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• Mouse wheel not scrolling in JDialog but working in JFrame

  - by Iulian Serbanoiu

  Hello, I'm facing a frustrating issue. I have an application where the scroll wheel doesn't work in a JDialog window (but works in a JFrame). Here's the code: import javax.swing.*; import java.awt.event.*; public class Failtest extends JFrame { public static void main(String[] args) { new Failtest(); } public Failtest() { super(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); setTitle("FRAME"); JScrollPane sp1 = new JScrollPane(getNewList()); add(sp1); setSize(150, 150); setVisible(true); JDialog d = new JDialog(this, false);// NOT WORKING //JDialog d = new JDialog((JFrame)null, false); // NOT WORKING //JDialog d = new JDialog((JDialog)null, false);// WORKING - WHY? d.setTitle("DIALOG"); d.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE); JScrollPane sp = new JScrollPane(getNewList()); d.add(sp); d.setSize(150, 150); d.setVisible(true); } public JList getNewList() { String objs[] = new String[30]; for(int i=0; i<objs.length; i++) { objs[i] = "Item "+i; } JList l = new JList(objs); return l; } } I found a solution which is present as a comment in the java code - the constructor receiving a (JDialog)null parameter. Can someone enlighten me? My opinion is that this is a java bug. Tested on Windows XP-SP3 with 1 JDK and 2 JREs: D:\Program Files\Java\jdk1.6.0_17\bin>javac -version javac 1.6.0_17 D:\Program Files\Java\jdk1.6.0_17\bin>java -version java version "1.6.0_17" Java(TM) SE Runtime Environment (build 1.6.0_17-b04) Java HotSpot(TM) Client VM (build 14.3-b01, mixed mode, sharing) D:\Program Files\Java\jdk1.6.0_17\bin>cd .. D:\Program Files\Java\jdk1.6.0_17>java -version java version "1.6.0_18" Java(TM) SE Runtime Environment (build 1.6.0_18-b07) Java HotSpot(TM) Client VM (build 16.0-b13, mixed mode, sharing) Thank you in advance, Iulian Serbanoiu PS: The problem is not new - the code is taken from a forum (here) where this problem was also mentioned - but no solutions to it (yet) LATER EDIT: The problem persists with jre/jdk_1.6.0_10, 1.6.0_16 also LATER EDIT 2: Back home, tested on linux (Ubuntu - lucid/lynx) - both with openjdk and sun-java from distribution repo and it works (I used the .class file compiled on Windows) !!! - so I believe I'm facing a JRE bug that happens on some Windows configurations.

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• Rx framework: How to wait for an event to be triggered in silverlight test

  - by user324255

  Hi, I have a ViewModel that starts loading the Model async in the constructor, and triggers an event when the Model is loaded. I got a test working with the silverlight unit test framework, like this : bool done = false; [TestMethod] [Asynchronous] public void Test_NoCustomerSelected() { ProjectListViewModel viewModel = null; EnqueueCallback(() => viewModel = new ProjectListViewModel()); EnqueueCallback(() => viewModel.ModelLoaded += new EventHandler<EventArgs>(viewModel_ModelLoaded)); EnqueueConditional(() => done); EnqueueCallback(() => Assert.IsNotNull(viewModel.FilteredProjectList)); EnqueueCallback(() => Assert.AreEqual(4, viewModel.FilteredProjectList.Count)); EnqueueTestComplete(); } void viewModel_ModelLoaded(object sender, EventArgs e) { done = true; } But I'm beginning playing with Rx Framework, and trying to get my test to work, but so far I have no luck. Here's 2 attempts : public void Test_NoCustomerSelected2() { ProjectListViewModel viewModel = null; viewModel = new ProjectListViewModel(eventAggregatorMock.Object, moduleManagerMock.Object); IObservable<IEvent<EventArgs>> eventAsObservable = Observable.FromEvent<EventArgs>( ev => viewModel.ModelLoaded += ev, ev => viewModel.ModelLoaded -= ev); eventAsObservable.Subscribe(args => viewModel_ModelLoaded(args.Sender, args.EventArgs)); eventAsObservable.First(); Assert.IsNotNull(viewModel.Model); Assert.AreEqual(4, viewModel.Model.Count); } [TestMethod] public void Test_NoCustomerSelected3() { ProjectListViewModel viewModel = null; var o = Observable.Start(() => viewModel = new ProjectListViewModel(eventAggregatorMock.Object, moduleManagerMock.Object)); IObservable<IEvent<EventArgs>> eventAsObservable = Observable.FromEvent<EventArgs>( ev => viewModel.ModelLoaded += ev, ev => viewModel.ModelLoaded -= ev); o.TakeUntil(eventAsObservable) .First(); Assert.IsNotNull(viewModel.Model); Assert.AreEqual(4, viewModel.Model.Count); } The first test goes in waiting forever, the second doesn't work because the viewModel is null when it does the FromEvent. Anyone has a clue on how to do this properly?

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• Getting XText to work

  - by Calmarius

  I know you don't like helping others in their homework but I have to make an XText grammar, write a sample code that matches this grammar and compile it to a html file. The lecturer showed us the steps and everything worked for him... He said "It's so simple it will be a 10 minute work for you". And I believed that. However at home almost nothing works as expected. And of course no more lectures to go only the exam avaits me where I have to show what I done to pass. Moreover the e-mail I sent him bounced back by the mailer-demon... I got Xtext along with Eclipse IDE from the xtext website and I unpacked it and I followed the steps in the official tuturial to get the default project template to work. The tutorial is found here: http://wiki.eclipse.org/Xtext/GettingStarted Now I'm at the step "Model". It says open the "MyModel.mydsl" I do that but the editor does not opened. It said: "Could not open the editor: The editor class could not be instantiated. This usually indicates a missing no-arg constructor or that the editor's class name was mistyped in plugin.xml." Since everything is generated, the error message does not helped me... There was an option to look at the stack trace (it was mile long) and on the top of it there was an exception: java.lang.IllegalStateException: The bundle has not yet been activated. Make sure the Manifest.MF contains 'Bundle-ActivationPolicy: lazy'. I opened Manifast.MF and Bundle-ActivationPolicy: lazy was set... I googled for the solution but no avail. It drove me nuts and I gave up. I have no experience with Eclipse and Java and XText, I just want to do my homework and forget everything until I will need it again... Anyone have experience with XText? Any help appreciated. ps: I will be on it too and I might resolve the problem in several hours. But now I am at a loss.

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• How to improve the builder pattern?

  - by tangens

  Motivation Recently I searched for a way to initialize a complex object without passing a lot of parameter to the constructor. I tried it with the builder pattern, but I don't like the fact, that I'm not able to check at compile time if I really set all needed values. Traditional builder pattern When I use the builder pattern to create my Complex object, the creation is more "typesafe", because it's easier to see what an argument is used for: new ComplexBuilder() .setFirst( "first" ) .setSecond( "second" ) .setThird( "third" ) ... .build(); But now I have the problem, that I can easily miss an important parameter. I can check for it inside the build() method, but that is only at runtime. At compile time there is nothing that warns me, if I missed something. Enhanced builder pattern Now my idea was to create a builder, that "reminds" me if I missed a needed parameter. My first try looks like this: public class Complex { private String m_first; private String m_second; private String m_third; private Complex() {} public static class ComplexBuilder { private Complex m_complex; public ComplexBuilder() { m_complex = new Complex(); } public Builder2 setFirst( String first ) { m_complex.m_first = first; return new Builder2(); } public class Builder2 { private Builder2() {} Builder3 setSecond( String second ) { m_complex.m_second = second; return new Builder3(); } } public class Builder3 { private Builder3() {} Builder4 setThird( String third ) { m_complex.m_third = third; return new Builder4(); } } public class Builder4 { private Builder4() {} Complex build() { return m_complex; } } } } As you can see, each setter of the builder class returns a different internal builder class. Each internal builder class provides exactly one setter method and the last one provides only a build() method. Now the construction of an object again looks like this: new ComplexBuilder() .setFirst( "first" ) .setSecond( "second" ) .setThird( "third" ) .build(); ...but there is no way to forget a needed parameter. The compiler wouldn't accept it. Optional parameters If I had optional parameters, I would use the last internal builder class Builder4 to set them like a "traditional" builder does, returning itself. Questions Is this a well known pattern? Does it have a special name? Do you see any pitfalls? Do you have any ideas to improve the implementation - in the sense of fewer lines of code?

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• Reflection to access advanced telephony features

  - by Tyler

  I am trying to use reflection to access some advanced features of the telephony api not published. Currently I am having trouble instantiating a serviceManager object that is needed to get the "phone" service as a binder which I can then use to instantiate a telephony object which is needed to make a call, end call, etc... currently when I make the call serviceManagerObject = tempInterfaceMethod.invoke(null, new Object[] { new Binder() }); it returns a nullPointerException. I believe this has to due with creating a new Binder instead of sending the appropriate binder (which I am unsure of which one is appropriate) public void placeReflectedCall() throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, InstantiationException { String serviceManagerName = "android.os.IServiceManager"; String serviceManagerNativeName = "android.os.ServiceManagerNative"; String telephonyName = "com.android.internal.telephony.ITelephony"; Class telephonyClass; Class telephonyStubClass; Class serviceManagerClass; Class serviceManagerStubClass; Class serviceManagerNativeClass; Class serviceManagerNativeStubClass; Method telephonyCall; Method telephonyEndCall; Method telephonyAnswerCall; Method getDefault; Method[] temps; Constructor[] serviceManagerConstructor; // Method getService; Object telephonyObject; Object serviceManagerObject; String number = "1111111111"; telephonyClass = Class.forName(telephonyName); telephonyStubClass = telephonyClass.getClasses()[0]; serviceManagerClass = Class.forName(serviceManagerName); serviceManagerNativeClass = Class.forName(serviceManagerNativeName); Method getService = // getDefaults[29]; serviceManagerClass.getMethod("getService", String.class); Method tempInterfaceMethod = serviceManagerNativeClass.getMethod( "asInterface", IBinder.class); // this does not work serviceManagerObject = tempInterfaceMethod.invoke(null, new Object[] { new Binder() }); IBinder retbinder = (IBinder) getService.invoke(serviceManagerObject, "phone"); Method serviceMethod = telephonyStubClass.getMethod("asInterface", IBinder.class); telephonyObject = serviceMethod .invoke(null, new Object[] { retbinder }); telephonyCall = telephonyClass.getMethod("call", String.class); telephonyEndCall = telephonyClass.getMethod("endCall"); telephonyAnswerCall = telephonyClass.getMethod("answerRingingCall"); telephonyCall.invoke(telephonyObject, number); } Thanks in advance for any answers.

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• Gridview get image from JSON using AsyncTask

  - by kongkea

  This project I've done with image in my drawable but now I want to get image url from JSON by using Asynctask and display it. and I make php that provide a json string like below. I want to get path of image(url) by using AsyncTask from JSON. I want to use data from json instead of public mThumbId = {...}; {"count":"28","data": [{"id":"1", "first_name":"man", "last_name":"woman", "username":"man", "password":"4f70432e636970de9929bcc6f1b72412", "email":"[email protected]", "url":"http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Images/MSH64_aerial_view_st_helens_from_NE_09-64_med.jpg"}, {"id":"2", "first_name":"first", "last_name":"Last Name", "username":"user", "password":"1a1dc91c907325c69271ddf0c944bc72", "email":"[email protected]", "url":"http://www.danheller.com/images/California/Marin/Scenics/bird-view-big.jpg"}, {"id":"3", "first_name":"first", "last_name":"Last Name", "username":"user", "password":"1a1dc91c907325c69271ddf0c944bc72", "email":"0", "url":"http://www.hermes.net.au/bodhi/images/view/large/view_03.jpg"}]} AndroidGridLayoutActivity GridView gridView = (GridView) findViewById(R.id.grid_view); gridView.setAdapter(new ImageAdapter(this)); gridView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View v, int position, long id) { Intent i = new Intent(getApplicationContext(), FullImageActivity.class); i.putExtra("id", position); startActivity(i); } }); ImageAdapter public class ImageAdapter extends BaseAdapter { private Context mContext; // Keep all Images in array public Integer[] mThumbIds = { R.drawable.pic_1, R.drawable.pic_2, R.drawable.pic_3, R.drawable.pic_4, R.drawable.pic_5, R.drawable.pic_6, R.drawable.pic_7, R.drawable.pic_8, R.drawable.pic_9, R.drawable.pic_10, R.drawable.pic_11, R.drawable.pic_12, R.drawable.pic_13, R.drawable.pic_14, R.drawable.pic_15 }; // Constructor public ImageAdapter(Context c){ mContext = c; } public int getCount() { return mThumbIds.length; } public Object getItem(int position) { return mThumbIds[position]; } public long getItemId(int position) { return 0; } public View getView(int position, View convertView, ViewGroup parent) { ImageView imageView = new ImageView(mContext); imageView.setImageResource(mThumbIds[position]); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); imageView.setLayoutParams(new GridView.LayoutParams(70, 70)); return imageView; } } FullImageActivity Intent i = getIntent(); int position = i.getExtras().getInt("id"); ImageAdapter imageAdapter = new ImageAdapter(this); ImageView imageView = (ImageView) findViewById(R.id.full_image_view); imageView.setImageResource(imageAdapter.mThumbIds[position]);

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• jQuery Datatables and ColumnFilterWidget integration issue

  - by user3520135

  I am trying to Place the ColumnFilterWidget plugin in the Header of the Datatables Table. Here are the changes i made in it : /** * Menu-based filter widgets based on distinct column values for a table. * * @class ColumnFilterWidgets * @constructor * @param {object} oDataTableSettings Settings for the target table. */ var ColumnFilterWidgets = function( oDataTableSettings ) { var me = this; var sExcludeList = ''; // me.$WidgetContainer = $( '<div class="column-filter-widgets"></div>' ); me.$WidgetContainer = $( '<tr class="head"></tr>' ); me.$MenuContainer = me.$WidgetContainer; me.$TermContainer = null; me.aoWidgets = []; me.sSeparator = ''; if ( 'oColumnFilterWidgets' in oDataTableSettings.oInit ) { if ( 'aiExclude' in oDataTableSettings.oInit.oColumnFilterWidgets ) { sExcludeList = '|' + oDataTableSettings.oInit.oColumnFilterWidgets.aiExclude.join( '|' ) + '|'; } if ( 'bGroupTerms' in oDataTableSettings.oInit.oColumnFilterWidgets && oDataTableSettings.oInit.oColumnFilterWidgets.bGroupTerms ) { me.$MenuContainer = $( '<div class="column-filter-widget-menus"></div>' ); me.$TermContainer = $( '<div class="column-filter-widget-selected-terms"></div>' ).hide(); } } // Add a widget for each visible and filtered column $.each( oDataTableSettings.aoColumns, function ( i, oColumn ) { var $columnTh = $( oColumn.nTh ); var $WidgetElem = $( '<th><div class="column-filter-widget"></div></th>' ); if ( oColumn.bVisible && sExcludeList.indexOf( '|' + i + '|' ) < 0 ) { me.aoWidgets.push( new ColumnFilterWidget( $WidgetElem, oDataTableSettings, i, me ) ); } me.$MenuContainer.append( $WidgetElem ); } ); if ( me.$TermContainer ) { me.$WidgetContainer.append( me.$MenuContainer ); me.$WidgetContainer.append( me.$TermContainer ); } oDataTableSettings.aoDrawCallback.push( { name: 'ColumnFilterWidgets', fn: function() { $.each( me.aoWidgets, function( i, oWidget ) { oWidget.fnDraw(); } ); } } ); return me; }; I added a extra <tr class='head'> inside the Datatable, and later on i am trying to append the Filters to that with attached to them,But instead of that it is creating new TR tag and then appending the filters in it. I even changed my dom of data tables to : dom: '<"clear">Cf<"clear">ltWrip', So the table elements should be there so that it can insert filters inside the head.

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• Blackberry Development, adding dynamic number of buttons and setting Fieldchangelistener() for them

  - by Nikesh Yadav

  Hi, I am adding dynamic number of buttons in a Blackberry application and trying to get different events on each button click. I am not able to apply the setchangelistener() for these array of buttons as once the loop finishes after adding all the buttons, the events gets generated only for the last indexed button. If I make us of getIndex(), it runs fine only if I am not adding any other fields on my screen, but if I add other fields along with these array of buttons, the getIndex() function count them in the indexing as well. Can anyone please help me out in setting FieldChangeListener to array of ButtonField? Here is a sample code of the way I am using the array of ButtonField. I the code I have added two test LabelField at the top of the screen, if I remove them the code will run fine and I will get different result for each button click, but if I keep them active, the indexing gets effected and the Button wont work. package buttonclickloop; import net.rim.device.api.ui.DrawStyle; import net.rim.device.api.ui.Field; import net.rim.device.api.ui.FieldChangeListener; import net.rim.device.api.ui.component.ButtonField; import net.rim.device.api.ui.component.LabelField; import net.rim.device.api.ui.container.HorizontalFieldManager; import net.rim.device.api.ui.container.MainScreen; public class ButtoncClickLoop extends MainScreen { int i = 0; private ButtonField[] btn = new ButtonField[50]; public ButtoncClickLoop() { // TODO Auto-generated constructor stub LabelField Field1 = new LabelField("Field1"); LabelField Field2 = new LabelField("Field2",DrawStyle.RIGHT | ButtonField.USE_ALL_WIDTH); HorizontalFieldManager FieldHmgr = new HorizontalFieldManager(); FieldHmgr.add(Field1); FieldHmgr.add(Field2); FieldHmgr.setMargin(0,0,10,5); add(FieldHmgr); while (i < 3){ FieldChangeListener listener = new FieldChangeListener() { public void fieldChanged(Field field, int context) { context = field.getIndex(); if (field == btn[context]){ add(new LabelField("Label" + context + "")); } } }; btn[i] = new ButtonField("Button" + i + ""); btn[i].setChangeListener(listener); add(btn[i]); i = i + 1; } } } Thanks, Nikesh

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• how to organise my abstraction?

  - by DaveM

  I have a problem that I can't decide how to best handle, so I'm asking for advice. Please bear with me if my question isn't clear, it is possiblybecause I'm not sure exacly how to solve! I have a set of function that I have in a class. These function are a set of lowest commonality. To be able to run this I need to generate certain info. But this info can arrive with my class from one of 2 routes. I'll try to summarise my situation.... Lets say that I have a class as follows. public class onHoliday(){ private Object modeOfTravel; private Object location; public onHoliday(Object vehicle, Location GPScoords) { private boolean haveFun(){//function to have fun, needs 4 people }//end haveFun() } } Lets imagine I can get to my holiday either by car or by bike. my haveFun() function is dependant my type of vehicle. But only loosely. I have another function that determines my vehicle type, and extracts the required values. for example if I send a car I may get 4 people in one go, but if I send I bike I need at least 2 to get the required 4 I have currently 2 options: Overload my constructor, so as I can send either 2 bikes or a single car into it, then I can call one of 2 intermediate functions (to get the names of my 4 people for instance) before I haveFun() - this is what I am currently doing. split the 2 constructors into 2 separate classes, and repeat my haveFun() in a third class, that becomes an object of my 2 other classes. my problem with this is that my intermediate functions are all but a few lines of code, and I don't want to have them in a separate file! (I allways put classes in separate files!) Please note, my haveFun() isn't something that I'm going to need outside of these 2 classes, or even being onHoliday (ie. there is no chance of me doing some haveFun() over a weekend or of an evening!). I have though about putting haveFun() into an interface, but it seems a bit worthless having an interface with only a single method! Even then I would have to have the method in both of the classes -one for bike and another for car! I have thought about having my onHoliday class accepting any object type, but then I don't want someone accidentally sending in a boat to my onHoliday class (imagine I can't swim, so its not about to happen). It may be important to note that my onHoliday class is package private, and final. It in fact is only accessed via other 'private methods' in other classes, and has only private methods itself. Thanks in advance. David

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• detect face from image and crop face from that photo

  - by Siddhpura Amit

  I have done coding in that i am successfully getting face with rectangle drawing now i want to crop that rectangle area. if there are many rectangle( mean many faces) than user can select one of the face or rectangle and that rectangle areal should be cropped can any body help me... Below is my code class AndroidFaceDetector extends Activity { public String path; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Bundle bundle = this.getIntent().getExtras(); path = bundle.getString("mypath"); setContentView(new myView(this)); } class myView extends View { private int imageWidth, imageHeight; private int numberOfFace = 5; private FaceDetector myFaceDetect; private FaceDetector.Face[] myFace; float myEyesDistance; int numberOfFaceDetected; Bitmap myBitmap; public myView(Context context) { super(context); System.out.println("CONSTRUCTOR"); System.out.println("path = "+path); if (path != null) { BitmapFactory.Options BitmapFactoryOptionsbfo = new BitmapFactory.Options(); BitmapFactoryOptionsbfo.inPreferredConfig = Bitmap.Config.RGB_565; myBitmap = BitmapFactory.decodeFile(path, BitmapFactoryOptionsbfo); imageWidth = myBitmap.getWidth(); imageHeight = myBitmap.getHeight(); myFace = new FaceDetector.Face[numberOfFace]; myFaceDetect = new FaceDetector(imageWidth, imageHeight, numberOfFace); numberOfFaceDetected = myFaceDetect.findFaces(myBitmap, myFace); } else { Toast.makeText(AndroidFaceDetector.this, "Please Try again", Toast.LENGTH_SHORT).show(); } } @Override protected void onDraw(Canvas canvas) { System.out.println("ON DRAW IS CALLED"); if (myBitmap != null) { canvas.drawBitmap(myBitmap, 0, 0, null); Paint myPaint = new Paint(); myPaint.setColor(Color.GREEN); myPaint.setStyle(Paint.Style.STROKE); myPaint.setStrokeWidth(3); for (int i = 0; i < numberOfFaceDetected; i++) { Face face = myFace[i]; PointF myMidPoint = new PointF(); face.getMidPoint(myMidPoint); myEyesDistance = face.eyesDistance(); canvas.drawRect((int) (myMidPoint.x - myEyesDistance), (int) (myMidPoint.y - myEyesDistance), (int) (myMidPoint.x + myEyesDistance), (int) (myMidPoint.y + myEyesDistance), myPaint); } } } } }

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• Haskell: Left-biased/short-circuiting function

  - by user2967411

  Two classes ago, our professor presented to us a Parser module. Here is the code: module Parser (Parser,parser,runParser,satisfy,char,string,many,many1,(+++)) where import Data.Char import Control.Monad import Control.Monad.State type Parser = StateT String [] runParser :: Parser a -> String -> [(a,String)] runParser = runStateT parser :: (String -> [(a,String)]) -> Parser a parser = StateT satisfy :: (Char -> Bool) -> Parser Char satisfy f = parser $ \s -> case s of [] -> [] a:as -> [(a,as) | f a] char :: Char -> Parser Char char = satisfy . (==) alpha,digit :: Parser Char alpha = satisfy isAlpha digit = satisfy isDigit string :: String -> Parser String string = mapM char infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a (+++) = mplus many, many1 :: Parser a -> Parser [a] many p = return [] +++ many1 p many1 p = liftM2 (:) p (many p) Today he gave us an assignment to introduce "a left-biased, or short-circuiting version of (+++)", called (<++). His hint was for us to consider the original implementation of (+++). When he first introduced +++ to us, this was the code he wrote, which I am going to call the original implementation: infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a p +++ q = Parser $ \s -> runParser p s ++ runParser q s I have been having tons of trouble since we were introduced to parsing and so it continues. I have tried/am considering two approaches. 1) Use the "original" implementation, as in p +++ q = Parser $ \s - runParser p s ++ runParser q s 2) Use the final implementation, as in (+++) = mplus Here are my questions: 1) The module will not compile if I use the original implementation. The error: Not in scope: data constructor 'Parser'. It compiles fine using (+++) = mplus. What is wrong with using the original implementation that is avoided by using the final implementation? 2) How do I check if the first Parser returns anything? Is something like (not (isNothing (Parser $ \s - runParser p s) on the right track? It seems like it should be easy but I have no idea. 3) Once I figure out how to check if the first Parser returns anything, if I am to base my code on the final implementation, would it be as easy as this?: -- if p returns something then p <++ q = mplus (Parser $ \s -> runParser p s) mzero -- else (<++) = mplus Best, Jeff

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• Help organising controllers logically

  - by kenny99

  Hi guys, I'm working on a site which i'm developing using an MVC structure. My models will represent all of data in the site, but i'm struggling a bit to decide on a good controller structure. The site will allow users to login/register and see personal data on a number of pages, but also still have access to public pages, e.g FAQs, Contact page etc. This is what I have at the moment... A Template Controller which handles main template display. The basic template for the site will remain the same whether or not you are logged in. A main Website Controller which extends the Template Controller and handles basic authentication. If the user is logged in, a User::control_panel() method is called from the constructor and this builds the control panel which will be present throughout the authenticated session. If user is not logged in, then a different view is loaded instead of the control panel, e.g with a login form. All protected/public page related controllers will extend the website controller. The user homepage has a number of widgets I want to display, which I'm doing via a Home Controller which extends the Website Controller. This controller generates these widgets via the following static calls: $this->template->content->featured_pet = Pet::featured(); $this->template->content->popular_names = Pet::most_popular(); $this->template->content->owner_map = User::generate_map(); $this->template->content->news = News::snippet(); I suppose the first thing I'm unsure about is if the above static calls to controllers (e.g Pet and User) are ok to remain static - these static methods will return views which are loaded into the main template. This is the way I've done things in the past but I'm curious to find out if this is a sensible approach. Other protected pages for signed in users will be similar to the Home Controller. Static pages will be handled by a Page Controller which will also extend the Website Controller, so that it will know whether or not the user control panel or login form should be shown on the left hand side of the template. The protected member only pages will not be routed to the Page Controller, this controller will only handle publicly available pages. One problem I have at the moment, is that if both public and protected pages extend the Website Controller, how do I avoid an infinite loop - for example, the idea is that the website controller should handle authentication then redirect to the requested controller (URL), but this will cause an infinite redirect loop, so i need to come up with a better way of dealing with this. All in all, does this setup make any sense?! Grateful for any feedback.

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• android - using resources drawable in content provider

  - by Russ Wheeler

  I am trying to pass back an image through a content provider in a separate app. I have two apps, one with the activity in (app a), the other with content provider (app b) I have app a reading an image off my SD card via app b using the following code. App a: public void but_update(View view) { ContentResolver resolver = getContentResolver(); Uri uri = Uri.parse("content://com.jash.cp_source_two.provider/note/1"); InputStream inStream = null; try { inStream = resolver.openInputStream(uri); Bitmap bitmap = BitmapFactory.decodeStream(inStream); image = (ImageView) findViewById(R.id.imageView1); image.setImageBitmap(bitmap); } catch(FileNotFoundException e) { Toast.makeText(getBaseContext(), "error = "+e, Toast.LENGTH_LONG).show(); } finally { if (inStream != null) { try { inStream.close(); } catch (IOException e) { Log.e("test", "could not close stream", e); } } } }; App b: @Override public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException { try { File path = new File(Environment.getExternalStorageDirectory().getAbsolutePath(),"pic2.png"); return ParcelFileDescriptor.open(path,ParcelFileDescriptor.MODE_READ_ONLY); } catch (FileNotFoundException e) { Log.i("r", "File not found"); throw new FileNotFoundException(); } } In app a I am able to display an image from app a's resources folder, using setImageURi and constructing a URI using the following code. int id = R.drawable.a2; Resources resources = getBaseContext().getResources(); Uri uri = Uri.parse(ContentResolver.SCHEME_ANDROID_RESOURCE + "://" + resources.getResourcePackageName(id) + '/' + resources.getResourceTypeName(id) + '/' + resources.getResourceEntryName(id) ); image = (ImageView) findViewById(R.id.imageView1); image.setImageURI(uri); However, if I try to do the same in app b (read from app b's resources folder rather than the image on the SD card) it doesn't work, saying it can't find the file, even though I am creating the path of the file from the resource, so it is definitely there. Any ideas? Does it restrict sending resources over the content provider somehow? P.S. I also got an error when I tried to create the file with File path = new File(uri); saying 'there is no applicable constructor to '(android.net.Uri)' though http://developer.android.com/reference/java/io/File.html#File(java.net.URI) Seems to think it's possible...unless java.net.URI is different to android.net.URI, in which case can I convert them? Thanks Russ

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• MVVM: how to set the datacontext of a user control

  - by EVA

  Hi, I'm writing an application in WPF, using the MVVm toolkit and have problems with hooking up the viewmodel and view. The model is created with ado.net entity framework. The viewmodel: public class CustomerViewModel { private Models.Customer customer; //constructor private ObservableCollection<Models.Customer> _customer = new ObservableCollection<Models.Customer>(); public ObservableCollection<Models.Customer> AllCustomers { get { return _customer; } } private Models.Customer _selectedItem; public Models.Customer SelectedItem { get { return _selectedItem; } } public void LoadCustomers() { List<Models.Customer> list = DataAccessLayer.getcustomers(); foreach (Models.Customer customer in list) { this._customer.Add(customer); } } } And the view (no code behind at the moment): <UserControl x:Class="Customers.Customer" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" xmlns:vm ="clr-namespace:Customers.ViewModels" d:DesignHeight="300" d:DesignWidth="300" xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit" > <Grid> <toolkit:DataGrid ItemsSource="{Binding AllCustomers}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}" AutoGenerateColumns="True"> </toolkit:DataGrid> <toolkit:DataGrid ItemsSource="{Binding SelectedItem.Orders}"> </toolkit:DataGrid> </Grid> </UserControl> And dataaccesslayer class: class DataAccessLayer { public List<Customer> customers = new List<Customer>(); public static List<Customer> getcustomers() { entities db = new entities(); var customers = from c in db.Customer.Include("Orders") select c; return customers.ToList(); } } The problem is that no data is displayed simply because the data context is not set. I tried to do it in a code-behind but is did not work. I would prefer to do it in a xaml file anyway. Another problem is with the SelectedItem binding - the code is never used. Thanks for help! Regards, EV.

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• Handwritten linked list is segfaulting and I don't understand why

  - by Born2Smile

  Hi I was working on a bit of fun, making an interface to run gnuplot from within c++, and for some reason the my linked list implementation fails. The code below fails on the line plots-append(&plot). Stepping through the code I discovered that for some reason the destructor ~John() is called immediately after the constructor John(), and I cannot seem to figure out why. The code included below is a stripped down version operating only on Plot*. Originally I made the linked list as a template class. And it worked fine as ll<int and ll<char* but for some reason it fails as ll<Plot*. Could youp please help me figure out why it fails? and perhaps help me understand how to make it work? In advance: Thanks a heap! //B2S #include <string.h class Plot{ char title[80]; public: Plot(){ } }; class Link{ Plot* element; Link* next; Link* prev; friend class ll; }; class ll{ Link* head; Link* tail; public: ll(){ head = tail = new Link(); head-prev = tail-prev = head-next = tail-next = head; } ~ll(){ while (head!=tail){ tail = tail-prev; delete tail-next; } delete head; } void append(Plot* element){ tail-element = element; tail-next = new Link(); tail-next-prev = tail; tail-next = tail; } }; class John{ ll* plots; public: John(){ plots= new ll(); } ~John(){ delete plots; } John(Plot* plot){ John(); plots-append(plot); } }; int main(){ Plot p; John k(&p); }

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• Java Threading Concept Understanding

  - by Nirmal

  Hello All... Recently I have gone through with one simple threading program, which leads me some issues for the related concepts... My sample program code looks like : class NewThread implements Runnable { Thread t; NewThread() { t = new Thread(this, "Demo Thread"); System.out.println("Child thread: " + t); t.start(); // Start the thread } public void run() { try { for (int i = 5; i > 0; i--) { System.out.println("Child Thread: " + i); Thread.sleep(500); } } catch (InterruptedException e) { System.out.println("Child interrupted."); } System.out.println("Exiting child thread."); } } class ThreadDemo { public static void main(String args[]) { new NewThread(); // create a new thread try { for (int i = 5; i > 0; i--) { System.out.println("Main Thread: " + i); Thread.sleep(1000); } } catch (InterruptedException e) { System.out.println("Main thread interrupted."); } System.out.println("Main thread exiting."); } } Now this program giving me the output as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Main Thread: 4 Child Thread: 3 Child Thread: 2 Main Thread: 3 Child Thread: 1 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. So, that's very much clear to me. But as soon as I am replacing the object creation code (calling of a NewThread class constructor) to as follows : NewThread nt = new NewThread(); // create a new thread the output becomes a bit varied like as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Child Thread: 3 Main Thread: 4 Child Thread: 2 Child Thread: 1 Main Thread: 3 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. And some times it's giving me same output in both the cases. So, i am not getting the exact change in both the scenario. I would like to know that you the variation in the output is coming here ? Thanks in advance...

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• Mixing policy-based design with CRTP in C++

  - by Eitan

  I'm attempting to write a policy-based host class (i.e., a class that inherits from its template class), with a twist, where the policy class is also templated by the host class, so that it can access its types. One example where this might be useful is where a policy (used like a mixin, really), augments the host class with a polymorphic clone() method. Here's a minimal example of what I'm trying to do: template <template <class> class P> struct Host : public P<Host<P> > { typedef P<Host<P> > Base; typedef Host* HostPtr; Host(const Base& p) : Base(p) {} }; template <class H> struct Policy { typedef typename H::HostPtr Hptr; Hptr clone() const { return Hptr(new H((Hptr)this)); } }; Policy<Host<Policy> > p; Host<Policy> h(p); int main() { return 0; } This, unfortunately, fails to compile, in what seems to me like circular type dependency: try.cpp: In instantiation of ‘Host<Policy>’: try.cpp:10: instantiated from ‘Policy<Host<Policy> >’ try.cpp:16: instantiated from here try.cpp:2: error: invalid use of incomplete type ‘struct Policy<Host<Policy> >’ try.cpp:9: error: declaration of ‘struct Policy<Host<Policy> >’ try.cpp: In constructor ‘Host<P>::Host(const P<Host<P> >&) [with P = Policy]’: try.cpp:17: instantiated from here try.cpp:5: error: type ‘Policy<Host<Policy> >’ is not a direct base of ‘Host<Policy>’ If anyone can spot an obvious mistake, or has successfuly mixing CRTP in policies, I would appreciate any help.

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• Mouse wheel not scrolling in JDialog

  - by Iulian Serbanoiu

  Hello, I'm facing a frustrating issue. I have an application where the scroll wheel doesn't work in a JDialog class. Here's the code: import javax.swing.*; import java.awt.event.*; public class Failtest extends JFrame { public static void main(String[] args) { new Failtest(); } public Failtest() { super(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); setTitle("FRAME"); JScrollPane sp1 = new JScrollPane(getNewList()); add(sp1); setSize(150, 150); setVisible(true); JDialog d = new JDialog(this, false);// NOT WORKING //JDialog d = new JDialog((JFrame)null, false); // NOT WORKING //JDialog d = new JDialog((JDialog)null, false);// WORKING - WHY? d.setTitle("DIALOG"); d.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE); JScrollPane sp = new JScrollPane(getNewList()); d.add(sp); d.setSize(150, 150); d.setVisible(true); } public JList getNewList() { String objs[] = new String[30]; for(int i=0; i<objs.length; i++) { objs[i] = "Item "+i; } JList l = new JList(objs); return l; } } I found a solution which is present as a comment in the java code - the constructor receiving a (JDialog)null parameter. Can someone enlighten me? My opinion is that this is a java bug. Tested on Windows XP-SP3 with 1 JDK and 2 JREs: D:\Program Files\Java\jdk1.6.0_17\bin>javac -version javac 1.6.0_17 D:\Program Files\Java\jdk1.6.0_17\bin>java -version java version "1.6.0_17" Java(TM) SE Runtime Environment (build 1.6.0_17-b04) Java HotSpot(TM) Client VM (build 14.3-b01, mixed mode, sharing) D:\Program Files\Java\jdk1.6.0_17\bin>cd .. D:\Program Files\Java\jdk1.6.0_17>java -version java version "1.6.0_18" Java(TM) SE Runtime Environment (build 1.6.0_18-b07) Java HotSpot(TM) Client VM (build 16.0-b13, mixed mode, sharing) Thank you in advance, Iulian Serbanoiu PS: The problem is not new - the code is taken from a forum (here) where this problem was also mentioned - but no solutions to it (yet)

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• using Java interfaces

  - by mike_hornbeck

  I need to create interface MultiLingual, that allows to display object's data in different languages (not data itself, but introduction like "Author", "Title" etc.). Printed data looks like this : 3 grudnia 1998 10th of June 1924 Autor: Tolkien Tytul: LoTR Wydawnictwo: Amazon 2010 Author: Mitch Albom Title: Tuesdays with Morrie Publishing House: Time Warner Books 2003 37 360,45 PLN 5,850.70 GBP 3rd of December 1998 10th of June 1924 Author: Tolkien Title: LoTR Publishing House: Amazon 2010 Author: Mitch Albom Title: Tuesdays with Morrie Publishing House: Time Warner Books 2003 37,360.45 GBP 5,850.70 GBP Test code looks like this : public class Main { public static void main(String[] args){ MultiLingual gatecrasher[]={ new Data(3,12,1998), new Data(10,6,1924,MultiLingual.ENG), new Book("LoTR", "Tolkien", "Amazon", 2010), new Book("Tuesdays with Morrie", "Mitch Albom", "Time Warner Books",2003, MultiLingual.ENG), new Money(1232895/33.0,MultiLingual.PL), new Money(134566/23.0,MultiLingual.ENG), }; for(int i=0;i < gatecrasher.length;i++) System.out.println(gatecrasher[i]+"\n"); for(int i=0;i < gatecrasher.length;i++) System.out.println(gatecrasher[i].get(MultiLingual.ENG)+"\n"); } } So i need to introduce constants ENG, PL in MultiLingual interface, as well as method get(int language) : public interface MultiLingual { int ENG = 0; int PL= 1; String get(int lang); } And then I have class Book. Problem starts with the constructors. One of them needs to take MultiLingual.ENG as argument, but how to achieve that ? Is this the proper way? : class Book implements MultiLingual { private String title; private String publisher; private String author; public Book(String t, String a, String p, int y, MultiLingual lang){ } Or should I treat this MultiLingual.ENG as int variable , that will just change automatically constants in interface? Second constructor for book doesn't take MultLingual as argument, but following implementation is somehow wrong : public Book(String t, String a, String p, int y){ Book someBook = new Book(t, a, p, y, MultiLingual m); } I could just send int m in place of MultiLingual m but then I will have no control if language is set to PL or ENG. And finally get() method for Boook but I think at least this should be working fine: public String get(int lang){ String data; if (lang == ENG){ data = "Author: "+this.author+"\n"+ "Title: "+this.title+"\n"+ "Publisher: "+this.publisher+"\n"; } else { data = "Autor: "+this.author+"\n"+ "Tytul: "+this.title+"\n"+ "Wydawca: "+this.publisher+"\n"; } return data; } @Override public String toString(){ return ""; } }

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• Catching an exception class within a template

  - by Todd Bauer

  I'm having a problem using the exception class Overflow() for a Stack template I'm creating. If I define the class regularly there is no problem. If I define the class as a template, I cannot make my call to catch() work properly. I have a feeling it's simply syntax, but I can't figure it out for the life of me. #include<iostream> #include<exception> using namespace std; template <class T> class Stack { private: T *stackArray; int size; int top; public: Stack(int size) { this->size = size; stackArray = new T[size]; top = 0; } ~Stack() { delete[] stackArray; } void push(T value) { if (isFull()) throw Overflow(); stackArray[top] = value; top++; } bool isFull() { if (top == size) return true; else return false; } class Overflow {}; }; int main() { try { Stack<double> Stack(5); Stack.push( 5.0); Stack.push(10.1); Stack.push(15.2); Stack.push(20.3); Stack.push(25.4); Stack.push(30.5); } catch (Stack::Overflow) { cout << "ERROR! The stack is full.\n"; } return 0; } The problem is in the catch (Stack::Overflow) statement. As I said, if the class is not a template, this works just fine. However, once I define it as a template, this ceases to work. I've tried all sorts of syntaxes, but I always get one of two sets of error messages from the compiler. If I use catch(Stack::Overflow): ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2316: 'Stack::Overflow' : cannot be caught as the destructor and/or copy constructor are inaccessible EDIT: I meant If I use catch(Stack<double>::Overflow) or any variety thereof: ch18pr01.cpp(89) : error C2061: syntax error : identifier 'Stack' ch18pr01.cpp(89) : error C2310: catch handlers must specify one type ch18pr01.cpp(95) : error C2317: 'try' block starting on line '75' has no catch handlers I simply can not figure this out. Does anyone have any idea?

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• Binding Silverlight UserControl custom properties to its' elements

  - by ghostskunks

  Hi. I'm trying to make a simple crossword puzzle game in Silverlight 2.0. I'm working on a UserControl-ish component that represents a square in the puzzle. I'm having trouble with binding up my UserControl's properties with its' elements. I've finally (sort of) got it working (may be helpful to some - it took me a few long hours), but wanted to make it more 'elegant'. I've imagined it should have a compartment for the content and a label (in the upper right corner) that optionally contains its' number. The content control probably be a TextBox, while label control could be a TextBlock. So I created a UserControl with this basic structure (the values are hardcoded at this stage): <UserControl x:Class="XWord.Square" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" FontSize="30" Width="100" Height="100"> <Grid x:Name="LayoutRoot" Background="White"> <Grid.ColumnDefinitions> <ColumnDefinition Width="*"/> <ColumnDefinition Width="Auto"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <TextBlock x:Name="Label" Grid.Row="0" Grid.Column="1" Text="7"/> <TextBox x:Name="Content" Grid.Row="1" Grid.Column="0" Text="A" BorderThickness="0" /> </Grid> </UserControl> I've also created DependencyProperties in the Square class like this: public static readonly DependencyProperty LabelTextProperty; public static readonly DependencyProperty ContentCharacterProperty; // ...(static constructor with property registration, .NET properties // omitted for brevity)... Now I'd like to figure out how to bind the Label and Content element to the two properties. I do it like this (in the code-behind file): Label.SetBinding( TextBlock.TextProperty, new Binding { Source = this, Path = new PropertyPath( "LabelText" ), Mode = BindingMode.OneWay } ); Content.SetBinding( TextBox.TextProperty, new Binding { Source = this, Path = new PropertyPath( "ContentCharacter" ), Mode = BindingMode.TwoWay } ); That would be more elegant done in XAML. Does anyone know how that's done?

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• How do you handle EF Data Contexts combined with asp.net custom membership/role providers

  - by KallDrexx

  I can't seem to get my head around how to implement a custom membership provider with Entity Framework data contexts into my asp.net MVC application. I understand how to create a custom membership/role provider by itself (using this as a reference). Here's my current setup: As of now I have a repository factory interface that allows different repository factories to be created (right now I only have a factory for EF repositories and and in memory repositories). The repository factory looks like this: public class EFRepositoryFactory : IRepositoryFactory { private EntitiesContainer _entitiesContext; /// <summary> /// Constructor that generates the necessary object contexts /// </summary> public EFRepositoryFactory() { _entitiesContext = new EntitiesContainer(); } /// <summary> /// Generates a new entity framework repository for the specified entity type /// </summary> /// <typeparam name="T">Type of entity to generate a repository for </typeparam> /// <returns>Returns an EFRepository</returns> public IRepository<T> GenerateRepository<T>() where T : class { return new EFRepository<T>(_entitiesContext); } } Controllers are passed an EF repository factory via castle Windsor. The controller then creates all the service/business layer objects it requires and passes in the repository factory into it. This means that all service objects are using the same EF data contexts and I do not have to worry about objects being used in more than one data context (which of course is not allowed and causes an exception). As of right now I am trying to decide how to generate my user and authorization service layers, and have run against a design roadblock. The User/Authization service will be a central class that handles the logic for logging in, changing user details, managing roles and determining what users have access to what. The problem is, using the current methodology the asp.net mvc controllers will initialize it's own EF repository factory via Windsor and the asp.net membership/role provider will have to initialize it's own EF repository factory. This means that each part of the site will then have it's own data context. This seems to mean that if asp.net authenticates a user, that user's object will be in the membership provider's data context and thus if I try to retrieve that user object in the service layer (say to change the user's name) I will get a duplication exception. I thought of making the repository factory class a singleton, but I don't see a way for that to work with castle Windsor. How do other people handle asp.net custom providers in a MVC (or any n-tier) architecture without having object duplication issues?

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• Error in creating template class

  - by Luciano

  I found this vector template class implementation, but it doesn't compile on XCode. Header file: // File: myvector.h #ifndef _myvector_h #define _myvector_h template <typename ElemType> class MyVector { public: MyVector(); ~MyVector(); int size(); void add(ElemType s); ElemType getAt(int index); private: ElemType *arr; int numUsed, numAllocated; void doubleCapacity(); }; #include "myvector.cpp" #endif Implementation file: // File: myvector.cpp #include <iostream> #include "myvector.h" template <typename ElemType> MyVector<ElemType>::MyVector() { arr = new ElemType[2]; numAllocated = 2; numUsed = 0; } template <typename ElemType> MyVector<ElemType>::~MyVector() { delete[] arr; } template <typename ElemType> int MyVector<ElemType>::size() { return numUsed; } template <typename ElemType> ElemType MyVector<ElemType>::getAt(int index) { if (index < 0 || index >= size()) { std::cerr << "Out of Bounds"; abort(); } return arr[index]; } template <typename ElemType> void MyVector<ElemType>::add(ElemType s) { if (numUsed == numAllocated) doubleCapacity(); arr[numUsed++] = s; } template <typename ElemType> void MyVector<ElemType>::doubleCapacity() { ElemType *bigger = new ElemType[numAllocated*2]; for (int i = 0; i < numUsed; i++) bigger[i] = arr[i]; delete[] arr; arr = bigger; numAllocated*= 2; } If I try to compile as is, I get the following error: "Redefinition of 'MyVector::MyVector()'" The same error is displayed for every member function (.cpp file). In order to fix this, I removed the '#include "myvector.h"' on the .cpp file, but now I get a new error: "Expected constructor, destructor, or type conversion before '<' token". A similar error is displayed for every member as well. Interestingly enough, if I move all the .cpp code to the header file, it compiles fine. Does that mean I can't implement template classes in separate files?

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• redoing object model construction to fit with asynchronous data fetching

  - by Andrew Patterson

  I have a modeled a set of objects that correspond with some real world concepts. TradeDrug, GenericDrug, TradePackage, DrugForm Underlying the simple object model I am trying to provide is a complex medical terminology that uses numeric codes to represent relationships and concepts, all accessible via a REST service - I am trying to hide away some of that complexity with an object wrapper. To give a concrete example I can call TradeDrug d = Searcher.FindTradeDrug("Zoloft") or TradeDrug d = new TradeDrug(34) where 34 might be the code for Zoloft. This will consult a remote server to find out some details about Zoloft. I might then call GenericDrug generic = d.EquivalentGeneric() System.Out.WriteLine(generic.ActiveIngredient().Name) in order to get back the generic drug sertraline as an object (again via a background REST call to the remote server that has all these drug details), and then perhaps find its ingredient. This model works fine and is being used in some applications that involve data processing. Recently however I wanted to do a silverlight application that used and displayed these objects. The silverlight environment only allows asynchronous REST/web service calls. I have no problems with how to make the asychhronous calls - but I am having trouble with what the design should be for my object construction. Currently the constructors for my objects do some REST calls sychronously. public TradeDrug(int code) { form = restclient.FetchForm(code) name = restclient.FetchName(code) etc.. } If I have to use async 'events' or 'actions' in order to use the Silverlight web client (I know silverlight can be forced to be a synchronous client but I am interested in asychronous approaches), does anyone have an guidance or best practice for how to structure my objects. I can pass in an action callback to the constructor public TradeDrug(int code, Action<TradeDrug> constructCompleted) { } but this then allows the user to have a TradeDrug object instance before what I want to construct is actually finished. It also doesn't support an 'event' async pattern because the object doesn't exist to add the event to until it is constructed. Extending that approach might be a factory object that itself has an asynchronous interface to objects factory.GetTradeDrugAsync(code, completedaction) or with a GetTradeDrugCompleted event? Does anyone have any recommendations?

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• Use native HBitmap in C# while preserving alpha channel/transparency. Please check this code, it works on my computer...

  - by David

  Let's say I get a HBITMAP object/handle from a native Windows function. I can convert it to a managed bitmap using Bitmap.FromHbitmap(nativeHBitmap), but if the native image has transparency information (alpha channel), it is lost by this conversion. There are a few questions on Stack Overflow regarding this issue. Using information from the first answer of this question (How to draw ARGB bitmap using GDI+?), I wrote a piece of code that I've tried and it works. It basically gets the native HBitmap width, height and the pointer to the location of the pixel data using GetObject and the BITMAP structure, and then calls the managed Bitmap constructor: Bitmap managedBitmap = new Bitmap(bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); As I understand (please correct me if I'm wrong), this does not copy the actual pixel data from the native HBitmap to the managed bitmap, it simply points the managed bitmap to the pixel data from the native HBitmap. And I don't draw the bitmap here on another Graphics (DC) or on another bitmap, to avoid unnecessary memory copying, especially for large bitmaps. I can simply assign this bitmap to a PictureBox control or the the Form BackgroundImage property. And it works, the bitmap is displayed correctly, using transparency. When I no longer use the bitmap, I make sure the BackgroundImage property is no longer pointing to the bitmap, and I dispose both the managed bitmap and the native HBitmap. The Question: Can you tell me if this reasoning and code seems correct. I hope I will not get some unexpected behaviors or errors. And I hope I'm freeing all the memory and objects correctly. private void Example() { IntPtr nativeHBitmap = IntPtr.Zero; /* Get the native HBitmap object from a Windows function here */ // Create the BITMAP structure and get info from our nativeHBitmap NativeMethods.BITMAP bitmapStruct = new NativeMethods.BITMAP(); NativeMethods.GetObjectBitmap(nativeHBitmap, Marshal.SizeOf(bitmapStruct), ref bitmapStruct); // Create the managed bitmap using the pointer to the pixel data of the native HBitmap Bitmap managedBitmap = new Bitmap( bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); // Show the bitmap this.BackgroundImage = managedBitmap; /* Run the program, use the image */ MessageBox.Show("running..."); // When the image is no longer needed, dispose both the managed Bitmap object and the native HBitmap this.BackgroundImage = null; managedBitmap.Dispose(); NativeMethods.DeleteObject(nativeHBitmap); } internal static class NativeMethods { [StructLayout(LayoutKind.Sequential)] public struct BITMAP { public int bmType; public int bmWidth; public int bmHeight; public int bmWidthBytes; public ushort bmPlanes; public ushort bmBitsPixel; public IntPtr bmBits; } [DllImport("gdi32", CharSet = CharSet.Auto, EntryPoint = "GetObject")] public static extern int GetObjectBitmap(IntPtr hObject, int nCount, ref BITMAP lpObject); [DllImport("gdi32.dll")] internal static extern bool DeleteObject(IntPtr hObject); }

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