesnt throws a timeout exception in C++0x?

    - by Vicente Botet Escriba
    C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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  • Disallow taking pointer/reference to const to a temporary object in C++ (no C++0X)

    - by KRao
    Hi, I am faced with the following issue. Consider the following class: //Will be similar to bost::reference_wrapper template<class T> class Ref { public: explicit Ref(T& t) : m_ptr(&t) {} private: T* m_ptr; }; and this function returning a double double fun() {return 1.0;} If we now have double x = 1.0; const double xc = 1.0; Ref<double> ref1(x); //OK Ref<const double> refc1(cx); //OK good so far, however: //Ref<double> ref2( fun() ); //Fails as I want it to Ref<const double> refc2( fun() ); //Works but I would like it not to Is there a way to modify Ref (the way you prefer) but not the function fun, so that the last line returns a compile-time error? Please notice you can modify the constructor signature (as long as I am able to initialise the Ref as intended). Thank you in advance for your help!

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  • enable_shared_from_this and inheritance

    - by DeadMG
    I've got a type which inherits from enable_shared_from_this<type>, and another type that inherits from this type. Now I can't use the shared_from_this method because it returns the base type and in a specific derived class method I need the derived type. Is it valid to just construct a shared_ptr from this directly? Edit: In a related question, how can I move from an rvalue of type shared_ptr<base> to a type of shared_ptr<derived>? I used dynamic_cast to verify that it really was the correct type, but now I can't seem to accomplish the actual move.

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  • How to see if turbo boost is working on I7 860 CPU?

    - by Jan Derk
    I just build myself a new system with a Intel I7 860 CPU. When loading it using a single threaded application like Super PI, CPU-Z shows 2.933Ghz as speed. Now I understood that the I7 goes into turbo boost mode up to 3.46GHz for a single core. How can I check that? Is there a utility to monitor CPU speed per core?

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  • Performance boost for MacBook: Hybrid hard drive or 4GB RAM?

    - by user13572
    I have an aluminium 13" MacBook with 2GB or RAM and 5400RPM 500GB hard drive. The main tasks I perform are developing iPhone and Mac apps in Xcode and websites in Coda. I want to improve the performance so I am considering buying 4GB of RAM or a 500GB Seagate solid-state hybrid drive. What is likely to provide the biggest performance boost?

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  • Is HTTP 404 appropriate for out of range page number on paged content?

    - by WooYek
    I have a site that is mainly showing a paged list of content (articles, data element's, etc.), and I'm wondering about returning HTTP 404 when user navigates outside of the available list range. Some sites just display "No results/Page number out of range" and some return additionally return HTTP 404 status. What's your take on that, and why? UPDATE It's not and api response. This question is in regard to user viewed pages that among other things show a list/table in the main area.

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  • Where can I find boost::fusion articles, examples, guides, tutorials?

    - by Kyle
    I am going to go ahead and shamelessly duplicate this question because the accepted answer is essentially "nope, no guides" and it's been nearly a year now since it's been asked. Does anyone know of any useful articles, guides, tutorials, etc. for boost::fusion besides the barebones documentation on boost.org? (which I'm sure is great as a reference after one has learned the library.) I'm completely open to, say, a link to a book on Amazon. Searched for it myself just now but all I came up with was green tea. The top links on Google aren't much better.

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  • As a programmer what single discovery has given you the greatest boost in productivity?

    - by ChrisInCambo
    This question has been inspired by my recent discovery/adoption of distributed version control. I started using it (mercurial) just because I liked the idea of still being able to make commits at times when I couldn't connect to the central server. I never expected it would give me a large boost in general productivity, but a pleasant side effect I discovered was that making a new clone every time I started a new task and giving that clone a descriptive folder name is extremely effective at keeping me on task resulting is a noticeable productivity increase. So as a programmer what single discovery has given you the greatest boost in productivity? Extra respect for answers which involve tools or practices that aren't so obvious from the outside!

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  • C++, name collision across different namespace

    - by aaa
    hello. I am baffled by the following name collision: namespace mp2 { boost::numeric::ublas::matrix_range<M> slice(M& m, const R1& r1, const R2& r2) { namespace ublas = boost::numeric::ublas; ublas::range r1_(r1.begin(), r1.end()), r2_(r2.begin(), r2.end()); return ublas::matrix_range<M>(m, r1_, r2_); } double energy(const Wavefunction &wf) { const Wavefunction::matrix& C = wf.coefficients(); int No = wf.occupied().size(); foreach (const Basis::MappedShell& P, basis.shells()) { slice(C, range(No), range(P)); the error from g++4.4 is 7 In file included from mp2.cpp:1: 8 /usr/include/boost/numeric/ublas/fwd.hpp: In function âdouble mp2::energy(const Wavefunction&)â: 9 /usr/include/boost/numeric/ublas/fwd.hpp:32: error: âboost::numeric::ublas::sliceâ is not a function, 10 ../../src/mp2/energy.hpp:98: error: conflict with âtemplate<class M, class R1, class R2> boost::numeric::ublas::matrix_range<M> mp2::slice(M&, const R1&, const R2&)â 11 ../../src/mp2/energy.hpp:123: error: in call to âsliceâ 12 /usr/include/boost/numeric/ublas/fwd.hpp:32: error: âboost::numeric::ublas::sliceâ is not a function, 13 ../../src/mp2/energy.hpp:98: error: conflict with âtemplate<class M, class R1, class R2> boost::numeric::ublas::matrix_range<M> mp2::slice(M&, const R1&, const R2&)â 14 ../../src/mp2/energy.hpp:129: error: in call to âsliceâ 15 make: *** [mp2.lo] Error 1 ublas segment is namespace boost { namespace numeric { namespace ublas { typedef basic_slice<> slice; why is slice in ublas collides with slice in mp2? I and fairly certain there is no using namespace ublas in the code and in includes. thank you

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  • Having trouble comparing a range of dates entered in a form with records in a mySQL database

    - by Andrew Fox
    I have a table called schedule and a column called Date where the column type is date. In that column I have a range of dates, which is currently from 2012-11-01 to 2012-11-30. I have a small form where the user can enter a range of dates (input names from and to) and I want to be able to compare the range of dates with the dates currently in the database. This is what I have: //////////////////////////////////////////////////////// //////First set the date range that we want to use////// //////////////////////////////////////////////////////// if(isset($_POST['from']) && ($_POST['from'] != NULL)) { $startDate = $_POST['from']; } else { //Default date is Today $startDate = date("Y-m-d"); } if(isset($_POST['to']) && ($_POST['to'] != NULL)) { $endDate = $_POST['to']; } else { //Default day is one month from today $endDate = date("Y-m-d", strtotime("+1 month")); } ////////////////////////////////////////////////////////////////////////////////////// //////Next calculate the total amount of days selected above to use as a limiter////// ////////////////////////////////////////////////////////////////////////////////////// $dayStart = strtotime($startDate); $dayEnd = strtotime($endDate); $total_days = abs($dayEnd - $dayStart) / 86400 +1; echo "Start Date: " . $startDate . "<br>End Date: " . $endDate . "<br>"; echo "Day Start: " . $dayStart . "<br>Day End: " . $dayEnd . "<br>"; echo "Total Days: " . $total_days . "<br>"; //////////////////////////////////////////////////////////////////////////////////// //////Then we're going to see if the dates selected are in the schedule table////// //////////////////////////////////////////////////////////////////////////////////// //Select all of the dates currently in the schedule table between the range selected. $sql = ("SELECT Date FROM schedule WHERE Date BETWEEN '$startDate' AND '$endDate' LIMIT $total_days"); //Run a check on the query to make sure it worked. If it failed then print the error. if(!$result_date_query = $mysqli->query($sql)) { die('There was an error getting the dates from the schedule table [' . $mysqli->error . ']'); } //Set the dates to an array for future use. // $current_dates = $result_date_query->fetch_assoc(); //Loop through the results while a result is being returned. while($row = $result_date_query->fetch_assoc()) { echo "Row: " . $row['Date'] . "<br>"; echo "Start day: " . date('Y-m-d', $dayStart) . "<br>"; //Set this loop to add 1 day to the Start Date until it reaches the End Date for($i = $dayStart; $i <= $dayEnd; $i = strtotime('+1 day', $i)) { $date = date('Y-m-d',$i); echo "Loop Start day: " . date('Y-m-d', $dayStart) . "<br>"; //Run a check to see if any of the dates selected are in the schedule table. if($row['Date'] != $date) { echo "Current Date: " . $row['Date'] . "<br>"; echo "Date: " . $date . "<br>"; echo "It appears as though you've selected some dates that are not in the schedule database.<br>Please correct the issue and try again."; return; } } } //Free the result so something else can use it. $result_date_query->free(); As you can see I've added in some echo statements so I can see what is being produced. From what I can see it looks like my $row['Date'] is not incrementing and staying at the same date. I originally had it set to a variable (currently commented out) but I thought that could be causing problems. I have created the table with dates ranging from 2012-11-01 to 2012-11-15 for testing and entered all of this php code onto phpfiddle.org but I can't get the username provided to connect. Here is the link: PHP Fiddle I'll be reading through the documentation to try and figure out the user connection problem in the meantime, I would really appreciate any direction or advice you can give me.

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  • Error occurred in deployment step ‘Add Solution’: Value does not fall within the expected range.

    - by ybbest
    I got this error when I deploy a new content type into SharePoint2010.This error message is not very helpful after a few hours of hard work, I find out there is a dash(-) in my contentID.It happen when I generate GUID using visual studio tool and copy it to the ID and forgot to delete the dash. After correct this, I press deploy again, it works like charm. If you got this error double-check your contentID. If you are not quite sure what is a Valid contentTypeID, check the MSDN documentation here.

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  • With a typical USB hard drive enclosure, is the full range of drive power management functionality available?

    - by intuited
    In what may be an unrelated matter: is it possible to suspend a PC without unmounting an attached USB-powered drive, and then remounting it on resume? This is the behaviour I'm currently seeing (running Ubuntu linux 10.10). Are there certain models or brands that provide more complete control over this aspect of drive operation? My Friendly Neighbourhood Computer Store carries (part of) the Vantec Nexstar product line.

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  • Randomly placing items script not working - sometimes items spawn in walls, sometimes items spawn in weird locations

    - by Timothy Williams
    I'm trying to figure out a way to randomly spawn items throughout my level, however I need to make sure they won't spawn inside another object (walls, etc.) Here's the code I'm currently using, it's based on the Physics.CheckSphere(); function. This runs OnLevelWasLoaded(); It spawns the items perfectly fine, but sometimes items spawn partway in walls. And sometimes items will spawn outside of the SpawnBox range (no clue why it does that.) //This is what randomly generates all the items. void SpawnItems () { if (Application.loadedLevelName == "Menu" || Application.loadedLevelName == "End Demo") return; //The bottom corner of the box we want to spawn items in. Vector3 spawnBoxBot = Vector3.zero; //Top corner. Vector3 spawnBoxTop = Vector3.zero; //If we're in the dungeon, set the box to the dungeon box and tell the items we want to spawn. if (Application.loadedLevelName == "dungeonScene") { spawnBoxBot = new Vector3 (8.857f, 0, 9.06f); spawnBoxTop = new Vector3 (-27.98f, 2.4f, -15); itemSpawn = dungeonSpawn; } //Spawn all the items. for (i = 0; i != itemSpawn.Length; i ++) { spawnedItem = null; //Zeroes out our random location Vector3 randomLocation = Vector3.zero; //Gets the meshfilter of the item we'll be spawning MeshFilter mf = itemSpawn[i].GetComponent<MeshFilter>(); //Gets it's bounds (see how big it is) Bounds bounds = mf.sharedMesh.bounds; //Get it's radius float maxRadius = new Vector3 (bounds.extents.x + 10f, bounds.extents.y + 10f, bounds.extents.z + 10f).magnitude * 5f; //Set which layer is the no walls layer var NoWallsLayer = 1 << LayerMask.NameToLayer("NoWallsLayer"); //Use that layer as your layermask. LayerMask layerMask = ~(1 << NoWallsLayer); //If we're in the dungeon, certain items need to spawn on certain halves. if (Application.loadedLevelName == "dungeonScene") { if (itemSpawn[i].name == "key2" || itemSpawn[i].name == "teddyBearLW" || itemSpawn[i].name == "teddyBearLW_Admiration" || itemSpawn[i].name == "radio") randomLocation = new Vector3(Random.Range(spawnBoxBot.x, -26.96f), Random.Range(spawnBoxBot.y, spawnBoxTop.y), Random.Range(spawnBoxBot.z, -2.141f)); else randomLocation = new Vector3(Random.Range(spawnBoxBot.x, spawnBoxTop.x), Random.Range(spawnBoxBot.y, spawnBoxTop.y), Random.Range(-2.374f, spawnBoxTop.z)); } //Otherwise just spawn them in the box. else randomLocation = new Vector3(Random.Range(spawnBoxBot.x, spawnBoxTop.x), Random.Range(spawnBoxBot.y, spawnBoxTop.y), Random.Range(spawnBoxBot.z, spawnBoxTop.z)); //This is what actually spawns the item. It checks to see if the spot where we want to instantiate it is clear, and if so it instatiates it. Otherwise we have to repeat the whole process again. if (Physics.CheckSphere(randomLocation, maxRadius, layerMask)) spawnedItem = Instantiate(itemSpawn[i], randomLocation, Random.rotation); else i --; //If we spawned something, set it's name to what it's supposed to be. Removes the (clone) addon. if (spawnedItem != null) spawnedItem.name = itemSpawn[i].name; } } What I'm asking for is if you know what's going wrong with this code that it would spawn stuff in walls. Or, if you could provide me with links/code/ideas of a better way to check if an item will spawn in a wall (some other function than Physics.CheckSphere). I've been working on this for a long time, and nothing I try seems to work. Any help is appreciated.

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  • How to cover the widest range of computers when publishing?

    - by DevilWithin
    When you plan a game, or even when you already made a game, and its time to publish, you wonder how much of your audience is covered by the game technology demands. I'm directing this essentialy to casual games, as I constantly see people having old laptops and being unable to replace them. Laptops with integrated cards whose OpenGL version doesn't even support textures larger than 1024x1024. These people may be avid gamers as well, and a reasonable share of the audience to consider giving them the chance to play casual games, once they cannot play any blockbusters. As I've seen happening, a very "noticeable" example is Angry Birds. It's gameplay is merely casual (I think nobody disagrees here) and still, it uses so high resolution textures that at least OpenGL 2.0 or around is needed, which blocks away a lot of people. So, the actual question is: what is a good tradeoff for this issue? Would it be better to just sacrifice the texture resolution for everyone, but have more supported hardware? Would it be better to keep the high quality and just slice the textures into smaller ones, sacrificing the performance a little bit? What else? Any ideas about this topic are welcome for discussion.

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