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  • What Windows message is fired for mouse-up with modifier keys?

    - by Greg
    My WndProc isn't seeing mouse-up notifications when I click with a modifier key (shift or control) pressed. I see them without the modifier key, and I see mouse-down notifications with the modifier keys. I'm using the Windows Forms NativeWindow wrapper to get Windows messages from the WndProc() method. I've tried tracking the notifications I do get, and I the only clue I see is WM_CAPTURECHANGED. I've tried calling SetCapture when I receive the WM_LBUTTONDOWN message, but it doesn't help. Without modifier (skipping paint, timer and NCHITTEST messages): WM_LBUTTONDOWN WM_SETCURSOR WM_MOUSEMOVE WM_SETCURSOR WM_LBUTTONUP With modifier (skipping paint, timer and NCHITTEST messages): WM_KEYDOWN WM_PARENTNOTIFY WM_MOUSEACTIVATE WM_MOUSEACTIVATE WM_SETCURSOR WM_LBUTTONDOWN WM_SETCURSOR (repeats) WM_KEYDOWN (repeats) WM_KEYUP If I hold the mouse button down for a long time, I can usually get a WM_LBUTTONUP notification, but it should be possible to make it more responsive.. What am I missing? Thanks.

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  • NHibernate - get List<long> representing primary keys?

    - by Nathan
    I have a situation where I definitely don't want to get the whole domain object. Basically, the entity has a primary key of long (.NET)/bigint(sql server 2005). I simply need to pass the primary key to an external system which will access the database directly - and since the list of ids could be large, I don't want to rehydrate the entire domain object just to get the Id. In linq2sql, I could accomplish this with a projection, but I am restricted to NHibernate 1.2.1.4000, which doesn't support Linq. Is there a way to accomplish this using NHibernate 1.2.1.4000? (I am open to using a named-query if that will work)

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  • Mock a void method which change the input value

    - by Kar
    Hi, How could I mock a void method with parameters and change the value parameters? My void method looks like this: public interface IFoo { void GetValue(int x, object y) // takes x and do something then access another class to get the value of y } I prepared a delegate class: private delegate void GetValueDelegate(int x, object y); private void GetValue(int x, object y) { // process x // prepare a new object obj if (y == null) y = new Object(); if (//some checks) y = obj; } I wrote something like this: Expect.Call(delegate {x.GetValue(5, null);}).Do (new GetValueDelegate(GetValue)).IgnoreArguments().Repeat.Any(); But seems like it's not working. Any clue on what could be wrong?

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  • [iPhone] How to order an array

    - by Fabrizio
    Hi all, I got an array in my app and I need to order by one of its key. Basically what the app does is taking latitude and longitude somewhere, calculate the distance from my actual position and create an array containing a key called "distance". I'm using myArray sortUsingDescriptors: [NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:@"distance" ascending:YES] autorelease]]]; I'm not sure it's working, I mean the first results are ordered but then it shows distance closer to the previous, as example: 0.8 km 1.6 km 1.9 km 10053.9 km 1098.0 km 2372.0 km 470.5 km Any suggestion? I thank you in advance for any kind of help. Fabrizio

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  • Devise authenticating with username instead of email

    - by teknull
    I'm new to Devise and have it working fine by using an email address as the authentication key. However, I have a use case which requires a username instead and I can't seem to get it working. I've added a string column, "username" to the users table, changed the fields from :email to :username in the sign-in form, and have changed the authentication key in devise.rb to :username yet when I go to sign in I'm met with this prompt: "Please enter an email address". What am I doing wrong? **new.html.erb** <div><%= f.label :username %><br /> <%= f.email_field :username %></div> **User.rb** class User < ActiveRecord::Base # Include default devise modules. Others available are: # :token_authenticatable, :encryptable, :confirmable, :lockable, :timeoutable and :omniauthable devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable, :authentication_keys => [:username] # Setup accessible (or protected) attributes for your model attr_accessible :email, :password, :password_confirmation, :remember_me, :username # attr_accessible :title, :body end **devise.rb** config.authentication_keys = [ :username ]

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  • "paste" listener on a SWT widget

    - by Fredrik
    I have an application with a SWT widget, say a org.eclipse.swt.widgets.Text, and want to add some control to the paste function. The idea is that if the user can paste a string of IDs, I detect that, run some code and paste the object that corresponds to the IDs. So I'm looking for some "ClipBoardListener" of some sort to add to my widget, but that doesnt seem to exist. A keylistener would only trap the pastes done by key and then you would have to deal with different key combos for pasting in different OS's. Based on this java 1.2 question I tried subclassing the text class and override the inser method, but that didnt work Exception in thread "main" org.eclipse.swt.SWTException: Subclassing not allowed Seemed like an ugly solution anyway.

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  • Need sorted dictionary designed to find values with keys less or greater than search value

    - by Captain Comic
    Hi I need to have objects sorted by price (decimal) value for fast access. I need to be able to find all objects with price more then A or less than B. I was thinkg about SortedList, but it does not provide a way to find ascending or descending enumerator starting from given key value (say give me all objects with price less than $120). Think of a system that accepts items for sell from users and stores them into that collection. Another users want to find items cheaper than $120. Basically what i need is tree-based collection and functionality to find node that is smaller\greater\equal to provided key. Please advice.

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  • Using a general class for execution with try/catch/finally?

    - by antirysm
    I find myself having a lot of this in different methods in my code: try { runABunchOfMethods(); } catch (Exception ex) { logger.Log(ex); } What about creating this: public static class Executor { private static ILogger logger; public delegate void ExecuteThis(); static Executor() { // logger = ...GetLoggerFromIoC(); } public static void Execute(ExecuteThis executeThis) { try { executeThis(); } catch (Exception ex) { logger.Log(ex); } } } And just using it like this: private void RunSomething() { Method1(someClassVar); Method2(someOtherClassVar); } ... Executor.Execute(RunSomething); Are there any downsides to this approach? (You could add Executor-methods and delegates when you want a finally and use generics for the type of Exeception you want to catch...)

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  • I18n - JSF variable value translation

    - by Yurish
    Hi! I am using Bundle Internationalization in my project. I have initialized bundle via <f:loadBundle basename="ui.all.bundles.AppResources_en" var="msg"/> When i need to translate some text, i am using a key to resourceBundle, to get a value of it, for example: #{msg.someText}. But, now i want to translate text, which key is a value of another variable. For example: I have variable String textToTransl. It`s value is status_booked. In my AppResources is defined, that status_booked means "It is booked!", so, when i am pointing it to #{msg.textToTransl} i need to see "It is booked!" How can i make it work?

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  • What preferred way to reconcile keyCode/charCode across browsers?

    - by Drew Turner
    Based on the properties of the keydown event I would like to ascertain what the current charCode are? Example. For the keydown event when the NumPad0, D0, and Colon key is pressed I would like to know what the associated charcode is. Currently I have a map that contains the charcode associated with that keyCode or use the current if charCode is not specified. keyCode = { Colon: 186, D0: 48, NumPad0: 96, }; charCodes = { 186: 59, 96: 48, }; shiftCharCodes = { 186: 58, 48: 41 }; Also in certain cases the keyCodes are different accross browsers? Example. The keydown event has different keyCode values across browsers. Colon Key (:/;) - keyCode is 59 on firefox - keyCode is 186 on IE/safari For more information http://www.quirksmode.org/js/keys.html

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  • jframe adding own design jinternal frame error

    - by Van Minh
    I designed a title bar color on my JInternal frame. Then I took attempt to add it to my JFrame, but I cannot. Here is the code of my title bar: public class MyIFtitleBar extends BasicInternalFrameTitlePane { public MyIFtitleBar(JInternalFrame jif) { super(jif); } protected void paintTitleBackground(Graphics g){ g.setColor(Color.pink); g.fillRect(0, 0, getWidth(), getHeight()); } } Here is my JInternal frame. I tried running it in its psvm method, that worked! public class FitnessProg_Frame extends javax.swing.JInternalFrame { public FitnessProg_Frame() { initComponents(); this.setUI(new BasicInternalFrameUI(this){ @Override protected JComponent createNorthPane(JInternalFrame jif) { return new MyIFtitleBar(jif); } }); } @SuppressWarnings("unchecked") private void initComponents() { setBackground(new java.awt.Color(255, 255, 255)); setBorder(new javax.swing.border.MatteBorder(null)); setTitle("Fitness Progarm"); setPreferredSize(new java.awt.Dimension(507, 304)); pack(); } } But when I add it to my JFrame I get an error: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException Here is my JFrame code: public class NewJFrame extends javax.swing.JFrame { public NewJFrame() { initComponents(); FitnessProg_Frame ff = new FitnessProg_Frame(); ff.setVisible(true); mydes.add(ff); // this line made errors } @SuppressWarnings("unchecked") private void initComponents() { mydes = new javax.swing.JDesktopPane(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); javax.swing.GroupLayout mydesLayout = new javax.swing.GroupLayout(mydes); mydes.setLayout(mydesLayout); mydesLayout.setHorizontalGroup( mydesLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 400, Short.MAX_VALUE) ); mydesLayout.setVerticalGroup( mydesLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 300, Short.MAX_VALUE) ); getContentPane().add(mydes, java.awt.BorderLayout.CENTER); pack(); } public static void main(String args[]) { try { for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) { if ("Nimbus".equals(info.getName())) { javax.swing.UIManager.setLookAndFeel(info.getClassName()); break; } } } catch (ClassNotFoundException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (InstantiationException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (IllegalAccessException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (javax.swing.UnsupportedLookAndFeelException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new NewJFrame().setVisible(true); } }); } private javax.swing.JDesktopPane mydes; }

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  • Java Best Practice for type resolution at runtime.

    - by Brian
    I'm trying to define a class (or set of classes which implement the same interface) that will behave as a loosely typed object (like JavaScript). They can hold any sort of data and operations on them depend on the underlying type. I have it working in three different ways but none seem ideal. These test versions only allow strings and integers and the only operation is add. Adding integers results in the sum of the integer values, adding strings concatenates the strings and adding an integer to a string converts the integer to a string and concatenates it with the string. The final version will have more types (Doubles, Arrays, JavaScript-like objects where new properties can be added dynamically) and more operations. Way 1: public interface DynObject1 { @Override public String toString(); public DynObject1 add(DynObject1 d); public DynObject1 addTo(DynInteger1 d); public DynObject1 addTo(DynString1 d); } public class DynInteger1 implements DynObject1 { private int value; public DynInteger1(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject1 add(DynObject1 d) { return d.addTo(this); } public DynObject1 addTo(DynInteger1 d) { return new DynInteger1(d.value + value); } public DynObject1 addTo(DynString1 d) { return new DynString1(d.toString()+Integer.toString(value)); } } ...and similar for DynString1 Way 2: public interface DynObject2 { @Override public String toString(); public DynObject2 add(DynObject2 d); } public class DynInteger2 implements DynObject2 { private int value; public DynInteger2(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject2 add(DynObject2 d) { Class c = d.getClass(); if(c==DynInteger2.class) { return new DynInteger2(value + ((DynInteger2)d).value); } else { return new DynString2(toString() + d.toString()); } } } ...and similar for DynString2 Way 3: public class DynObject3 { private enum ObjectType { Integer, String }; Object value; ObjectType type; public DynObject3(Integer v) { value = v; type = ObjectType.Integer; } public DynObject3(String v) { value = v; type = ObjectType.String; } @Override public String toString() { return value.toString(); } public DynObject3 add(DynObject3 d) { if(type==ObjectType.Integer && d.type==ObjectType.Integer) { return new DynObject3(Integer.valueOf(((Integer)value).intValue()+((Integer)value).intValue())); } else { return new DynObject3(value.toString()+d.value.toString()); } } } With the if-else logic I could use value.getClass()==Integer.class instead of storing the type but with more types I'd change this to use a switch statement and Java doesn't allow switch to use Classes. Anyway... My question is what is the best way to go about something thike this?

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  • page.replace_html for entire div not partial?

    - by odpogn
    My sites navigation is within my <%= render 'layouts/header' %. I want to use ajax so that when a user clicks on a navigation link, only the refreshes. is not a partial, is there a way to refresh the content of that div without using a partial? <div id="container"> <%= render 'layouts/header' %> <div id="content"> <% flash.each do |key, value| %> <div class="flash <%= key %>"><%= value %></div> <% end %> <%= yield %> </div> </div>

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  • WPF multibound textblock not updating

    - by Superstringcheese
    I want to create a program which calculates how long it will take to repeat a process a certain number of times. I've scaled this down a lot for this example. So, I have some textboxes which are bound to properties in a class: Count: <TextBox x:Name="txtCount" Text="{Binding Count, Mode=TwoWay}" Width="50"/> Days: <TextBox x:Name="txtDays" Text="{Binding Days, Mode=TwoWay}" Width="50"/> and a textblock which is multibound like so: <TextBlock x:Name="tbkTotal"> <TextBlock.Text> <MultiBinding StringFormat="Days: {0}, Count: {1}"> <Binding Path="Days" /> /* This isn't updating */ <Binding Path="Count" /> </MultiBinding> </TextBlock.Text> </TextBlock> My DataContext is set in the Window1.xaml.cs file. public Window1() { InitializeComponent(); Sample sample = new Sample(); this.DataContext = sample; } I can update the multibound textblock with the Count property just fine, but the Days property always shows 0, even though the Days input accurately reflects changes. I believe that this is because my accessors are different for Days - namely, the Set method. This class is in a different file. public class Sample : INotifyPropertyChanged { private int _count; private TimeSpan _span; public int Count { get { return _count; } set { _count = value; NotifyPropertyChanged("Count"); /* Doesn't seem to be needed, actually */ } } public TimeSpan Span { get { return _span; } } /* The idea is to provide a property for Days, Hours, Minutes, etc. as conveniences to the inputter */ public double Days { get { return _span.Days; } set { TimeSpan ts = new TimeSpan(); double val = value > 0 ? value : 0; ts = TimeSpan.FromDays(val); _span.Add(ts); NotifyPropertyChanged("Span"); /* Here I can only get it to work if I notify that Span has changed - doesn't seem to be aware that the value behind Days has changed. */ } } private void NotifyPropertyChanged(string property) { if (null != this.PropertyChanged) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } public Sample() { _count = 0; _span = new TimeSpan(); } public event PropertyChangedEventHandler PropertyChanged; }

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  • How to prevent duplicates, macro or something?

    - by blez
    Well, the problem is that I've got a lot of code like this for each event passed to the GUI, how can I shortify this? Macros wont do the work I guess. Is there a more generic way to do something like a 'template' ? private delegate void DownloadProgressDelegate(object sender, DownloaderProgressArgs e); void DownloadProgress(object sender, DownloaderProgressArgs e) { if (this.InvokeRequired) { this.BeginInvoke(new DownloadProgressDelegate(DownloadProgress), new object[] { sender, e }); return; } label2.Text = d.speedOutput.ToString(); } private delegate void DownloadSpeedDelegate(object sender, DownloaderProgressArgs e); void DownloadSpeed(object sender, DownloaderProgressArgs e) { if (this.InvokeRequired) { this.BeginInvoke(new DownloadSpeedDelegate(DownloadSpeed), new object[] { sender, e }); return; } string speed = ""; speed = (e.DownloadSpeed / 1024).ToString() + "kb/s"; label3.Text = speed; }

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  • C++ using cdb_read returns extra characters on some reads

    - by Moe Be
    Hi All, I am using the following function to loop through a couple of open CDB hash tables. Sometimes the value for a given key is returned along with an additional character (specifically a CTRL-P (a DLE character/0x16/0o020)). I have checked the cdb key/value pairs with a couple of different utilities and none of them show any additional characters appended to the values. I get the character if I use cdb_read() or cdb_getdata() (the commented out code below). If I had to guess I would say I am doing something wrong with the buffer I create to get the result from the cdb functions. Any advice or assistance is greatly appreciated. char* HashReducer::getValueFromDb(const string &id, vector <struct cdb *> &myHashFiles) { unsigned char hex_value[BUFSIZ]; size_t hex_len; //construct a real hex (not ascii-hex) value to use for database lookups atoh(id,hex_value,&hex_len); char *value = NULL; vector <struct cdb *>::iterator my_iter = myHashFiles.begin(); vector <struct cdb *>::iterator my_end = myHashFiles.end(); try { //while there are more databases to search and we have not found a match for(; my_iter != my_end && !value ; my_iter++) { //cerr << "\n looking for this MD5:" << id << " hex(" << hex_value << ") \n"; if (cdb_find(*my_iter, hex_value, hex_len)){ //cerr << "\n\nI found the key " << id << " and it is " << cdb_datalen(*my_iter) << " long\n\n"; value = (char *)malloc(cdb_datalen(*my_iter)); cdb_read(*my_iter,value,cdb_datalen(*my_iter),cdb_datapos(*my_iter)); //value = (char *)cdb_getdata(*my_iter); //cerr << "\n\nThe value is:" << value << " len is:" << strlen(value)<< "\n\n"; }; } } catch (...){} return value; }

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  • textbox, combobox in WPF listview.

    - by RAJ K
    hello everyone, I am porting an application from foxpro to C#.Net. This is a wine shop billing software. Its billing interface screenshot link is here http://picasaweb.google.com/raj.kishor09/RAJK?feat=directlink But my client wants similar interface on WPF too. I think listview can help me in this regard but don't know how to implement. i figured out that each row of listview should have 2 textbox, 1 combobox and few textblock or label. Not only this but cursor should jump from one control to other control using "Enter/Return" key instead of "Tab" key. Please help me with some code lines. Please guys help me......

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • How do I create a thread-safe write-once read-many value in Java?

    - by Software Monkey
    This is a problem I encounter frequently in working with more complex systems and which I have never figured out a good way to solve. It usually involves variations on the theme of a shared object whose construction and initialization are necessarily two distinct steps. This is generally because of architectural requirements, similar to applets, so answers that suggest I consolidate construction and initialization are not useful. By way of example, let's say I have a class that is structured to fit into an application framework like so: public class MyClass { private /*ideally-final*/ SomeObject someObject; MyClass() { someObject=null; } public void startup() { someObject=new SomeObject(...arguments from environment which are not available until startup is called...); } public void shutdown() { someObject=null; // this is not necessary, I am just expressing the intended scope of someObject explicitly } } I can't make someObject final since it can't be set until startup() is invoked. But I would really like it to reflect it's write-once semantics and be able to directly access it from multiple threads, preferably avoiding synchronization. The idea being to express and enforce a degree of finalness, I conjecture that I could create a generic container, like so: public class WoRmObject<T> { private T object; WoRmObject() { object=null; } public WoRmObject set(T val) { object=val; return this; } public T get() { return object; } } and then in MyClass, above, do: private final WoRmObject<SomeObject> someObject; MyClass() { someObject=new WoRmObject<SomeObject>(); } public void startup() { someObject.set(SomeObject(...arguments from environment which are not available until startup is called...)); } Which raises some questions for me: Is there a better way, or existing Java object (would have to be available in Java 4)? Is this thread-safe provided that no other thread accesses someObject.get() until after it's set() has been called. The other threads will only invoke methods on MyClass between startup() and shutdown() - the framework guarantees this. Given the completely unsynchronized WoRmObject container, it is ever possible under either JMM to see a value of object which is neither null nor a reference to a SomeObject? In other words, does has the JMM always guaranteed that no thread can observe the memory of an object to be whatever values happened to be on the heap when the object was allocated.

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  • pyramid traversal resource url no attribute __name__

    - by Santana
    So I have: resources.py: def _add(obj, name, parent): obj.__name__ = name obj.__parent__ = parent return obj class Root(object): __parent__ = __name__ = None def __init__(self, request): super(Root, self).__init__() self.request = request self.collection = request.db.post def __getitem__(self, key): if u'profile' in key: return Profile(self.request) class Profile(dict): def __init__(self, request): super(Profile, self).__init__() self.__name__ = u'profile' self.__parent__ = Root self.collection = request.db.posts def __getitem__(self, name): post = Dummy(self.collection.find_one(dict(username=name))) return _add(post, name, self) and I'm using MongoDB and pyramid_mongodb views.py: @view_config(context = Profile, renderer = 'templates/mytemplate.pt') def test_view(request): return {} and in mytemplate.pt: <p tal:repeat='item request.context'> ${item} </p> I can echo what's in the database (I'm using mongodb), but when I provided a URL for each item using resource_url() <p tal:repeat='item request.context'> <a href='${request.resource_url(item)}'>${item}</a> </p> I got an error: 'dict' object has no attribute '__name__', can someone help me?

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  • Simple Emacs keybindings

    - by User1
    I have two operations that I do all the time in Emacs: Create a new buffer and paste the clipboard. [C-S-n] Close the current buffer. [C-S-w] Switch to the last viewed buffer [C-TAB] I feel like a keyboard acrobat when doing the first two operations. I think it would be worth trying some custom keybindings and macros. A few questions about this customization: How would I make a macro for #1? Are these good keybindings (i know this is a bit subjective, but they might be used by something popular that I don't use) Has anyone found a Ctrl-Tab macro that will act like Alt-Tab in Linux/Windows? Specifically, I want it have a stack of buffers according to the last viewed timestamp (most recent on top). I want to continue cycling through the stack until I let go of the ctrl key. When the ctrl key is released, I want the current buffer to get an updated position on the stack.

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  • C++ - what does the colon after a constructor mean?

    - by waitinforatrain
    I'd happily Google this but don't know what to call it to Google it. I have a piece of code here: class demo { private: unsigned char len, *dat; public: demo(unsigned char le = 5, unsigned char default) : len(le) { dat = new char[len]; for (int i = 0; i <= le; i++) dat[i] = default; } void ~demo(void) { delete [] *dat; } }; class newdemo : public demo { private: int *dat1; public: newdemo(void) : demo(0, 0) { *dat1 = 0; return 0; } }; (It's from a past exam paper and the question is to correct errors in the code so ignore errors!) My question is, what are the ": len(le) " and " : demo(0, 0)" called? Something to do with inheritance?

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  • replacing data.frame element-wise operations with data.table (that used rowname)

    - by Harold
    So lets say I have the following data.frames: df1 <- data.frame(y = 1:10, z = rnorm(10), row.names = letters[1:10]) df2 <- data.frame(y = c(rep(2, 5), rep(5, 5)), z = rnorm(10), row.names = letters[1:10]) And perhaps the "equivalent" data.tables: dt1 <- data.table(x = rownames(df1), df1, key = 'x') dt2 <- data.table(x = rownames(df2), df2, key = 'x') If I want to do element-wise operations between df1 and df2, they look something like dfRes <- df1 / df2 And rownames() is preserved: R> head(dfRes) y z a 0.5 3.1405463 b 1.0 1.2925200 c 1.5 1.4137930 d 2.0 -0.5532855 e 2.5 -0.0998303 f 1.2 -1.6236294 My poor understanding of data.table says the same operation should look like this: dtRes <- dt1[, !'x', with = F] / dt2[, !'x', with = F] dtRes[, x := dt1[,x,]] setkey(dtRes, x) (setkey optional) Is there a more data.table-esque way of doing this? As a slightly related aside, more generally, I would have other columns such as factors in each data.table and I would like to omit those columns while doing the element-wise operations, but still have them in the result. Does this make sense? Thanks!

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  • Using SQL to get the Last Reply on a Post

    - by Anraiki
    I am trying to replicate a forum function by getting the last reply of a post. For clarity, see PHPBB: there are four columns, and the last column is what I like to replicate. I have my tables created as such: discussion_id (primary key) user_id parent_id comment status pubdate I was thinking of creating a Link Table that would update for each time the post is replied to. The link table would be as follow: discussion_id (primary key) last_user_id last_user_update However, I am hoping that theres a advance query to achieve this method. That is, grabbing each Parent Discussion, and finding the last reply in each of those Parent Discussions. Am I right that there is such a query?

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