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  • SEO: Nested List vs List, Split Over Divs vs Definition List

    - by Jon P
    From an SEO perspective which, if any, is better: Option 1: Nested lists with h2 tags <ul id="mainpoints"> <li><h2>Powerful Analysis</h2> <ul> <li>Charting and indicators</li> <li>Daily trading signals</li> <li>Company health checks</li> </ul> </li> <li><h2>World Market Data</h2> <ul> [List Items removed for brevity] </ul> </li> <li><h2>Daily Market Data</h2> <ul> [List Items removed for brevity] </ul> </li> </ul> Option 2: Divs with h2 and lists <div id="mainpoints"> <div> <h2>Powerful Analysis</h2> <ul> <li>Charting and indicators</li> <li>Daily trading signals</li> <li>Company health checks</li> </ul> </div> <div> <h2>World Market Data</h2> <ul> [List Items removed for brevity] </ul> </div> <div> <h2>Daily Market Data</h2> <ul> [List Items removed for brevity] </ul> </div> </div> Option 3: Definition List <dl id="mainpoints"> <dt>Powerful Analysis</dt> <dd>- Charting and indicators</dd> <dd>- Daily trading signals</dd> <dd>- Company health checks</dd> <dt>World Market Data</dt> [List Items removed for brevity] <dt>Daily Market Data</dt> [List Items removed for brevity] </dl> My instincts tell me that semanticaly the pure list options (1 & 3) are the best and that h2 may be more SEO friendly (1 & 2) which would point to option 1 as being the best option. I do love the lean makeup of the definition list but will I take an SEO hit by losing the h2 tags? Before anyone asks, h2 is not valid markup in a dt tag. Are my instincts right with a nested list being the way to go?

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  • Complex error handling

    - by Caspin
    I've got a particularly ornery piece of network code. I'm using asio but that really doesn't matter for this question. I assume there is no way to unbind a socket other than closing it. The problem is that open(), bind(), and listen() can all throw a system_error. So I handled the code with a simple try/catch. The code as written in broken. using namespace boost::asio; class Thing { public: ip::tcp::endpoint m_address; ip::tcp::acceptor m_acceptor; /// connect should handle all of its exceptions internally. bool connect() { try { m_acceptor.open( m_address.protocol() ); m_acceptor.set_option( tcp::acceptor::reuse_address(true) ); m_acceptor.bind( m_address ); m_acceptor.listen(); m_acceptor.async_accept( /*stuff*/ ); } catch( const boost::system::system_error& error ) { assert(acceptor.is_open()); m_acceptor.close(); return false; } return true; } /// don't call disconnect unless connect previously succeeded. void disconnect() { // other stuff needed to disconnect is ommited m_acceptor.close(); } }; The error is if the socket fails to connect it will try to close it in the catch block and throw another system_error about closing an acceptor that has never been opened. One solution is to add an if( acceptor.is_open() ) in the catch block but that tastes wrong. Kinda like mixing C-style error checking with c++ exceptions. If I where to go that route, I may as well use the non-throwing version of open(). boost::system::error_code error; acceptor.open( address.protocol, error ); if( ! error ) { try { acceptor.set_option( tcp::acceptor::reuse_address(true) ); acceptor.bind( address ); acceptor.listen(); acceptor.async_accept( /*stuff*/ ); } catch( const boost::system::system_error& error ) { assert(acceptor.is_open()); acceptor.close(); return false; } } return !error; Is there an elegant way to handle these possible exceptions using RAII and try/catch blocks? Am I just wrong headed in trying to avoid if( error condition ) style error handling when using exceptions?

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  • Portability of pthreads-win32 over various compilers.

    - by Artyom
    Hello, I'm using pthreads-win32 for portable threading support for windows. At least, according to the documentation pthreads-win32 should work with MSVC and even MSVC builds provided. But I don't know if the library is tested with latest MSVC compilers like MSVC-2008 and if it is supported under 64bit windows. Does anybody aware of any issues with this library? Note: Do not even try to recommend using Boost.Thread, I'm not interested in. And I'm familiar with Boost.Thread library

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  • Is this an idiomatic way to pass mocks into objects?

    - by Billy ONeal
    I'm a bit confused about passing in this mock class into an implementation class. It feels wrong to have all this explicitly managed memory flying around. I'd just pass the class by value but that runs into the slicing problem. Am I missing something here? Implementation: namespace detail { struct FileApi { virtual HANDLE CreateFileW( __in LPCWSTR lpFileName, __in DWORD dwDesiredAccess, __in DWORD dwShareMode, __in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes, __in DWORD dwCreationDisposition, __in DWORD dwFlagsAndAttributes, __in_opt HANDLE hTemplateFile ) { return ::CreateFileW(lpFileName, dwDesiredAccess, dwShareMode, lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile); } virtual void CloseHandle(HANDLE handleToClose) { ::CloseHandle(handleToClose); } }; } class File : boost::noncopyable { HANDLE hWin32; boost::scoped_ptr<detail::FileApi> fileApi; public: File( __in LPCWSTR lpFileName, __in DWORD dwDesiredAccess, __in DWORD dwShareMode, __in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes, __in DWORD dwCreationDisposition, __in DWORD dwFlagsAndAttributes, __in_opt HANDLE hTemplateFile, __in detail::FileApi * method = new detail::FileApi() ) { fileApi.reset(method); hWin32 = fileApi->CreateFileW(lpFileName, dwDesiredAccess, dwShareMode, lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile); } }; namespace detail { struct FileApi { virtual HANDLE CreateFileW( __in LPCWSTR lpFileName, __in DWORD dwDesiredAccess, __in DWORD dwShareMode, __in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes, __in DWORD dwCreationDisposition, __in DWORD dwFlagsAndAttributes, __in_opt HANDLE hTemplateFile ) { return ::CreateFileW(lpFileName, dwDesiredAccess, dwShareMode, lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile); } virtual void CloseHandle(HANDLE handleToClose) { ::CloseHandle(handleToClose); } }; } class File : boost::noncopyable { HANDLE hWin32; boost::scoped_ptr<detail::FileApi> fileApi; public: File( __in LPCWSTR lpFileName, __in DWORD dwDesiredAccess, __in DWORD dwShareMode, __in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes, __in DWORD dwCreationDisposition, __in DWORD dwFlagsAndAttributes, __in_opt HANDLE hTemplateFile, __in detail::FileApi * method = new detail::FileApi() ) { fileApi.reset(method); hWin32 = fileApi->CreateFileW(lpFileName, dwDesiredAccess, dwShareMode, lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile); } ~File() { fileApi->CloseHandle(hWin32); } }; Tests: namespace detail { struct MockFileApi : public FileApi { MOCK_METHOD7(CreateFileW, HANDLE(LPCWSTR, DWORD, DWORD, LPSECURITY_ATTRIBUTES, DWORD, DWORD, HANDLE)); MOCK_METHOD1(CloseHandle, void(HANDLE)); }; } using namespace detail; using namespace testing; TEST(Test_File, OpenPassesArguments) { MockFileApi * api = new MockFileApi; EXPECT_CALL(*api, CreateFileW(Eq(L"BozoFile"), Eq(56), Eq(72), Eq(reinterpret_cast<LPSECURITY_ATTRIBUTES>(67)), Eq(98), Eq(102), Eq(reinterpret_cast<HANDLE>(98)))) .Times(1).WillOnce(Return(reinterpret_cast<HANDLE>(42))); File test(L"BozoFile", 56, 72, reinterpret_cast<LPSECURITY_ATTRIBUTES>(67), 98, 102, reinterpret_cast<HANDLE>(98), api); }

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  • Qt cross thread call

    - by QLatvia
    I have a Qt/C++ application, with the usual GUI thread, and a network thread. The network thread is using an external library, which has its own select() based event loop... so the network thread isn't using Qt's event system. At the moment, the network thread just emit()s signals when various events occur, such as a successful connection. I think this works okay, as the signals/slots mechanism posts the signals correctly for the GUI thread. Now, I need for the network thread to be able to call the GUI thread to ask questions. For example, the network thread may require the GUI thread to request put up a dialog, to request a password. Does anyone know a suitable mechanism for doing this? My current best idea is to have the network thread wait using a QWaitCondition, after emitting an object (emit passwordRequestedEvent(passwordRequest);. The passwordRequest object would have a handle on the particular QWaitCondition, and so can signal it when a decision has been made.. Is this sort of thing sensible? or is there another option?

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  • Why is overloading operator&() prohibited for classes stored in STL containers?

    - by sharptooth
    Suddenly in this article ("problem 2") I see a statement that C++ Standard prohibits using STL containers for storing elemants of class if that class has an overloaded operator&(). Having overloaded operator&() can indeed be problematic, but looks like a default "address-of" operator can be used easily through a set of dirty-looking casts that are used in boost::addressof() and are believed to be portable and standard-compilant. Why is having an overloaded operator&() prohibited for classes stored in STL containers while the boost::addressof() workaround exists?

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  • conditionally enabling constructor

    - by MK
    Here is how I can conditionally enable a constructor of a class : struct Foo { template<class T> Foo( T* ptr, boost::enable_if<is_arithmetic<T> >::type* = NULL ) {} }; I would like to know why I need to do the enabling via a dummy parameter. Why can I not just write : struct Foo { template<class T> Foo( boost::enable_if<is_arithmetic<T>, T>::type* = NULL ) {} };

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  • C++, what does this syntax mean?

    - by aaa
    i found this in this file: http://www.boost.org/doc/libs/1_43_0/boost/spirit/home/phoenix/core/actor.hpp What does this syntax means? struct actor ... { ... template <typename T0, typename T1> typename result<actor(T0&,T1&)>::type // this line thank you

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  • Conway's Game of Life - C++ and Qt

    - by Jeff Bridge
    I've done all of the layouts and have most of the code written even. But, I'm stuck in two places. 1) I'm not quite sure how to set up the timer. Am I using it correctly in the gridwindow class? And, am I used the timer functions/signals/slots correctly with the other gridwindow functions. 2) In GridWindow's timerFired() function, I'm having trouble checking/creating the vector-vectors. I wrote out in the comments in that function exactly what I am trying to do. Any help would be much appreciated. main.cpp // Main file for running the grid window application. #include <QApplication> #include "gridwindow.h" //#include "timerwindow.h" #include <stdexcept> #include <string> #include <fstream> #include <sstream> #include <iostream> void Welcome(); // Welcome Function - Prints upon running program; outputs program name, student name/id, class section. void Rules(); // Rules Function: Prints the rules for Conway's Game of Life. using namespace std; // A simple main method to create the window class and then pop it up on the screen. int main(int argc, char *argv[]) { Welcome(); // Calls Welcome function to print student/assignment info. Rules(); // Prints Conway's Game Rules. QApplication app(argc, argv); // Creates the overall windowed application. int rows = 25, cols = 35; //The number of rows & columns in the game grid. GridWindow widget(NULL,rows,cols); // Creates the actual window (for the grid). widget.show(); // Shows the window on the screen. return app.exec(); // Goes into visual loop; starts executing GUI. } // Welcome Function: Prints my name/id, my class number, the assignment, and the program name. void Welcome() { cout << endl; cout << "-------------------------------------------------------------------------------------------------" << endl; cout << "Name/ID - Gabe Audick #7681539807" << endl; cout << "Class/Assignment - CSCI-102 Disccusion 29915: Homework Assignment #4" << endl; cout << "-------------------------------------------------------------------------------------------------" << endl << endl; } // Rules Function: Prints the rules for Conway's Game of Life. void Rules() { cout << "Welcome to Conway's Game of Life." << endl; cout << "Game Rules:" << endl; cout << "\t 1) Any living cell with fewer than two living neighbours dies, as if caused by underpopulation." << endl; cout << "\t 2) Any live cell with more than three live neighbours dies, as if by overcrowding." << endl; cout << "\t 3) Any live cell with two or three live neighbours lives on to the next generation." << endl; cout << "\t 4) Any dead cell with exactly three live neighbours becomes a live cell." << endl << endl; cout << "Enjoy." << endl << endl; } gridcell.h // A header file for a class representing a single cell in a grid of cells. #ifndef GRIDCELL_H_ #define GRIDCELL_H_ #include <QPalette> #include <QColor> #include <QPushButton> #include <Qt> #include <QWidget> #include <QFrame> #include <QHBoxLayout> #include <iostream> // An enum representing the two different states a cell can have. enum CellType { DEAD, // DEAD = Dead Cell. --> Color = White. LIVE // LIVE = Living Cell. ---> Color = White. }; /* Class: GridCell. A class representing a single cell in a grid. Each cell is implemented as a QT QFrame that contains a single QPushButton. The button is sized so that it takes up the entire frame. Each cell also keeps track of what type of cell it is based on the CellType enum. */ class GridCell : public QFrame { Q_OBJECT // Macro allowing us to have signals & slots on this object. private: QPushButton* button; // The button inside the cell that gives its clickability. CellType type; // The type of cell (DEAD or LIVE.) public slots: void handleClick(); // Callback for handling a click on the current cell. void setType(CellType type); // Cell type mutator. Calls the "redrawCell" function. signals: void typeChanged(CellType type); // Signal to notify listeners when the cell type has changed. public: GridCell(QWidget *parent = NULL); // Constructor for creating a cell. Takes parent widget or default parent to NULL. virtual ~GridCell(); // Destructor. void redrawCell(); // Redraws cell: Sets new type/color. CellType getType() const; //Simple getter for the cell type. private: Qt::GlobalColor getColorForCellType(); // Helper method. Returns color that cell should be based from its value. }; #endif gridcell.cpp #include <iostream> #include "gridcell.h" #include "utility.h" using namespace std; // Constructor: Creates a grid cell. GridCell::GridCell(QWidget *parent) : QFrame(parent) { this->type = DEAD; // Default: Cell is DEAD (white). setFrameStyle(QFrame::Box); // Set the frame style. This is what gives each box its black border. this->button = new QPushButton(this); //Creates button that fills entirety of each grid cell. this->button->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); // Expands button to fill space. this->button->setMinimumSize(19,19); //width,height // Min height and width of button. QHBoxLayout *layout = new QHBoxLayout(); //Creates a simple layout to hold our button and add the button to it. layout->addWidget(this->button); setLayout(layout); layout->setStretchFactor(this->button,1); // Lets the buttons expand all the way to the edges of the current frame with no space leftover layout->setContentsMargins(0,0,0,0); layout->setSpacing(0); connect(this->button,SIGNAL(clicked()),this,SLOT(handleClick())); // Connects clicked signal with handleClick slot. redrawCell(); // Calls function to redraw (set new type for) the cell. } // Basic destructor. GridCell::~GridCell() { delete this->button; } // Accessor for the cell type. CellType GridCell::getType() const { return(this->type); } // Mutator for the cell type. Also has the side effect of causing the cell to be redrawn on the GUI. void GridCell::setType(CellType type) { this->type = type; redrawCell(); } // Handler slot for button clicks. This method is called whenever the user clicks on this cell in the grid. void GridCell::handleClick() { // When clicked on... if(this->type == DEAD) // If type is DEAD (white), change to LIVE (black). type = LIVE; else type = DEAD; // If type is LIVE (black), change to DEAD (white). setType(type); // Sets new type (color). setType Calls redrawCell() to recolor. } // Method to check cell type and return the color of that type. Qt::GlobalColor GridCell::getColorForCellType() { switch(this->type) { default: case DEAD: return Qt::white; case LIVE: return Qt::black; } } // Helper method. Forces current cell to be redrawn on the GUI. Called whenever the setType method is invoked. void GridCell::redrawCell() { Qt::GlobalColor gc = getColorForCellType(); //Find out what color this cell should be. this->button->setPalette(QPalette(gc,gc)); //Force the button in the cell to be the proper color. this->button->setAutoFillBackground(true); this->button->setFlat(true); //Force QT to NOT draw the borders on the button } gridwindow.h // A header file for a QT window that holds a grid of cells. #ifndef GRIDWINDOW_H_ #define GRIDWINDOW_H_ #include <vector> #include <QWidget> #include <QTimer> #include <QGridLayout> #include <QLabel> #include <QApplication> #include "gridcell.h" /* class GridWindow: This is the class representing the whole window that comes up when this program runs. It contains a header section with a title, a middle section of MxN cells and a bottom section with buttons. */ class GridWindow : public QWidget { Q_OBJECT // Macro to allow this object to have signals & slots. private: std::vector<std::vector<GridCell*> > cells; // A 2D vector containing pointers to all the cells in the grid. QLabel *title; // A pointer to the Title text on the window. QTimer *timer; // Creates timer object. public slots: void handleClear(); // Handler function for clicking the Clear button. void handleStart(); // Handler function for clicking the Start button. void handlePause(); // Handler function for clicking the Pause button. void timerFired(); // Method called whenever timer fires. public: GridWindow(QWidget *parent = NULL,int rows=3,int cols=3); // Constructor. virtual ~GridWindow(); // Destructor. std::vector<std::vector<GridCell*> >& getCells(); // Accessor for the array of grid cells. private: QHBoxLayout* setupHeader(); // Helper function to construct the GUI header. QGridLayout* setupGrid(int rows,int cols); // Helper function to constructor the GUI's grid. QHBoxLayout* setupButtonRow(); // Helper function to setup the row of buttons at the bottom. }; #endif gridwindow.cpp #include <iostream> #include "gridwindow.h" using namespace std; // Constructor for window. It constructs the three portions of the GUI and lays them out vertically. GridWindow::GridWindow(QWidget *parent,int rows,int cols) : QWidget(parent) { QHBoxLayout *header = setupHeader(); // Setup the title at the top. QGridLayout *grid = setupGrid(rows,cols); // Setup the grid of colored cells in the middle. QHBoxLayout *buttonRow = setupButtonRow(); // Setup the row of buttons across the bottom. QVBoxLayout *layout = new QVBoxLayout(); // Puts everything together. layout->addLayout(header); layout->addLayout(grid); layout->addLayout(buttonRow); setLayout(layout); } // Destructor. GridWindow::~GridWindow() { delete title; } // Builds header section of the GUI. QHBoxLayout* GridWindow::setupHeader() { QHBoxLayout *header = new QHBoxLayout(); // Creates horizontal box. header->setAlignment(Qt::AlignHCenter); this->title = new QLabel("CONWAY'S GAME OF LIFE",this); // Creates big, bold, centered label (title): "Conway's Game of Life." this->title->setAlignment(Qt::AlignHCenter); this->title->setFont(QFont("Arial", 32, QFont::Bold)); header->addWidget(this->title); // Adds widget to layout. return header; // Returns header to grid window. } // Builds the grid of cells. This method populates the grid's 2D array of GridCells with MxN cells. QGridLayout* GridWindow::setupGrid(int rows,int cols) { QGridLayout *grid = new QGridLayout(); // Creates grid layout. grid->setHorizontalSpacing(0); // No empty spaces. Cells should be contiguous. grid->setVerticalSpacing(0); grid->setSpacing(0); grid->setAlignment(Qt::AlignHCenter); for(int i=0; i < rows; i++) //Each row is a vector of grid cells. { std::vector<GridCell*> row; // Creates new vector for current row. cells.push_back(row); for(int j=0; j < cols; j++) { GridCell *cell = new GridCell(); // Creates and adds new cell to row. cells.at(i).push_back(cell); grid->addWidget(cell,i,j); // Adds to cell to grid layout. Column expands vertically. grid->setColumnStretch(j,1); } grid->setRowStretch(i,1); // Sets row expansion horizontally. } return grid; // Returns grid. } // Builds footer section of the GUI. QHBoxLayout* GridWindow::setupButtonRow() { QHBoxLayout *buttonRow = new QHBoxLayout(); // Creates horizontal box for buttons. buttonRow->setAlignment(Qt::AlignHCenter); // Clear Button - Clears cell; sets them all to DEAD/white. QPushButton *clearButton = new QPushButton("CLEAR"); clearButton->setFixedSize(100,25); connect(clearButton, SIGNAL(clicked()), this, SLOT(handleClear())); buttonRow->addWidget(clearButton); // Start Button - Starts game when user clicks. Or, resumes game after being paused. QPushButton *startButton = new QPushButton("START/RESUME"); startButton->setFixedSize(100,25); connect(startButton, SIGNAL(clicked()), this, SLOT(handleStart())); buttonRow->addWidget(startButton); // Pause Button - Pauses simulation of game. QPushButton *pauseButton = new QPushButton("PAUSE"); pauseButton->setFixedSize(100,25); connect(pauseButton, SIGNAL(clicked()), this, SLOT(handlePause())); buttonRow->addWidget(pauseButton); // Quit Button - Exits program. QPushButton *quitButton = new QPushButton("EXIT"); quitButton->setFixedSize(100,25); connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); buttonRow->addWidget(quitButton); return buttonRow; // Returns bottom of layout. } /* SLOT method for handling clicks on the "clear" button. Receives "clicked" signals on the "Clear" button and sets all cells to DEAD. */ void GridWindow::handleClear() { for(unsigned int row=0; row < cells.size(); row++) // Loops through current rows' cells. { for(unsigned int col=0; col < cells[row].size(); col++) { GridCell *cell = cells[row][col]; // Grab the current cell & set its value to dead. cell->setType(DEAD); } } } /* SLOT method for handling clicks on the "start" button. Receives "clicked" signals on the "start" button and begins game simulation. */ void GridWindow::handleStart() { this->timer = new QTimer(this); // Creates new timer. connect(this->timer, SIGNAL(timeout()), this, SLOT(timerFired())); // Connect "timerFired" method class to the "timeout" signal fired by the timer. this->timer->start(500); // Timer to fire every 500 milliseconds. } /* SLOT method for handling clicks on the "pause" button. Receives "clicked" signals on the "pause" button and stops the game simulation. */ void GridWindow::handlePause() { this->timer->stop(); // Stops the timer. delete this->timer; // Deletes timer. } // Accessor method - Gets the 2D vector of grid cells. std::vector<std::vector<GridCell*> >& GridWindow::getCells() { return this->cells; } void GridWindow::timerFired() { // I'm not sure how to write this code. // I want to take the original vector-vector, and also make a new, empty vector-vector of the same size. // I would then go through the code below with the original vector, and apply the rules to the new vector-vector. // Finally, I would make the new vector-vecotr the original vector-vector. (That would be one step in the simulation.) cout << cells[1][2]; /* for (unsigned int m = 0; m < original.size(); m++) { for (unsigned int n = 0; n < original.at(m).size(); n++) { unsigned int neighbors = 0; //Begin counting number of neighbors. if (original[m-1][n-1].getType() == LIVE) // If a cell next to [i][j] is LIVE, add one to the neighbor count. neighbors += 1; if (original[m-1][n].getType() == LIVE) neighbors += 1; if (original[m-1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n-1].getType() == LIVE) neighbors += 1; if (original[m][n+1].getType() == LIVE) neighbors += 1; if (original[m+1][n-1].getType() == LIVE) neighbors += 1; if (original[m+1][n].getType() == LIVE) neighbors += 1; if (original[m+1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n].getType() == LIVE && neighbors < 2) // Apply game rules to cells: Create new, updated grid with the roundtwo vector. roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == LIVE && neighbors > 3) roundtwo[m][n].setType(DEAD); else if (original[m][n].getType() == LIVE && (neighbors == 2 || neighbors == 3)) roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == DEAD && neighbors == 3) roundtwo[m][n].setType(LIVE); } }*/ }

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  • WinXP How to Tunnel LPT over USB

    - by Michael Pruitt
    I have a windows program that accesses a device connected to a LPT (1-3) 25 pin port. The communication is bidirectional, and I suspected the control lines are also accessed directly. I would like to migrate the device to a machine that does not have a LPT port. I saw the dos2usb software, but that takes the output (from a DOS program) and 'prints' it formatted for a specific printer. I need a raw LPT connection, and a cable that provides access to all the control signals. I do have a USB to 36-pin Centronics that may have the extra signals. I use it with a vinyl cutter that doesn't like most of the USB dongles. It comes up as USB001. Would adding and sharing a generic printer, then mapping LPT1 to the share get me closer? Would that work for a parallel port scanner? My preferred solution is a USB cable with a driver that will map it to LPT1, LPT2, or LPT3.

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  • Can I get my video card to output a DVI and VGA signal at the same time?

    - by Roy Pardee
    Hey All, I've got: a lovely 24" monitor, w/both DVI and VGA inputs, a personal desktop w/a Radeon HD Pro 2400 video card (both DVI and VGA outputs) a work laptop w/both outputs, and a KVM switch that handles VGA only Right now I've got laptop connected to the monitor's VGA, and the desktop connected to the DVI. This works, but requires me to switch the KVM and monitor input sources separately, which annoys me (I switch back & forth a lot to make skype calls & manage my music). I'd like to feed both VGA and DVI signals out of my desktop so I can do quick things on my desktop & switch right back, but then when I'm done working, switch the monitor over to DVI to get the crisper picture. Alas, just attaching both VGA and DVI cables to my desktop's video card did not do the trick. Can this card be persuaded to output both signals at the same time? Many thanks! -Roy

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  • LLVM-3.1 libLLVMSupport.a undefined reference to `dladdr'

    - by user91387
    I'm trying to compile using the llvm-3.1 package. I'm running 12.04 x64 (3.2.0-26 kernel) && 12.10 (3.5.0-4) x64 backported llvm-3.1 from quantal, then debian experimental. Next I tried 12.10 with the native ubuntu llvm-3.1 package; this failed as well. user@system:/tmp/llvm-test# make compiling cpp yacc file: decaf-llvm.y output file: decaf-llvm bison -b decaf-llvm -d decaf-llvm.y /bin/mv -f decaf-llvm.tab.c decaf-llvm.tab.cc flex -odecaf-llvm.lex.cc decaf-llvm.lex g++ -o ./decaf-llvm decaf-llvm.tab.cc decaf-llvm.lex.cc decaf-stdlib.c `llvm-config --cppflags --ldflags --libs core jit native` -ly -ll /usr/lib/llvm-3.1/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x6c): undefined reference to `dladdr' /usr/lib/llvm-3.1/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x18f): undefined reference to `dladdr' collect2: error: ld returned 1 exit status make: *** [decaf-llvm] Error 1 I know the code works as I've run it in centos fine using llvm-3.1-6.fc18(rpm) Google was a bit helpful with this: "On some systems, incluning Ubuntu 11.10, linking may fail with message that libLLVMSupport.a in function PrintStackTrace(void*) has undefined reference to dladdr." "Workaround is to compile LLVM with cmake specifying the following variable: -DCMAKE_EXE_LINKER_FLAGS=-ldl" http://svn.dsource.org/projects/bindings/trunk/llvm-3.0/Readme I double checked y ldflags and everything seems ok. user@system:/llvm-config --ldflags -L/usr/lib/llvm-3.1/lib -lpthread -lffi -ldl -lm I'm unclear of what to do next; any suggestions?

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  • What's the best way to clean up after a fork bomb?

    - by raldi
    $ ls bash: no more processes Uh oh. Looks like someone made a fork bomb. Where I used to work, this pretty much meant that the shared server would need to be power-cycled, since even the sysadmins with root often couldn't get the problem cleaned up. Often, they couldn't even get a prompt. I've heard a few tricks (notably, to send STOP signals rather than KILL signals, since the latter would allow the remaining threads to immediately replace the killed ones), but I've never seen a comprehensive guide entitled So, You Have Yourself a Fork Bomb? Let's make one.

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  • New monitor connected to HDMI adaptor doesn't show output after booting

    - by Paul
    Hello out there in the multiple monitors’ world. I am a very old newbie in your world and need help. I just purchased a new Asus VH236H monitor and hooked it up the HDMI port of an ATI Radeon HD4300 / 4500 Series display adaptor. I left the old Princeton LCD19 (TMDS) hooked up to the DVI port of the same display adaptor. Both monitors displayed the boot sequence, after I fired good old Sarastro2 (Asus P5Q Pro Turbo – Dual Core E5300 – 2.60 GHz) up. The Asus lacked one half of a second behind the Princeton until the Windows 7 Ultimate SP 1 boot up was complete. Then the Asus displayed “HDMI NO SIGNAL” and went into hibernation. The Princeton stayed lit up as before. Both monitors are displayed on the “Screen Resolution Setup Display” and I plaid around with them for a while. The only thing I accomplished was to shove the desktop icons from the Princeton to the still hibernating Asus. The “Multiple displays:” is set to “Extend these displays”, the Orientation is “Landscape” and the Resolutions are set on both to the “recommended” one. Both monitors show that they work properly in the advanced Properties display. What am I doing wrong, what am I missing? Never mind the opinions about the different resolutions of the two monitors. I always can unhook the Princeton and give it to a Goodwill Store if I do not like the setup. I just would like to make it work. Any constructive help is very much appreciated, Thank you. Thank you Anees Bakrain Only the ATI Radeon HD 4300/4500 Series adapter is displayed in the Device Manager, for that reason I have to assume that the onboard display adaptor is not active. All 40 drivers of Sarastro2 are up to date and the HDMI cable can not be the problem because both monitors displayed the boot sequence up to the moment when Windows 7 was loaded completely. This was the moment, when the Asus monitor lost its signal. Both connectors, HDMI and DVI are connected and removing the DVI connector would not solve my problem of running both monitors simultaneously. However, your suggestions shifted my seventy one year old brain into the next gear. The only question remaining is; “Why the signals to the Asus monitor stop after the sequence is complete”. The ATI Radeon HD 4300/4500 Series adapter seems to be capable of sending simultaneous HDMI and DVI signals, what is done during the boot sequence. Why do the signals change after the boot sequence is complete is the key question or der springende Punkt? Is this a correct assumption slhck?

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  • Help deciding on language for a complex desktop - web application

    - by user967834
    I'm about to start working on a fairly complex project needing a desktop GUI as well as a web interface and I need to decide on a language(s) to use. This is from an electrical engineering/robotics background. These are the requirements: Program will have to read data from multiple sensors and inputs (motion sensor, temperature sensor, capacitive sensor, infrared, magnetic sensors, etc) through a port on a computer - so either through USB or ethernet. Program will have to be able to send control signals based on this input. Program will have to continuously monitor all input signals at all times - so realtime data. Program will require authentication. Program will need to be controllable from a web interface from anywhere via logging in to a website. Web interface will also need to have realtime feedback once authenticated. What language do you think would best accomplish this? I was thinking maybe saving everything into a database which can be accessed by both the desktop and web app? And would Python be able to do all of this? Or something like a remote desktop app? I know this is a complex project but let's assume I can learn any language. Has anyone done something like this and if so how did you accomplish it?

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  • How to retry connections with wget?

    - by Andrei
    I have a very unstable internet connection, and sometimes have to download files as large as 200 MB. The problem is that the speed frequently drops and sits at --, -K/s and the process remains alive. I thought just to send some KILL signals to the process, but as I read in the wget manual about signals it doesn't help. How can I force wget to reinitialize itself and pick the download up where it left off after the connection drops and comes back up again? I would like to leave wget running, and when I come back, I want to see it downloading, and not waiting with speed --,-K/s.

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  • Use of for_each on map elements

    - by Antonio
    I have a map where I'd like to perform a call on every data type object member function. I yet know how to do this on any sequence but, is it possible to do it on an associative container? The closest answer I could find was this: Boost.Bind to access std::map elements in std::for_each. But I cannot use boost in my project so, is there an STL alternative that I'm missing to boost::bind? If not possible, I thought on creating a temporary sequence for pointers to the data objects and then, call for_each on it, something like this: class MyClass { public: void Method() const; } std::map<int, MyClass> Map; //... std::vector<MyClass*> Vector; std::transform(Map.begin(), Map.end(), std::back_inserter(Vector), std::mem_fun_ref(&std::map<int, MyClass>::value_type::second)); std::for_each(Vector.begin(), Vector.end(), std::mem_fun(&MyClass::Method)); It looks too obfuscated and I don't really like it. Any suggestions?

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  • Find max integer size that a floating point type can handle without loss of precision

    - by Checkers
    Double has range more than a 64-bit integer, but its precision is less dues to its representation (since double is 64-bit as well, it can't fit more actual values). So, when representing larger integers, you start to lose precision in the integer part. #include <boost/cstdint.hpp> #include <limits> template<typename T, typename TFloat> void maxint_to_double() { T i = std::numeric_limits<T>::max(); TFloat d = i; std::cout << std::fixed << i << std::endl << d << std::endl; } int main() { maxint_to_double<int, double>(); maxint_to_double<boost::intmax_t, double>(); maxint_to_double<int, float>(); return 0; } This prints: 2147483647 2147483647.000000 9223372036854775807 9223372036854775800.000000 2147483647 2147483648.000000 Note how max int can fit into a double without loss of precision and boost::intmax_t (64-bit in this case) cannot. float can't even hold an int. Now, the question: is there a way in C++ to check if the entire range of a given integer type can fit into a loating point type without loss of precision? Preferably, it would be a compile-time check that can be used in a static assertion, and would not involve enumerating the constants the compiler should know or can compute.

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  • What would be the safest way to store objects of classes derived from a common interface in a common

    - by Svenstaro
    I'd like to manage a bunch of objects of classes derived from a shared interface class in a common container. To illustrate the problem, let's say I'm building a game which will contain different actors. Let's call the interface IActor and derive Enemy and Civilian from it. Now, the idea is to have my game main loop be able to do this: // somewhere during init std::vector<IActor> ActorList; Enemy EvilGuy; Civilian CoolGuy; ActorList.push_back(EvilGuy); ActorList.push_back(CoolGuy); and // main loop while(!done) { BOOST_FOREACH(IActor CurrentActor, ActorList) { CurrentActor.Update(); CurrentActor.Draw(); } } ... or something along those lines. This example obviously won't work but that is pretty much the reason I'm asking here. I'd like to know: What would be the best, safest, highest-level way to manage those objects in a common heterogeneous container? I know about a variety of approaches (Boost::Any, void*, handler class with boost::shared_ptr, Boost.Pointer Container, dynamic_cast) but I can't decide which would be the way to go here. Also I'd like to emphasize that I want to stay away as far as possible from manual memory management or nested pointers. Help much appreciated :).

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  • What is the rationale to non allow overloading of C++ conversions operator with non-member functio

    - by Vicente Botet Escriba
    C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration operator boost::posix_time::ptime( const boost::chrono::time_point& from) { using namespace boost; typedef chrono::time_point time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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