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• C# -Interview Question Anonymous Type

  - by Amutha

  Recently i was asked to prove the power of C# 3.0 in a single line( might be tricky) i wrote new int[] { 1, 2, 3 }.Union(new int[]{10,23,45}). ToList().ForEach(x => Console.WriteLine(x)); and explained you can have (i) anonymous array (ii) extension method (iii)lambda and closure all in a single line.I got spot offer. But..... The interviewer asked me how will you convert an anonymous type into know type :( I am 100% sure ,we can not do that.The interviewer replied there is 200% chance to do that if you have a small work around.I was clueless. As usual,I am waiting for your valuable reply(Is it possible?).

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• How do you delete rows from UITableView?

  - by James

  This has been bugging me for hours now and i have not been able to figure it out. I am importing data into a tableview using core data and NSMutableArray. As shown below. CORE DATA ARRAY NSMutableArray *mutableFetchResults = [CoreDataHelper getObjectsFromContext:@"Spot" :@"Name" :YES :managedObjectContext]; self.entityArray = mutableFetchResults; TABLE VIEW - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { NSManagedObject *object = (NSManagedObject *)[entityArray objectAtIndex:indexPath.row]; NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; } NSString *lat1 = [object valueForKey:@"Email"]; //NSLog(@"Current Spot Latitude:%@",lat1); float lat2 = [lat1 floatValue]; //NSLog(@"Current Spot Latitude Float:%g", lat2); NSString *long1 = [object valueForKey:@"Description"]; //NSLog(@"Current Spot Longitude:%@",long1); float long2 = [long1 floatValue]; //NSLog(@"Current Spot Longitude Float:%g", long2); //Getting current location from NSDictionary CoreDataTestAppDelegate *appDelegate = (CoreDataTestAppDelegate *) [[UIApplication sharedApplication] delegate]; NSString *locLat = [NSString stringWithFormat:appDelegate.latitude]; float locLat2 = [locLat floatValue]; //NSLog(@"Lat: %g",locLat2); NSString *locLong = [NSString stringWithFormat:appDelegate.longitude]; float locLong2 = [locLong floatValue]; //NSLog(@"Long: %g",locLong2); //Distance Shizzle //Prime's Location CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:lat2 longitude:long2]; //Home Location CLLocation *loc2 = [[CLLocation alloc] initWithLatitude:locLat2 longitude:locLong2]; double distance = [loc1 getDistanceFrom: loc2] / 1000; int myInt = (int)(distance + (distance>0 ? 0.5 : -0.5)); //NSLog(@"INT VAL :%i", myInt); NSMutableString* converted = [NSMutableString stringWithFormat:@"%.1f", distance]; [converted appendString: @" Km"]; //NSLog(@"Distance between Prime and home = %g", converted); if (myInt < 11) { cell.textLabel.text = [object valueForKey:@"Name"]; cell.detailTextLabel.text = [NSString stringWithFormat:converted]; } else { } // Configure the cell... return cell; } I am trying to get the table only to display results that are within a certain distance. This method here works apart from the fact that the results over a certain distance are still in the table, they are just not graphically visible. I am led to believe that i have to carry out the filtering process before the formatting the table but i can not seem to do this. Please help. My xcode skills are not brilliant so code suggestions would be helpfull.

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• compiler warning at C++ template base class

  - by eike

  I get a compiler warning, that I don't understand in that context, when I compile the "Child.cpp" from the following code. (Don't wonder: I stripped off my class declarations to the bare minuum, so the content will not make much sense, but you will see the problem quicker). I get the warning with VS2003 and VS2008 on the highest warning level. The code AbstractClass.h : #include <iostream> template<typename T> class AbstractClass { public: virtual void Cancel(); // { std::cout << "Abstract Cancel" << std::endl; }; virtual void Process() = 0; }; //outside definition. if I comment out this and take the inline //definition like above (currently commented out), I don't get //a compiler warning template<typename T> void AbstractClass<T>::Cancel() { std::cout << "Abstract Cancel" << std::endl; } Child.h : #include "AbstractClass.h" class Child : public AbstractClass<int> { public: virtual void Process(); }; Child.cpp : #include "Child.h" #include <iostream> void Child::Process() { std::cout << "Process" << std::endl; } The warning The class "Child" is derived from "AbstractClass". In "AbstractClass" there's the public method "AbstractClass::Cancel()". If I define the method outside of the class body (like in the code you see), I get the compiler warning... AbstractClass.h(7) : warning C4505: 'AbstractClass::Cancel' : unreferenced local function has been removed with [T=int] ...when I compile "Child.cpp". I do not understand this, because this is a public function and the compiler can't know if I later reference this method or not. And, in the end, I reference this method, because I call it in main.cpp and despite this compiler warning, this method works if I compile and link all files and execute the program: //main.cpp #include <iostream> #include "Child.h" int main() { Child child; child.Cancel(); //works, despite the warning } If I do define the Cancel() function as inline (you see it as out commented code in AbstractClass.h), then I don't get the compiler warning. Of course my program works, but I want to understand this warning or is this just a compiler mistake? Furthermore, if do not implement AbsctractClass as a template class (just for a test purpose in this case) I also don't get the compiler warning...?

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• How to format a function pointer?

  - by Longpoke

  Is there any way to print a pointer to a function in ANSI C? Of course this means you have to cast the function pointer to void pointer, but it appears that's not possible?? #include <stdio.h> int main() { int (*funcptr)() = main; printf("%p\n", (void* )funcptr); printf("%p\n", (void* )main); return 0; } $ gcc -ansi -pedantic -Wall test.c -o test test.c: In function 'main': test.c:6: warning: ISO C forbids conversion of function pointer to object pointer type test.c:7: warning: ISO C forbids conversion of function pointer to object pointer type $ ./test 0x400518 0x400518 It's "working", but non-standard...

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• Faster way to iterate through a jagged array?

  - by George Johnston

  I would like to iterate through an array that covers every pixel on my screen. i.e: for (int y = 598; y > 0; y--) { for (int x = 798; x > 0; x--) { if (grains[x][y]) { spriteBatch.Draw(Grain, new Vector2(x,y), Color.White); } } } ...my texture is a 1x1 pixel image that is drawn to the screen when the array value is true. It runs decent -- but there is definitely lag the more screen I cover. Is there a better way to accomplish what I am trying to achieve?

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• Updating a TableView with a WebService and Saving to CoreData

  - by jcady

  I am working on a project where I have a table view that is currently updated via a web request that returns XML. I implemented -(int)numberOfRowsInTableView:(NSTableView*)tv and -(id)tableView:(NSTableView *)tv objectValueForTableColumn:(NSTableColumn*)tableColumn row:(int)row in my XML parsing class, and have the table updated with the data that is pulled down from the server. I want to save the data that is pulled down using Core Data, so that the table can be saved/loaded. Then later on application start when the web request is made, it will only add data that is not already present. (The XML is sorted by release date, so later I will check to see which release dates are not loaded up from the Core Data store, and only load newer entries.) How would I go about implementing this? I am a very new Cocoa developer, but have gone through the entire Hillegass book. Thanks so much.

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• How do I copy object in Qt?

  - by Martin

  I'm using Qt and have some real basic problems. I have created my own widget MyTest that have a variable obj. I need to set this variable obj from an object outside of the widget so that the variable is copied not just a pointer to another object. I get an error message and can't figure out how to do this basic stuff. This is the code I'm using: MyTest.h: class MyTest : public QWidget { Q_OBJECT public: void setObj(QObject &inobj); QObject obj; .... } MyTest.cpp: void MyTest::setObj(QObject &inobj) { obj = inobj; //HERE I get the error message: "illegal access from 'QObject' to protected/private member 'QObject::operator=(const QObject &)'" } main.cpp: int main(int argc, char *argv[]) { QApplication a(argc, argv); QObject *ob = new QObject(); MyTest w; w.setObj(*ob); } Thanks for your help!

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• CUDA threads output different value

  - by kar

  HAi, I wrote a cuda program , i have given the kernel function below. The device memory is allocated through CUDAMalloc(); the value of *md is 10; __global__ void add(int *md) { int x,oper=2; x=threadIdx.x; * md = *md*oper; if(x==1) { *md = *md*0; } if(x==2) { *md = *md*10; } if(x==3) { *md = *md+1; } if(x==4) { *md = *md-1; } } executed the above code add<<<1,5>>(*md) , add<<<1,4>>>(*md) for <<<1,5>>> the output is 19 for <<<1,4>>> the output is 21 1) I have doubt that cudaMalloc() will allocate in device main memory? 2) Why the last thread alone is executed always in the above program? Thank you

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• const return value and template instantiation

  - by Rimo

  From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. .... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. .... While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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• Read and write struct in C

  - by Sergey

  I have a struct: typedef struct student { char fname[30]; char sname[30]; char tname[30]; Faculty fac; int course; char group[10]; int room; int bad; } Student; I read it from the file: Database * dbOpen(char *fname) { FILE *fp = fopen(fname, "rb"); List *lst, *temp; Student *std; Database *db = malloc(sizeof(*db)); if (!fp) return NULL; FileNameS = fname; std = malloc(sizeof(*std)); if (!fread(std, sizeof(*std), 1, fp)) { db->head = db->tail = NULL; return db; } lst = malloc(sizeof(*lst)); lst->s = std; lst->prev = NULL; db->head = lst; while (!feof(fp)) { fread(std, sizeof(*std), 1, fp); temp = malloc(sizeof(*temp)); temp->s = std; temp->prev = lst; lst->next = temp; lst = temp; } lst->next = NULL; db->tail = lst; fclose(fp); return db; } And I have a problem... At the last record i have a such file pointer: `fp 0x10311448 {_ptr=0x00344b90 "???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? _ _iobuf * ` And i read last record 2 times... Save file code: void * dbClose(Database *db) { FILE *fp = fopen(FileNameS, "w+b"); List *lst, *temp; lst = db->head; while(lst != NULL) { fwrite(lst->s, sizeof(*(lst->s)), 1, fp); temp = lst; lst = lst->next; free(temp); } free(db); fclose(fp); }

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• Agilent E4426B signal generator locks up during multiple GPIB *SAV operations

  - by aspiehler

  I have a test fixture with an Agilent E4426B RF signal generator connected to a PC via a National Instrument Ethernet-to-GPIB bridge. My software is attempting to sanitize the instrument by presetting it and then saving the current state to all of the memory locations writable via the standard SCPI command "*SAV x,y". The loop works to a point, but eventually the instrument responds with an error and continuously displays the "L" icon on the front display and a "Remote preset" message at the bottom. At that point it won't respond to any more remote commands and I have to either cycle power or press LOCAL, then PRESET at which point it takes about 3 minutes to finish presetting. At that point the "L" icon is still present and and the next GPIB command sent to the instrument causes it to report a -113 error (undefined header) in the instrument error queue. I fired up NI spy to see what was happening, and found that the error was happening at the same point in the loop - "*SAV 6,2" in this case. From NI Spy: Send (0, 0x0017, "*SAV 6,2", 8 (0x8), NLend (0,0x01)) Process ID: 0x00000520 Thread ID: 0x00000518 ibsta:0xc168 iberr: 6 ibcntl: 2(0x2) And here's the code from the instrument driver: int CHP_E4426b::Erase() { if ((m_StatusCode = Initialize()) != GPIB_SUCCESS) // basically just sends "*RST" return m_StatusCode; m_SaveState = "*SAV %d, %d"; for (int i=0; i < 10; i++) for (int j=0; j < 100; j++) { sprintf(m_CmdString, m_SaveState, j, i); if ((m_StatusCode = Send(m_CmdString, strlen(m_CmdString))) != GPIB_SUCCESS) return m_StatusCode; } return GPIB_SUCCESS; } I tried putting a small Sleep() delay (10-20 ms) at the end of the inner loop, and to my surprise it caused the error to show up earlier rather than later. 10 ms caused the loop to error out at 44,1 and 20 ms was even sooner. I've already eliminated faulty cabling or the instrument as the culprit. This same type of sequence works without any error on a higher end signal generator, so I'm tempted to chalk this up to a bug in the instrument's firmware.

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• SurfaceView for Camera Preview won't get destroyed when pressing Power-Botton

  - by for3st

  I want to implement a camera preview. For that I have a custom View CameraView extends ViewGroup that in the constructor programatically creates an surfaceView. I have the following components (higly simplified for beverity): ScannerFragment.java public View onCreateView(..) { //inflate view and get cameraView } public void onResume() { //open camera -> set rotation -> startPreview (in a thread) -> //set preview callback -> start decoding worker } public void onPause() { // stop decoding worker -> stop Preview -> release camera } CameraView.java extends ViewGroup public void setUpCalledInConstructor(Context context) { //create a surfaceview and add it to this viewgroup -> //get SurfaceHolder and set callback } /* SurfaceHolder.Callback */ public void surfaceCreated(SurfaceHolder holder) { camera.setPreviewDisplay(holder); } public void surfaceDestroyed(SurfaceHolder holder) { //NOTHING is done here } public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { camera.getParameters().setPreviewSize(previewSize.width, previewSize.height); } fragment_scanner.xml <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <com.myapp.camera.CameraView android:id="@+id/cameraPreview" android:layout_width="match_parent" android:layout_height="match_parent"/> </RelativeLayout> I think I have set the lifecycle correct (getting resources onResume(), releasing it onPause() roughly said) and the following works just fine: pressing home and returning pressing Taskswitcher and returning rotation But one thing doesn't work and that is when I press the power-button on the device and then return to the camera-preview. The result is: the preview is stuck with the image that was last captured before button was pressed. If I rotate it works fine again, since it will get through the lifecycle. After some research I found out that this is probably due to the fact that surfaceView won't get destroyed when the power-button is pressed, i.e. SurfaceHolder.Callback.surfaceDestroyed(SurfaceHolder holder) won't be called. And in fact when I compare the (very verbose) log output of the home-button-case and the power-button-case it's the same except that 'surfaceDestroyed' won't get called. So far I found no solution whatsoever to work around it. I purposely avoid any resource cleaning code in my surfaceDestroyed(), but this does not help. My idea was to manually destroy the surfaceView like asked in this question but this seems not possible. I also tested other applications with surfaceViews/cameras and they don't seem to have this issue. So I would appreciate any hints or tips on that.

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• Thread Local Storage and local method variables

  - by miguel

  In c#, each thread has its own stack space. If this is the case, why is the following code not thread-safe? (It is stated that this code is thread-safe on this post: Locking in C# class Foo { private int count = 0; public void TrySomething() { count++; } } As count is an int (stack variable), surely this value would be isolated to an individual thread, on its own stack, and therefore thread-safe? I am probably missing something here, but I dont understand what is actually in Thread Local Storage if not stack-based variables for the thread?

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• Detecting Infinite recursion in Python or dynamic languages

  - by drozzy

  Recently I tried compiling program something like this with GCC: int f(int i){ if(i<0){ return 0;} return f(i-1); and it ran just fine. When I inspected the stack frames the compiler optimized the program to use only one frame, by just jumping back to the beginning of the function and only replacing the arguments to f. And - the compiler wasn't even running in optimized mode. Now, when I try the same thing in Python - I hit maximum recursion wall (or stack overflow). Is there way that a dynamic language like python can take advantage of these nice optimizations? Maybe it's possible to use a compiler instead of an interpreter to make this work? Just curious!

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• value of type 'string' cannot be converted to 'Devart.data.postgresql.PgSqlParameter'

  - by hector

  The following is my PostgreSQL table structure and the vb.net code to insert into the tables.Using Devart's Component For PostgreSQL Connect table gtab83 CREATE TABLE gtab83 ( orderid integer NOT NULL DEFAULT nextval('seq_gtab83_id'::regclass), acid integer, slno integer, orderdte date ) table gtab84 CREATE TABLE gtab84 ( orderdetid integer DEFAULT nextval('seq_gtab84_id'::regclass), productid integer, qty integer, orderid integer ) Code to insert into the above tables is below '1.)INSERT INTO gtab83(orderid,acid, slno, orderdte) VALUES (?, ?, ?); '2.)INSERT INTO gtab84(orderdetid,productid, qty, orderid) VALUES (?, ?, ?); Try Dim cmd As PgSqlCommand = New PgSqlCommand("", Myconnstr) cmd.CommandText = _ "INSERT INTO GTAB83(ACID,SLNO,ORDERDTE)" & _ "VALUES " & _ "(@acid,@slno,@orderdte);" Dim paramAcid As PgSqlParameter = New PgSqlParameter("@acid", PgSqlType.Int, 0) Dim paramSlno As PgSqlParameter = New PgSqlParameter("@slno", PgSqlType.Int, 0) Dim paramOrderdte As PgSqlParameter = New PgSqlParameter("@orderdte", PgSqlType.Date, 0) paramAcid = cboCust.SelectedValue paramSlno = txtOrderNO.Text #ERROR# paramOrderdte = (txtDate.Text, "yyyy-MM-dd") #ERROR# Catch ex As Exception End Try ERROR : value of type 'string' cannot be converted to 'Devart.data.postgresql.PgSqlParameter'

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• Swing: Scroll to bottom of JScrollPane, conditional on current viewport location

  - by I82Much

  Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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• Chaining multiple ShellExecute calls

  - by IVlad

  Consider the following code and its executable - runner.exe: #include <iostream> #include <string> #include <windows.h> using namespace std; int main(int argc, char *argv[]) { SHELLEXECUTEINFO shExecInfo; shExecInfo.cbSize = sizeof(SHELLEXECUTEINFO); shExecInfo.fMask = NULL; shExecInfo.hwnd = NULL; shExecInfo.lpVerb = "open"; shExecInfo.lpFile = argv[1]; string Params = ""; for ( int i = 2; i < argc; ++i ) Params += argv[i] + ' '; shExecInfo.lpParameters = Params.c_str(); shExecInfo.lpDirectory = NULL; shExecInfo.nShow = SW_SHOWNORMAL; shExecInfo.hInstApp = NULL; ShellExecuteEx(&shExecInfo); return 0; } These two batch files both do what they're supposed to, which is run notepad.exe and run notepad.exe and tell it to try to open test.txt: 1. runner.exe notepad.exe 2. runner.exe notepad.exe test.txt Now, consider this batch file: 3. runner.exe runner.exe notepad.exe This one should run runner.exe and send notepad.exe as one of its command line arguments, shouldn't it? Then, that second instance of runner.exe should run notepad.exe - which doesn't happen, I get a "Windows cannot find 'am'. Make sure you typed the name correctly, and then try again" error. If I print the argc argument, it's 14 for the second instance of runner.exe, and they are all weird stuff like Files\Microsoft, SQL, Files\Common and so on. I can't figure out why this happens. I want to be able to string as many runner.exe calls using command line arguments as possible, or at least 2. How can I do that? I am using Windows 7 if that makes a difference.

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• jquery thickbox not working in 2005 ASP.NET

  - by Alex

  public void DisplayThickBox(Page page, int width, int height) { string script = "<script type='text/javascript'>"; script += "$(document).ready(function(){"; script += "tb.show('null', 'auto-insurance-redirect.aspx?keepThis=true&TB_iframe=true&height=" + height.ToString() + "&amp;width=" + width.ToString() + "',null);"; script += "});"; script +="</script>"; ScriptManager.RegisterStartupScript(page, page.GetType(), "", script, true); } ^^^Method to display the thickbox...^^^ DisplayThickBox(this, 518, 321); ^^^Call to method in the click event of the button that fires it...^^^ Page is just refreshing and the thickbox is never displayed. I'm trying to call the javascript manually since im doing some other stuff before i display the thickbox in the code behind...

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• Faster way to iterate through a jaggad array?

  - by George Johnston

  I would like to iterate through an array that covers every pixel on my screen. i.e: for (int y = 598; y > 0; y--) { for (int x = 798; x > 0; x--) { if (grains[x][y]) { spriteBatch.Draw(Grain, new Vector2(x,y), Color.White); } } } ...my texture is a 1x1 pixel image that is drawn to the screen when the array value is true. It runs decent -- but there is definitely lag the more screen I cover. Is there a better way to accomplish what I am trying to achieve?

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• Why looping in Delphi faster than C#?

  - by isa

  Delphi: procedure TForm1.Button1Click(Sender: TObject); var I,Tick:Integer; begin Tick := GetTickCount(); for I := 0 to 1000000000 do begin end; Button1.Caption := IntToStr(GetTickCount()-Tick)+' ms'; end; C#: private void button1_Click(object sender, EventArgs e) { int tick = System.Environment.TickCount; for (int i = 0; i < 1000000000; ++i) { } tick = System.Environment.TickCount - tick; button1.Text = tick.ToString()+" ms"; } Delphi gives around 515 ms C# gives around 3775 ms

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• Rails Joins and include columns from joins table

  - by seth.vargo

  I don't understand how to get the columns I want from rails. I have two models - A User and a Profile. A User :has_many Profile (because users can revert back to an earlier version of their profile): > DESCRIBE users; +----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | username | varchar(255) | NO | UNI | NULL | | | password | varchar(255) | NO | | NULL | | | last_login | datetime | YES | | NULL | | +----------------+--------------+------+-----+---------+----------------+   > DESCRIBE profiles; +----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_id | int(11) | NO | MUL | NULL | | | first_name | varchar(255) | NO | | NULL | | | last_name | varchar(255) | NO | | NULL | | | . . . . . . | | . . . . . . | | . . . . . . | +----------------+--------------+------+-----+---------+----------------+ In SQL, I can run the query: > SELECT * FROM profiles JOIN users ON profiles.user_id = users.id LIMIT 1; +----+-----------+----------+---------------------+---------+---------------+-----+ | id | username | password | last_login | user_id | first_name | ... | +----+-----------+----------+---------------------+---------+---------------+-----+ | 1 | john | ****** | 2010-12-30 18:04:28 | 1 | John | ... | +----+-----------+----------+---------------------+---------+---------------+-----+ See how I get all the columns for BOTH tables JOINED together? However, when I run this same query in Rails, I don't get all the columns I want - I only get those from Profile: # in rails console >> p = Profile.joins(:user).limit(1) >> [#<Profile ...>] >> p.first_name >> NoMethodError: undefined method `first_name' for #<ActiveRecord::Relation:0x102b521d0> from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.1/lib/active_record/relation.rb:373:in `method_missing' from (irb):8 # I do NOT want to do this (AKA I do NOT want to use "includes") >> p.user >> NoMethodError: undefined method `user' for #<ActiveRecord::Relation:0x102b521d0> from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.1/lib/active_record/relation.rb:373:in method_missing' from (irb):9 I want to (efficiently) return an object that has all the properties of Profile and User together. I don't want to :include the user because it doesn't make sense. The user should always be part of the most recent profile as if they were fields within the Profile model. How do I accomplish this?

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• C# Language Design: explicit interface implementation of an event

  - by ControlFlow

  Small question about C# language design :)) If I had an interface like this: interface IFoo { int Value { get; set; } } It's possible to explicitly implement such interface using C# 3.0 auto-implemented properties: sealed class Foo : IFoo { int IFoo.Value { get; set; } } But if I had an event in the interface: interface IFoo { event EventHandler Event; } And trying to explicitly implement it using field-like event: sealed class Foo : IFoo { event EventHandler IFoo.Event; } I will get the following compiler error: error CS0071: An explicit interface implementation of an event must use event accessor syntax I think that field-like events is the some kind of dualism for auto-implemented properties. So my question is: what is the design reason for such restriction done?

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• Containers of reference_wrappers (comparison operators required?)

  - by kloffy

  If you use stl containers together with reference_wrappers of POD types, the following code works just fine: int i = 3; std::vector< boost::reference_wrapper<int> > is; is.push_back(boost::ref(i)); std::cout << (std::find(is.begin(),is.end(),i)!=is.end()) << std::endl; However, if you use non-POD types such as (contrived example): struct Integer { int value; bool operator==(const Integer& rhs) const { return value==rhs.value; } bool operator!=(const Integer& rhs) const { return !(*this == rhs); } }; It doesn't suffice to declare those comparison operators, instead you have to declare: bool operator==(const boost::reference_wrapper<Integer>& lhs, const Integer& rhs) { return boost::unwrap_ref(lhs)==rhs; } And possibly also: bool operator==(const Integer& lhs, const boost::reference_wrapper<Integer>& rhs) { return lhs==boost::unwrap_ref(rhs); } In order to get the equivalent code to work: Integer j = { 0 }; std::vector< boost::reference_wrapper<Integer> > js; js.push_back(boost::ref(j)); std::cout << (std::find(js.begin(),js.end(),j)!=js.end()) << std::endl; Now, I'm wondering if this is really the way it's meant to be done, since it seems impractical. It just seems there should be a simpler solution, e.g. templates: template<class T> bool operator==(const boost::reference_wrapper<T>& lhs, const T& rhs) { return boost::unwrap_ref(lhs)==rhs; } template<class T> bool operator==(const T& lhs, const boost::reference_wrapper<T>& rhs) { return lhs==boost::unwrap_ref(rhs); } There's probably a good reason why reference_wrapper behaves the way it does (possibly to accomodate non-POD types without comparison operators?). Maybe there already is an elegant solution and I just haven't found it.

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• First ASM program

  - by Tal

  Hello, I'm trying to run my first ASM 8086 program on MASM on Windows Vista 64bit OS. I put this program on my MASM editor: .model small .stack .data message db "Hello world, I'm learning Assembly !!!", "$" .code main proc mov ax,seg message mov ds,ax mov ah,09 lea dx,message int 21h mov ax,4c00h int 21h main endp end main and the MASM editor gives me this output that I got no idea what's wrong with the program: Assembling: D:\masm32\First.asm D:\masm32\First.asm(9) : error A2004: symbol type conflict D:\masm32\First.asm(19) : warning A4023: with /coff switch, leading underscore required for start address : main _ Assembly Error Where is the problem with this code? This is my first ASM program please remember. Thank you :)

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• EF Code First Detached Entity not updating object reference

  - by Alvaro

  I'm posting the exact entity: public class Person : ContactableEntity { public Plan Plan { get; set; } public int Record { get; set; } public int PersonTypeValue { get; set; } } I'm using the following code to update in a disconected context fashion: public void Update(DbSet MySet, object Obj) { MySet.Attach(Obj); var Entry = this.Entry(Obj); Entry.State = EntityState.Modified; this.SaveChanges(); } This is a method exposed by my dbContext Called this way: PersistentManager.Update(PersistentManager.Personas,UpdatedPersona); The problem is, EF will update any property but the referenced Plan object. Can someone tell me where is the mistake? In advance : the entity reaches the point of update with all the properties correctly set. EF just fails to update the FK in the Database (no exception though)

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