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• JTable Delete All Rows Exception

  - by Dimitri

  Hi, I'm trying to delete all entrys from my abstractTableModel. As long as I don't delete the last remaining row, everything works fine, but as soon as I delete this one, I get an ArrayOutOfBoundsException. I'm using a DefaultRowSorter and this seems to be the Exception. Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0 at java.util.Vector.get(Vector.java:694) at graphics.tableModel.MyTableModel.getValueAt(MyTableModel.java:78) at graphics.tableModel.MyTableModel.getColumnClass(MyTableModel.java:90) at javax.swing.table.TableRowSorter.useToString(TableRowSorter.java:224) at javax.swing.DefaultRowSorter.updateUseToString(DefaultRowSorter.java:607) at javax.swing.DefaultRowSorter.sort(DefaultRowSorter.java:556) at javax.swing.DefaultRowSorter.shouldOptimizeChange(DefaultRowSorter.java:1008) at javax.swing.DefaultRowSorter.rowsDeleted(DefaultRowSorter.java:866) at javax.swing.JTable.notifySorter(JTable.java:4262) at javax.swing.JTable.sortedTableChanged(JTable.java:4106) at javax.swing.JTable.tableChanged(JTable.java:4383) at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableModel.java:280) my Code to delete all Rows: public void deleteAll() { int size = data.size()-1; data.clear(); this.fireTableRowsDeleted(0, size); } Same thing happens with simply deleting the last existing row. public void deleteRow(int row) { data.remove(row); } the way i'm calling deleteRow: for (int i = rows.length - 1; i >=0; i--) { tm.deleteRow(rows[i]); } tm.fireTableDataChanged(); thanks for your help

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• Looking for ideas how to refactor my (complex) algorithm

  - by _simon_

  I am trying to write my own Game of Life, with my own set of rules. First 'concept', which I would like to apply, is socialization (which basicaly means if the cell wants to be alone or in a group with other cells). Data structure is 2-dimensional array (for now). In order to be able to move a cell to/away from a group of another cells, I need to determine where to move it. The idea is, that I evaluate all the cells in the area (neighbours) and get a vector, which tells me where to move the cell. Size of the vector is 0 or 1 (don't move or move) and the angle is array of directions (up, down, right, left). This is a image with representation of forces to a cell, like I imagined it (but reach could be more than 5): Let's for example take this picture: Forces from lower left neighbour: down (0), up (2), right (2), left (0) Forces from right neighbour : down (0), up (0), right (0), left (2) sum : down (0), up (2), right (0), left (0) So the cell should go up. I could write an algorithm with a lot of if statements and check all cells in the neighbourhood. Of course this algorithm would be easiest if the 'reach' parameter is set to 1 (first column on picture 1). But what if I change reach parameter to 10 for example? I would need to write an algorithm for each 'reach' parameter in advance... How can I avoid this (notice, that the force is growing potentialy (1, 2, 4, 8, 16, 32,...))? Can I use specific design pattern for this problem? Also: the most important thing is not speed, but to be able to extend initial logic. Things to take into consideration: reach should be passed as a parameter i would like to change function, which calculates force (potential, fibonacci) a cell can go to a new place only if this new place is not populated watch for corners (you can't evaluate right and top neighbours in top-right corner for example)

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• Correlating traditional Windows joystick axes with HID

  - by Wade Williams

  I'm a bit confused on the description of joystick axes and I'm hoping that someone has a link or document which could help clear my confusion. I'm not a Windows guy, so trying to port some traditional Windows gameport code has me a bit confused. We all know about the common first three axes: X Y Z My understanding was that in the gameport-style interface the three other axes are: R U V However, looking in my IOHIDUsageTables (OS X), I see: kHIDUsage_GD_X = 0x30, /* Dynamic Value */ kHIDUsage_GD_Y = 0x31, /* Dynamic Value */ kHIDUsage_GD_Z = 0x32, /* Dynamic Value */ kHIDUsage_GD_Rx = 0x33, /* Dynamic Value */ kHIDUsage_GD_Ry = 0x34, /* Dynamic Value */ kHIDUsage_GD_Rz = 0x35, /* Dynamic Value */ kHIDUsage_GD_Vx = 0x40, /* Dynamic Value */ kHIDUsage_GD_Vy = 0x41, /* Dynamic Value */ kHIDUsage_GD_Vz = 0x42, /* Dynamic Value */ kHIDUsage_GD_Vbrx = 0x43, /* Dynamic Value */ kHIDUsage_GD_Vbry = 0x44, /* Dynamic Value */ kHIDUsage_GD_Vbrz = 0x45, /* Dynamic Value */ kHIDUsage_GD_Vno = 0x46, /* Dynamic Value */ This has me a bit confused due to the three R axis (though that does not appear to be uncommon) and the lack of a U axis. Two questions: 1) Can anyone confirm to what axis the traditional U axis would be? I saw one document describe it as "the axis for rudder pedals" leading me to believe it would be Rz. 2) Can anyone describe in more detail the typical usages of the V and Vbr axes? I understand the descriptions are "vector" and "relative vector,' respectively, but I'm having difficult visualizing what that means in terms of a physical device. All enlightenment and documentation pointers welcome.

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• Java SAX ContentHandler to create new objects for every root node

  - by behrk2

  Hello everyone, I am using SAX to parse some XML. Let's say I have the following XML document: <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> And I also have an Elements class: public static Elements { String element; public Elements() { } public void setElement(String element){ this.element = element; } public String getElement(){ return element; } } I am looking to write a ContentHandler that follows the following algorithm: Vector v; for every <queue> root node { Element element = new Element(); for every <element> child node{ element.setElement(value of current element); } v.addElement(element); } So, I want to create a bunch of Element objects and add each to a vector...with each Element object containing its own String values (from the child nodes found within the root nodes. I know how to parse out the elements and all of those details, but can someone show me a sample of how to structure my ContentHandler to allow for the above algorithm? Thanks!

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• Extract <name> attribute from KML

  - by Ozaki

  I am using OpenLayers for a mapping service. In which I have several KML layers that are using KML feeds from server to populate data on the map. It currently plots: images / points / vector lines & shapes. But on these points it will not add a label with the value of the for the placemark in the KML. What I have currently tried is: ////////////////////KML Feed for * Layer// var surveylinelayer = new OpenLayers.Layer.Vector("First KML Layer", { projection: new OpenLayers.Projection("EPSG:4326"), strategies: [new OpenLayers.Strategy.Fixed()], protocol: new OpenLayers.Protocol.HTTP({ url: firstKMLURL, format: new OpenLayers.Format.KML({ extractStyles: true, extractAttributes: true }) }), styleMap: new OpenLayers.StyleMap({ "default": KMLStyle }) }); then the Style as follows: var KMLStyle = new OpenLayers.Style({ //label: "${name}", // This method will display nothing fillOpacity: 1, pointRadius: 10, fontColor: "#7E3C1C", fontSize: "13px", fontFamily: "Courier New, monospace", fontWeight: "strong", labelXOffset: "0", labelYOffset: "-15" }, { //dynamic label context: { label: function(feature) { return "Feature Name: " + feature.attributes.name; // also displays nothing } } }); Example of the KML: <Placemark> <name>POI1</name> <Style> <LabelStyle> <color>ffffffff</color> </LabelStyle> </Style> <Point> <coordinates>0.000,0.000</coordinates> </Point> </Placemark> When debugging I just hit "feature is undefined" and am unsure why it would be undefined in this instance?

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• OpenCV: Shift/Align face image relative to reference Image (Image Registration)

  - by Abhischek

  I am new to OpenCV2 and working on a project in emotion recognition and would like to align a facial image in relation to a reference facial image. I would like to get the image translation working before moving to rotation. Current idea is to run a search within a limited range on both x and y coordinates and use the sum of squared differences as error metric to select the optimal x/y parameters to align the image. I'm using the OpenCV face_cascade function to detect the face images, all images are resized to a fixed (128x128). Question: Which parameters of the Mat image do I need to modify to shift the image in a positive/negative direction on both x and y axis? I believe setImageROI is no longer supported by Mat datatypes? I have the ROIs for both faces available however I am unsure how to use them. void alignImage(vector<Rect> faceROIstore, vector<Mat> faceIMGstore) { Mat refimg = faceIMGstore[1]; //reference image Mat dispimg = faceIMGstore[52]; // "displaced" version of reference image //Rect refROI = faceROIstore[1]; //Bounding box for face in reference image //Rect dispROI = faceROIstore[52]; //Bounding box for face in displaced image Mat aligned; matchTemplate(dispimg, refimg, aligned, CV_TM_SQDIFF_NORMED); imshow("Aligned image", aligned); } The idea for this approach is based on Image Alignment Tutorial by Richard Szeliski Working on Windows with OpenCV 2.4. Any suggestions are much appreciated.

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• So can unique_ptr be used safely in stl collections?

  - by DanDan

  I am confused with unique_ptr and rvalue move philosophy. Let's say we have two collections: std::vector<std::auto_ptr<int>> autoCollection; std::vector<std::unique_ptr<int>> uniqueCollection; Now I would expect the following to fail, as there is no telling what the algorithm is doing internally and maybe making internal pivot copies and the like, thus ripping away ownership from the auto_ptr: std::sort(autoCollection.begin(), autoCollection.end()); I get this. And the compiler rightly disallows this happening. But then I do this: std::sort(uniqueCollection.begin(), uniqueCollection.end()); And this compiles. And I do not understand why. I did not think unique_ptrs could be copied. Does this mean a pivot value cannot be taken, so the sort is less efficient? Or is this pivot actually a move, which in fact is as dangerous as the collection of auto_ptrs, and should be disallowed by the compiler? I think I am missing some crucial piece of information, so I eagerly await someone to supply me with the aha! moment.

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• boost lambda::bind return type selection

  - by psaghelyi

  I would like to call a member through lambda::bind. Unfortunately I have got to members with the same name but different return type. Is there a way to help the lambda::bind to deduce the right return type for a member function call? #include <vector> #include <iostream> #include <algorithm> #include <boost/bind.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> using namespace std; using namespace boost; struct A { A (const string & name) : m_name(name) {} string & name () { return m_name; } const string & name () const { return m_name; } string m_name; }; vector<A> av; int main () { av.push_back (A ("some name")); // compiles fine find_if(av.begin(), av.end(), bind<const string &>(&A::name, _1) == "some name"); // error: call of overloaded 'bind(<unresolved overloaded function type>, const boost::lambda::lambda_functor<boost::lambda::placeholder<1> >&)' is ambiguous find_if(av.begin(), av.end(), lambda::bind(&A::name, lambda::_1) == "some name"); return 0; }

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• Bluetooth connection. Problem with sony ericsson.

  - by Hugi

  I have bt client and server. Then i use method Connector.open, client connects to the port, but passed so that my server does not see them. Nokia for all normal, but with sony ericsson i have this problem. On bt adapter open one port (com 5). Listings Client /* * To change this template, choose Tools | Templates * and open the template in the editor. */ import java.util.Vector; import javax.bluetooth.*; import javax.microedition.midlet.*; import javax.microedition.lcdui.*; import javax.microedition.io.*; import java.io.*; /** * @author ????????????? */ public class Client extends MIDlet implements DiscoveryListener, CommandListener { private static Object lock=new Object(); private static Vector vecDevices=new Vector(); private ServiceRecord[] servRec = new ServiceRecord[INQUIRY_COMPLETED]; private Form form = new Form( "Search" ); private List voteList = new List( "Vote list", List.IMPLICIT ); private List vote = new List( "", List.EXCLUSIVE ); private RemoteDevice remoteDevice; private String connectionURL = null; protected int stopToken = 255; private Command select = null; public void startApp() { //view form Display.getDisplay(this).setCurrent(form); try { //device search print("Starting device inquiry..."); getAgent().startInquiry(DiscoveryAgent.GIAC, this); try { synchronized(lock){ lock.wait(); } }catch (InterruptedException e) { e.printStackTrace(); } //device count int deviceCount=vecDevices.size(); if(deviceCount <= 0) { print("No Devices Found ."); } else{ remoteDevice=(RemoteDevice)vecDevices.elementAt(0); print( "Server found" ); //create uuid UUID uuid = new UUID(0x1101); UUID uuids[] = new UUID[] { uuid }; //search service print( "Searching for service..." ); getAgent().searchServices(null,uuids,remoteDevice,this); } } catch( Exception e) { e.printStackTrace(); } } //if deivce discovered add to vecDevices public void deviceDiscovered(RemoteDevice btDevice, DeviceClass cod) { //add the device to the vector try { if(!vecDevices.contains(btDevice) && btDevice.getFriendlyName(true).equals("serverHugi")){ vecDevices.addElement(btDevice); } } catch( IOException e ) { } } public synchronized void servicesDiscovered(int transID, ServiceRecord[] servRecord) { //for each service create connection if( servRecord!=null && servRecord.length>0 ){ print( "Service found" ); connectionURL = servRecord[0].getConnectionURL(ServiceRecord.NOAUTHENTICATE_NOENCRYPT,false); //connectionURL = servRecord[0].getConnectionURL(ServiceRecord.AUTHENTICATE_NOENCRYPT,false); } if ( connectionURL != null ) { showVoteList(); } } public void serviceSearchCompleted(int transID, int respCode) { //print( "serviceSearchCompleted" ); synchronized(lock){ lock.notify(); } } //This callback method will be called when the device discovery is completed. public void inquiryCompleted(int discType) { synchronized(lock){ lock.notify(); } switch (discType) { case DiscoveryListener.INQUIRY_COMPLETED : print("INQUIRY_COMPLETED"); break; case DiscoveryListener.INQUIRY_TERMINATED : print("INQUIRY_TERMINATED"); break; case DiscoveryListener.INQUIRY_ERROR : print("INQUIRY_ERROR"); break; default : print("Unknown Response Code"); break; } } //add message at form public void print( String msg ) { form.append( msg ); form.append( "\n\n" ); } public void pauseApp() { } public void destroyApp(boolean unconditional) { } //get agent :))) private DiscoveryAgent getAgent() { try { return LocalDevice.getLocalDevice().getDiscoveryAgent(); } catch (BluetoothStateException e) { throw new Error(e.getMessage()); } } private synchronized String getMessage( final String send ) { StreamConnection stream = null; DataInputStream in = null; DataOutputStream out = null; String r = null; try { //open connection stream = (StreamConnection) Connector.open(connectionURL); in = stream.openDataInputStream(); out = stream.openDataOutputStream(); out.writeUTF( send ); out.flush(); r = in.readUTF(); print( r ); in.close(); out.close(); stream.close(); return r; } catch (IOException e) { } finally { if (stream != null) { try { stream.close(); } catch (IOException e) { } } return r; } } private synchronized void showVoteList() { String votes = getMessage( "c_getVotes" ); voteList.append( votes, null ); select = new Command( "Select", Command.OK, 4 ); voteList.addCommand( select ); voteList.setCommandListener( this ); Display.getDisplay(this).setCurrent(voteList); } private synchronized void showVote( int index ) { String title = getMessage( "c_getVote_"+index ); vote.setTitle( title ); vote.append( "Yes", null ); vote.append( "No", null ); vote.setCommandListener( this ); Display.getDisplay(this).setCurrent(vote); } public void commandAction( Command c, Displayable d ) { if ( c == select && d == voteList ) { int index = voteList.getSelectedIndex(); print( ""+index ); showVote( index ); } } } Use BlueCove in this program. Server /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package javaapplication4; import java.io.*; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import javax.bluetooth.*; import javax.microedition.io.*; import javaapplication4.Connect; /** * * @author ????????????? */ public class SampleSPPServer { protected static int endToken = 255; private static Lock lock=new ReentrantLock(); private static StreamConnection conn = null; private static StreamConnectionNotifier streamConnNotifier = null; private void startServer() throws IOException{ //Create a UUID for SPP UUID uuid = new UUID("1101", true); //Create the service url String connectionString = "btspp://localhost:" + uuid +";name=Sample SPP Server"; //open server url StreamConnectionNotifier streamConnNotifier = (StreamConnectionNotifier)Connector.open( connectionString ); while ( true ) { Connect ct = new Connect( streamConnNotifier.acceptAndOpen() ); ct.getMessage(); } } /** * @param args the command line arguments */ public static void main(String[] args) { //display local device address and name try { LocalDevice localDevice = LocalDevice.getLocalDevice(); localDevice.setDiscoverable(DiscoveryAgent.GIAC); System.out.println("Name: "+localDevice.getFriendlyName()); } catch( Throwable e ) { e.printStackTrace(); } SampleSPPServer sampleSPPServer=new SampleSPPServer(); try { //start server sampleSPPServer.startServer(); } catch( IOException e ) { e.printStackTrace(); } } } Connect /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package javaapplication4; import java.io.*; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import javax.bluetooth.*; import javax.microedition.io.*; /** * * @author ????????????? */ public class Connect { private static DataInputStream in = null; private static DataOutputStream out = null; private static StreamConnection connection = null; private static Lock lock=new ReentrantLock(); public Connect( StreamConnection conn ) { connection = conn; } public synchronized void getMessage( ) { Thread t = new Thread() { public void run() { try { in = connection.openDataInputStream(); out = connection.openDataOutputStream(); String r = in.readUTF(); System.out.println("read:" + r); if ( r.equals( "c_getVotes" ) ) { out.writeUTF( "vote1" ); out.flush(); } if ( r.equals( "c_getVote_0" ) ) { out.writeUTF( "Vote1" ); out.flush(); } out.close(); in.close(); } catch (Throwable e) { } finally { if (in != null) { try { in.close(); } catch (IOException e) { } } try { connection.close(); } catch( IOException e ) { } } } }; t.start(); } }

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• Updating / refreshing a geojson layer

  - by Ozaki

  TLDR My geoJSON layer will display the vector mark but will not destroy the features or re add the features in causing a moving / updating look to the OpenLayers map. Hey S O. I have a geojson layer set up as follows: //GeoJSON Layer// var layer1 = new OpenLayers.Layer.GML("My GeoJSON Layer", "coordinates", {format: OpenLayers.Format.GeoJSON, styleMap: style_red}); My features are set up as follows: var f = new OpenLayers.Feature.Vector(null,style_red); var style_red = OpenLayers.Util.extend({}, layer_style); style_red.strokeColor = "red"; style_red.fillColor = "black"; style_red.fillOpacity = 0.5; style_red.graphicName = "circle"; style_red.pointRadius = 3.8; style_red.strokeWidth = 2; style_red.strokeLinecap = "butt"; and my layer updating function: function UpdateLayer(){ var p = new OpenLayers.Format.GeoJSON({ 'internalProjection': new OpenLayers.Projection("EPSG:900913"), 'externalProjection': new OpenLayers.Projection("EPSG:4326") }); var url = "coordinates.geojson"; OpenLayers.loadURL(url, {}, null, function(r) { var f = p.read(r.responseText); map.layers[1].destroyFeatures(); map.layers[1].addFeatures(f); }); setTimeout("UpdateLayer()",1000) } Any idea what I am doing wrong or what I am missing?

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• Overlay only draws between first 2 points in Android

  - by LordSnoutimus

  Hi, I am experiencing an unusual error using ItemizedOverlay in Android. I am creating a GPS tracking device that plots a route between waypoints stored in a database. When I provide the first two sets of longitude and latitude points through the emulator in Eclipse, it draws a red line just how I want it, but if I send another GPS point, it animates to the point, but does not draw a line from the last point. public class MyOverlay extends ItemizedOverlay { // private Projection projection; private Paint linePaint; private Vector points; public MyOverlay(Drawable defaultMarker) { super(defaultMarker); points = new Vector<GeoPoint>(); //set colour, stroke width etc. linePaint = new Paint(); linePaint.setARGB(255, 255, 0, 0); linePaint.setStrokeWidth(3); linePaint.setDither(true); linePaint.setStyle(Style.FILL); linePaint.setAntiAlias(true); linePaint.setStrokeJoin(Paint.Join.ROUND); linePaint.setStrokeCap(Paint.Cap.ROUND); } public void addPoint(GeoPoint point) { points.addElement(point); } public void draw(Canvas canvas, MapView view, boolean shadow) { int size = points.size(); Point lastPoint = new Point(); if(size == 0) return; view.getProjection().toPixels(points.get(0), lastPoint); Point point = new Point(); for(int i = 1; i<size; i++){ view.getProjection().toPixels(points.get(i), point); canvas.drawLine(lastPoint.x, lastPoint.y, point.x, point.y, linePaint); lastPoint = point; } } @Override protected OverlayItem createItem(int arg0) { // TODO Auto-generated method stub return null; } @Override public int size() { // TODO Auto-generated method stub return 0; } }

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• Trying to use boost lambda, but my code won't compile

  - by hamishmcn

  Hi, I am trying to use boost lambda to avoid having to write trivial functors. For example, I want to use the lambda to access a member of a struct or call a method of a class, eg: #include <vector> #include <utility> #include <algorithm> #include <boost/lambda/lambda.hpp> using namespace std; using namespace boost::lambda; vector< pair<int,int> > vp; vp.push_back( make_pair<int,int>(1,1) ); vp.push_back( make_pair<int,int>(3,2) ); vp.push_back( make_pair<int,int>(2,3) ); sort(vp.begin(), vp.end(), _1.first > _2.first ); When I try and compile this I get the following errors: error C2039: 'first' : is not a member of 'boost::lambda::lambda_functor<T>' with [ T=boost::lambda::placeholder<1> ] error C2039: 'first' : is not a member of 'boost::lambda::lambda_functor<T>' with [ T=boost::lambda::placeholder<2> ] Since vp contains pair<int,int> I thought that _1.first should work. What I am doing wrong?

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• Using boost::random as the RNG for std::random_shuffle

  - by Greg Rogers

  I have a program that uses the mt19937 random number generator from boost::random. I need to do a random_shuffle and want the random numbers generated for this to be from this shared state so that they can be deterministic with respect to the mersenne twister's previously generated numbers. I tried something like this: void foo(std::vector<unsigned> &vec, boost::mt19937 &state) { struct bar { boost::mt19937 &_state; unsigned operator()(unsigned i) { boost::uniform_int<> rng(0, i - 1); return rng(_state); } bar(boost::mt19937 &state) : _state(state) {} } rand(state); std::random_shuffle(vec.begin(), vec.end(), rand); } But i get a template error calling random_shuffle with rand. However this works: unsigned bar(unsigned i) { boost::mt19937 no_state; boost::uniform_int<> rng(0, i - 1); return rng(no_state); } void foo(std::vector<unsigned> &vec, boost::mt19937 &state) { std::random_shuffle(vec.begin(), vec.end(), bar); } Probably because it is an actual function call. But obviously this doesn't keep the state from the original mersenne twister. What gives? Is there any way to do what I'm trying to do without global variables?

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• Varying performance of MSVC release exe

  - by Andrew

  Hello everyone, I am curious what could be the reason for highly varying performance of the same executable. Sometimes, I run it and it takes 20 seconds and sometimes it is 110. Source is compiled with MSVC in Release mode with standard options. The code is here: vector<double> Un; vector<double> Ucur; double *pUn, *pUcur; ... // time marching for (old_time=time-logfreq, time+=dt; time <= end_time; time+=dt) { for (i=1, j=Un.size()-1, pUn=&Un[1], pUcur=&Ucur[1]; i < j; ++i, ++pUn, ++pUcur) { *pUcur = (*pUn)*(1.0-0.5*alpha*( *(pUn+1) - *(pUn-1) )); } Ucur[0] = (Un[0])*(1.0-0.5*alpha*( Un[1] - Un[j] )); Ucur[j] = (Un[j])*(1.0-0.5*alpha*( Un[0] - Un[j-1] )); Un = Ucur; }

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• How to have a policy class implement a virtual function?

  - by dehmann

  I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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• How to perform spatial partitioning in n-dimensions?

  - by kevin42

  I'm trying to design an implementation of Vector Quantization as a c++ template class that can handle different types and dimensions of vectors (e.g. 16 dimension vectors of bytes, or 4d vectors of doubles, etc). I've been reading up on the algorithms, and I understand most of it: here and here I want to implement the Linde-Buzo-Gray (LBG) Algorithm, but I'm having difficulty figuring out the general algorithm for partitioning the clusters. I think I need to define a plane (hyperplane?) that splits the vectors in a cluster so there is an equal number on each side of the plane. [edit to add more info] This is an iterative process, but I think I start by finding the centroid of all the vectors, then use that centroid to define the splitting plane, get the centroid of each of the sides of the plane, continuing until I have the number of clusters needed for the VQ algorithm (iterating to optimize for less distortion along the way). The animation in the first link above shows it nicely. My questions are: What is an algorithm to find the plane once I have the centroid? How can I test a vector to see if it is on either side of that plane?

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• How to parse out base file name using Script-Fu

  - by ongle

  Using Gimp 2.6.6 for MAC OS X (under X11) as downloaded from gimp.org. I'm trying to automate a boring manual process with Script-Fu. I needed to parse the image file name to save off various layers as new files using a suffix on the original file name. My original attempts went like this but failed because (string-search ...) doesn't seem to be available under 2.6 (a change to the scripting engine?). (set! basefilename (substring filename 0 (string-search "." filename))) Then I tried to use this information to parse out the base file name using regex but (re-match-nth ...) is not recognized either. (if (re-match "^(.*)[.]([^.]+)$" filename buffer) (set! basefilename (re-match-nth orig-name buffer 1)) ) And while pulling the value out of the vector ran without error, the resulting value is not considered a string when it is passed into (string-append ...). (if (re-match "^(.*)[.]([^.]+)$" filename buffer) (set! basefilename (vector-ref buffer 1)) ) So I guess my question is, how would I parse out the base file name?

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• C++ classes with members referencing each other

  - by Saad Imran.

  I'm trying to write 2 classes with members that reference each other. I'm not sure if I'm doing something wrong or it's just not possible. Can anyone help me out here... Source.cpp #include "Headers.h" using namespace std; void main() { Network* network = new Network(); system("pause"); return; } Headers.h #ifndef Headers_h #define Headers_h #include <iostream> #include <vector> #include "Network.h" #include "Router.h" #endif Network.h #include "Headers.h" class Network { protected: vector<Router> Routers; }; Router.h #include "Headers.h" class Router { protected: Network* network; public: }; The errors I'm getting are: error C2143: syntax error : missing ';' before '<' error C2238: unexpected token(s) preceding ';' error C4430: missing type specifier - int assumed. I'm pretty sure I'm not missing any semicolons or stuff like that. The program works find if I take out one of the members. I tried finding similar questions and the solution was to use pointers, but that's what I'm doing and it does't seem to be working!

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• Help with java executors: wait for task termination.

  - by Raffo

  I need to submit a number of task and then wait for them until all results are available. Each of them adds a String to a Vector (that is synchronized by default). Then I need to start a new task for each result in the Vector but I need to do this only when all the previous tasks have stopped doing their job. I want to use Java Executor, in particular I tried using Executors.newFixedThreadPool(100) in order to use a fixed number of thread (I have a variable number of task that can be 10 or 500) but I'm new with executors and I don't know how to wait for task termination. This is something like a pseudocode of what my program needs to do: EecutorService e = Executors.newFixedThreadPool(100); while(true){ /*do something*/ for(...){ <start task> } <wait for all task termination> for each String in result{ <start task> } <wait for all task termination> } I can't do a e.shutdown because I'm in a while(true) and I need to reuse the executorService... Can you help me? Can you suggest me a guide/book about java executors??

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• Oracle doesn't remove cursors after closing result set

  - by Vladimir

  Note: we reuse single connection. ************************************************ public Connection connection() {                try {            if ((connection == null) || (connection.isClosed()))            {               if (connection!=null) log.severe("Connection was closed !");                connection = DriverManager.getConnection(jdbcURL, username, password);            }        } catch (SQLException e) {            log.severe("can't connect: " + e.getMessage());        }        return connection;            } ************************************************** public IngisObject[] select(String query, String idColumnName, String[] columns) { Connection con = connection(); Vector<IngisObject> objects = new Vector<IngisObject>(); try {     Statement stmt = con.createStatement();     String sql = query;     ResultSet rs =stmt.executeQuery(sql);//oracle increases cursors count here     while(rs.next()) {        IngisObject o = new IngisObject("New Result");        o.setIdColumnName(idColumnName);                    o.setDatabase(this);        for(String column: columns) o.attrs().put(column, rs.getObject(column));        objects.add(o);        }     rs.close();// oracle don't decrease cursor count here, while it's expected     stmt.close();     } catch (SQLException ex) {     System.out.println(query);     ex.printStackTrace(); }

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• Perceptron Classification and Model Training

  - by jake pinedo

  I'm having an issue with understanding how the Perceptron algorithm works and implementing it. cLabel = 0 #class label: corresponds directly with featureVectors and tweets for m in range(miters): for point in featureVectors: margin = answers[cLabel] * self.dot_product(point, w) if margin <= 0: modifier = float(lrate) * float(answers[cLabel]) modifiedPoint = point for x in modifiedPoint: if x != 0: x *= modifier newWeight = [modifiedPoint[i] + w[i] for i in range(len(w))] w = newWeight self._learnedWeight = w This is what I've implemented so far, where I have a list of class labels in answers and a learning rate (lrate) and a list of feature vectors. I run it for the numbers of iterations in miter and then get the final weight at the end. However, I'm not sure what to do with this weight. I've trained the perceptron and now I have to classify a set of tweets, but I don't know how to do that. EDIT: Specifically, what I do in my classify method is I go through and create a feature vector for the data I'm given, which isn't a problem at all, and then I take the self._learnedWeight that I get from the earlier training code and compute the dot-product of the vector and the weight. My weight and feature vectors include a bias in the 0th term of the list so I'm including that. I then check to see if the dotproduct is less than or equal to 0: if so, then I classify it as -1. Otherwise, it's 1. However, this doesn't seem to be working correctly.

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• A linked list with multiple heads in Java

  - by Emile

  Hi, I have a list in which I'd like to keep several head pointers. I've tried to create multiple ListIterators on the same list but this forbid me to add new elements in my list... (see Concurrent Modification exception). I could create my own class but I'd rather use a built-in implementation ;) To be more specific, here is an inefficient implementation of two basic operations and the one wich doesn't work : class MyList <E { private int[] _heads; private List<E _l; public MyList ( int nbHeads ) { _heads = new int[nbHeads]; _l = new LinkedList<E(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { return _l.get(_heads[head++]); // ugly } } class MyList <E { private Vector<ListIterator<E _iters; private List<E _l; public MyList ( int nbHeads ) { _iters = new Vector<ListIterator<E(nbHeads); _l = new LinkedList<E(); for( ListIterator<E iter : _iters ) iter = _l.listIterator(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { // ConcurrentModificationException because of the add() return _iters.get(head).next(); } } Emile

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• Project Euler Problem #11

  - by SoulBeaver

  Source: http://projecteuler.net/index.php?section=problems&id=11 Quick overview: Take a 20x20 grid of numbers and compute the largest product of 4 pairs of numbers in either horizontal, vertical, or diagonal. My current approach is to divide the 20x20 grid up into single rows and single columns and go from there with a much more manageable grid. The code I'm using to divide the rows into rows is void fillRows ( string::const_iterator& fieldIter, list<int>& rowElements, vector<list<int>>& rows ) { int count(0); for( ; fieldIter < field.end(); ++fieldIter ) { if(isdigit(field[*fieldIter])) { rowElements.push_back(toInt(field[*fieldIter])); ++count; } if(count == 40) { rows.push_back(rowElements); count = 0; rowElements.clear(); } } } Short explanation: I have the field set as static const std::string field and I am filling a vector with lists of rows. Why a list? Because the queue doesn't have a clear function. Also practice using STL container lists and not ones I write myself. However, this thing isn't working. Oftentimes I see it omitting a character( function toInt parses the const char as int ) and I end up with 18 rows, two rows short of the 20x20 grid. The length of the rows seem good. Rows: 18 RowElements[0]: 40 (instead of pairs I saved each number individually. Will fix that later) What am I doing wrong?

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• Why is creating a ring buffer shared by different processes so hard (in C++), what I am doing wrong?

  - by recipriversexclusion

  I am being especially dense about this but it seems I'm missing an important, basic point or something, since what I want to do should be common: I need to create a fixed-size ring buffer object from a manager process (Process M). This object has write() and read() methods to write/read from the buffer. The read/write methods will be called by independent processes (Process R and W) I have implemented the buffer, SharedBuffer<T&>, it allocates buffer slots in SHM using boost::interprocess and works perfectly within a single process. I have read the answers to this question and that one on SO, as well as asked my own, but I'm still in the dark about how to have different processes access methods from a common object. The Boost doc has an example of creating a vector in SHM, which is very similar to what I want, but I want to instantiate my own class. My current options are: Use placement new, as suggested by Charles B. to my question; however, he cautions that it's not a good idea to put non-POD objects in SHM. But my class needs the read/write methods, how can I handle those? Add an allocator to my class definition, e.g. have SharedBuffer<T&, Alloc> and proceed similarly to the vector example given in boost. This sounds really complicated. Change SharedBuffer to a POD class, i.e. get rid of all the methods. But then how to synchronize reading and writing between processes? What am I missing? Fixed-length ring buffers are very common, so either this problem has a solution or else I'm doing something wrong.

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• C++ Returning Multiple Items

  - by Travis Parks

  I am designing a class in C++ that extracts URLs from an HTML page. I am using Boost's Regex library to do the heavy lifting for me. I started designing a class and realized that I didn't want to tie down how the URLs are stored. One option would be to accept a std::vector<Url> by reference and just call push_back on it. I'd like to avoid forcing consumers of my class to use std::vector. So, I created a member template that took a destination iterator. It looks like this: template <typename TForwardIterator, typename TOutputIterator> TOutputIterator UrlExtractor::get_urls( TForwardIterator begin, TForwardIterator end, TOutputIterator dest); I feel like I am overcomplicating things. I like to write fairly generic code in C++, and I struggle to lock down my interfaces. But then I get into these predicaments where I am trying to templatize everything. At this point, someone reading the code doesn't realize that TForwardIterator is iterating over a std::string. In my particular situation, I am wondering if being this generic is a good thing. At what point do you start making code more explicit? Is there a standard approach to getting values out of a function generically?

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