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  • OpenGL antialiasing not working

    - by user146780
    I'v been trying to anti alias with OGL. I found a code chunk that is supposed to do this but I see no antialiasing. I also reset my settings in Nvidia Control Panel but no luck. Does this code in fact antialias the cube? GLboolean polySmooth = GL_TRUE; static void init(void) { glCullFace (GL_BACK); glEnable (GL_CULL_FACE); glBlendFunc (GL_SRC_ALPHA_SATURATE, GL_ONE); glClearColor (0.0, 0.0, 0.0, 0.0); } #define NFACE 6 #define NVERT 8 void drawCube(GLdouble x0, GLdouble x1, GLdouble y0, GLdouble y1, GLdouble z0, GLdouble z1) { static GLfloat v[8][3]; static GLfloat c[8][4] = { {0.0, 0.0, 0.0, 1.0}, {1.0, 0.0, 0.0, 1.0}, {0.0, 1.0, 0.0, 1.0}, {1.0, 1.0, 0.0, 1.0}, {0.0, 0.0, 1.0, 1.0}, {1.0, 0.0, 1.0, 1.0}, {0.0, 1.0, 1.0, 1.0}, {1.0, 1.0, 1.0, 1.0} }; /* indices of front, top, left, bottom, right, back faces */ static GLubyte indices[NFACE][4] = { {4, 5, 6, 7}, {2, 3, 7, 6}, {0, 4, 7, 3}, {0, 1, 5, 4}, {1, 5, 6, 2}, {0, 3, 2, 1} }; v[0][0] = v[3][0] = v[4][0] = v[7][0] = x0; v[1][0] = v[2][0] = v[5][0] = v[6][0] = x1; v[0][1] = v[1][1] = v[4][1] = v[5][1] = y0; v[2][1] = v[3][1] = v[6][1] = v[7][1] = y1; v[0][2] = v[1][2] = v[2][2] = v[3][2] = z0; v[4][2] = v[5][2] = v[6][2] = v[7][2] = z1; #ifdef GL_VERSION_1_1 glEnableClientState (GL_VERTEX_ARRAY); glEnableClientState (GL_COLOR_ARRAY); glVertexPointer (3, GL_FLOAT, 0, v); glColorPointer (4, GL_FLOAT, 0, c); glDrawElements(GL_QUADS, NFACE*4, GL_UNSIGNED_BYTE, indices); glDisableClientState (GL_VERTEX_ARRAY); glDisableClientState (GL_COLOR_ARRAY); #else printf ("If this is GL Version 1.0, "); printf ("vertex arrays are not supported.\n"); exit(1); #endif } /* Note: polygons must be drawn from front to back * for proper blending. */ void display(void) { if (polySmooth) { glClear (GL_COLOR_BUFFER_BIT); glEnable (GL_BLEND); glEnable (GL_POLYGON_SMOOTH); glDisable (GL_DEPTH_TEST); } else { glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glDisable (GL_BLEND); glDisable (GL_POLYGON_SMOOTH); glEnable (GL_DEPTH_TEST); } glPushMatrix (); glTranslatef (0.0, 0.0, -8.0); glRotatef (30.0, 1.0, 0.0, 0.0); glRotatef (60.0, 0.0, 1.0, 0.0); drawCube(-0.5, 0.5, -0.5, 0.5, -0.5, 0.5); glPopMatrix (); glFlush (); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(30.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } void keyboard(unsigned char key, int x, int y) { switch (key) { case `t': case `T': polySmooth = !polySmooth; glutPostRedisplay(); break; case 27: exit(0); /* Escape key */ break; default: break; } } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_ALPHA | GLUT_DEPTH); glutInitWindowSize(200, 200); glutCreateWindow(argv[0]); init (); glutReshapeFunc (reshape); glutKeyboardFunc (keyboard); glutDisplayFunc (display); glutMainLoop(); return 0; } Thanks

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  • I am getting the error Wrong type argument to unary minus and Expected ';' before ':' token

    - by James B.
    I am getting the error Wrong type argument to unary minus and Expected ';' before ':' token The error occurs at the - (NSIndexPath *).... line I am really New at this, so if there is anymore info needed, please ask, if you need to see the entire app, please e-mail me @ james at sevenotwo dot com. the app isn't really complicated. it is based on the sample code on Apple's website for the iphonedatacorerecipes code. #pragma mark - #pragma mark Editing rows - (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSIndexPath *rowToSelect = indexPath; NSInteger section = indexPath.section; BOOL isEditing = self.editing; // If editing, don't allow notes to be selected // Not editing: Only allow notes to be selected if ((isEditing && section == NOTES_SECTION) || (!isEditing && section != NOTES_SECTION)) { [tableView deselectRowAtIndexPath:indexPath animated:YES]; rowToSelect = nil; } return rowToSelect; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSInteger section = indexPath.section; UIViewController *nextViewController = nil; /* What to do on selection depends on what section the row is in. For Type, Notes, and Instruments, create and push a new view controller of the type appropriate for the next screen. */ switch (section) { case TYPE_SECTION: nextViewController = [[TypeSelectionViewController alloc] initWithStyle:UITableViewStyleGrouped]; ((TypeSelectionViewController *)nextViewController).doctor = doctor; break; case NOTES_SECTION: nextViewController = [[NotesViewController alloc] initWithNibName:@"NotesView" bundle:nil]; ((NotesViewController *)nextViewController).doctor = doctor; break; case INSTRUMENTS_SECTION: nextViewController = [[InstrumentDetailViewController alloc] initWithStyle:UITableViewStyleGrouped]; ((InstrumentDetailViewController *)nextViewController).doctor = doctor; if (indexPath.row < [doctor.instruments count]) { Instrument *instrument = [instruments objectAtIndex:indexPath.row]; ((InstrumentDetailViewController *)nextViewController).instrument = instrument; } break; default: break; } // If we got a new view controller, push it . if (nextViewController) { [self.navigationController pushViewController:nextViewController animated:YES]; [nextViewController release]; } } - (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCellEditingStyle style = UITableViewCellEditingStyleNone; // Only allow editing in the instruments section. // In the instruments section, the last row (row number equal to the count of instruments) is added automatically (see tableView:cellForRowAtIndexPath:) to provide an insertion cell, so configure that cell for insertion; the other cells are configured for deletion. if (indexPath.section == INSTRUMENTS_SECTION) { // If this is the last item, it's the insertion row. if (indexPath.row == [doctor.instruments count]) { style = UITableViewCellEditingStyleInsert; } else { style = UITableViewCellEditingStyleDelete; } } return style; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { // Only allow deletion, and only in the instruments section if ((editingStyle == UITableViewCellEditingStyleDelete) && (indexPath.section == INSTRUMENTS_SECTION)) { // Remove the corresponding instrument object from the doctor's instrument list and delete the appropriate table view cell. Instrument *instrument = [instruments objectAtIndex:indexPath.row]; [doctor removeInstrumentsObject:instrument]; [instruments removeObject:instrument]; NSManagedObjectContext *context = instrument.managedObjectContext; [context deleteObject:instrument]; [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationTop]; } }

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  • AlerDialog is not created - java.lang.IllegalArgumentException: Activity#onCreateDialog did not crea

    - by Jayomat
    Hi, I want to create a normal AlertDialog. I used the example provided by the android dev docs. I just changed the DIALOG_PAUSED_ID to DIALOG_DELETEDB. If I execute my code and press the button which in return should create the dialog, I get the following error log: 04-29 01:01:20.973: WARN/dalvikvm(1168): threadid=3: thread exiting with uncaught exception (group=0x4001b188) 04-29 01:01:20.973: ERROR/AndroidRuntime(1168): Uncaught handler: thread main exiting due to uncaught exception 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): java.lang.IllegalArgumentException: Activity#onCreateDialog did not create a dialog for id 4 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.app.Activity.createDialog(Activity.java:871) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.app.Activity.showDialog(Activity.java:2483) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at mjb.project.AVV.Favs.onMenuItemSelected(Favs.java:111) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:730) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:139) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:855) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.view.menu.IconMenuView.invokeItem(IconMenuView.java:525) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.view.menu.IconMenuItemView.performClick(IconMenuItemView.java:122) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.view.View.onTouchEvent(View.java:4179) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.widget.TextView.onTouchEvent(TextView.java:6540) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.view.View.dispatchTouchEvent(View.java:3709) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.os.Handler.dispatchMessage(Handler.java:99) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.os.Looper.loop(Looper.java:123) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at android.app.ActivityThread.main(ActivityThread.java:4363) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at java.lang.reflect.Method.invokeNative(Native Method) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at java.lang.reflect.Method.invoke(Method.java:521) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 04-29 01:01:20.993: ERROR/AndroidRuntime(1168): at dalvik.system.NativeStart.main(Native Method) so here are the "relevant" code parts: define the ID: private static final int DELETE_DB_ID = 3; private Dialog dialog; static final int DIALOG_DELETEDB = 4; onCreateDialog(...): protected Dialog onCreateDialog(int id) { switch(id) { case DIALOG_DELETEDB: // do the work to define the pause Dialog AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage("Are you sure you want to exit?") .setCancelable(false) .setPositiveButton("Yes", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { Favs.this.finish(); } }) .setNegativeButton("No", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { dialog.cancel(); } }); AlertDialog alert = builder.create(); alert.show(); break; default: dialog = null; } return dialog; } Here I try to "create" the dialog: @Override public boolean onMenuItemSelected(int featureId, MenuItem item) { switch(item.getItemId()) { case ADD_ID: createNote(); return true; case DELETE_DB_ID: showDialog(DIALOG_DELETEDB); return true; } return super.onMenuItemSelected(featureId, item); } As I already said, I just copied the code and changed the name. Unfortunately, I don't understand the error log message.. :/ Somehow I think I don't return the created dialog, but I cannot see "where" my reference is or where/what I have to return... thanks in advance for help.

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  • c# SendMessage and Skype woes

    - by Xcelled194
    I'm trying to create an add-on to Skype with C#. I don't want to use Skype4COM, as I'd like the experience with messages and such. Unfortunately, the messages are tripping me up. I've got the pumps and such set up. They all work, and my app successfully sends the "APIDiscover" message to Skype, gets a "PendingAuth" response and then the "AttachSuccess" message. However, when I try to send "ping" to Skype (to which it should reply "pong") nothing happens. The return code from SendMessage is 0 but Marshall.GetLastWin32Error is 1400 (Invalid handle). The handle was returned with the AttachSuccess method. The equivalent C++ code does work, so I'm at a loss. First is the C++ code I'm using as a guide: Here's the (cut down) message pump. You can ignore everything but where I put the //<---- static LRESULT APIENTRY SkypeAPITest_Windows_WindowProc( HWND hWindow, UINT uiMessage, WPARAM uiParam, LPARAM ulParam) { LRESULT lReturnCode; bool fIssueDefProc; lReturnCode=0; fIssueDefProc=false; switch(uiMessage) { case WM_COPYDATA: if( hGlobal_SkypeAPIWindowHandle==(HWND)uiParam ) { PCOPYDATASTRUCT poCopyData=(PCOPYDATASTRUCT)ulParam; printf( "Message from Skype(%u): %.*s\n", poCopyData->dwData, poCopyData->cbData, poCopyData->lpData); lReturnCode=1; } break; default: if( uiMessage==uiGlobal_MsgID_SkypeControlAPIAttach ) { switch(ulParam) { case SKYPECONTROLAPI_ATTACH_SUCCESS: printf("!!! Connected; to terminate issue #disconnect\n"); hGlobal_SkypeAPIWindowHandle=(HWND)uiParam;//<---- Right here is where we receive the handle from Skype. break; } if( fIssueDefProc ) lReturnCode=DefWindowProc( hWindow, uiMessage, uiParam, ulParam); return(lReturnCode); } and this is the (again dumbed down) "sending message" code void __cdecl Global_InputProcessingThread(void *) { static char acInputRow[1024]; bool fProcessed; if( SendMessageTimeout( HWND_BROADCAST, uiGlobal_MsgID_SkypeControlAPIDiscover, (WPARAM)hInit_MainWindowHandle, 0, SMTO_ABORTIFHUNG, 1000, NULL)!=0 ) { while(Global_Console_ReadRow( acInputRow, sizeof(acInputRow)-1)) { if( fProcessed==false && hGlobal_SkypeAPIWindowHandle!=NULL ) { COPYDATASTRUCT oCopyData; // send command to skype oCopyData.dwData=0; oCopyData.lpData=acInputRow; oCopyData.cbData=strlen(acInputRow)+1; if( oCopyData.cbData!=1 ) { if( SendMessage( hGlobal_SkypeAPIWindowHandle, WM_COPYDATA, (WPARAM)hInit_MainWindowHandle, (LPARAM)&oCopyData)==FALSE ) { hGlobal_SkypeAPIWindowHandle=NULL; printf("!!! Disconnected\n"); } } } } } SendMessage( hInit_MainWindowHandle, WM_CLOSE, 0, 0); SetEvent(hGlobal_ThreadShutdownEvent); fGlobal_ThreadRunning=false; } And now here's my C# public bool PreFilterMessage(ref Message m) { Console.WriteLine(m.ToString()); if (m.Msg == WM_COPYDATA && SkypeAPIWindowHandle == m.WParam) { SkypeMessage(m); return true; } if (m.Msg == MsgApiAttach) { switch (m.LParam.ToInt32()) { case (int)SkypeControlAPIAttach.SUCCESS: SkypeAPIWindowHandle = m.WParam; //Here's where we set the Skype Handle AttachSuccess(m); return true; } } return false; //Defer all other messages } And here is my DLL import and Sending code [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] static extern IntPtr SendMessageA(IntPtr hWnd, UInt32 Msg, IntPtr wParam, ref MsgHelper.COPYDATASTRUCT lParam); public static void Command(string c) { if (c.Last() != '\0') c += "\0"; //Make string null terminated Console.WriteLine(); MsgHelper.COPYDATASTRUCT cda = new MsgHelper.COPYDATASTRUCT(); cda.dwData = new IntPtr(0); cda.lpData = c; cda.cbData = c.Length + 1; Marshal.GetLastWin32Error(); //Clear last error Console.WriteLine(SendMessageA(mHelper.SkypeAPIWindowHandle, MsgHelper.WM_COPYDATA, IntPtr.Zero, ref cda)); Console.WriteLine(Marshal.GetLastWin32Error()); } COPYDATASTRUCT is: public struct COPYDATASTRUCT { public IntPtr dwData; public int cbData; [MarshalAs(UnmanagedType.LPStr)] public string lpData; } I think that's everything. Let me know if I forgot something. Any ideas why I'm getting the 1400?

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  • SQLAlchemy session management in long-running process

    - by codeape
    Scenario: A .NET-based application server (Wonderware IAS/System Platform) hosts automation objects that communicate with various equipment on the factory floor. CPython is hosted inside this application server (using Python for .NET). The automation objects have scripting functionality built-in (using a custom, .NET-based language). These scripts call Python functions. The Python functions are part of a system to track Work-In-Progress on the factory floor. The purpose of the system is to track the produced widgets along the process, ensure that the widgets go through the process in the correct order, and check that certain conditions are met along the process. The widget production history and widget state is stored in a relational database, this is where SQLAlchemy plays its part. For example, when a widget passes a scanner, the automation software triggers the following script (written in the application server's custom scripting language): ' wiget_id and scanner_id provided by automation object ' ExecFunction() takes care of calling a CPython function retval = ExecFunction("WidgetScanned", widget_id, scanner_id); ' if the python function raises an Exception, ErrorOccured will be true ' in this case, any errors should cause the production line to stop. if (retval.ErrorOccured) then ProductionLine.Running = False; InformationBoard.DisplayText = "ERROR: " + retval.Exception.Message; InformationBoard.SoundAlarm = True end if; The script calls the WidgetScanned python function: # pywip/functions.py from pywip.database import session from pywip.model import Widget, WidgetHistoryItem from pywip import validation, StatusMessage from datetime import datetime def WidgetScanned(widget_id, scanner_id): widget = session.query(Widget).get(widget_id) validation.validate_widget_passed_scanner(widget, scanner) # raises exception on error widget.history.append(WidgetHistoryItem(timestamp=datetime.now(), action=u"SCANNED", scanner_id=scanner_id)) widget.last_scanner = scanner_id widget.last_update = datetime.now() return StatusMessage("OK") # ... there are a dozen similar functions My question is: How do I best manage SQLAlchemy sessions in this scenario? The application server is a long-running process, typically running months between restarts. The application server is single-threaded. Currently, I do it the following way: I apply a decorator to the functions I make avaliable to the application server: # pywip/iasfunctions.py from pywip import functions def ias_session_handling(func): def _ias_session_handling(*args, **kwargs): try: retval = func(*args, **kwargs) session.commit() return retval except: session.rollback() raise return _ias_session_handling # ... actually I populate this module with decorated versions of all the functions in pywip.functions dynamically WidgetScanned = ias_session_handling(functions.WidgetScanned) Question: Is the decorator above suitable for handling sessions in a long-running process? Should I call session.remove()? The SQLAlchemy session object is a scoped session: # pywip/database.py from sqlalchemy.orm import scoped_session, sessionmaker session = scoped_session(sessionmaker()) I want to keep the session management out of the basic functions. For two reasons: There is another family of functions, sequence functions. The sequence functions call several of the basic functions. One sequence function should equal one database transaction. I need to be able to use the library from other environments. a) From a TurboGears web application. In that case, session management is done by TurboGears. b) From an IPython shell. In that case, commit/rollback will be explicit. (I am truly sorry for the long question. But I felt I needed to explain the scenario. Perhaps not necessary?)

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  • Help to solve "Robbery Problem"

    - by peiska
    Hello, Can anybody help me with this problem in C or Java? The problem is taken from here: http://acm.pku.edu.cn/JudgeOnline/problem?id=1104 Inspector Robstop is very angry. Last night, a bank has been robbed and the robber has not been caught. And this happened already for the third time this year, even though he did everything in his power to stop the robber: as quickly as possible, all roads leading out of the city were blocked, making it impossible for the robber to escape. Then, the inspector asked all the people in the city to watch out for the robber, but the only messages he got were of the form "We don't see him." But this time, he has had enough! Inspector Robstop decides to analyze how the robber could have escaped. To do that, he asks you to write a program which takes all the information the inspector could get about the robber in order to find out where the robber has been at which time. Coincidentally, the city in which the bank was robbed has a rectangular shape. The roads leaving the city are blocked for a certain period of time t, and during that time, several observations of the form "The robber isn't in the rectangle Ri at time ti" are reported. Assuming that the robber can move at most one unit per time step, your program must try to find the exact position of the robber at each time step. Input The input contains the description of several robberies. The first line of each description consists of three numbers W, H, t (1 <= W,H,t <= 100) where W is the width, H the height of the city and t is the time during which the city is locked. The next contains a single integer n (0 <= n <= 100), the number of messages the inspector received. The next n lines (one for each of the messages) consist of five integers ti, Li, Ti, Ri, Bi each. The integer ti is the time at which the observation has been made (1 <= ti <= t), and Li, Ti, Ri, Bi are the left, top, right and bottom respectively of the (rectangular) area which has been observed. (1 <= Li <= Ri <= W, 1 <= Ti <= Bi <= H; the point (1, 1) is the upper left hand corner, and (W, H) is the lower right hand corner of the city.) The messages mean that the robber was not in the given rectangle at time ti. The input is terminated by a test case starting with W = H = t = 0. This case should not be processed. Output For each robbery, first output the line "Robbery #k:", where k is the number of the robbery. Then, there are three possibilities: If it is impossible that the robber is still in the city considering the messages, output the line "The robber has escaped." In all other cases, assume that the robber really is in the city. Output one line of the form "Time step : The robber has been at x,y." for each time step, in which the exact location can be deduced. (x and y are the column resp. row of the robber in time step .) Output these lines ordered by time . If nothing can be deduced, output the line "Nothing known." and hope that the inspector will not get even more angry. Output a blank line after each processed case.

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  • DEV C ++ Error: expected declaration before '}' token

    - by Francesca
    What does this mean? My program goes like this: (NOTE: The line that has the error was the line coming before case 2.) case 1: { cout<< "C * H * E * M * I * S * T * R * Y \n\n"; cout<< "1) What is the valence electron configuration of Selenium (Se)?\n\n"; cout<< "\na) 1s2 2s2 2p6 3s2\n\n"; cout<< "\nb) 1s2 2s2 2p2\n\n"; cout<< "\nc)4s2 4p4\n\n"; cout<< "\nd) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'c') { cout<<"Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is C. Please press the enter key to proceed to the next question.\n\n"; getch (); } getch (); cout<< "2) Which element yields the biggest atomic radius?\n\n"; cout<< "\na) Ca\n\n"; cout<< "\nb) Xe\n\n"; cout<< "\nc) B\n\n"; cout<< "\nd) Cs\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'd') { cout<< "Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is D. Please press the enter key to proceed to the next question.\n\n"; getch (); } cout<< "3) Name the ionic compound K2 Cr2 O7\n\n"; cout<< "\na) potassium chloride\n\n"; cout<< "\nb) potassium carbonate\n\n"; cout<< "\nc) potassium chromite\n\n"; cout<< "\nd) potassium chromate\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'd') { cout<< "Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is D. Please press the enter key to proceed to the next question.\n\n"; getch (); } } case 2: { cout<< "G * E * O * M * E * T * R * Y \n\n"; The error, as noted in the title is expected declaration before '}' token at the line noted in my opening paragraph.

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  • boost::serialization with mutable members

    - by redmoskito
    Using boost::serialization, what's the "best" way to serialize an object that contains cached, derived values in mutable members, such that cached members aren't serialized, but on deserialization, they are initialized the their appropriate default. A definition of "best" follows later, but first an example: class Example { public: Example(float n) : num(n), sqrt_num(-1.0) {} float get_num() const { return num; } // compute and cache sqrt on first read float get_sqrt() const { if(sqrt_num < 0) sqrt_num = sqrt(num); return sqrt_num; } template <class Archive> void serialize(Archive& ar, unsigned int version) { ... } private: float num; mutable float sqrt_num; }; On serialization, only the "num" member should be saved. On deserialization, the sqrt_num member must be initialized to its sentinel value indicating it needs to be computed. What is the most elegant way to implement this? In my mind, an elegant solution would avoid splitting serialize() into separate save() and load() methods (which introduces maintenance problems). One possible implementation of serialize: template <class Archive> void serialize(Archive& ar, unsigned int version) { ar & num; sqrt_num = -1.0; } This handles the deserialization case, but in the serialization case, the cached value is killed and must be recomputed. Also, I've never seen an example of boost::serialize that explicitly sets members inside of serialize(), so I wonder if this is generally not recommended. Some might suggest that the default constructor handles this, for example: int main() { Example e; { std::ifstream ifs("filename"); boost::archive::text_iarchive ia(ifs); ia >> e; } cout << e.get_sqrt() << endl; return 0; } which works in this case, but I think fails if the object receiving the deserialized data has already been initialized, as in the example below: int main() { Example ex1(4); Example ex2(9); cout << ex1.get_sqrt() << endl; // outputs 2; cout << ex2.get_sqrt() << endl; // outputs 3; // the following two blocks should implement ex2 = ex1; // save ex1 to archive { std::ofstream ofs("filename"); boost::archive::text_oarchive oa(ofs); oa << ex1; } // read it back into ex2 { std::ifstream ifs("filename"); boost::archive::text_iarchive ia(ifs); ia >> ex2; } // these should be equal now, but aren't, // since Example::serialize() doesn't modify num_sqrt cout << ex1.get_sqrt() << endl; // outputs 2; cout << ex2.get_sqrt() << endl; // outputs 3; return 0; } I'm sure this issue has come up with others, but I have struggled to find any documentation on this particular scenario. Thanks!

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  • Common Mercator Projection formulas for Google Maps not working correctly

    - by Tom Halladay
    I am building a Tile Overlay server for Google maps in C#, and have found a few different code examples for calculating Y from Latitude. After getting them to work in general, I started to notice certain cases where the overlays were not lining up properly. To test this, I made a test harness to compare Google Map's Mercator LatToY conversion against the formulas I found online. As you can see below, they do not match in certain cases. Case #1 Zoomed Out: The problem is most evident when zoomed out. Up close, the problem is barely visible. Case #2 Point Proximity to Top & Bottom of viewing bounds: The problem is worse in the middle of the viewing bounds, and gets better towards the edges. This behavior can negate the behavior of Case #1 The Test: I created a google maps page to display red lines using the Google Map API's built in Mercator conversion, and overlay this with an image using the reference code for doing Mercator conversion. These conversions are represented as black lines. Compare the difference. The Results: Check out the top-most and bottom-most lines: The problem gets visually larger but numerically smaller as you zoom in: And it all but disappears at closer zoom levels, regardless of screen orientation. The Code: Google Maps Client Side Code: var lat = 0; for (lat = -80; lat <= 80; lat += 5) { map.addOverlay(new GPolyline([new GLatLng(lat, -180), new GLatLng(lat, 0)], "#FF0033", 2)); map.addOverlay(new GPolyline([new GLatLng(lat, 0), new GLatLng(lat, 180)], "#FF0033", 2)); } Server Side Code: Tile Cutter : http://mapki.com/wiki/Tile_Cutter OpenStreetMap Wiki : http://wiki.openstreetmap.org/wiki/Mercator protected override void ImageOverlay_ComposeImage(ref Bitmap ZipCodeBitMap) { Graphics LinesGraphic = Graphics.FromImage(ZipCodeBitMap); Int32 MapWidth = Convert.ToInt32(Math.Pow(2, zoom) * 255); Point Offset = Cartographer.Mercator2.toZoomedPixelCoords(North, West, zoom); TrimPoint(ref Offset, MapWidth); for (Double lat = -80; lat <= 80; lat += 5) { Point StartPoint = Cartographer.Mercator2.toZoomedPixelCoords(lat, -179, zoom); Point EndPoint = Cartographer.Mercator2.toZoomedPixelCoords(lat, -1, zoom); TrimPoint(ref StartPoint, MapWidth); TrimPoint(ref EndPoint, MapWidth); StartPoint.X = StartPoint.X - Offset.X; EndPoint.X = EndPoint.X - Offset.X; StartPoint.Y = StartPoint.Y - Offset.Y; EndPoint.Y = EndPoint.Y - Offset.Y; LinesGraphic.DrawLine(new Pen(Color.Black, 2), StartPoint.X, StartPoint.Y, EndPoint.X, EndPoint.Y); LinesGraphic.DrawString( lat.ToString(), new Font("Verdana", 10), new SolidBrush(Color.Black), new Point( Convert.ToInt32((width / 3.0) * 2.0), StartPoint.Y)); } } protected void TrimPoint(ref Point point, Int32 MapWidth) { point.X = Math.Max(point.X, 0); point.X = Math.Min(point.X, MapWidth - 1); point.Y = Math.Max(point.Y, 0); point.Y = Math.Min(point.Y, MapWidth - 1); } So, Anyone ever experienced this? Dare I ask, resolved this? Or simply have a better C# implementation of Mercator Project coordinate conversion? Thanks!

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  • being able to solve google code jam problem sets

    - by JPro
    This is not a homework question, but rather my intention to know if this is what it takes to learn programming. I keep loggin into TopCoder not to actually participate but to get the basic understand of how the problems are solved. But to my knowledge I don't understand what the problem is and how to translate the problem into an algorithm that can solve it. Just now I happen to look at ACM ICPC 2010 World Finals which is being held in china. The teams were given problem sets and one of them is this: Given at most 100 points on a plan with distinct x-coordinates, find the shortest cycle that passes through each point exactly once, goes from the leftmost point always to the right until it reaches the rightmost point, then goes always to the left until it gets back to the leftmost point. Additionally, two points are given such that the the path from left to right contains the first point, and the path from right to left contains the second point. This seems to be a very simple DP: after processing the last k points, and with the first path ending in point a and the second path ending in point b, what is the smallest total length to achieve that? This is O(n^2) states, transitions in O(n). We deal with the two special points by forcing the first path to contain the first one, and the second path contain the second one. Now I have no idea what I am supposed to solve after reading the problem set. and there's an other one from google code jam: Problem In a big, square room there are two point light sources: one is red and the other is green. There are also n circular pillars. Light travels in straight lines and is absorbed by walls and pillars. The pillars therefore cast shadows: they do not let light through. There are places in the room where no light reaches (black), where only one of the two light sources reaches (red or green), and places where both lights reach (yellow). Compute the total area of each of the four colors in the room. Do not include the area of the pillars. Input * One line containing the number of test cases, T. Each test case contains, in order: * One line containing the coordinates x, y of the red light source. * One line containing the coordinates x, y of the green light source. * One line containing the number of pillars n. * n lines describing the pillars. Each contains 3 numbers x, y, r. The pillar is a disk with the center (x, y) and radius r. The room is the square described by 0 = x, y = 100. Pillars, room walls and light sources are all disjoint, they do not overlap or touch. Output For each test case, output: Case #X: black area red area green area yellow area Is it required that people who program should be should be able to solve these type of problems? I would apprecite if anyone can help me interpret the google code jam problem set as I wish to participate in this years Code Jam to see if I can do anthing or not. Thanks.

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  • Sending emails in web applications

    - by Denise
    Hi everyone, I'm looking for some opinions here, I'm building a web application which has the fairly standard functionality of: Register for an account by filling out a form and submitting it. Receive an email with a confirmation code link Click the link to confirm the new account and log in When you send emails from your web application, it's often (usually) the case that there will be some change to the persistence layer. For example: A new user registers for an account on your site - the new user is created in the database and an email is sent to them with a confirmation link A user assigns a bug or issue to someone else - the issue is updated and email notifications are sent. How you send these emails can be critical to the success of your application. How you send them depends on how important it is that the intended recipient receives the email. We'll look at the following four strategies in relation to the case where the mail server is down, using example 1. TRANSACTIONAL & SYNCHRONOUS The sending of the email fails and the user is shown an error message saying that their account could not be created. The application will appear to be slow and unresponsive as the application waits for the connection timeout. The account is not created in the database because the transaction is rolled back. TRANSACTIONAL & ASYNCHRONOUS The transactional definition here refers to sending the email to a JMS queue or saving it in a database table for another background process to pick up and send. The user account is created in the database, the email is sent to a JMS queue for processing later. The transaction is successful and committed. The user is shown a message saying that their account was created and to check their email for a confirmation link. It's possible in this case that the email is never sent due to some other error, however the user is told that the email has been sent to them. There may be some delay in getting the email sent to the user if application support has to be called in to diagnose the email problem. NON-TRANSACTIONAL & SYNCHRONOUS The user is created in the database, but the application gets a timeout error when it tries to send the email with the confirmation link. The user is shown an error message saying that there was an error. The application is slow and unresponsive as it waits for the connection timeout When the mail server comes back to life and the user tries to register again, they are told their account already exists but has not been confirmed and are given the option of having the email re-sent to them. NON-TRANSACTIONAL & ASYNCHRONOUS The only difference between this and transactional & asynchronous is that if there is an error sending the email to the JMS queue or saving it in the database, the user account is still created but the email is never sent until the user attempts to register again. What I'd like to know is what have other people done here? Can you recommend any other solutions other than the 4 I've mentioned above? What's a reasonable way of approaching this problem? I don't want to over-engineer a system that's dealing with the (hopefully) rare situation where my mail server goes down! The simplest thing to do is to code it synchronously, but are there any other pitfalls to this approach? I guess I'm wondering if there's a best practice, I couldn't find much out there by googling.

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  • CustomListAdapter Problem in Android? Getting ClassCast Exception? How???

    - by Praveen Chandrasekaran
    i want to improve the list view's performance. this is the code for my getView method in my Adapter? public View getView(int arg0, View text_view_name, ViewGroup parent) { try { if (text_view_name == null) { text_view_name = mInflater.inflate( R.layout.bs_content_list_item1, null); text_view_name.setTag(R.id.text1_detail1, text_view_name .findViewById(R.id.text1_detail1)); text_view_name.setTag(R.id.text3_detail1, text_view_name .findViewById(R.id.text3_detail1)); text_view_name.setTag(R.id.eve_img_detail1, text_view_name .findViewById(R.id.eve_img_detail1)); } text1 = (TextView) text_view_name.getTag(R.id.text1_detail1); // text2 = (TextView) text_view_name.getTag(R.id.text2); text3 = (TextView) text_view_name.getTag(R.id.text3_detail1); img = (ImageView) text_view_name.getTag(R.id.eve_img_detail1); text1.setText(VAL1[arg0]); text3.setText(VAL3[arg0]); if (!mBusy) { img_value = new URL(VAL4[arg0]); mIcon11 = BitmapFactory.decodeStream(img_value.openConnection() .getInputStream()); img.setImageBitmap(mIcon11); text_view_name.setTag(R.id.eve_img_detail1, null); } else { img.setImageResource(R.drawable.icon); text_view_name.setTag(R.id.eve_img_detail1, text_view_name .findViewById(R.id.eve_img_detail1)); } } catch (Exception e) { name = "Exception in MultiLine_bar_details1 getView"; Log.v(TAG, name + e); } return text_view_name; } this is the code for scrollstatechanged method: public void onScrollStateChanged(AbsListView view, int scrollState) { switch (scrollState) { case OnScrollListener.SCROLL_STATE_IDLE: try { MultiLine_bar_details1.mBusy = false; int first = view.getFirstVisiblePosition(); int count = view.getCount(); for (int i = 0; i < count; i++) { ImageView t = (ImageView) view.getChildAt(i);// here getting the ClassCastException if (t.getTag(R.id.eve_img_detail1) != null) { MultiLine_bar_details1.img_value = new URL( MultiLine_bar_details1.VAL4[first + i]); MultiLine_bar_details1.mIcon11 = BitmapFactory .decodeStream(MultiLine_bar_details1.img_value .openConnection().getInputStream()); MultiLine_bar_details1.img.setImageBitmap(MultiLine_bar_details1.mIcon11); t.setTag(R.id.eve_img_detail1, null); } } } catch (Exception e) { Log.v(TAG, "Idle" + e); } // mStatus.setText("Idle"); break; case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL: MultiLine_bar_details1.mBusy = true; break; case OnScrollListener.SCROLL_STATE_FLING: MultiLine_bar_details1.mBusy = true; break; } } getting the Exception in Idle state: 05-03 16:47:15.201: VERBOSE/BS_Bars(258): Idlejava.lang.ClassCastException: android.widget.LinearLayout this is very complicated for me to get the output properly. actually i have the listview with custom adapter. that icons makes the listview scroll very slow.i am getting the images for icons from the image urls. upto this(above code) i can improve the scroll performance of my list view. but the image icons are not proper in the corresponding order. its dynamically changing when i scroll the listview.. i refered the commonsware busy coder guide and this blog. My very Big question is "How can we access the single view in scrollstatechanged parameter AbsListView? " what is the problem in it? how to do it better? Any Idea?

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  • CustomListAdapter Problem in Android? How???

    - by Praveen Chandrasekaran
    i want to improve the list view's performance. this is the code for my getView method in my Adapter? public View getView(int arg0, View text_view_name, ViewGroup parent) { try { if (text_view_name == null) { text_view_name = mInflater.inflate( R.layout.bs_content_list_item1, null); text_view_name.setTag(R.id.text1_detail1, text_view_name .findViewById(R.id.text1_detail1)); text_view_name.setTag(R.id.text3_detail1, text_view_name .findViewById(R.id.text3_detail1)); text_view_name.setTag(R.id.eve_img_detail1, text_view_name .findViewById(R.id.eve_img_detail1)); } text1 = (TextView) text_view_name.getTag(R.id.text1_detail1); // text2 = (TextView) text_view_name.getTag(R.id.text2); text3 = (TextView) text_view_name.getTag(R.id.text3_detail1); img = (ImageView) text_view_name.getTag(R.id.eve_img_detail1); text1.setText(VAL1[arg0]); text3.setText(VAL3[arg0]); if (!mBusy) { img_value = new URL(VAL4[arg0]); mIcon11 = BitmapFactory.decodeStream(img_value.openConnection() .getInputStream()); img.setImageBitmap(mIcon11); text_view_name.setTag(R.id.eve_img_detail1, null); } else { img.setImageResource(R.drawable.icon); text_view_name.setTag(R.id.eve_img_detail1, text_view_name .findViewById(R.id.eve_img_detail1)); } } catch (Exception e) { name = "Exception in MultiLine_bar_details1 getView"; Log.v(TAG, name + e); } return text_view_name; } this is the code for scrollstatechanged method: public void onScrollStateChanged(AbsListView view, int scrollState) { switch (scrollState) { case OnScrollListener.SCROLL_STATE_IDLE: try { MultiLine_bar_details1.mBusy = false; int first = view.getFirstVisiblePosition(); int count = view.getCount(); for (int i = 0; i < count; i++) { ImageView t = (ImageView) view.getChildAt(i); if (t.getTag(R.id.eve_img_detail1) != null) { MultiLine_bar_details1.img_value = new URL( MultiLine_bar_details1.VAL4[first + i]); MultiLine_bar_details1.mIcon11 = BitmapFactory .decodeStream(MultiLine_bar_details1.img_value .openConnection().getInputStream()); MultiLine_bar_details1.img.setImageBitmap(MultiLine_bar_details1.mIcon11); t.setTag(R.id.eve_img_detail1, null); } } } catch (Exception e) { Log.v(TAG, "Idle" + e); } // mStatus.setText("Idle"); break; case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL: MultiLine_bar_details1.mBusy = true; break; case OnScrollListener.SCROLL_STATE_FLING: MultiLine_bar_details1.mBusy = true; break; } } this is very complicated for me to get the output properly. actually i have the listview with custom adapter. that icons makes the listview scroll very slow.i am getting the images for icons from the image urls. upto this(above code) i can improve the scroll performance of my list view. but the image icons are not proper in the corresponding order. its dynamically changing when i scroll the listview.. i refered the commonsware busy coder guide and this blog. My very Big question is "How can we access the single view in scrollstatechanged parameter AbsListView? " what is the problem in it? how to do it better? Any Idea?

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  • Logging Errors with messages in Codeigniter

    - by user1260776
    I’m using codeigniter on a production server, and I’m not able to properly log the errors generated to the file. I edited php.ini like this- error_reporting = E_ALL | E_NOTICE | E_STRICT|E_WARNING display_errors = Off log_errors = On error_log = "/var/log/php-scripts.log" // This is where I would like to log all the errors and notices.. And php-scripts.log is able to show the logs like this- [06-Jun-2012 03:22:20 UTC] PHP Deprecated: Directive 'safe_mode' is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:26:06 UTC] PHP Deprecated: Directive 'safe_mode' is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:05 UTC] PHP Deprecated: Directive 'safe_mode' is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:07 UTC] PHP Deprecated: Directive 'safe_mode' is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:11 UTC] PHP Deprecated: Directive 'safe_mode' is deprecated in PHP 5.3 and greater in Unknown on line 0 Now, the “index.php” settings in my “public_html” folder, (i’ve rest of CI folder outside public_html) I’ve these settings- define('ENVIRONMENT', 'production'); if (defined('ENVIRONMENT')) { switch (ENVIRONMENT) { case 'development': error_reporting(E_ALL); break; case 'testing': case 'production': error_reporting(0); break; default: exit('The application environment is not set correctly.'); } } Though everything seems to be fine, now, I’ll just change Environment to “development”, this is what I get on my website homepage- A PHP Error was encountered Severity: Warning Message: fclose() expects parameter 1 to be resource, null given Filename: core/Common.php Line Number: 91 A PHP Error was encountered Severity: Warning Message: Cannot modify header information - headers already sent by (output started at /home/theuser/codeigniter/system/core/Exceptions.php:185) Filename: core/Security.php Line Number: 188 The “rest” of the page is also displayed. And when I look at php-scripts.log, I’m not able to see any of these logs there- [06-Jun-2012 03:22:20 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:26:06 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:05 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:07 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:11 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:30:45 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 [06-Jun-2012 03:37:41 UTC] PHP Deprecated: Directive ‘safe_mode’ is deprecated in PHP 5.3 and greater in Unknown on line 0 One more thing is I don’t know how/where codeigniter itself would log all the errors. The permissions of “application/logs” folder is “777”, but there is no log file (I was expecting that CodeIgniter would automatically create a log file, should I create one, if I’ve to log errors there). I’ve set these configurations in config/config.php $config['log_threshold'] = 4; $config['log_path'] = ''; //hoping it would log errors at "default" location... Ideally, I just wish all those errors, warning, and notices (with messages) that were displayed on my webpage were sent to log-file /var/log/php-scripts.log when the “Environment” is “Production”. If it’s not possible, I would also be fine, If i can log it somewhere else. Now, I’m confused as to what should be the settings in the “index.php” page or some other configuration, so as to supress all the errors and warnings on the webpage when environment is "Production", and send all those errors, warnings, and notices to php-scripts.log. (or any other file) my php version is PHP 5.3.13 with Suhosin v0.9.33 Please help me with this. Thank you

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  • In XSLT is it possible to use the value of an xpath expression in a call to a template using an par

    - by Cell
    I am performing an xsl transform and in it I call a template with a param using the following code <xsl:call-template name="GenerateColumns"> <xsl:with-param name="curRow" select="$curRow"/> <xsl:with-param name="curCol" select="$curCol + 1"/> </xsl:call-template> This calls a template function which outputs part of a table element in HTML. The curRow and curCol are used to determine which row and column we are in the table. gbl_maxCols is set to the number of columns in an html table <xsl:template name="GenerateColumns"> <xsl:when test="$curCol &lt;= $gbl_maxCols"> <td> <xsl:attribute="colspan"> <xsl:value-of select="/page/column/@skipColumns"/> </xsl:attribute> </xsl:when> </xsl:template> The result of this function is a set of td elements, however some of these elements (those with a skipColumn attribute greater than 1 span more than 1 column, I need to skip this many columns with the next call to generateColumns. this works just like I would expect in the case where I simply increment the curCol param but I have a case where I need to use the value from the xml attribute skipColumns in the math to calculate the value for curCol. In the above case I iterate through all the columns and this works for the majority of my use cases. However in same cases I need to skip over some of the columns and need to pass in that value from the xml attribute to calculate how many columns I need to skip. My naive first attempt was something like this <xsl:call-template name="GenerateColumns"> <xsl:with-param name="curRow" select="$curRow"/> <xsl:with-param name="curCol" select="$curCol + /page/column/@skipColumns"/> </xsl:call-template> But unforutnately this does not seem to work. Is there any way to use an attribute from an xml page in the calculation for the value of a param in xsl. My xml page is something like this (edited heavily since the xml file is rather large) <page> <column name="blank" skipColumns="1"/> <column name="blank" skipColumns="1"/> <column name="test" skipColumns="3"/> <column name="blank" skipColumns="1"/> <column name="test2" skipColumns="6"/> </page> after all of this I would like to have a set of td elements like the following <td></td><td></td><td colSpan="3"></td><td></td><td colSpan="6"></td> if I just iterate through the columns I instead end up with something like this which gives me more td elements than I should have <td></td><td></td><td colSpan="3"></td><td></td><td colSpan="6"></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td> Edited to provide more information

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  • How to find problem with PHP XSLTProcessor when return from transformToXML is false and libxml_get_

    - by John
    I'm working on the code below to allow HTTP user agents that cannot perform XSL transformations to view the resources on my server. I'm mystified because the result of transformToXML is false, but the result of libxml_get_errors() is an empty array. As you can see, the code outputs the LibXSLT version ID and I'm getting the problem on WinVista with version 1.1.24. Is libxml_get_errors() not the right function to get the errors from the XSLTProcessor object? If you're interested in the XML documents, you can get them from http://bobberinteractive.com/index.xhtml and .../stylesheets/layout.xsl <?php //redirect browsers that can handle the source files. if (strpos ( $_SERVER ['HTTP_ACCEPT'], 'application/xhtml+xml' )) { header ( "HTTP/1.1 301 Moved Permanently" ); header ( "Location: http://" . $_SERVER ['SERVER_NAME'] . "/index.xhtml" ); header ( "Content-Type: text/text" ); echo "\nYour browser is capable of processing the <a href='/index.xhtml' site contents on its own."; die (); } //start by checking the template $baseDir = dirname ( __FILE__ ); $xslDoc = new DOMDocument (); if (! $xslDoc-load ( $baseDir . '/stylesheets/layout.xsl' )) { header ( "HTTP/1.1 500 Server Error" ); header ( "Content-Type: text/plain" ); echo "\n Can't load " . $baseDir . '/stylesheets/layout.xsl'; die (); } //resolve the requested resource (browsers that need transformation will request the resource without the suffix) $uri = $_SERVER ['REQUEST_URI']; $len = strlen ( $uri ); if (1 = $len || '/' == substr ( $uri, $len - 1 )) { $fileName = $baseDir . "/index.xhtml"; // use 'default' document if pathname ends in '/' } else { $fileName = $baseDir . (1 load ( $fileName )) { header ( "HTTP/1.1 500 Server Error" ); echo "\n Can't load " . $fileName; die (); } // now start the XSL template processing $proc = new XSLTProcessor (); $proc-importStylesheet ( $xslDoc ); $doc = $proc-transformToXML ( $xmlDoc ); if (false === $doc) { header ( "HTTP/1.1 500 Server Error" ); header ( "Content-Type: text/plain" ); echo "\n"; // HERE is where it gets strange: the value of $doc is false and libxml_get_errors returns 0 entries. display_xml_errors ( libxml_get_errors() ); die (); } header ( "Content-Type: text/html" ); echo "\n"; echo $doc; function display_xml_errors($errors) { echo count ( $errors ) . " Error(s) from LibXSLT " . LIBXSLT_DOTTED_VERSION; for($i = 0; $i level) { case LIBXML_ERR_WARNING : $return .= "Warning $error-code: "; break; case LIBXML_ERR_ERROR : $return .= "Error $error-code: "; break; case LIBXML_ERR_FATAL : $return .= "Fatal Error $error-code: "; break; } $return .= trim ( $error-message ) . "\n Line: $error-line" . "\n Column: $error-column"; if ($error-file) { $return .= "\n File: $error-file"; } echo "$return\n\n--------------------------------------------\n\n"; } }

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  • Trying to sentinel loop this program.

    - by roger34
    Okay, I spent all this time making this for class but I have one thing that I can't quite get: I need this to sentinel loop continuously (exiting upon entering x) so that the System.out.println("What type of Employee? Enter 'o' for Office " + "Clerical, 'f' for Factory, or 's' for Saleperson. Enter 'x' to exit." ); line comes back up after they enter the first round of information. Also, I can't leave this up long on the (very) off chance a classmate might see this and steal the code. Full code following: import java.util.Scanner; public class Project1 { public static void main (String args[]){ Scanner inp = new Scanner( System.in ); double totalPay; System.out.println("What type of Employee? Enter 'o' for Office " + "Clerical, 'f' for Factory, or 's' for Saleperson. Enter 'x' to exit." ); String response= inp.nextLine(); while (!response.toLowerCase().equals("o")&&!response.toLowerCase().equals("f") &&!response.toLowerCase().equals("s")&&!response.toLowerCase().equals("x")){ System.out.print("\nInvalid selection,please enter your choice again:\n"); response=inp.nextLine(); } char choice = response.toLowerCase().charAt( 0 ); switch (choice){ case 'o': System.out.println("Enter your hourly rate:"); double officeRate=inp.nextDouble(); System.out.println("Enter the number of hours worked:"); double officeHours=inp.nextDouble(); totalPay = officeCalc(officeRate,officeHours); taxCalc(totalPay); break; case 'f': System.out.println("How many Widgets did you produce during the week?"); double widgets=inp.nextDouble(); totalPay=factoryCalc(widgets); taxCalc(totalPay); break; case 's': System.out.println("What were your total sales for the week?"); double totalSales=inp.nextDouble(); totalPay=salesCalc(totalSales); taxCalc(totalPay); break; } } public static double taxCalc(double totalPay){ double federal=totalPay*.22; double state =totalPay*.055; double netPay = totalPay - federal - state; federal =federal*Math.pow(10,2); federal =Math.round(federal); federal= federal/Math.pow(10,2); state =state*Math.pow(10,2); state =Math.round(state); state= state/Math.pow(10,2); totalPay =totalPay*Math.pow(10,2); totalPay =Math.round(totalPay); totalPay= totalPay/Math.pow(10,2); netPay =netPay*Math.pow(10,2); netPay =Math.round(netPay); netPay= netPay/Math.pow(10,2); System.out.printf("\nTotal Pay \t: %1$.2f.\n", totalPay); System.out.printf("State W/H \t: %1$.2f.\n", state); System.out.printf("Federal W/H : %1$.2f.\n", federal); System.out.printf("Net Pay \t: %1$.2f.\n", netPay); return totalPay; } public static double officeCalc(double officeRate,double officeHours){ double overtime=0; if (officeHours>=40) overtime = officeHours-40; else overtime = 0; if (officeHours >= 40) officeHours = 40; double otRate = officeRate * 1.5; double totalPay= (officeRate * officeHours) + (otRate*overtime); return totalPay; } public static double factoryCalc(double widgets){ double totalPay=widgets*.35 +300; return totalPay; } public static double salesCalc(double totalSales){ double totalPay = totalSales * .05 + 500; return totalPay; } }

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  • Did I find a bug in PHP's `crypt()`?

    - by Nathan Long
    I think I may have found a bug in PHP's crypt() function under Windows. However: I recognize that it's probably my fault. PHP is used by millions and worked on by thousands; my code is used by tens and worked on by me. (This argument is best explained on Coding Horror.) So I'm asking for help: show me my fault. I've been trying to find it for a few days now, with no luck. The setup I'm using a Windows server installation with Apache 2.2.14 (Win32) and PHP 5.3.2. My development box runs Windows XP Professional; the 'production' server (this is an intranet setup) runs Windows Storage Server 2003. The problem happens on both. I don't see anything in php.ini related to crypt(), but will happily answer questions about my config. The problem Several scripts in my PHP app occasionally hang: the page sits there on 'waiting for localhost' and never finishes. Each of these scripts uses crypt to hash a user's password before storing it in the database, or, in the case of the login page, to hash the entered password before comparing it to the version stored in the database. Since the login page is the simplest, I focused on it for testing. I repeatedly logged in, and found that it would hang maybe 4 out of 10 times. As an experiment, I changed the login page to use the plain text password and changed my password in the database to its plain text version. The page stopped hanging. I saw that PHP's latest version lists this bugfix: Fixed bug #51059 (crypt crashes when invalid salt are [sic] given). So I created a very simple test script, as follows, using the same salt given in an official example: $foo = crypt('rasmuslerdorf','r1'); echo $foo; This page, too, will hang, if I reload it like crazy. I only see it hanging in Chrome, but regardless of browser, the effect on Apache is the same. Effect on Apache When these pages hang, Apache's server-status page (which I explained here, regarding a different problem) increments the number of requests being processed and decrements the number of idle workers. The requests being processed almost all have a status of 'Sending Reply,' though sometimes for a moment they will show either 'Reading request' or 'keepalive (read).' Eventually, Apache may crash. When it does, the Windows crash report looks like this: szAppName: httpd.exe szAppVer: 2.2.14.0 szModName: php5ts.dll szModVer: 5.3.1.0 // OK, this report was before I upgraded to PHP 5.3.2, // but that didn't fix it offset: 00a2615 Is it my fault? I'm tempted to file a bug report to PHP on this. The argument against it is, as stated above, that bugs are nearly always my fault. However, my argument in favor of 'it's PHP's fault' is: I'm using Windows, whereas most servers use Linux (I don't get to choose this), so the chances are greater that I've found an edge case There was recently a bug with crypt(), so maybe it still has issues I have made the simplest test case I can, and I still have the problem Can anyone duplicate this? Can you suggest where I've gone wrong? Should I file the bug after all? Thanks in advance for any help you may give.

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  • Paging, sorting and filtering in a stored procedure (SQL Server)

    - by Fruitbat
    I was looking at different ways of writing a stored procedure to return a "page" of data. This was for use with the asp ObjectDataSource, but it could be considered a more general problem. The requirement is to return a subset of the data based on the usual paging paremeters, startPageIndex and maximumRows, but also a sortBy parameter to allow the data to be sorted. Also there are some parameters passed in to filter the data on various conditions. One common way to do this seems to be something like this: [Method 1] ;WITH stuff AS ( SELECT CASE WHEN @SortBy = 'Name' THEN ROW_NUMBER() OVER (ORDER BY Name) WHEN @SortBy = 'Name DESC' THEN ROW_NUMBER() OVER (ORDER BY Name DESC) WHEN @SortBy = ... ELSE ROW_NUMBER() OVER (ORDER BY whatever) END AS Row, ., ., ., FROM Table1 INNER JOIN Table2 ... LEFT JOIN Table3 ... WHERE ... (lots of things to check) ) SELECT * FROM stuff WHERE (Row > @startRowIndex) AND (Row <= @startRowIndex + @maximumRows OR @maximumRows <= 0) ORDER BY Row One problem with this is that it doesn't give the total count and generally we need another stored procedure for that. This second stored procedure has to replicate the parameter list and the complex WHERE clause. Not nice. One solution is to append an extra column to the final select list, (SELECT COUNT(*) FROM stuff) AS TotalRows. This gives us the total but repeats it for every row in the result set, which is not ideal. [Method 2] An interesting alternative is given here (http://www.4guysfromrolla.com/articles/032206-1.aspx) using dynamic SQL. He reckons that the performance is better because the CASE statement in the first solution drags things down. Fair enough, and this solution makes it easy to get the totalRows and slap it into an output parameter. But I hate coding dynamic SQL. All that 'bit of SQL ' + STR(@parm1) +' bit more SQL' gubbins. [Method 3] The only way I can find to get what I want, without repeating code which would have to be synchronised, and keeping things reasonably readable is to go back to the "old way" of using a table variable: DECLARE @stuff TABLE (Row INT, ...) INSERT INTO @stuff SELECT CASE WHEN @SortBy = 'Name' THEN ROW_NUMBER() OVER (ORDER BY Name) WHEN @SortBy = 'Name DESC' THEN ROW_NUMBER() OVER (ORDER BY Name DESC) WHEN @SortBy = ... ELSE ROW_NUMBER() OVER (ORDER BY whatever) END AS Row, ., ., ., FROM Table1 INNER JOIN Table2 ... LEFT JOIN Table3 ... WHERE ... (lots of things to check) SELECT * FROM stuff WHERE (Row > @startRowIndex) AND (Row <= @startRowIndex + @maximumRows OR @maximumRows <= 0) ORDER BY Row (Or a similar method using an IDENTITY column on the table variable). Here I can just add a SELECT COUNT on the table variable to get the totalRows and put it into an output parameter. I did some tests and with a fairly simple version of the query (no sortBy and no filter), method 1 seems to come up on top (almost twice as quick as the other 2). Then I decided to test probably I needed the complexity and I needed the SQL to be in stored procedures. With this I get method 1 taking nearly twice as long as the other 2 methods. Which seems strange. Is there any good reason why I shouldn't spurn CTEs and stick with method 3? UPDATE - 15 March 2012 I tried adapting Method 1 to dump the page from the CTE into a temporary table so that I could extract the TotalRows and then select just the relevant columns for the resultset. This seemed to add significantly to the time (more than I expected). I should add that I'm running this on a laptop with SQL Server Express 2008 (all that I have available) but still the comparison should be valid. I looked again at the dynamic SQL method. It turns out I wasn't really doing it properly (just concatenating strings together). I set it up as in the documentation for sp_executesql (with a parameter description string and parameter list) and it's much more readable. Also this method runs fastest in my environment. Why that should be still baffles me, but I guess the answer is hinted at in Hogan's comment.

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  • mediaelement.js control sizes are wrong when clip nested in a hidden element

    - by Martin Francis
    It's a nasty one this. In an audio control placed within a container element whose display property is initially set to none, the audio clip does NOT correctly size the progress bar when it is initialised. This is clear when the container's display property is changed from 'none' to '' (which is equivalent to 'static'). But who would ever do that? I make extensive use of 'tabbed' display arrangements on community sites like this one: http://www.churchesInBracebridge.ca Owing to the page arrangement, the audio controls which you see under 'sermons' (which at the time of writing still using Flash rather than John's excellent library here) are initially rendered in a div that is hidden. Simplified Test case Rather than have anyone have to wade through all of that, here's a much simplified test case: http://jsfiddle.net/sJL6T/36 Here's the full page source for those who'd prefer to work with it that way. <!DOCTYPE html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"/> <title>MediaElementPlayer.js</title> <script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script> <script src="http://mediaelementjs.com/js/mejs-2.13.1/mediaelement-and-player.js"></script> <link rel="stylesheet" href="http://mediaelementjs.com/js/mejs-2.13.1/mediaelementplayer.css" /> <script type="text/javascript"> function toggle(id){ document.getElementById(id).style.display= (document.getElementById(id).style.display=='none' ? '' : 'none'); } </script> </head> <body> <h1>MediaElementPlayer.js</h1> <h2 onclick="return toggle('test1')">Initially Hidden (Click to toggle)</h2> <div id='test1' style='display:none'> <audio controls="controls"> <source src="http://mediaelementjs.com/media/AirReview-Landmarks-02-ChasingCorporate.mp3" type="audio/mp3" /> </audio> </div> <h2 onclick="return toggle('test2')">Initially Shown (Click to toggle)</h2> <div id='test2' style=''> <audio controls="controls"> <source src="http://mediaelementjs.com/media/AirReview-Landmarks-02-ChasingCorporate.mp3" type="audio/mp3" /> </audio> </div> <script> $('audio').mediaelementplayer(); </script> </body> </html> Possible Workarounds Now I know that Google maps has the same quirk and there are two possible ways I've used to deal with that: Use absolute positioning in a displayed div to place the element 10,000px to the left then bring it onto the stage when we want to see it Have the map pane displayed when loading then hide it as soon as it's loaded (ugly I know, but it usually works) However either approach would be a pain to do, as I have a lot of legacy code using the simpler div hiding method. I know that JQuery can get the dimensions of an element event if it is hidden - someone thoughtfully fiddled that and it does work: http://jsfiddle.net/sJL6T/9 Perhaps it may be possible to modify the actual library to find correct dimensions, even if the container itself is hidden? That would be wonderful, if it can be done! Initial experiments on mediaelement-and-player.js code I found that when I provided a fixed value in the setControlsSize function for railWidth, I got consistent results with both controls in the test case above (and obviously I'm working with my own copy of the library to do that, not the one stored at mediaelementjs.com): // outer area rail.width(railWidth); Change to this: // outer area railWidth=216; rail.width(railWidth); Many thanks in anticipation! Martin Francis <<

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  • ublas::bounded_vector<> being resized?

    - by n2liquid
    Now, seriously... I'll refrain from using bad words here because we're talking about the Boost fellows. It MUST be my mistake to see things this way, but I can't understand why, so I'll ask it here; maybe someone can enlighten me in this matter. Here it goes: uBLAS has this nice class template called bounded_vector<> that's used to create fixed-size vectors (or so I thought). From the Effective uBLAS wiki (http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Effective_UBLAS): The default uBLAS vector and matrix types are of variable size. Many linear algebra problems involve vectors with fixed size. 2 and 3 elements are common in geometry! Fixed size storage (akin to C arrays) can be implemented efficiently as it does not involve the overheads (heap management) associated with dynamic storage. uBLAS implements fixed sizes by changing the underling storage of a vector/matrix to a "bounded_array" from the default "unbounded_array". Alright, this bounded_vector<> thing is used to free you from specifying the underlying storage of the vector to a bounded_array<> of the specified size. Here I ask you: doesn't it look like this bounded vector thing has fixed size to you? Well, it doesn't have. At first I felt betrayed by the wiki, but then I reconsidered the meaning of "bounded" and I think I can let it pass. But in case you, like me (I'm still uncertain), is still wondering if this makes sense, what I found out is that the bounded_vector<> actually can be resized, it may only not be greater than the size specified as template parameter. So, first off, do you think they've had a good reason not to make a real fixed<< size vector or matrix type? Do you think it's okay to "sell" this bounded -- as opposed to fixed-size -- vector to the users of my library as a "fixed-size" vector replacement, even named "Vector3" or "Vector2", like the Effective uBLAS wiki did? Do you think I should somehow implement a vector with fixed size for this purpose? If so, how? (Sorry, but I'm really new to uBLAS; just tried it today) I am developing a 3D game. Should uBLAS be used for the calculations involved in this ("hey, geometry!", per Effective uBLAS wiki)? What replacement would you suggest, if not? -- edit And just in case, yes, I've read this warning: It should be noted that this only changes the storage uBLAS uses for the vector3. uBLAS will still use all the same algorithm (which assume a variable size) to manipulate the vector3. In practice this seems to have no negative impact on speed. The above runs just as quickly as a hand crafted vector3 which does not use uBLAS. The only negative impact is that the vector3 always store a "size" member which in this case is redundant [or isn't it? I mean......]. I see it uses the same algorithm, assuming a variable size, but if an operation were to actually change its size, shouldn't it be stopped (assertion)? ublas::bounded_vector<float,3> v3; ublas::bounded_vector<float,2> v2; v3 = v2; std::cout << v3.size() << '\n'; // prints 2 Oh, come on, isn't this just plain betrayal?

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  • How do I return a message if $_GET is null or does not match any database entries?

    - by CT
    I am working on designing an IT Asset database. Here I am working on a page used to view details on a specific asset determined by an asset id. Here I grab $id from $_GET["id"]; When $id is null, the page does not load. When $id does not match any entry within the database, the page loads but no asset table is printed. In both these cases, I would like to display a message like "There is no database entry for that Asset ID" How would this be handled? Thank you. <?php /* * View Asset * */ # include functions script include "functions.php"; $id = $_GET["id"]; ConnectDB(); $type = GetAssetType($id); ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="stylesheet" type="text/css" href="style.css" /> <title>Wagman IT Asset</title> </head> <body> <div id="page"> <div id="header"> <img src="images/logo.png" /> </div> </div> <div id="content"> <div id="container"> <div id="main"> <div id="menu"> <ul> <table width="100%" border="0"> <tr> <td width="15%"></td> <td width="30%%"><li><a href="index.php">Search Assets</a></li></td> <td width="30%"><li><a href="addAsset.php">Add Asset</a></li></td> <td width="25%"></td> </tr> </table> </ul> </div> <div id="text"> <ul> <li> <h1>View Asset</h1> </li> </ul> <br /> <?php switch ($type){ case "Server": $result = QueryServer($id); $ServerArray = GetServerData($result); PrintServerTable($ServerArray); break; case "Desktop"; break; case "Laptop"; break; } ?> </div> </div> </div> <div class="clear"></div> <div id="footer" align="center"> <p>&nbsp;</p> </div> </div> <div id="tagline"> Wagman Construction - Bridging Generations since 1902 </div> </body> </html>

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  • Editing a Gridview row with drop-down lists gets too wide - how can I use popup panels instead?

    - by David
    I have a series of GridViews in a Tab Panel - databound to a generic List of Business Objects. The columns in the Gridview are all similar to the following: <asp:TemplateField HeaderText="Company" SortExpression="Company.ShortName"> <ItemTemplate> <asp:Label ID="lblCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:Label> </ItemTemplate> <EditItemTemplate> <asp:DropDownList ID="ddlCompany" runat="server"></asp:DropDownList> </EditItemTemplate> </asp:TemplateField> The GridView generates the "Edit" link at the beginning of the row, all the events fire ok. The problem is that the data is getting long. When in 'display mode', it's fine because the GridView control is smart enough to break some text into multiple lines (in particular Project, Title and Worker names can get pretty long). The problem come in editing mode. Drop-down lists DON'T break entries into multiple lines (for obvious reasons). Going into Edit ode on a row in the Gridview can make the Griview expand horizontally to twice the screen size (blowing through the width limits in the Master page and CSS but that's only a related problem). What I need is something like the ModalPopup - but trying to tie it to an ID in an EditItemTemplate gives me errors when the page renders (because the 'ddlXXXX' doesn't exist at the time). In addition I don't know how to dynamically populate the panel so that I can get a response from it (like the ID of the Company they selected). I'm also trying to avoid javascript and would like this to be a 'pure' aspx/code-behind solution (for simplicity's sake among others). All the examples I find are of Modal Popups with the panels pre-defined. Even if it (the popup panel) were something like a list of checkboxes, it could be databound to the SortedList I have ready to go and an OK/Cancel button combination to accept or ignore things. I'm just not sure of what goes where. I'm open to suggestions. Thanks in advance. EDIT: Final solution looks as follows: <asp:TemplateField HeaderText="Company" SortExpression="Company.ShortName"> <ItemTemplate> <asp:Label ID="lblCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:Label> </ItemTemplate> <EditItemTemplate> <asp:LinkButton ID="lnkCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:LinkButton> <asp:Panel ID="pnlCompany" runat="server" style="display:none"> <div> <asp:DropDownList ID="ddlCompany" runat="server" ></asp:DropDownList> <br/> <asp:ImageButton ID="btnOKCo" runat="server" ImageUrl="~/Images/greencheck.gif" OnCommand="PopupButton_Command" CommandName="SelectCO" /> <asp:ImageButton ID="btnCxlCo" runat="server" ImageUrl="~/Images/RedX.gif" /> </div> </asp:Panel> <cc1:ModalPopupExtender ID="mpeCompany" runat="server" TargetControlID="lnkCompany" PopupControlID="pnlCompany" BackgroundCssClass="modalBackground" CancelControlID="btnCxlCo" DropShadow="true" PopupDragHandleControlID="pnlCompany" /> </EditItemTemplate> </asp:TemplateField> And in the code-behind, lstIDLabor is the generic List of data lines (of which Company is one of the properties that is also a business object) that is bound to the GridView: Sub PopupButton_Command(ByVal sender As Object, ByVal e As CommandEventArgs) Dim intRow As Integer Dim intVal As Integer RestoreFromSessionVariables() Select Case e.CommandName Case "SelectCO" intRow = grdIDCostLabor.EditIndex Dim ddlCo As DropDownList = CType(grdIDCost.Rows(intRow).FindControl("ddlCompany"), DropDownList) intVal = ddlCo.SelectedValue lstIDLabor(intRow).CompanyID = intVal lstIDLabor(intRow).Company = Company.Read(intVal) Case Else ' End Select MakeSessionVariables() BindGrids() End Sub

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  • Lock free multiple readers single writer

    - by dummzeuch
    I have got an in memory data structure that is read by multiple threads and written by only one thread. Currently I am using a critical section to make this access threadsafe. Unfortunately this has the effect of blocking readers even though only another reader is accessing it. There are two options to remedy this: use TMultiReadExclusiveWriteSynchronizer do away with any blocking by using a lock free approach For 2. I have got the following so far (any code that doesn't matter has been left out): type TDataManager = class private FAccessCount: integer; FData: TDataClass; public procedure Read(out _Some: integer; out _Data: double); procedure Write(_Some: integer; _Data: double); end; procedure TDataManager.Read(out _Some: integer; out _Data: double); var Data: TDAtaClass; begin InterlockedIncrement(FAccessCount); try // make sure we get both values from the same TDataClass instance Data := FData; // read the actual data _Some := Data.Some; _Data := Data.Data; finally InterlockedDecrement(FAccessCount); end; end; procedure TDataManager.Write(_Some: integer; _Data: double); var NewData: TDataClass; OldData: TDataClass; ReaderCount: integer; begin NewData := TDataClass.Create(_Some, _Data); InterlockedIncrement(FAccessCount); OldData := TDataClass(InterlockedExchange(integer(FData), integer(NewData)); // now FData points to the new instance but there might still be // readers that got the old one before we exchanged it. ReaderCount := InterlockedDecrement(FAccessCount); if ReaderCount = 0 then // no active readers, so we can safely free the old instance FreeAndNil(OldData) else begin /// here is the problem end; end; Unfortunately there is the small problem of getting rid of the OldData instance after it has been replaced. If no other thread is currently within the Read method (ReaderCount=0), it can safely be disposed and that's it. But what can I do if that's not the case? I could just store it until the next call and dispose it there, but Windows scheduling could in theory let a reader thread sleep while it is within the Read method and still has got a reference to OldData. If you see any other problem with the above code, please tell me about it. This is to be run on computers with multiple cores and the above methods are to be called very frequently. In case this matters: I am using Delphi 2007 with the builtin memory manager. I am aware that the memory manager probably enforces some lock anyway when creating a new class but I want to ignore that for the moment. Edit: It may not have been clear from the above: For the full lifetime of the TDataManager object there is only one thread that writes to the data, not several that might compete for write access. So this is a special case of MREW.

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  • Php template caching design

    - by Thomas
    Hello to all, I want to include caching in my app design. Caching templates for starters. The design I have used so far is very modular. I have created an ORM implementation for all my tables and each table is represented by the corresponding class. All the requests are handled by one controller which routes them to the appropriate webmethod functions. I am using a template class for handling UI parts. What I have in mind for caching includes the implementation of a separate Cache class for handling caching with the flexibility to either store in files, apc or memcache. Right now I am testing with file caching. Some thoughts Should I include the logic of checking for cached versions in the Template class or in the webmethods which handle the incoming requests and which eventually call the Template class. In the first case, things are pretty simple as I will not have to change anything more than pass the template class an extra argument (whether to load from cache or not). In the second case however, I am thinking of checking for a cached version immediately in the webmethod and if found return it. This will save all the processing done until the logic reaches the template (first case senario). Both senarios however, rely on an accurate mechanism of invalidating caches, which brings as to Invalidating caches As I see it (and you can add your input freely) a template cached file, becomes invalidate if: a. the expiration set, is reached. b. the template file itself is updated (ie by the developer when adding a new line) c. the webmethod that handles the request changes (ie the developer adds/deletes something in the code) d. content coming from the db and ending in the template file is modified I am thinking of storing a json encoded array inside the cached file. The first value will be the expiration timestamp of the cache. The second value will be the modification time of the php file with the code handling the request (to cope with option c above) The third will be the content itself The validation process I am considering, according to the above senarios, is: a. If the expiration of the cached file (stored in the array) is reached, delete the cache file b. if the cached file's mod time is smaller than the template's skeleton file mod time, delete the cached file c. if the mod time of the php file is greated than the one stored in the cache, delete the cached file. d. This is tricky. In the ORM implementation I ahve added event handlers (which fire when adding, updating, deleting objects). I could delete the cache file every time an object thatprovides content to the template, is modified. The problem is how to keep track which cached files correpond to each schema object. Take this example, a user has his shortprofile page and a full profile page (2 templates) These templates can be cached. Now, every time the user modifies his profile, the event handler would need to know which templates or cached files correspond to the User, so that these files can be deleted. I could store them in the db but I am looking for a beter approach

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