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  • How to implement escape Sequence in SDL

    - by Sa'me Smd
    Im trying to use the STL library inside the SDL. but it gives me the error "undeclared identifier" Is there any way i can use "\n"or even cout<<endl; Can the function SDL_WarpMousewhich places the mouse cursor on a desired location on screen help me with this. Because i want to put a tile on the next line sequence. I hope you get the Question. Its very vague and messed up question though (sorry for that). EDIT: void putMap(SDL_Surface* tile, SDL_Surface* screen) { for(int y = 0; y < 21; y++) { for(int x = 0; x < 60; x++) { if(maze[x][y] != '#') { apply_surface( x*10 , y*10 , tile, screen); } } cout<<endl; } } c:\documents and settings\administrator\my documents\visual studio 2008\projects\craptest\craptest\main.cpp(605) : error C2065: 'cout' : undeclared identifier c:\documents and settings\administrator\my documents\visual studio 2008\projects\craptest\craptest\main.cpp(605) : error C2065: 'endl' : undeclared identifier This is my apply_surface funtion. void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination ) { //Make a temporary rectangle to hold the offsets SDL_Rect offset; //Give the offsets to the rectangle offset.x = x; offset.y = y; //Blit the surface SDL_BlitSurface( source, NULL, destination, &offset ); }

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  • Draw a position from a 2d Array on respected canvas location

    - by Anon
    Background: I have two 2d arrays. Each index within each 2d array represents a tile which is drawn on a square canvas suitable for 8 x 8 tiles. The first 2d array represents the ground tiles and is looped and drawn on the canvas using the following code: //Draw the map from the land 2d array map = new Canvas(mainFrame, 20, 260, 281, 281); for(int i=0; i < world.length; i++){ for(int j=0; j < world[i].length; j++){ for(int x=0; x < 280; x=x+35){ for(int y=0; y < 280; y=y+35){ Point p = new Point(x,y); map.add(new RectangleObject(p,35,35,Colour.green)); } } } } This creates a grid of green tiles 8 x 8 across as intended. The second 2d array represents the position on the ground. This 2d array has everyone of its indexes as null apart from one which is comprised of a Person class. Problem I am unsure of how I can draw the position on the grid. I was thinking of a similar loop, so it draws over the previous 2d array another set of 64 tiles. Only this time they are all transparent but the one tile which isn't null. In other words, the tile where Person is located. I wanted to use a search throughout the loop using a comparative if statement along the lines of if(!(world[] == null)){ map.add(new RectangleObject(p,35,35,Colour.red));} However my knowledge is limited and I am confused on how to implement it.

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  • g++ Linking Error on Mac while compiling FFMPEG

    - by Saptarshi Biswas
    g++ on Snow Leopard is throwing linking errors on the following piece of code test.cpp #include <iostream> using namespace std; #include <libavcodec/avcodec.h> // required headers #include <libavformat/avformat.h> int main(int argc, char**argv) { av_register_all(); // offending library call return 0; } When I try to compile this using the following command g++ test.cpp -I/usr/local/include -L/usr/local/lib \ -lavcodec -lavformat -lavutil -lz -lm -o test I get the error Undefined symbols: "av_register_all()", referenced from: _main in ccUD1ueX.o ld: symbol(s) not found collect2: ld returned 1 exit status Interestingly, if I have an equivalent c code, test.c #include <stdio.h> #include <libavcodec/avcodec.h> #include <libavformat/avformat.h> int main(int argc, char**argv) { av_register_all(); return 0; } gcc compiles it just fine gcc test.c -I/usr/local/include -L/usr/local/lib \ -lavcodec -lavformat -lavutil -lz -lm -o test I am using Mac OS X 10.6.5 $ g++ --version i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664) $ gcc --version i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664) FFMPEG's libavcodec, libavformat etc. are C libraries and I have built them on my machine like thus: ./configure --enable-gpl --enable-pthreads --enable-shared \ --disable-doc --enable-libx264 make && sudo make install As one would expect, libavformat indeed contains the symbol av_register_all $ nm /usr/local/lib/libavformat.a | grep av_register_all 0000000000000000 T _av_register_all 00000000000089b0 S _av_register_all.eh I am inclined to believe g++ and gcc have different views of the libraries on my machine. g++ is not able to pick up the right libraries. Any clue?

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  • Project euler problem 45

    - by Peter
    Hi, I'm not yet a skilled programmer but I thought this was an interesting problem and I thought I'd give it a go. Triangle, pentagonal, and hexagonal numbers are generated by the following formulae: Triangle T_(n)=n(n+1)/2 1, 3, 6, 10, 15, ... Pentagonal P_(n)=n(3n-1)/2 1, 5, 12, 22, 35, ... Hexagonal H_(n)=n(2n-1) 1, 6, 15, 28, 45, ... It can be verified that T_(285) = P_(165) = H_(143) = 40755. Find the next triangle number that is also pentagonal and hexagonal. Is the task description. I know that Hexagonal numbers are a subset of triangle numbers which means that you only have to find a number where Hn=Pn. But I can't seem to get my code to work. I only know java language which is why I'm having trouble finding a solution on the net womewhere. Anyway hope someone can help. Here's my code public class NextNumber { public NextNumber() { next(); } public void next() { int n = 144; int i = 165; int p = i * (3 * i - 1) / 2; int h = n * (2 * n - 1); while(p!=h) { n++; h = n * (2 * n - 1); if (h == p) { System.out.println("the next triangular number is" + h); } else { while (h > p) { i++; p = i * (3 * i - 1) / 2; } if (h == p) { System.out.println("the next triangular number is" + h); break; } else if (p > h) { System.out.println("bummer"); } } } } } I realize it's probably a very slow and ineffecient code but that doesn't concern me much at this point I only care about finding the next number even if it would take my computer years :) . Peter

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  • while loop in c#

    - by Nave Tseva
    I have this code: using System; namespace _121119_zionAVGfilter { class Program { static void Main(string[] args) { int cnt = 0, zion, sum = 0; double avg; Console.Write("Enter first zion \n"); zion = int.Parse(Console.ReadLine()); while (zion != -1) { while (zion < -1 || zion > 100) { Console.Write("zion can be between 0 to 100 only! \nyou can rewrite the zion here, or Press -1 to see the avg\n"); zion = int.Parse(Console.ReadLine()); } cnt++; sum = sum + zion; Console.Write("Enter next zion, if you want to exit tap -1 \n"); zion = int.Parse(Console.ReadLine()); if (cnt != 0){} } if (cnt == 0) { Console.WriteLine("something doesn't make sence"); } else { avg = (double)sum / cnt; Console.Write("the AVG is {0}", avg); } Console.ReadLine(); } } } The problem here is that if in the beginning I enter a negative or bigger than hundred number, I will get this message: "zion can be between 0 to 100 only! \nyou can rewrite the zion here, or Press -1 to see the avg\n". If I then meenter -1, this what that shows up instead of the AVG: "Enter next zion, if you want to exit tap -1 \n." How can I solve this problem so when the number is negative or bigger than hundred and than tap -1 I will see the AVG an not another message?

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  • From where starts the process' memory space and where does it end?

    - by nhaa123
    Hi, I'm trying to dump memory from my application where the variables lye. Here's the function: void MyDump(const void *m, unsigned int n) { const unsigned char *p = reinterpret_cast<const unsigned char *(m); char buffer[16]; unsigned int mod = 0; for (unsigned int i = 0; i < n; ++i, ++mod) { if (mod % 16 == 0) { mod = 0; std::cout << " | "; for (unsigned short j = 0; j < 16; ++j) { switch (buffer[j]) { case 0xa: case 0xb: case 0xd: case 0xe: case 0xf: std::cout << " "; break; default: std::cout << buffer[j]; } } std::cout << "\n0x" << std::setfill('0') << std::setw(8) << std::hex << (long)i << " | "; } buffer[i % 16] = p[i]; std::cout << std::setw(2) << std::hex << static_cast<unsigned int(p[i]) << " "; if (i % 4 == 0 && i != 1) std::cout << " "; } } Now, how can I know from which address starts my process memory space, where all the variables are stored? And how do I now, how long the area is? For instance: MyDump(0x0000 /* <-- Starts from here? */, 0x1000 /* <-- This much? */); Best regards, nhaa123

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  • division with wrong result

    - by PeterK
    Hi, I am trying to divide integers but get 0 as result. I just do not understand what i am doing wrong. I am using only int's in this example but get the same result testing with float or double. The code i use is: int wrongAnswers = askedQuestions - playerResult; int percentCorrect = (playerResult / askedQuestions) * 100; int percentWrong = (wrongAnswers / askedQuestions) * 100; NSLog(@"askedQuestions: %i", askedQuestions); NSLog(@"playerResult: %i", playerResult); NSLog(@"wrongAnswers: %i", wrongAnswers); NSLog(@"percentCorrect: %i", percentCorrect); NSLog(@"percentWrong: %i", percentWrong); NSLog(@"calc: %i", (wrongAnswers + playerResult)); NSLog(@"wrong answers %: %i %%", ((wrongAnswers / askedQuestions) * 100)); The result i get is: 2011-01-09 16:45:53.411 XX[8296:207] askedQuestions: 5 2011-01-09 16:45:53.412 XX[8296:207] playerResult: 2 2011-01-09 16:45:53.412 XX[8296:207] wrongAnswers: 3 2011-01-09 16:45:53.413 XX[8296:207] percentCorrect: 0 % 2011-01-09 16:45:53.414 XX[8296:207] percentWrong: 0 % 2011-01-09 16:45:53.414 XX[8296:207] calc: 5 2011-01-09 16:45:53.415 XX[8296:207] wrong answers : 0 % I would very much appreciate help :-)

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  • C: Proper syntax for allocating memory using pointers to pointers.

    - by ~kero-05h
    This is my first time posting here, hopefully I will not make a fool of myself. I am trying to use a function to allocate memory to a pointer, copy text to the buffer, and then change a character. I keep getting a segfault and have tried looking up the answer, my syntax is probably wrong, I could use some enlightenment. /* My objective is to pass a buffer to my Copy function, allocate room, and copy text to it. Then I want to modify the text and print it.*/ #include <stdio.h> #include <stdlib.h> #include <string.h> int Copy(char **Buffer, char *Text); int main() { char *Text = malloc(sizeof(char) * 100); char *Buffer; strncpy(Text, "1234567890\n", 100); Copy(&Buffer, Text); } int Copy(char **Buffer, char *Text) { int count; count = strlen(Text)+1; *Buffer = malloc(sizeof(char) * count); strncpy(*Buffer, Text, 5); *Buffer[2] = 'A'; /* This results in a segfault. "*Buffer[1] = 'A';" results in no differece in the output. */ printf("%s\n", *Buffer); }

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  • Explain this C# code: byte* p = (byte*) (void*) Scan0;

    - by qulzam
    I found the code from the net in which i cant understand this line:- byte* p = (byte*)(void*)Scan0; There Scan0 is System.IntPtr. It is code of C#.Net. Plz Explain the above line. The complete code is given below. this is code to convert a image in grayscale. public static Image GrayScale(Bitmap b) { BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte* p = (byte*)(void*)Scan0; int nOffset = stride - b.Width * 3; byte red, green, blue; for (int y = 0; y < b.Height; ++y) { for (int x = 0; x < b.Width; ++x) { blue = p[0]; green = p[1]; red = p[2]; p[0] = p[1] = p[2] = (byte)(.299 * red + .587 * green + .114 * blue); p += 3; } p += nOffset; } } b.UnlockBits(bmData); return (Image)b; } I understand all the code but only have the problem on this line. byte* p = (byte*)(void*)Scan0;

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  • GDI+ Rotated sub-image

    - by Andrew Robinson
    I have a rather large (30MB) image that I would like to take a small "slice" out of. The slice needs to represent a rotated portion of the original image. The following works but the corners are empty and it appears that I am taking a rectangular area of the original image, then rotating that and drawing it on an unrotated surface resulting in the missing corners. What I want is a rotated selection on the original image that is then drawn on an unrotated surface. I know I can first rotate the original image to accomplish this but this seems inefficient given its size. Any suggestions? Thanks, public Image SubImage(Image image, int x, int y, int width, int height, float angle) { var bitmap = new Bitmap(width, height); using (Graphics graphics = Graphics.FromImage(bitmap)) { graphics.TranslateTransform(bitmap.Width / 2.0f, bitmap.Height / 2.0f); graphics.RotateTransform(angle); graphics.TranslateTransform(-bitmap.Width / 2.0f, -bitmap.Height / 2.0f); graphics.DrawImage(image, new Rectangle(0, 0, width, height), x, y, width, height, GraphicsUnit.Pixel); } return bitmap; }

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  • Is private members hacking a defined behaviour ?

    - by ereOn
    Hi, Lets say I have the following class: class BritneySpears { public: int getValue() { return m_value; }; private: int m_value; }; Which is an external library (that I can't change). I obviously can't change the value of m_value, only read it. Even subclassing BritneySpears won't work. What if I define the following class: class AshtonKutcher { public: int getValue() { return m_value; }; public: int m_value; }; And then do: BritneySpears b; // Here comes the ugly hack AshtonKutcher* a = reinterpret_cast<AshtonKutcher*>(&b); a->m_value = 17; // Print out the value std::cout << b.getValue() << std::endl; I know this is a bad practice. But just for curiosity: is this guaranted to work ? Is it a defined behaviour ? Bonus question: Have you ever had to use such an ugly hack ? Thanks !

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  • Why do bind1st and bind2nd require constant function objects?

    - by rlbond
    So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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  • non static method cannot be referenced from a static context.

    - by David
    First some code: import java.util.*; ... class TicTacToe { ... public static void main (String[]arg) { Random Random = new Random() ; toerunner () ; // this leads to a path of methods that eventualy gets us to the rest of the code } ... public void CompTurn (int type, boolean debug) { ... boolean done = true ; int a = 0 ; while (!done) { a = Random.nextInt(10) ; if (debug) { int i = 0 ; while (i<20) { System.out.print (a+", ") ; i++; }} if (possibles[a]==1) done = true ; } this.board[a] = 2 ; } ... } //to close the class Here is the error message: TicTacToe.java:85: non-static method nextInt(int) cannot be referenced from a static context a = Random.nextInt(10) ; ^ What exactly went wrong? What does that error message "non static method cannot be referenced from a static context" mean?

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  • Problem with setjmp/longjmp

    - by user294732
    The code below is just not working. Can anybody point out why #define STACK_SIZE 1524 static void mt_allocate_stack(struct thread_struct *mythrd) { unsigned int sp = 0; void *stck; stck = (void *)malloc(STACK_SIZE); sp = (unsigned int)&((stck)); sp = sp + STACK_SIZE; while((sp % 8) != 0) sp--; #ifdef linux (mythrd->saved_state[0]).__jmpbuf[JB_BP] = (int)sp; (mythrd->saved_state[0]).__jmpbuf[JB_SP] = (int)sp-500; #endif } void mt_sched() { fprintf(stdout,"\n Inside the mt_sched"); fflush(stdout); if ( current_thread->state == NEW ) { if ( setjmp(current_thread->saved_state) == 0 ) { mt_allocate_stack(current_thread); fprintf(stdout,"\n Jumping to thread = %u",current_thread->thread_id); fflush(stdout); longjmp(current_thread->saved_state, 2); } else { new_fns(); } } } All I am trying to do is to run the new_fns() on a new stack. But is is showing segmentation fault at new_fns(). Can anybody point me out what's wrong.

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  • c# delegate and abstract class

    - by BeraCim
    Hi all: I currently have 2 concrete methods in 2 abstract classes. One class contains the current method, while the other contains the legacy method. E.g. // Class #1 public abstract class ClassCurrent<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllRootNodes(int i) { //some code } } // Class #2 public abstract class MyClassLegacy<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllLeafNodes(int j) { //some code } } I want the corresponding method to run in their relative scenarios in the app. I'm planning to write a delegate to handle this. The idea is that I can just call the delegate and write logic in it to handle which method to call depending on which class/project it is called from (at least thats what I think delegates are for and how they are used). However, I have some questions on that topic (after some googling): 1) Is it possible to have a delegate that knows the 2 (or more) methods that reside in different classes? 2) Is it possible to make a delegate that spawns off abstract classes (like from the above code)? (My guess is a no, since delegates create concrete implementation of the passed-in classes) 3) I tried to write a delegate for the above code. But I'm being technically challenged: public delegate List GetAllNodesDelegate(int k); GetAllNodesDelegate del = new GetAllNodesDelegate(ClassCurrent.GetAllRootNodes); I got the following error: An object reference is required for the non-static field, method, property ClassCurrent<BaseNode>.GetAllRootNodes(int) I might have misunderstood something... but if I have to manually declare a delegate at the calling class, AND to pass in the function manually as above, then I'm starting to question whether delegate is a good way to handle my problem. Thanks.

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  • Is there a faster way to parse through a large file with regex quickly?

    - by Ray Eatmon
    Problem: Very very, large file I need to parse line by line to get 3 values from each line. Everything works but it takes a long time to parse through the whole file. Is it possible to do this within seconds? Typical time its taking is between 1 minute and 2 minutes. Example file size is 148,208KB I am using regex to parse through every line: Here is my c# code: private static void ReadTheLines(int max, Responder rp, string inputFile) { List<int> rate = new List<int>(); double counter = 1; try { using (var sr = new StreamReader(inputFile, Encoding.UTF8, true, 1024)) { string line; Console.WriteLine("Reading...."); while ((line = sr.ReadLine()) != null) { if (counter <= max) { counter++; rate = rp.GetRateLine(line); } else if(max == 0) { counter++; rate = rp.GetRateLine(line); } } rp.GetRate(rate); Console.ReadLine(); } } catch (Exception e) { Console.WriteLine("The file could not be read:"); Console.WriteLine(e.Message); } } Here is my regex: public List<int> GetRateLine(string justALine) { const string reg = @"^\d{1,}.+\[(.*)\s[\-]\d{1,}].+GET.*HTTP.*\d{3}[\s](\d{1,})[\s](\d{1,})$"; Match match = Regex.Match(justALine, reg, RegexOptions.IgnoreCase); // Here we check the Match instance. if (match.Success) { // Finally, we get the Group value and display it. string theRate = match.Groups[3].Value; Ratestorage.Add(Convert.ToInt32(theRate)); } else { Ratestorage.Add(0); } return Ratestorage; } Here is an example line to parse, usually around 200,000 lines: 10.10.10.10 - - [27/Nov/2002:16:46:20 -0500] "GET /solr/ HTTP/1.1" 200 4926 789

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  • Boost Date_Time problem compiling a simple program

    - by Andry
    Hello! I'm writing a very stupid program using Boost Date_Time library. int main(int srgc, char** argv) { using namespace boost::posix_time; date d(2002,Feb,1); //an arbitrary date ptime t1(d, hours(5)+nanosec(100)); //date + time of day offset ptime t2 = t1 - minutes(4)+seconds(2); ptime now = second_clock::local_time(); //use the clock date today = now.date(); //Get the date part out of the time } Well I cannot compile it, compiler does not recognize a type... Well I used many features of Boost libs like serialization and more... I correctly built them and, looking in my /usr/local/lib folder I can see that libboost_date_time.so is there (a good sign which means I was able to build that library) When I compile I write the following: g++ -lboost_date_time main.cpp But the errors it showed me when I specify the lib are the same of those ones where I do not specify any lib. What is this? Anyone knows? The error is main.cpp: In function ‘int main(int, char**)’: main.cpp:9: error: ‘date’ was not declared in this scope main.cpp:9: error: expected ‘;’ before ‘d’ main.cpp:10: error: ‘d’ was not declared in this scope main.cpp:10: error: ‘nanosec’ was not declared in this scope main.cpp:13: error: expected ‘;’ before ‘today’

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  • How to embed XBase expressions in an Xtext DSL

    - by Marcus Mathioudakis
    I am writing a simple little DSL for specifying constraints on messages, and Have been trying without success for a while to embed XBase expressions into the language. The Grammar looks like this: grammar org.xtext.businessrules.BusinessRules with org.eclipse.xtext.xbase.Xbase //import "http://www.eclipse.org/xtext/xbase/Xbase" as xbase import "http://www.eclipse.org/xtext/common/JavaVMTypes" as jvmTypes generate businessRules "http://www.xtext.org/businessrules/BusinessRules" Start: rules+=Constraint*; Constraint: {Constraint} 'FOR' 'PAYLOAD' payload=PAYLOAD 'ELEMENT' element=ID 'CONSTRAINED BY' constraint=XExpression; PAYLOAD: "SimulationSessionEvents" |"stacons" |"any" ; Range: 'above' min=INT ('below' max=INT)? |'below' max=INT ('above' min=INT)? ; When trying to parse a file such as: FOR PAYLOAD SimulationSessionEvents ELEMENT matrix CONSTRAINED BY ... I can't get it to work for ... = any kind of Arithmetic expression, although it works for ...= loop or if expression, or even just a number. As soon as I do something like '-5' or '4-5' it says Couldn't resolve reference to JvmIdentifiableElement '-', even though the Xbase.xtext Grammar looks like it allows these expressions. I don't think I'm missing any Jars, as it doesn't complain when I run the mwe workflow, but only when trying to parse the input file. Any help would be much appreciated.

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  • Web service performing asynchronous call

    - by kornelijepetak
    I have a webservice method FetchNumber() that fetches a number from a database and then returns it to the caller. But just before it returns the number to the caller, it needs to send this number to another service so instantiates and runs the BackgroundWorker whose job is to send this number to another service. public class FetchingNumberService : System.Web.Services.WebService { [WebMethod] public int FetchNumber() { int value = Database.GetNumber(); AsyncUpdateNumber async = new AsyncUpdateNumber(value); return value; } } public class AsyncUpdateNumber { public AsyncUpdateNumber(int number) { sendingNumber = number; worker = new BackgroundWorker(); worker.DoWork += asynchronousCall; worker.RunWorkerAsync(); } private void asynchronousCall(object sender, DoWorkEventArgs e) { // Sending a number to a service (which is Synchronous) here } private int sendingNumber; private BackgroundWorker worker; } I don't want to block the web service (FetchNumber()) while sending this number to another service, because it can take a long time and the caller does not care about sending the number to another service. Caller expects this to return as soon as possible. FetchNumber() makes the background worker and runs it, then finishes (while worker is running in the background thread). I don't need any progress report or return value from the background worker. It's more of a fire-and-forget concept. My question is this. Since the web service object is instantiated per method call, what happens when the called method (FetchNumber() in this case) is finished, while the background worker it instatiated and ran is still running? What happens to the background thread? When does GC collect the service object? Does this prevent the background thread from executing correctly to the end? Are there any other side-effects on the background thread? Thanks for any input.

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  • Creating a [materialised]view from generic data in Oracle/Mysql

    - by Andrew White
    I have a generic datamodel with 3 tables CREATE TABLE Properties ( propertyId int(11) NOT NULL AUTO_INCREMENT, name varchar(80) NOT NULL ) CREATE TABLE Customers ( customerId int(11) NOT NULL AUTO_INCREMENT, customerName varchar(80) NOT NULL ) CREATE TABLE PropertyValues ( propertyId int(11) NOT NULL, customerId int(11) NOT NULL, value varchar(80) NOT NULL ) INSERT INTO Properties VALUES (1, 'Age'); INSERT INTO Properties VALUES (2, 'Weight'); INSERT INTO Customers VALUES (1, 'Bob'); INSERT INTO Customers VALUES (2, 'Tom'); INSERT INTO PropertyValues VALUES (1, 1, '34'); INSERT INTO PropertyValues VALUES (2, 1, '80KG'); INSERT INTO PropertyValues VALUES (1, 2, '24'); INSERT INTO PropertyValues VALUES (2, 2, '53KG'); What I would like to do is create a view that has as columns all the ROWS in Properties and has as rows the entries in Customers. The column values are populated from PropertyValues. e.g. customerId Age Weight 1 34 80KG 2 24 53KG I'm thinking I need a stored procedure to do this and perhaps a materialised view (the entries in the table "Properties" change rarely). Any tips?

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  • process semaphores linux - wait

    - by coubeatczech
    Hi, I try to code a simple program that starts and waits on the system semaphore until it gets terminated by signal. union semun { int val; struct semid_ds *buf; unsigned short int *array; struct seminfo *__buf; }; int main(){ int semaphores = semget(IPC_PRIVATE,1,IPC_CREAT | 0666); union semun arg; arg.val = 0; semctl(semaphores,0,SETVAL,arg); struct sembuf operations[1]; operations[0].sem_num = 0; operations[0].sem_op = -1; operations[0].sem_flg = 0; semop(semaphores,operations,1); fprintf(stderr,"Why?\n"); return 0; } I expect, that everytime this program gets executed, nothing actually happens and it waits on the semaphore, but everytime it goes through the semaphore and writes Why?. Why?

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  • What's the most efficient query?

    - by Aaron Carlino
    I have a table named Projects that has the following relationships: has many Contributions has many Payments In my result set, I need the following aggregate values: Number of unique contributors (DonorID on the Contribution table) Total contributed (SUM of Amount on Contribution table) Total paid (SUM of PaymentAmount on Payment table) Because there are so many aggregate functions and multiple joins, it gets messy do use standard aggregate functions the the GROUP BY clause. I also need the ability to sort and filter these fields. So I've come up with two options: Using subqueries: SELECT Project.ID AS PROJECT_ID, (SELECT SUM(PaymentAmount) FROM Payment WHERE ProjectID = PROJECT_ID) AS TotalPaidBack, (SELECT COUNT(DISTINCT DonorID) FROM Contribution WHERE RecipientID = PROJECT_ID) AS ContributorCount, (SELECT SUM(Amount) FROM Contribution WHERE RecipientID = PROJECT_ID) AS TotalReceived FROM Project; Using a temporary table: DROP TABLE IF EXISTS Project_Temp; CREATE TEMPORARY TABLE Project_Temp (project_id INT NOT NULL, total_payments INT, total_donors INT, total_received INT, PRIMARY KEY(project_id)) ENGINE=MEMORY; INSERT INTO Project_Temp (project_id,total_payments) SELECT `Project`.ID, IFNULL(SUM(PaymentAmount),0) FROM `Project` LEFT JOIN `Payment` ON ProjectID = `Project`.ID GROUP BY 1; INSERT INTO Project_Temp (project_id,total_donors,total_received) SELECT `Project`.ID, IFNULL(COUNT(DISTINCT DonorID),0), IFNULL(SUM(Amount),0) FROM `Project` LEFT JOIN `Contribution` ON RecipientID = `Project`.ID GROUP BY 1 ON DUPLICATE KEY UPDATE total_donors = VALUES(total_donors), total_received = VALUES(total_received); SELECT * FROM Project_Temp; Tests for both are pretty comparable, in the 0.7 - 0.8 seconds range with 1,000 rows. But I'm really concerned about scalability, and I don't want to have to re-engineer everything as my tables grow. What's the best approach?

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  • Linker error: wants C++ virtual base class destructor

    - by jdmuys
    Hi, I have a link error where the linker complains that my concrete class's destructor is calling its abstract superclass destructor, the code of which is missing. This is using GCC 4.2 on Mac OS X from XCode. I saw http://stackoverflow.com/questions/307352/g-undefined-reference-to-typeinfo but it's not quite the same thing. Here is the linker error message: Undefined symbols: "ConnectionPool::~ConnectionPool()", referenced from: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool()in RKConnector.o ld: symbol(s) not found collect2: ld returned 1 exit status Here is the abstract base class declaration: class ConnectionPool { public: static ConnectionPool* newPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~ConnectionPool() =0; virtual int keepAlive() =0; virtual int disconnect() =0; virtual sql::Connection * getConnection(char *compression_scheme = NULL) =0; virtual void releaseConnection(sql::Connection * theConnection) =0; }; Here is the concrete class declaration: class AlwaysConnectedConnectionZPool: public ConnectionPool { protected: <snip data members> public: AlwaysConnectedConnectionZPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~AlwaysConnectedConnectionZPool(); virtual int keepAlive(); // will make sure the connection doesn't time out. Call regularly virtual int disconnect(); // disconnects/destroys all connections. virtual sql::Connection * getConnection(char *compression_scheme = NULL); virtual void releaseConnection(sql::Connection * theConnection); }; Needless to say, all those members are implemented. Here is the destructor: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool() { printf("AlwaysConnectedConnectionZPool destructor call"); // nothing to destruct in fact } and also maybe the factory routine: ConnectionPool* ConnectionPool::newPool(std::string h, short p, std::string u, std::string pw, std::string b) { return new AlwaysConnectedConnectionZPool(h, p, u, pw, b); } I can fix this by artificially making my abstract base class concrete. But I'd rather do something better. Any idea? Thanks

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  • c# string interning

    - by CodingThunder
    I am trying to understand string interning and why is doesn't seem to work in my example. The point of the example is to show Example 1 uses less (a lot less memory) as it should only have 10 strings in memory. However, in the code below both example use roughly the same amount of memory (virtual size and working set). Please advice why example 1 isn't using a lot less memory? Thanks Example 1: IList<string> list = new List<string>(10000); for (int i = 0; i < 10000; i++) { for (int k = 0; k < 10; k++) { list.Add(string.Intern(k.ToString())); } } Console.WriteLine("intern Done"); Console.ReadLine(); Example 2: IList<string> list = new List<string>(10000); for (int i = 0; i < 10000; i++) { for (int k = 0; k < 10; k++) { list.Add(k.ToString()); } } Console.WriteLine("intern Done"); Console.ReadLine();

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  • Help in J2ME for creating image and parse it

    - by HAMED
    Can anyone tell me how i can parse a png image into many png images in J2ME??? for examole:I just wnat to have a source image 150*150 pixel and parse it to 10 image with 15*15 pixel. I write an elemantary code that have exeption. This is my code: public class HelloMIDlet extends MIDlet implements CommandListener { private boolean midletPaused = false; private Command exitCommand; private Form form; private StringItem stringItem; Image im , im2; Form form1 = null; public HelloMIDlet() { try { // create source image im = Image.createImage("/image1.JPG"); int height = im.getHeight() ; int width = im.getWidth() ; int x = 0 ; int y = 0 ; while ( y < height ){ while ( x < width ){ // create 15*15 pixel of source image im2 = im.createImage(im, x, y, 15, 15, Sprite.TRANS_NONE) ; x += 15 ; } y += 15 ; x = 0 ; } } catch (IOException ex) { ex.printStackTrace(); } } please help me to make it right....It's emergency! Thanks a lot guys...

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