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  • Subgraph isomorphism on disconnected graphs with connection rules

    - by Mac
    Hello I was wondering if anyone knows about a solution to the following problem: Given a graph g as query and a set of graphs B with connection rules R. The connection rules describe how two graphs out of B can be linked together. Linking points are marked vertexes. Find all combination of graphs in B that contain g as a subgraph. Regards Mac

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  • Meta tag og:title inside Facebook Application is ignored

    - by Militaru
    I have a Facebook Application with an iframe based canvas that contains a like button (also iframe), in the head of my iframe i've specified the standard meta tags (og:title, og:url, og:site_name) and they seem to work fine (the information is displayed correctly in the profile wall) except for the title. I've tested various links of the app with the Facebook URL Linter and the ug:title tag is ignored completly. Have any of you had any trouble with the open graph tags inside facebook applications? Any ideeas are apreciated, thanks.

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  • AST generation for a an application developed both in visual basic and c#

    - by Dev
    Hi, I'm currently understanding one application developed both in visual basic and c#. Running through the code is getting tough as code is around 50KLOC. So i'm planning for generation of AST (abstract syntax tree). Will it be possible to generate for both language together. Atleast a call graph generation will be helpful (but can't find any tool which works for both languages) Please let me know if this question is confusing. Thanks in Advance Dev

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  • Bipartite matching in Python

    - by vailen
    Does anybody know any module in Python that computes the best bipartite matching? I have tried the following two: munkres hungarian However, in my case, I have to deal with non-complete graph (i.e., there might not be an edge between two nodes), and therefore, there might not be a match if the node has no edge. The above two packages seem not to be able to deal with this. Any advice?

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  • graphing amplitude

    - by John
    I was wondering if someone could point me to a good tutorial or show me how to graph the amplitude from a bytearray. The audio format I am using is: ULAW 8000.0 Hz, 8 bit, mono, 1 bytes/frame.

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  • Change Target of Edge in BGL

    - by Sunny
    If my BGL graph contain edge from node x to node y, and I want to change the target of this edge, so that now it's pointing from x to z, how it can be done? Are there any functions in BGL for that?

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  • Second min cost spanning tree.

    - by Evil
    Hello. I'm writing an algorithm for finding the second min cost spanning tree. my idea was as follows: 1) Use kruskals to find lowest MST. 2) Delete the lowest cost edge of the MST. 3) Run kruskals again on the entire graph. 4) return the new MST. My question is this: Will this work? Is there a better way perhaps to do this?

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  • Returning all "positions" of a list

    - by Daymor
    I Have a list with "a" and "b" and the "b"'s are somewhat of a path and "a"'s are walls. Im writing a program to make a graph of all the possible moves. I got the code running to check the first "b" for possible moves, but i have NO Idea how im going to find all "b"'s , even less check them all without repeating. Major issue im having is getting the tuple coordinates of the "b"'s out of the list. Any pointers/tips?

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  • Looking for a specific python gui module to perform the following task

    - by Sadaf Amouz
    I am looking for a GUI python module that is best suited for the following job: I am trying to plot a graph with many columns (perhaps hundreds), each column representing an individual. The user should be able to drag the columns around and drop them onto different columns to switch the two. Also, there are going to be additional dots drawn on the columns and by hovering over those dots, the user should see the values corresponding to those dots. What is the best way to approach this?

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  • Assigning XY positions to points based on a "weight" between them

    - by sanity
    I have a bunch of points in a graph, and for every pair of these points I have "weight" value indicating what their proximity should be, between -1 and 1. I want to choose XY coordinates for these points such that those that have a proximity of 1 are in the same position, and those with a proximity of -1 are distant from each-other. All points must reside within a bounded area. What algorithms should I investigate to achieve this?

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  • Grapher: Edit Equations Without GUI

    - by Nathan G.
    I'm trying to edit the equation of a Grapher file without opening the Grapher UI. I've gotten as far as knowing that I need a hex editor to do this. I can't, however, find my equation in that file to change it. Does anyone know how Grapher stores this information, and how to change it? My ultimate goal is to be able to change the file through the shell so I can open it and have Grapher show me my new equation (that was set with the CL). Thanks! I will set a bounty if necessary.

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  • using munin-plugins-rails to monitor rails app perfromance

    - by user2099762
    I have been trying to configure munin-plugins-rails to monitor the performance of our rails apps from Munin. The graphs appear, but no data is shown in the graphs. The log files show Error output from : 2013/06/27-15:39:06 [5540] Request-log-analyzer, by Willem van Bergen and $ 2013/06/27-15:39:06 [5540] Website: http://railsdoctors.com I have tried running Request-log-analyzer manually and pointing it at the production log file, and this reports as % for every item. There is data in the log file. I have tried changing the version of the gems installed, and also the type of the log file, but no luck. Any ideas anyone? Thanks

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  • Qt, MSVC, and /Zc:wchar_t- == I want to blow up the world

    - by Noah Roberts
    So Qt is compiled with /Zc:wchar_t- on windows. What this means is that instead of wchar_t being a typedef for some internal type (__wchar_t I think) it becomes a typedef for unsigned short. The really cool thing about this is that the default for MSVC is the opposite, which of course means that the libraries you're using are likely compiled with wchar_t being a different type than Qt's wchar_t. This doesn't become an issue of course until you try to use something like std::wstring in your code; especially when one or more libraries have functions that accept it as parameters. What effectively happens is that your code happily compiles but then fails to link because it's looking for definitions using std::wstring<unsigned short...> but they only contain definitions expecting std::wstring<__wchar_t...> (or whatever). So I did some web searching and ran into this link: http://bugreports.qt.nokia.com/browse/QTBUG-6345 Based on the statement by Thiago Macieira, "Sorry, we will not support building Qt like this," I've been worried that fixing Qt to work like everything else might cause some problem and have been trying to avoid it. We recompiled all of our support libraries with the /Zc:wchar_t- flag and have been fairly content with that until a couple days ago when we started trying to port over (we're in the process of switching from Wx to Qt) some serialization code. Because of how win32 works, and because Wx just wraps win32, we've been using std::wstring to represent string data with the intent of making our product as i18n ready as possible. We did some testing and Wx did not work with multibyte characters when trying to print special stuff (even not so special stuff like the degree symbol was an issue). I'm not so sure that Qt has this problem since QString isn't just a wrapper to the underlying _TCHAR type but is a Unicode monster of some sort. At any rate, the serialization library in boost has compiled parts. We've attempted to recompile boost with /Zc:wchar_t- but so far our attempts to tell bjam to do this have gone unheeded. We're at an impasse. From where I'm sitting I have three options: Recompile Qt and hope it works with /Zc:wchar_t. There's some evidence around the web that others have done this but I have no way of predicting what will happen. All attempts to ask Qt people on forums and such have gone unanswered. Hell, even in that very bug report someone asks why and it just sat there for a year. Keep fighting with bjam until it listens. Right now I've got someone under me doing that and I have more experience fighting with things to get what I want but I do have to admit to getting rather tired of it. I'm also concerned that I'll KEEP running into this issue just because Qt wants to be a c**t. Stop using wchar_t for anything. Unfortunately my i18n experience is pretty much 0 but it seems to me that I just need to find the right to/from function in QString (it has a BUNCH) to encode the Unicode into 8-bytes and visa-versa. UTF8 functions look promising but I really want to be sure that no data will be lost if someone from Zimbabfuckegypt starts writing in their own language and the documentation in QString frightens me a little into thinking that could happen. Of course, I could always run into some library that insists I use wchar_t and then I'm back to 1 or 2 but I rather doubt that would happen. So, what's my question... Which of these options is my best bet? Is Qt going to eventually cause me to gouge out my own eyes because I decided to compile it with /Zc:wchar_t anyway? What's the magic incantation to get boost to build with /Zc:wchar_t- and will THAT cause permanent mental damage? Can I get away with just using the standard 8-bit (well, 'common' anyway) character classes and be i18n compliant/ready? How do other Qt developers deal with this mess?

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  • Real-time graphing in Java

    - by thodinc
    I have an application which updates a variable about between 5 to 50 times a second and I am looking for some way of drawing a continuous XY plot of this change in real-time. Though JFreeChart is not recommended for such a high update rate, many users still say that it works for them. I've tried using this demo and modified it to display a random variable, but it seems to use up 100% CPU usage all the time. Even if I ignore that, I do not want to be restricted to JFreeChart's ui class for constructing forms (though I'm not sure what its capabilities are exactly). Would it be possible to integrate it with Java's "forms" and drop-down menus? (as are available in VB) Otherwise, are there any alternatives I could look into? EDIT: I'm new to Swing, so I've put together a code just to test the functionality of JFreeChart with it (while avoiding the use of the ApplicationFrame class of JFree since I'm not sure how that will work with Swing's combo boxes and buttons). Right now, the graph is being updated immediately and CPU usage is high. Would it be possible to buffer the value with new Millisecond() and update it maybe twice a second? Also, can I add other components to the rest of the JFrame without disrupting JFreeChart? How would I do that? frame.getContentPane().add(new Button("Click")) seems to overwrite the graph. package graphtest; import java.util.Random; import javax.swing.JFrame; import org.jfree.chart.ChartFactory; import org.jfree.chart.ChartPanel; import org.jfree.chart.JFreeChart; import org.jfree.chart.axis.ValueAxis; import org.jfree.chart.plot.XYPlot; import org.jfree.data.time.Millisecond; import org.jfree.data.time.TimeSeries; import org.jfree.data.time.TimeSeriesCollection; public class Main { static TimeSeries ts = new TimeSeries("data", Millisecond.class); public static void main(String[] args) throws InterruptedException { gen myGen = new gen(); new Thread(myGen).start(); TimeSeriesCollection dataset = new TimeSeriesCollection(ts); JFreeChart chart = ChartFactory.createTimeSeriesChart( "GraphTest", "Time", "Value", dataset, true, true, false ); final XYPlot plot = chart.getXYPlot(); ValueAxis axis = plot.getDomainAxis(); axis.setAutoRange(true); axis.setFixedAutoRange(60000.0); JFrame frame = new JFrame("GraphTest"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ChartPanel label = new ChartPanel(chart); frame.getContentPane().add(label); //Suppose I add combo boxes and buttons here later frame.pack(); frame.setVisible(true); } static class gen implements Runnable { private Random randGen = new Random(); public void run() { while(true) { int num = randGen.nextInt(1000); System.out.println(num); ts.addOrUpdate(new Millisecond(), num); try { Thread.sleep(20); } catch (InterruptedException ex) { System.out.println(ex); } } } } }

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  • Background changes by itself and procedure repeats many times until I release the mouse button

    - by Robert
    Dear community, I am a student, and I'm working on a little slots game (if the same random number comes up 3 timed, you win). I use Borland Pascal 7. I use graph to make this a bit more visual, but when I start the game my background turns from black to grey, and the other problem is that if I click the game start button, the game runs many times until I release the mouse button. How can I solve this? Here is my full program: program slots; uses mymouse,graph,crt; var gdriver,gmode,coin:integer; m:mouserec; a,b,c,coins:string; procedure gomb(x1,y1,x2,y2:integer;szoveg:string); var j,n:integer; begin setcolor(blue); rectangle(x1,y1,x2,y2); setfillstyle(1,blue); floodfill(x1+2,y1+2,blue); setcolor(0); outtextxy((x1+x2)div 2 -textwidth(szoveg) div 2 ,(y1+y2) div 2-textheight(szoveg) div 2,szoveg); end; procedure randomal(var a,b,c:string); begin randomize; STR(random(2)+1,a); STR(random(2)+1,b); STR(random(2)+1,c); end; procedure menu; begin; settextstyle(0,0,1); outtextxy(20,10,'Meno menu'); gomb(20,20,90,50,'Teglalap'); gomb(20,60,90,90,'Inditas'); gomb(20,100,90,130,'Harmadik'); gomb(20,140,90,170,'Negyedik'); end; procedure teglalap(x1,x2,y1,y2,tinta:integer); begin setcolor(tinta); rectangle(x1,x2,y1,y2); end; procedure jatek(var a,b,c:string;var coin:integer;coins:string); begin; clrscr; menu; randomal(a,b,c); if ((a=b) AND (b=c)) then coin:=coin+1 else coin:=coin-1; settextstyle(0,0,3); setbkcolor(black); outtextxy(200,20,a); outtextxy(240,20,b); outtextxy(280,20,c); STR(coin,coins); outtextxy(400,400,coins); end; procedure eger; begin; mouseinit; mouseon; menu; repeat getmouse(m); if (m.left) and (m.x20) ANd (m.x<90) and (m.y20) and (m.y<50) then teglalap(90,90,300,300,blue); if (m.left) and (m.x20) AND (m.x<90) and (m.y60) and (m.y<90) then jatek(a,b,c,coin,coins); until ((m.left) and (m.x20) ANd (m.x<140) and (m.y140) and (m.y<170)); end; begin coin:=50; gdriver:=detect; initgraph(gdriver, gmode, ''); eger; end. Thank you very much, Robert

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  • Facebook Invalid OAuth access token signature trying to post an attachment to group wall from PHP

    - by Volodymyr B
    I am an administrator (manager role) of a Facebook Group. I created an app, and stored its id and secret. I want my app to be able to post something on the Facebook group's feed. But when I attempt to post, I get the error 190 Invalid OAuth access token signature, even though I able to successfully obtain the access_token with publish_stream and offline_access scopes. It has the form of NNNNNNNNNNNNNNN|XXXXXXXXXXXXXXXXXXXXXXXXXXX, where N is a number (15) and X is a letter or a number (27). What should I do more to get this accomplished? Here is the code I am using: public static function postToFB($message, $image, $link) { //Get App Token $token = self::getFacebookToken(); // Create FB Object Instance $facebook = new Facebook(array( 'appId' => self::fb_appid, 'secret' => self::fb_secret, 'cookie' => true )); //$token = $facebook->getAccessToken(); //Try to Publish on wall or catch the Facebook exception try { $attachment = array('access_token' => $token, 'message' => $message, 'picture' => $image, 'link' => $link, //'name' => '', //'caption' => '', 'description' => 'More...', //'actions' => array(array('name' => 'Action Text', 'link' => 'http://apps.facebook.com/xxxxxx/')) ); $result = $facebook->api('/'.self::fb_groupid.'/feed/', 'post', $attachment); } catch (FacebookApiException $e) { //If the post is not published, print error details echo '<pre>'; print_r($e); echo '</pre>'; } } Code which returns the token //Function to Get Access Token public static function getFacebookToken($appid = self::fb_appid, $appsecret = self::fb_secret) { $args = array( 'grant_type' => 'client_credentials', 'client_id' => $appid, 'client_secret' => $appsecret, 'redirect_uri' => 'https://www.facebook.com/connect/login_success.html', 'scope' => 'publish_stream,offline_access' ); $ch = curl_init(); $url = 'https://graph.facebook.com/oauth/access_token'; curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, false); curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); curl_setopt($ch, CURLOPT_POST, true); curl_setopt($ch, CURLOPT_POSTFIELDS, $args); try { $data = curl_exec($ch); } catch (Exception $exc) { error_log($exc->getMessage()); } return json_encode($data); } If I uncomment $token = $facebook->getAccessToken(); in the posting code, it gives me yet another error (#200) The user hasn't authorized the application to perform this action. The token I get using developers.facebook.com/tools/explorer/ is of another form, much longer and with it I am able to post to the group page feed. How do I do it without copy/paste from Graph API Explorer and how do I post as a group instead of posting as a user? Thanks.

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  • BFS Shortest Path: Edge weight either 1 or 2

    - by Hackster
    I am trying to implement a shortest path algorithm using BFS. That is I am trying to find the shortest path from a specified vertex to every other vertex. However, its a special case where all edge weights are either 1 or 2. I know it could be done with Dijkstra's algorithm but I must use Breadth First Search. So far I have a working version of BFS that searches first for a vertex connected with an edge of weight 1. If it cannot find it, then returns a vertex connected with an edge of weight 2. After thinking about it, this is not the correct way to find the shortest path. The problem is I cannot think of any reasoning why BFS would work with weights 1 or 2, as opposed to any weight. Here is the code: public void addEdge(int start, int end, int weight) { adjMat[start][end] = 1; adjMat[end][start] = 1; edge_weight[start][end] = weight; edge_weight[end][start] = weight; } // ------------------------------------------------------------- public void bfs() // breadth-first search { // begin at vertex 0 vertexList[0].wasVisited = true; // mark it displayVertex(0); // display it theQueue.insert(0); // insert at tail int v2; while( !theQueue.isEmpty() ) // until queue empty, { int v1 = theQueue.remove(); // remove vertex at head // until it has no unvisited neighbors while( (v2=getAdjUnvisitedVertex(v1)) != -1 ){// get one, vertexList[v2].wasVisited = true; // mark it displayVertex(v2); // display it theQueue.insert(v2); // insert it } } // end while(queue not empty) // queue is empty, so we're done for(int j=0; j<nVerts; j++) // reset flags vertexList[j].wasVisited = false; } // end bfs() // ------------------------------------------------------------- // returns an unvisited vertex adj to v -- ****WITH WEIGHT 1**** public int getAdjUnvisitedVertex(int v) { for (int j = 0; j < nVerts; j++) if (adjMat[v][j] == 1 && vertexList[j].wasVisited == false && edge_weight[v][j] == 1){ //System.out.println("Vertex found with 1:"+ vertexList[j].label); return j; } for (int k = 0; k < nVerts; k++) if (adjMat[v][k] == 1 && vertexList[k].wasVisited == false && edge_weight[v][k] == 2){ //System.out.println("Vertex found with 2:"+vertexList[k].label); return k; } return -1; } // end getAdjUnvisitedVertex() // ------------------------------------------------------------- } //////////////////////////////////////////////////////////////// public class BFS{ public static void main(String[] args) { Graph theGraph = new Graph(); theGraph.addVertex('A'); // 0 (start for bfs) theGraph.addVertex('B'); // 1 theGraph.addVertex('C'); // 2 theGraph.addEdge(0, 1,2); // AB theGraph.addEdge(1, 2,1); // BC theGraph.addEdge(2, 0,1); // AD System.out.print("Visits: "); theGraph.bfs(); // breadth-first search System.out.println(); } // end main() } The problem then is, that I don't know why BFS can work for the shortest path problem with edges of weight 1 or 2 as opposed to any edges of any weight. Any help is appreciated. Thanks!

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  • Core Plot: x-axis labels not plotted when using scaleToFitPlots

    - by AlexR
    Problem: I can't get Core Plot (1.1) to plot automatic labels for my x-axis when using autoscaling ([plotSpace scaleToFitPlots:[graph allPlots]). What I have tried: I changed the values for the offsets and paddings, but this did not change the result. However, when turning autoscale off (not using [plotSpace scaleToFitPlots:[graph allPlots]]and setting the y scale automatically, the automatic labeling of the x-axis works. Question: Is there a bug in Core Plot or what did I do wrong? I would appreciate any help! Thank you! This is how I have set up my chart: CPTBarPlot *barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor blueColor] horizontalBars:NO]; barPlot.baseValue = CPTDecimalFromInt(0); barPlot.barOffset = CPTDecimalFromFloat(0.0f); // CPTDecimalFromFloat(0.5f); barPlot.barWidth = CPTDecimalFromFloat(0.4f); barPlot.barCornerRadius = 4; barPlot.labelOffset = 5; barPlot.dataSource = self; barPlot.delegate = self; graph = [[CPTXYGraph alloc]initWithFrame:self.view.bounds]; self.hostView.hostedGraph = graph; graph.paddingLeft = 40.0f; graph.paddingTop = 30.0f; graph.paddingRight = 30.0f; graph.paddingBottom = 50.0f; [graph addPlot:barPlot]; graph.plotAreaFrame.masksToBorder = NO; graph.plotAreaFrame.cornerRadius = 0.0f; graph.plotAreaFrame.borderLineStyle = borderLineStyle; double xAxisStart = 0; CPTXYAxisSet *xyAxisSet = (CPTXYAxisSet *)graph.axisSet; CPTXYAxis *xAxis = xyAxisSet.xAxis; CPTMutableLineStyle *lineStyle = [xAxis.axisLineStyle mutableCopy]; lineStyle.lineCap = kCGLineCapButt; xAxis.axisLineStyle = lineStyle; xAxis.majorTickLength = 10; xAxis.orthogonalCoordinateDecimal = CPTDecimalFromDouble(yAxisStart); xAxis.paddingBottom = 5; xyAxisSet.delegate = self; xAxis.delegate = self; xAxis.labelOffset = 0; xAxis.labelingPolicy = CPTAxisLabelingPolicyAutomatic; [plotSpace scaleToFitPlots:[graph allPlots]]; CPTMutablePlotRange *yRange = plotSpace.yRange.mutableCopy; [yRange expandRangeByFactor:CPTDecimalFromDouble(1.3)]; plotSpace.yRange = yRange; NSInteger xLength = CPTDecimalIntegerValue(plotSpace.xRange.length) + 1; plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(xAxisStart) length:CPTDecimalFromDouble(xLength)] ;

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  • Binary serialization/de-serialization in C++ and C#

    - by 6pack kid
    Hello. I am working on a distributed application which has two components. One is written in standard C++ (not managed C++) and the other one is written in C#. Both are communicating via a message bus. I have a situation in which I need to pass objects from C++ to C# application and for this I need to serialize those objects in C++ and de-serialize them in C# (something like marshaling/un-marshaling in .NET). I need to perform this serialization in binary and not in XML (due to performance reasons). I have used Boost.Serialization to do this when both ends were implemented in C++ but now that I have a .NET application on one end, Boost.Serialization is not a viable solution. I am looking for a solution that allows me to perform (de)serialization across C++ and .NET boundary i.e., cross platform binary serialization. I know I can implement the (de)serialization code in a C++ dll and use P/Invoke in the .NET application, but I want to keep that as a last resort. Also, I want to know if I use some standard like gzip, will that be efficient? Are there any other alternatives to gzip? What are the pros/cons of them? Thanks

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  • Looking to reimplement build toolchain from bash/grep/sed/awk/(auto)make/configure to something more

    - by wash
    I currently maintain a few boxes that house a loosely related cornucopia of coding projects, databases and repositories (ranging from a homebrew *nix distro to my class notes), maintained by myself and a few equally pasty-skinned nerdy friends (all of said cornucopia is stored in SVN). The vast majority of our code is in C/C++/assembly (a few utilities are in python/perl/php, we're not big java fans), compiled in gcc. Our build toolchain typically consists of a hodgepodge of make, bash, grep, sed and awk. Recent discovery of a Makefile nearly as long as the program it builds (as well as everyone's general anxiety with my cryptic sed and awking) has motivated me to seek a less painful build system. Currently, the strongest candidate I've come across is Boost Build/Bjam as a replacement for GNU make and python as a replacement for our build-related bash scripts. Are there any other C/C++/asm build systems out there worth looking into? I've browsed through a number of make alternatives, but I haven't found any that are developed by names I know aside from Boost's. (I should note that an ability to easily extract information from svn commandline tools such as svnversion is important, as well as enough flexibility to configure for builds of asm projects as easily as c/c++ projects)

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  • C++ meta-splat function

    - by aaa
    hello. Is there an existing function (in boost mpl or fusion) to splat meta-vector to variadic template arguments? for example: splat<vector<T1, T2, ...>, function>::type same as function<T1, T2, ...> my search have not found one, and I do not want to reinvent one if it already exists. edit: after some tinkering, apparently it's next to impossible to accomplish this in general way, as it would require declaring full template template parameter list for all possible cases. only reasonable solution is to use macro: #define splat(name, function) \ template<class T, ...> struct name; \ template<class T> \ struct name<T,typename boost::enable_if_c< \ result_of::size<T>::value == 1>::type> { \ typedef function< \ typename result_of::value_at_c<T,0>::type \ > type; \ }; Oh well. thank you

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  • How to handle 'this' pointer in constructor?

    - by Kyle
    I have objects which create other child objects within their constructors, passing 'this' so the child can save a pointer back to its parent. I use boost::shared_ptr extensively in my programming as a safer alternative to std::auto_ptr or raw pointers. So the child would have code such as shared_ptr<Parent>, and boost provides the shared_from_this() method which the parent can give to the child. My problem is that shared_from_this() cannot be used in a constructor, which isn't really a crime because 'this' should not be used in a constructor anyways unless you know what you're doing and don't mind the limitations. Google's C++ Style Guide states that constructors should merely set member variables to their initial values. Any complex initialization should go in an explicit Init() method. This solves the 'this-in-constructor' problem as well as a few others as well. What bothers me is that people using your code now must remember to call Init() every time they construct one of your objects. The only way I can think of to enforce this is by having an assertion that Init() has already been called at the top of every member function, but this is tedious to write and cumbersome to execute. Are there any idioms out there that solve this problem at any step along the way?

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  • A generic C++ library that provides QtConcurrent functionality?

    - by Lucas
    QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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  • C++ variable to const expression

    - by user1344784
    template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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