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• SDL with OpenGL (freeglut) crashes on call to glutBitmapCharacter

  - by stett

  I have a program using OpenGL through freeglut under SDL. The SDL/OpenGL initialization is as follows: // Initialize SDL SDL_Init(SDL_INIT_VIDEO); // Create the SDL window SDL_SetVideoMode(SCREEN_W, SCREEN_H, SCREEN_DEPTH, SDL_OPENGL); // Initialize OpenGL glClearColor(BG_COLOR_R, BG_COLOR_G, BG_COLOR_B, 1.f); glViewport(0, 0, SCREEN_W, SCREEN_H); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0.0f, SCREEN_W, SCREEN_H, 0.0f, -1.0f, 1.0f); glEnable(GL_TEXTURE_2D); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); I've been using glBegin() ... glEnd() blocks without any trouble to draw primitives. However, in this program when I call any glutBitmapX function, the program simply exits without an error status. The code I'm using to draw text is: glColor3f(1.f, 1.f, 1.f); glRasterPos2f(x, y); glutStrokeString(GLUT_BITMAP_8_BY_13, (const unsigned char*)"test string"); In previous similar programs I've used glutBitmapCharacter and glutStrokeString to draw text and it's seemed to work. The only difference being that I'm using freeglut with SDL now instead of just GLUT as I did in previous programs. Is there some fundamental problem with my setup that I'm not seeing, or is there a better way of drawing text?

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• convert MsSql StoredPorcedure to MySql

  - by karthik

  I need to covert the following SP of MsSql To MySql. I am new to MySql.. Help needed. CREATE PROC InsertGenerator (@tableName varchar(100)) as --Declare a cursor to retrieve column specific information --for the specified table DECLARE cursCol CURSOR FAST_FORWARD FOR SELECT column_name,data_type FROM information_schema.columns WHERE table_name = @tableName OPEN cursCol DECLARE @string nvarchar(3000) --for storing the first half --of INSERT statement DECLARE @stringData nvarchar(3000) --for storing the data --(VALUES) related statement DECLARE @dataType nvarchar(1000) --data types returned --for respective columns SET @string='INSERT '+@tableName+'(' SET @stringData='' DECLARE @colName nvarchar(50) FETCH NEXT FROM cursCol INTO @colName,@dataType IF @@fetch_status<0 begin print 'Table '+@tableName+' not found, processing skipped.' close curscol deallocate curscol return END WHILE @@FETCH_STATUS=0 BEGIN IF @dataType in ('varchar','char','nchar','nvarchar') BEGIN SET @stringData=@stringData+'''''''''+ isnull('+@colName+','''')+'''''',''+' END ELSE if @dataType in ('text','ntext') --if the datatype --is text or something else BEGIN SET @stringData=@stringData+'''''''''+ isnull(cast('+@colName+' as varchar(2000)),'''')+'''''',''+' END ELSE IF @dataType = 'money' --because money doesn't get converted --from varchar implicitly BEGIN SET @stringData=@stringData+'''convert(money,''''''+ isnull(cast('+@colName+' as varchar(200)),''0.0000'')+''''''),''+' END ELSE IF @dataType='datetime' BEGIN SET @stringData=@stringData+'''convert(datetime,''''''+ isnull(cast('+@colName+' as varchar(200)),''0'')+''''''),''+' END ELSE IF @dataType='image' BEGIN SET @stringData=@stringData+'''''''''+ isnull(cast(convert(varbinary,'+@colName+') as varchar(6)),''0'')+'''''',''+' END ELSE --presuming the data type is int,bit,numeric,decimal BEGIN SET @stringData=@stringData+'''''''''+ isnull(cast('+@colName+' as varchar(200)),''0'')+'''''',''+' END SET @string=@string+@colName+',' FETCH NEXT FROM cursCol INTO @colName,@dataType END

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• Getting bizarre "expected primary-expression" error.

  - by Fecal Brunch

  Hi, I'm getting a really strange error when making a method call: /* input.cpp */ #include <ncurses/ncurses.h> #include "input.h" #include "command.h" Input::Input () { raw (); noecho (); } Command Input::next () { char input = getch (); Command nextCommand; switch (input) { case 'h': nextCommand.setAction (ACTION_MOVELEFT); break; case 'j': nextCommand.setAction (ACTION_MOVEDOWN); break; case 'k': nextCommand.setAction (ACTION_MOVEUP); break; case 'l': nextCommand.setAction (ACTION_MOVERIGHT); break; case 'y': nextCommand.setAction (ACTION_MOVEUPLEFT); break; case 'u': nextCommand.setAction (ACTION_MOVEUPRIGHT); break; case 'n': nextCommand.setAction (ACTION_MOVEDOWNLEFT); break; case 'm': nextCommand.setAction (ACTION_MOVEDOWNRIGHT); break; case '.': nextCommand.setAction (ACTION_WAIT); break; } return nextCommand; } and the error: Administrator@RHYS ~/code/rogue2 $ make g++ -c -Wall -pedantic -g3 -O0 input.cpp input.cpp: In member function `Command Input::next()': input.cpp:21: error: expected primary-expression before '=' token input.cpp:24: error: expected primary-expression before '=' token input.cpp:27: error: expected primary-expression before '=' token input.cpp:30: error: expected primary-expression before '=' token input.cpp:33: error: expected primary-expression before '=' token input.cpp:36: error: expected primary-expression before '=' token input.cpp:39: error: expected primary-expression before '=' token input.cpp:42: error: expected primary-expression before '=' token input.cpp:45: error: expected primary-expression before '=' token make: *** [input.o] Error 1 Sorry about the lack of linenumbers, the errors occur on the lines "nextCommand.setAction(...)", which is totally bizarre considering that they don't contain a '='. Any ideas? Thanks, Rhys

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• How to assign a table view controller to a table view on iPhone?

  - by Tattat

  I have a CharTableController, View and TableView on my IB. The CharTableController is using "CharTableController" in class identity. And this is how I implemented in the .h, and I want use the "CharTableController" to control the table only: @interface CharTableController : UITableViewController <UITableViewDelegate, UITableViewDataSource>{ // IBOutlet UILabel *debugLabel; NSArray *listData; } //@property (nonatomic, retain) IBOutlet UILabel *debugLabel; @property (nonatomic, retain) NSArray *listData; @end It is the .m: #import "CharTableController.h" @implementation CharTableController @synthesize listData; - (void)viewDidLoad { //NSLog(@"bulll"); // [debugLabel setText:@"success"]; NSArray *array = [[NSArray alloc] initWithObjects:@"A", @"B", @"C", @"D", @"E", nil]; self.listData = array; [array release]; [super viewDidLoad]; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.listData count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:SimpleTableIdentifier] autorelease]; NSUInteger row = [indexPath row]; cell.textLabel.text = [listData objectAtIndex:row]; } return cell; } @end In the IB, I already assign the CharTableController's view to Table View in IB. And Table View is under the View, in IB. After I run the program, I can see the table view, but I can't see any char in the table view, why? What's wrong with my code? thz.

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• Drawing only part of a

  - by Ben Reeves

  ..Continued on from my previous question I have a 320*480 RGB565 framebuffer which I wish to draw using OpenGL ES 1.0 on the iPhone. - (void)setupView { glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES, (int[4]){0, 0, 480, 320}); glEnable(GL_TEXTURE_2D); } // Updates the OpenGL view when the timer fires - (void)drawView { // Make sure that you are drawing to the current context [EAGLContext setCurrentContext:context]; //Get the 320*480 buffer const int8_t * frameBuf = [source getNextBuffer]; //Create enough storage for a 512x512 power of 2 texture int8_t lBuf[2*512*512]; memcpy (lBuf, frameBuf, 320*480*2); //Upload the texture glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 512, 512, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, lBuf); //Draw it glDrawTexiOES(0, 0, 1, 480, 320); [context presentRenderbuffer:GL_RENDERBUFFER_OES]; } If I produce the original texture in 512*512 the output is cropped incorrectly but other than that looks fine. However using the require output size of 320*480 everything is distorted and messed up. I'm pretty sure it's the way I'm copying the framebuffer into the new 512*512 buffer. I have tried this routine int8_t lBuf[512][512][2]; const char * frameDataP = frameData; for (int ii = 0; ii < 480; ++ii) { memcpy(lBuf[ii], frameDataP, 320); frameDataP += 320; } Which is better, but the width appears to be stretched and the height is messed up. Any help appreciated.

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• Reading text files line by line, with exact offset/position reporting

  - by Benjamin Podszun

  Hi. My simple requirement: Reading a huge ( a million) line test file (For this example assume it's a CSV of some sorts) and keeping a reference to the beginning of that line for faster lookup in the future (read a line, starting at X). I tried the naive and easy way first, using a StreamWriter and accessing the underlying BaseStream.Position. Unfortunately that doesn't work as I intended: Given a file containing the following Foo Bar Baz Bla Fasel and this very simple code using (var sr = new StreamReader(@"C:\Temp\LineTest.txt")) { string line; long pos = sr.BaseStream.Position; while ((line = sr.ReadLine()) != null) { Console.Write("{0:d3} ", pos); Console.WriteLine(line); pos = sr.BaseStream.Position; } } the output is: 000 Foo 025 Bar 025 Baz 025 Bla 025 Fasel I can imagine that the stream is trying to be helpful/efficient and probably reads in (big) chunks whenever new data is necessary. For me this is bad.. The question, finally: Any way to get the (byte, char) offset while reading a file line by line without using a basic Stream and messing with \r \n \r\n and string encoding etc. manually? Not a big deal, really, I just don't like to build things that might exist already..

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• Volatile fields in C#

  - by Danny Chen

  From the specification 10.5.3 Volatile fields: The type of a volatile field must be one of the following: A reference-type. The type byte, sbyte, short, ushort, int, uint, char, float, bool, System.IntPtr, or System.UIntPtr. An enum-type having an enum base type of byte, sbyte, short, ushort, int, or uint. First I want to confirm my understanding is correct: I guess the above types can be volatile because they are stored as a 4-bytes unit in memory(for reference types because of its address), which guarantees the read/write operation is atomic. A double/long/etc type can't be volatile because they are not atomic reading/writing since they are more than 4 bytes in memory. Is my understanding correct? And the second, if the first guess is correct, why a user defined struct with only one int field in it(or something similar, 4 bytes is ok) can't be volatile? Theoretically it's atomic right? Or it's not allowed simply because that all user defined structs(which is possibly more than 4 bytes) are not allowed to volatile by design?

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• Binary files printing and desired precision

  - by yCalleecharan

  Hi, I'm printing a variable say z1 which is a 1-D array containing floating point numbers to a text file so that I can import into Matlab or GNUPlot for plotting. I've heard that binary files (.dat) are smaller than .txt files. The definition that I currently use for printing to a .txt file is: void create_out_file(const char *file_name, const long double *z1, size_t z_size){ FILE *out; size_t i; if((out = _fsopen(file_name, "w+", _SH_DENYWR)) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < z_size; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } I have three questions: Are binary files really more compact than text files?; If yes, I would like to know how to modify the above code so that I can print the values of the array z1 to a binary file. I've read that fprintf has to be replaced with fwrite. My output file say dodo.dat should contain the values of array z1 with one floating number per line. I have %.16Le up in my code but I think that %.15Le is right as I have 15 precision digits with long double. I have put a dot (.) in the width position as I believe that this allows expansion to an arbitrary field to hold the desired number. Am I right? As an example with %.16Le, I can have an output like 1.0047914240730432e-002 which gives me 16 precision digits and the width of the field has the right width to display the number correctly. Is placing a dot (.) in the width position instead of a width value a good practice? Thanks a lot...

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• What's wrong with my code? (pdcurses/getmaxyx)

  - by flarn2006

  It gives me an access violation on the getmaxyx line (second line in the main function) and also gives me these two warnings: LINK : warning LNK4049: locally defined symbol "_stdscr" imported LINK : warning LNK4049: locally defined symbol "_SP" imported Yes, it's the same code as in another question I asked, it's just that I'm making it more clear. And yes, I have written programs with pdcurses before with no problems. #include <time.h> #include <curses.h> #include "Ball.h" #include "Paddle.h" #include "config.h" int main(int argc, char *argv[]) { int maxY, maxX; getmaxyx(stdscr, maxY, maxX); Paddle *paddleLeft = new Paddle(0, KEY_L_UP, KEY_L_DOWN); Paddle *paddleRight = new Paddle(maxX, KEY_R_UP, KEY_R_DOWN); Ball *ball = new Ball(paddleLeft, paddleRight); int key = 0; initscr(); cbreak(); noecho(); curs_set(0); while (key != KEY_QUIT) { key = getch(); paddleLeft->OnKeyPress(key); paddleRight->OnKeyPress(key); } endwin(); return 0; }

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• Communication between parent and child

  - by Pierre

  Hi every one ! I have a little problem. I have to code a simple C application that creat a process and his child (fork()) and I have to do an operation. Parent initialize the values and child calculate. I write this : #include #include #include #include #include typedef struct { int op1; char op; int op2; }Operation; Operation *varOP; void finalResult() { float result = 0; if(varOP-op == '+') result = (varOP-op1 + varOP-op2); if(varOP-op == '-') result = (varOP-op1 - varOP-op2); if(varOP-op == '*') result = (varOP-op1 * varOP-op2); if(varOP-op == '+') result = (varOP-op1 / varOP-op2); printf("%f",result); } int main () { int p; varOP = (Operation *)malloc(sizeof(Operation)); p = fork(); if(p == 0) // If child { signal(SIGUSR1, finalResult ); pause(); } if(p 0) // If parent { varOP-op = '+'; varOP-op1 = 2; varOP-op2 = 3; kill(p, SIGUSR1); wait(NULL); } return 0; } But my child is never called. Is there something wrong with my code? Thanks for your help !

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• Weird problem with string function

  - by wrongusername

  I'm having a weird problem with the following function, which returns a string with all the characters in it after a certain point: string after(int after, string word) { char temp[word.size() - after]; cout << word.size() - after << endl; //output here is as expected for(int a = 0; a < (word.size() - after); a++) { cout << word[a + after]; //and so is this temp[a] = word[a + after]; cout << temp[a]; //and this } cout << endl << temp << endl; //but output here does not always match what I want string returnString = temp; return returnString; } The thing is, when the returned string is 7 chars or less, it works just as expected. When the returned string is 8 chars or more, then it starts spewing nonsense at the end of the expected output. For example, the lines cout << after(1, "12345678") << endl; cout << after(1, "123456789") << endl; gives an output of: 7 22334455667788 2345678 2345678 8 2233445566778899 23456789?,?D~ 23456789?,?D~ What can I do to fix this error, and are there any default C++ functions that can do this for me?

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• Is my method for avoiding dynamic_cast<> faster than dynamic_cast<> itself ?

  - by ereOn

  Hi, I was answering a question a few minutes ago and it raised to me another one: In one of my projects, I do some network message parsing. The messages are in the form of: [1 byte message type][2 bytes payload length][x bytes payload] The format and content of the payload are determined by the message type. I have a class hierarchy, based on a common class Message. To instanciate my messages, i have a static parsing method which gives back a Message* depending on the message type byte. Something like: Message* parse(const char* frame) { // This is sample code, in real life I obviously check that the buffer // is not NULL, and the size, and so on. switch(frame[0]) { case 0x01: return new FooMessage(); case 0x02: return new BarMessage(); } // Throw an exception here because the mesage type is unknown. } I sometimes need to access the methods of the subclasses. Since my network message handling must be fast, I decived to avoid dynamic_cast<> and I added a method to the base Message class that gives back the message type. Depending on this return value, I use a static_cast<> to the right child type instead. I did this mainly because I was told once that dynamic_cast<> was slow. However, I don't know exactly what it really does and how slow it is, thus, my method might be as just as slow (or slower) but far more complicated. What do you guys think of this design ? Is it common ? Is it really faster than using dynamic_cast<> ? Any detailed explanation of what happen under the hood when one use dynamic_cast<> is welcome !

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• I am trying to have a wall follow robot but there are errors on the names not being declared in my s

  - by Sam

  #include <iostream> #include <libplayerc++/playerc++.h> using namespace std; int main(int argc, char *argv[]) { using namespace PlayerCc; PlayerClient robot("localhost"); BumperProxy bp(&robot,0); Position2dProxy pp(&robot,0); pp.SetMotorEnable(true); for(;;) double turnrate, speed; double error; bool wall; motor_a_speed(0); motor_c_speed(0); while(1) { front_bumper = SENSOR_2; left_bumper = SENSOR_3; if (front_bumper > 2) { if (left_bumper < 3) { motor_a_speed(5); motor_c_speed(drive_speed); motor_a_dir(fwd); motor_c_dir(fwd); } else { motor_a_speed(drive_speed); motor_c_speed(5); motor_a_dir(rev); motor_c_dir(rev); } } else { motor_a_speed(drive_speed); motor_c_speed(drive_speed); motor_a_dir(brake); motor_c_dir(brake); mrest(100); cputs("bump"); motor_a_dir(fwd); motor_c_dir(rev); msleep(450); cputs("right"); motor_a_speed(10); motor_a_dir(fwd); motor_c_dir(fwd); mrest(1300); } pp.SetSpeed(speed, turnrate); } }

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• Mac OS X and static boost libs -> std::string fail

  - by Ionic

  Hi all, I'm experiencing some very weird problems with static boost libraries under Mac OS X 10.6.6. The error message is main(78485) malloc: *** error for object 0x1000e0b20: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug [1] 78485 abort (core dumped) and a tiny bit of example code which will trigger this problem: #define BOOST_FILESYSTEM_VERSION 3 #include <boost/filesystem.hpp> #include <iostream> int main (int argc, char **argv) { std::cout << boost::filesystem::current_path ().string () << '\n'; } This problem always occurs when linking the static boost libraries into the binary. Linking dynamically will work fine, though. I've seen various reports for quite a similar OS X bug with GCC 4.2 and the _GLIBCXX_DEBUG macro set, but this one seems even more generic, as I'm neither using XCode, nor setting the macro (even undefining it does not help. I tried it just to make sure it's really not related to this problem.) Does anybody have any pointers to why this is happening or even maybe a solution (rather than using the dynamic library workaround)? Best regards, Mihai

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• PowerShell PSCX Read-Archive: Cannot bind parameter... problem

  - by Robert

  I'm running across a problem I can't seem to wrap my head around using the Read-Archive cmdlet available via PowerShell Community Extensions (v2.0.3782.38614). Here is a cut down sample used to exhibit the problem I'm running into: $mainPath = "p:\temp" $dest = Join-Path $mainPath "ps\CenCodes.zip" Read-Archive -Path $dest -Format zip Running the above produces the following error: Read-Archive : Cannot bind parameter 'Path'. Cannot convert the "p:\temp\ps\CenCodes.zip" value of type "System.String" to type "Pscx.IO.PscxPathInfo". At line:3 char:19 + Read-Archive -Path <<<< $dest -Format zip + CategoryInfo : InvalidArgument: (:) [Read-Archive], ParameterBindingException + FullyQualifiedErrorId : CannotConvertArgumentNoMessage,Pscx.Commands.IO.Compression.ReadArchiveCommand If I do not use Join-Path to build the path passed to Read-Archive it works, as in this example: $mainPath = "p:\temp" $path = $mainPath + "\ps\CenCodes.zip" Read-Archive -Path $path -Format zip Output from above: ZIP Folder: CenCodes.zip#\ Index LastWriteTime Size Ratio Name ----- ------------- ---- ----- ---- 0 6/17/2010 2:03 AM 3009106 24.53 % CenCodes.xls Even more confusing is if I compare the two variables passed as the Path argument in the two Read-Archive samples above, they seem identical: This... Write-Host "dest=$dest" Write-Host "path=$path" Write-Host ("path -eq dest is " + ($dest -eq $path).ToString()) Outputs... dest=p:\temp\ps\CenCodes.zip path=p:\temp\ps\CenCodes.zip path -eq dest is True Anyone have any ideas as to why the first sample gripes but the second one works fine?

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• recommended format to save time with MJD + BCD format in database

  - by pierr

  Hi, There is a time represented in MJD and BCD format with 5 bytes .I am wondering what is the recommended format to save this date-time in the sqlite database so that user can search against it ? My first attempt is to save it just as it is, that is a 5 bytes string. The user will use the same format to search and the result will be converted to unix time by the user with following code. However, later, I was suggested to save the time in the integer - the UTC time, for example. But I can not find a standard way to do the conversion. I feel this is a common issue and would like to hear your comments. time_t sidate_to_unixtime(unsigned char sidate[]) { int k = 0; struct tm tm; double mjd; /* check for the undefined value */ if ((sidate[0] == 0xff) && (sidate[1] == 0xff) && (sidate[2] == 0xff) && (sidate[3] == 0xff) && (sidate[4] == 0xff)) { return -1; } memset(&tm, 0, sizeof(tm)); mjd = (sidate[0] << 8) | sidate[1]; tm.tm_year = (int) ((mjd - 15078.2) / 365.25); tm.tm_mon = (int) (((mjd - 14956.1) - (int) (tm.tm_year * 365.25)) / 30.6001); tm.tm_mday = (int) mjd - 14956 - (int) (tm.tm_year * 365.25) - (int) (tm.tm_mon * 30.6001); if ((tm.tm_mon == 14) || (tm.tm_mon == 15)) k = 1; tm.tm_year += k; tm.tm_mon = tm.tm_mon - 2 - k * 12; tm.tm_sec = bcd_to_integer(sidate[4]); tm.tm_min = bcd_to_integer(sidate[3]); tm.tm_hour = bcd_to_integer(sidate[2]); return mktime(&tm); }

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• Why do I get two clicked or released signals when using a custom slot for a QPushButton ?

  - by Chris

  here's the main code at first I thought is was the message box but setting a label instead has the same effect. #include <time.h> #include "ui_mainwindow.h" #include <QMessageBox> class MainWindow : public QWidget, private Ui::MainWindow { Q_OBJECT public: MainWindow(QWidget *parent = 0); void makeSum(void); private: int r1; int r2; private slots: void on_pushButton_released(void); }; MainWindow::MainWindow(QWidget *parent) : QWidget(parent) { setupUi(this); } void MainWindow::on_pushButton_released(void) { bool ok; int a = lineEdit->text().toInt(&ok, 10); if (ok) { if (r1+r2==a) { QMessageBox::information( this, "Sums","Correct!" ); } else { QMessageBox::information( this, "Sums","Wrong!" ); } } else { QMessageBox::information( this, "Sums","You need to enter a number" ); } makeSum(); } void MainWindow::makeSum(void) { r1 = rand() % 10 + 1; r2 = rand() % 10 + 1; label->setText(QString::number(r1)); label_3->setText(QString::number(r2)); } int main(int argc, char *argv[]) { srand ( time(NULL) ); QApplication app(argc, argv); MainWindow mw; mw.makeSum(); mw.show(); return app.exec(); } #include "main.moc"

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• How to asynchronously read to std::string using Boost::asio?

  - by SpyBot

  Hello. I'm learning Boost::asio and all that async stuff. How can I asynchronously read to variable user_ of type std::string? Boost::asio::buffer(user_) works only with async_write(), but not with async_read(). It works with vector, so what is the reason for it not to work with string? Is there another way to do that besides declaring char user_[max_len] and using Boost::asio::buffer(user_, max_len)? Also, what's the point of inheriting from boost::enable_shared_from_this<Connection> and using shared_from_this() instead of this in async_read() and async_write()? I've seen that a lot in the examples. Here is a part of my code: class Connection { public: Connection(tcp::acceptor &acceptor) : acceptor_(acceptor), socket_(acceptor.get_io_service(), tcp::v4()) { } void start() { acceptor_.get_io_service().post( boost::bind(&Connection::start_accept, this)); } private: void start_accept() { acceptor_.async_accept(socket_, boost::bind(&Connection::handle_accept, this, placeholders::error)); } void handle_accept(const boost::system::error_code& err) { if (err) { disconnect(); } else { async_read(socket_, boost::asio::buffer(user_), boost::bind(&Connection::handle_user_read, this, placeholders::error, placeholders::bytes_transferred)); } } void handle_user_read(const boost::system::error_code& err, std::size_t bytes_transferred) { if ( err or (bytes_transferred != sizeof(user_)) ) { disconnect(); } else { ... } } ... void disconnect() { socket_.shutdown(tcp::socket::shutdown_both); socket_.close(); socket_.open(tcp::v4()); start_accept(); } tcp::acceptor &acceptor_; tcp::socket socket_; std::string user_; std::string pass_; ... };

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• How to pass a function in a function?

  - by SoulBeaver

  That's an odd title. I would greatly appreciate it if somebody could clarify what exactly I'm asking because I'm not so sure myself. I'm watching the Stanford videos on Programming Paradigms(that teacher is awesome) and I'm up to video five when he started doing this: void *lSearch( void* key, void* base, int elemSize, int n, int (*cmpFn)(void*, void*)) Naturally, I thought to myself, "Oi, I didn't know you could declare a function and define it later!". So I created my own C++ test version. int foo(int (*bar)(void*, void*)); int bar(void* a, void* b); int main(int argc, char** argv) { int *func = 0; foo(bar); cin.get(); return 0; } int foo(int (*bar)(void*, void*)) { int c(10), d(15); int *a = &c; int *b = &d; bar(a, b); return 0; } int bar(void* a, void* b) { cout << "Why hello there." << endl; return 0; } The question about the code is this: it fails if I declare function int *bar as a parameter of foo, but not int (*bar). Why!? Also, the video confuses me in the fact that his lSearch definition void* lSearch( /*params*/ , int (*cmpFn)(void*, void*)) is calling cmpFn in the definition, but when calling the lSearch function lSearch( /*params*/, intCmp ); also calls the defined function int intCmp(void* elem1, void* elem2); and I don't get how that works. Why, in lSearch, is the function called cmpFn, but defined as intCmp, which is of type int, not int* and still works? And why does the function in lSearch not have to have defined parameters?

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• Project Euler Problem #11

  - by SoulBeaver

  Source: http://projecteuler.net/index.php?section=problems&id=11 Quick overview: Take a 20x20 grid of numbers and compute the largest product of 4 pairs of numbers in either horizontal, vertical, or diagonal. My current approach is to divide the 20x20 grid up into single rows and single columns and go from there with a much more manageable grid. The code I'm using to divide the rows into rows is void fillRows ( string::const_iterator& fieldIter, list<int>& rowElements, vector<list<int>>& rows ) { int count(0); for( ; fieldIter < field.end(); ++fieldIter ) { if(isdigit(field[*fieldIter])) { rowElements.push_back(toInt(field[*fieldIter])); ++count; } if(count == 40) { rows.push_back(rowElements); count = 0; rowElements.clear(); } } } Short explanation: I have the field set as static const std::string field and I am filling a vector with lists of rows. Why a list? Because the queue doesn't have a clear function. Also practice using STL container lists and not ones I write myself. However, this thing isn't working. Oftentimes I see it omitting a character( function toInt parses the const char as int ) and I end up with 18 rows, two rows short of the 20x20 grid. The length of the rows seem good. Rows: 18 RowElements[0]: 40 (instead of pairs I saved each number individually. Will fix that later) What am I doing wrong?

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• How to test for existence of a script-scoped variable in PowerShell?

  - by Damian Powell

  Is it possible to test for the existence of a script-scoped variable in PowerShell? I've been using the PowerShell Community Extensions (PSCX) but I've noticed that if you import the module while Set-PSDebug -Strict is set, an error is produced: The variable '$SCRIPT:helpCache' cannot be retrieved because it has not been set. At C:\Users\...\Modules\Pscx\Modules\GetHelp\Pscx.GetHelp.psm1:5 char:24 While investigating how I might fix this, I found this piece of code in Pscx.GetHelp.psm1: #requires -version 2.0 param([string[]]$PreCacheList) if ((!$SCRIPT:helpCache) -or $RefreshCache) { $SCRIPT:helpCache = @{} } This is pretty straight forward code; if the cache doesn't exist or needs to be refreshed, create a new, empty cache. The problem is that calling $SCRIPT:helpCache while Set-PSDebug -Strict is in force casues the error because the variable hasn't been defined yet. Ideally, we could use a Test-Variable cmdlet but such a thing doesn't exist! I thought about looking in the variable: provider but I don't know how to determine the scope of a variable. So my question is: how can I test for the existence of a variable while Set-PSDebug -Strict is in force, without causing an error?

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• Is extending a base class with non-virtual destructor dangerous in C++

  - by Akusete

  Take the following code class A { }; class B : public A { }; class C : public A { int x; }; int main (int argc, char** argv) { A* b = new B(); A* c = new C(); //in both cases, only ~A() is called, not ~B() or ~C() delete b; //is this ok? delete c; //does this line leak memory? return 0; } when calling delete on a class with a non-virtual destructor with member functions (like class C), can the memory allocator tell what the proper size of the object is? If not, is memory leaked? Secondly, if the class has no member functions, and no explicit destructor behaviour (like class B), is everything ok? I ask this because I wanted to create a class to extend std::string, (which I know is not recommended, but for the sake of the discussion just bear with it), and overload the +=,+ operator. -Weffc++ gives me a warning because std::string has a non virtual destructor, but does it matter if the sub-class has no members and does not need to do anything in its destructor? -- FYI the += overload was to do proper file path formatting, so the path class could be used like class path : public std::string { //... overload, +=, + //... add last_path_component, remove_path_component, ext, etc... }; path foo = "/some/file/path"; foo = foo + "filename.txt"; //and so on... I just wanted to make sure someone doing this path* foo = new path(); std::string* bar = foo; delete bar; would not cause any problems with memory allocation

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• gcc, strict-aliasing, and horror stories

  - by Joseph Quinsey

  In http://stackoverflow.com/questions/2906365/gcc-strict-aliasing-and-casting-through-a-union I asked whether anyone had encountered problems with union punning through pointers. So far, the answer seems to be No. This question is broader: do you have any horror stories about gcc and strict-aliasing? Background: Quoting from AndreyT's answer in http://stackoverflow.com/questions/2771023/c99-strict-aliasing-rules-in-c-gcc/2771041#2771041: "Strict aliasing rules are rooted in parts of the standard that were present in C and C++ since the beginning of [standardized] times. The clause that prohibits accessing object of one type through a lvalue of another type is present in C89/90 (6.3) as well as in C++98 (3.10/15). ... It is just that not all compilers wanted (or dared) to enforce it or rely on it." Well, gcc is now daring to do so, with its -fstrict-aliasing switch. And this has caused some problems. See, for example, the excellent article http://davmac.wordpress.com/2009/10/ about a Mysql bug, and the equally excellent discussion in http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html. Some other less-relevant links: http://stackoverflow.com/questions/1225741/performance-impact-of-fno-strict-aliasing http://stackoverflow.com/questions/754929/strict-aliasing http://stackoverflow.com/questions/262379/when-is-char-safe-for-strict-pointer-aliasing http://stackoverflow.com/questions/725138/how-to-detect-strict-aliasing-at-compile-time So to repeat, do you have a horror story of your own? Problems not indicated by -Wstrict-aliasing would, of course, be preferred. And other C compilers are also welcome.

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• Windows Service doesn't start process with different credentials

  - by Marcus

  I have a Windows Service, running as a user, that should start several processes under different user credentials. I'm using the following code to start a process: Dim winProcess As New System.Diagnostics.Process With winProcess .StartInfo.Arguments = "some_args" .StartInfo.CreateNoWindow = True .StartInfo.ErrorDialog = False .StartInfo.FileName = "C:\TEMP\ProcessFromService\ProcessFromService\bin\Debug\ProcessFromService.exe" .StartInfo.UseShellExecute = False .StartInfo.WindowStyle = ProcessWindowStyle.Hidden 'Opgave WorkingDirectory kan soms tot problemen leiden, indien betreffende directory 'niet bereikbaar (rechten) is voor opgegeven gebruiker. 'Beter dus om deze niet op te geven. '.StartInfo.WorkingDirectory = My.Computer.FileSystem.SpecialDirectories.Temp .StartInfo.Domain = "" .StartInfo.UserName = "MyUserId" Dim strPassword As String = "MyPassword" Dim ssPassword As New Security.SecureString For Each chrPassword As Char In strPassword.ToCharArray ssPassword.AppendChar(chrPassword) Next .StartInfo.Password = ssPassword .Start() End With The process is correctly started when I use the same credentials as of which the Windows Service is running under. The process is not started, without any error, when I use different credentials. In other words: If the Windows Service is running as UserA then I can start a process running as UserA. If the Windows Service is running as UserB then I can not start a process running as UserA. I have created a test project in which I can reproduce this problem. If you put this project in C:\Temp then the used paths will be correct. You can download this test project here: https://dl.dropboxusercontent.com/u/5391091/ProcessFromService.zip NB: I hope this info is enough to explain it. If you need more info, please let me know and I will add it.

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