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  • How to determine the end of an integer array when manipulating with integer pointer?

    - by AKN
    Here is the code: int myInt[] ={ 1, 2, 3, 4, 5 }; int *myIntPtr = &myInt[0]; while( *myIntPtr != NULL ) { cout<<*myIntPtr<<endl; myIntPtr++; } Output: 12345....<junks>.......... For Character array: (Since we have a NULL character at the end, no problem while iterating) char myChar[] ={ 'A', 'B', 'C', 'D', 'E', '\0' }; char *myCharPtr = &myChar[0]; while( *myCharPtr != NULL ) { cout<<*myCharPtr<<endl; myCharPtr++; } Output: ABCDE My question is since we say to add NULL character as end of the strings, we rule out such issues! If in case, it is rule to add 0 to the end of integer array, we could have avoided this problem. What say?

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  • abstract class in C++

    - by Alexander
    I have a derived derived class from an abstract class. The code is below. I have a FishTank class which is derived from an Aquarium and Aquarium is derived from item. My question is that should I put the definition of virtual int minWidth() const = 0; in aquarium again or is the code below sufficient? class Item{ public: virtual int minWidth() const = 0; }; class Aquarium{ public: virtual int calWidth() = 0; // Pure virtual function. }; class FishTank : public Aquarium{ public: FishTank(int base1, int base2, int height); ~FishTank(); int calWidth(); int minWidth(); };

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  • How to implement square root and exponentiation on arbitrary length numbers?

    - by tomp
    I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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  • How return a std::string from C's "getcwd" function

    - by rubenvb
    Sorry to keep hammering on this, but I'm trying to learn :). Is this any good? And yes, I care about memory leaks. I can't find a decent way of preallocating the char*, because there simply seems to be no cross-platform way. const string getcwd() { char* a_cwd = getcwd(NULL,0); string s_cwd(a_cwd); free(a_cwd); return s_cwd; } UPDATE2: without Boost or Qt, the most common stuff can get long-winded (see accepted answer)

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  • How to move the mouse

    - by GroundZero
    I'm making a little bot in C#. At the moment it works pretty well, it can load text from a file and type it for you. But for now, I need to manualy click the textfield to put the focus on it, remaximize my form and then click the Type-button. After the typing, I need to manualy slide the scorebar and press submit. I'd like to know how I can move my mouse with C# and if possible, if possible I'd like to load the mouse positions from a xml-file. I need to move to the textfield, click in it to focus on it, start the type script, move to the slider, hold the mouse down on it while dragging, releasing it on the correct position & clicking on the submitbutton This is what I have for now: To load in the variables, I'm using this script: private void Initialize() { XmlTextReader reader = new XmlTextReader(Application.StartupPath + @"..\..\..\CursorPositions.xml"); while (reader.Read()) { switch (reader.NodeType) { case XmlNodeType.Element: // The node is an element. element = reader.Value; break; case XmlNodeType.Text: //Display the text in each element. switch (element) { case "Textbox-X": textX = int.Parse(reader.Value); break; case "Textbox-Y": textY = int.Parse(reader.Value); break; case "SliderBegin-X": sliderX = int.Parse(reader.Value); break; case "SliderBegin-Y": sliderY = int.Parse(reader.Value); break; case "SubmitButton-X": submitX = int.Parse(reader.Value); break; case "SubmitButton-Y": submitY = int.Parse(reader.Value); break; } break; } } This is the xml-file: <?xml version="1.0" encoding="utf-8" ?> <CursorPositions> <Textbox-X>430</Textbox-X> <Textbox-Y>270</Textbox-Y> <SliderBegin-X>430</SliderBegin-X> <SliderBegin-Y>470</SliderBegin-Y> <SubmitButton-X>860</SubmitButton-X> <SubmitButton-Y>365</SubmitButton-Y> </CursorPositions> To move the mouse I'm using this piece of code: public partial class FrmMain : Form { [System.Runtime.InteropServices.DllImport("user32.dll")] public static extern void mouse_event(int dwFlags, int dx, int dy, int cButtons, int dwExtraInfo); public const int MOUSEEVENTF_LEFTDOWN = 0x0002; public const int MOUSEEVENTF_LEFTUP = 0x0004; public const int MOUSEEVENTF_RIGHTDOWN = 0x0008; public const int MOUSEEVENTF_RIGHTUP = 0x0010; ... private void btnStart_Click(object sender, EventArgs e) { // start button (de)activates loop if (!running) { btnStart.Text = "Stop"; btnStart.Cursor = Cursors.No; running = true; } else { btnStart.Text = "Start"; btnStart.Cursor = Cursors.AppStarting; running = false; } while (running) { // move to textbox & type Cursor.Position = new Point(textX, textY); mouse_event(MOUSEEVENTF_LEFTDOWN, textX, textY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, textX, textY, 0, 0); Type(); // wait 90 seconds till slider available Thread.Sleep(90 * 1000); // move to slider & slide according to score Cursor.Position = new Point(sliderX, sliderY); mouse_event(MOUSEEVENTF_LEFTDOWN, sliderX, sliderY, 0, 0); Cursor.Position = new Point(sliderX + 345 / 10 * score, sliderY); mouse_event(MOUSEEVENTF_LEFTUP, sliderX + 345 / 10 * score, sliderY, 0, 0); // submit Cursor.Position = new Point(submitX, submitY); mouse_event(MOUSEEVENTF_LEFTDOWN, submitX, submitY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, submitX, submitY, 0, 0); // wait 10 sec to be sure it's submitted Thread.Sleep(10 * 1000); // refresh page SendKeys.SendWait("{F5}"); // get new text NewText(); // wait 10 sec to refresh and load song Thread.Sleep(10 * 1000); } } } PS: I get the coordinates via my form. I've got 2 labels that show my X & Y coordinates. To capture them outside the form, I press and hold my Left Mouse Button and 'drag' it outside the form to the correct place. This way I get the coordinates of my mouse outside the form

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  • How to free memory in try-catch blocks?

    - by Kra
    Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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  • How to get Doxygen to recognize custom latex command

    - by Halpo
    Is there a way to use extra latex packages and/or extra latex commands with Doxygen code documentation system. For example I define the shortcut in a custom sty file. \newcommand{\tf}{\Theta_f} Then I use it about 300 time in the code, which is across about a dozen files. /*! Stochastic approximation of the latent response*/ void dual_bc_genw( //... double const * const psi, ///< \f$ \psi = B\tf \f$ //... ){/* lots of brilliant code */} But how do I get the system to recognize the extra package.

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  • some logical error in taking up character in java

    - by Himanshu Aggarwal
    This is my code... class info{ public static void main (String[]args) throws IOException{ char gen; while(true) { //problem occurs with this while System.out.print("\nENTER YOUR GENDER (M/F) : "); gen=(char)System.in.read(); if(gen=='M' || gen=='F' || gen=='m' || gen=='f'){ break; } } System.out.println("\nGENDER = "+gen); } } This is my output... ENTER YOUR GENDER (M/F) : h ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : m GENDER = m Could someone please help me understand why it is asking for the gender so many times.

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  • How to sanely read and dump structs to disk when some fields are pointers?

    - by bp
    Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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  • How to return a string literal from a function

    - by skydoor
    Hi I am always confused about return a string literal or a string from a function. I was told that there might be memory leak because you don't know when the memory will be deleted? For example, in the code below, how to implement foo() so that make the output of the code is "Hello World"? void foo ( ) // you can add parameters here. { } int main () { char *c; foo ( ); printf ("%s",c); return 0; } Also if the return type of foo() is not void, but you can return char*, what should it be.

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  • Assigning large UInt32 constants in VB.Net

    - by Kumba
    I inquired on VB's erratic behavior of treating all numerics as signed types back in this question, and from the accepted answer there, was able to get by. Per that answer: Visual Basic Literals Also keep in mind you can add literals to your code in VB.net and explicitly state constants as unsigned. So I tried this: Friend Const POW_1_32 As UInt32 = 4294967296UI And VB.NET throws an Overflow error in the IDE. Pulling out the integer overflow checks doesn't seem to help -- this appears to be a flaw in the IDE itself. This, however, doesn't generate an error: Friend Const POW_1_32 As UInt64 = 4294967296UL So this suggests to me that the IDE isn't properly parsing the code and understanding the difference between Int32 and UInt32. Any suggested workarounds and/or possible clues on when MS will make unsigned data types intrinsic to the framework instead of the hacks they currently are?

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  • Legality Of Re-Implementing An Existing API (e.g. GNU implementing the UNIX APIs)

    - by splicer
    I've often wondered about this. I'm not looking for legal advice, just casual opinions ;) If some company publishes an API on the web for their closed-source library, would it be legal for another party to release an open-source implementation of that API? Are function declarations considered source code? Take GNU implementing the UNIX APIs, for example. The UNIX standard gives the following function declaration and defines its required behaviour in English: char * mktemp(char *template); Now, consider an API that lists and declares and describes several thousand (more much complex) functions, enums, etc.; an API which defines a solution to a non-trival set of problems. If an open-source project publishes C headers that copy (verbatim) the function definitions contained in the closed-source company's published API, doesn't that violate some sort copyright law?

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  • Why does accessing a member of a malloced array of structs seg fault?

    - by WSkinner
    I am working through Learn C The Hard Way and am stumped on something. I've written a simplified version of the problem I am running into to make it easier to get down to it. Here is the code: #include <stdlib.h> #define GROUP_SIZE 10 #define DATA_SIZE 64 struct Dummy { char *name; }; struct Group { struct Dummy **dummies; }; int main() { struct Group *group1 = malloc(sizeof(struct Group)); group1->dummies = malloc(sizeof(struct Dummy) * GROUP_SIZE); struct Dummy *dummy1 = group1->dummies[3]; // Why does this seg fault? dummy1->name = (char *) malloc(DATA_SIZE); return 0; } when I try to set the name pointer on one of my dummies I get a seg fault. Using valgrind it tells me this is uninitialized space. Why is this?

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  • error in encryption program

    - by Raja
    #include<iostream> #include<math.h> #include<string> using namespace std; int gcd(int n,int m) { if(m<=n && n%m ==0) return m; if(n<m) return gcd(m,n); else return gcd(m,n%m); } int REncryptText(char m) { int p = 11, q = 3; int e = 3; int n = p * q; int phi = (p - 1) * (q - 1); int check1 = gcd(e, p - 1); int check2 = gcd(e, q - 1); int check3 = gcd(e, phi); // // Compute d such that ed = 1 (mod phi) //i.e. compute d = e-1 mod phi = 3-1 mod 20 //i.e. find a value for d such that phi divides (ed-1) //i.e. find d such that 20 divides 3d-1. //Simple testing (d = 1, 2, ...) gives d = 7 // double d = Math.Pow(e, -1) % phi; int d = 7; // public key = (n,e) // (33,3) //private key = (n,d) //(33 ,7) double g = pow(m,e); int ciphertext = g %n; // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. //double decrypt = Math.Pow(ciphertext, d) % n; return ciphertext; } int main() { char plaintext[80],str[80]; cout<<" enter the text you want to encrpt"; cin.get(plaintext,79); int l =strlen(plaintext); for ( int i =0 ; i<l ; i++) { char s = plaintext[i]; str[i]=REncryptText(s); } for ( int i =0 ; i<l ; i++) { cout<<"the encryption of string"<<endl; cout<<str[i]; } return 0; }

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  • C++ : size of int, long, etc...

    - by Jérôme
    I'm looking for detailed informations regarding the size of basic C++ types. I know that it depends on the architecture (16 bits, 32 bits, 64 bits) and the compiler. But are there any standards ? I'm using Visual Studio 2008 on a 32 bit achitecture. Here is what I get : char : 1 byte short : 2 bytes int : 4 bytes long : 4 bytes float : 4 bytes double : 8 bytes I tried to find, without much success, reliable informations telling the sizes of char, short, int , long, double, float (and other types I don't think of) under different architecture and compiler.

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  • inline and member initializers

    - by Alexander
    When should I inline a member function and when should I use member initializers? My code is below.. I would like to modify it so I could make use some inline when appropriate and member initializers: #include "Books.h" Book::Book(){ nm = (char*)""; thck = 0; wght = 0; } Book::Book(const char *name, int thickness, int weight){ nm = strdup(name); thck = thickness; wght = weight; } Book::~Book(){ } const char* Book::name(){ return nm; } int Book::thickness(){ return thck; } int Book::weight(){ return wght; } // // Prints information about the book using this format: // "%s (%d mm, %d dg)\n" // void Book::print(){ printf("%s (%d mm, %d dg)\n", nm, thck, wght); } Bookcase::Bookcase(int id){ my_id = id; no_shelf = 0; } int Bookcase::id(){ return my_id; } Bookcase::~Bookcase(){ for (int i = 0; i < no_shelf; i++) delete my_shelf[i]; } bool Bookcase::addShelf(int width, int capacity){ if(no_shelf == 10) return false; else{ my_shelf[no_shelf] = new Shelf(width, capacity); no_shelf++; return true; } } bool Bookcase::add(Book *bp){ int index = -1; int temp_space = -1; for (int i = 0; i < no_shelf; i++){ if (bp->weight() + my_shelf[i]->curCapacity() <= my_shelf[i]->capacity()){ if (bp->thickness() + my_shelf[i]->curWidth() <= my_shelf[i]->width() && temp_space < (my_shelf[i]->width() - my_shelf[i]->curWidth())){ temp_space = (my_shelf[i]->width()- my_shelf[i]->curWidth()); index = i; } } } if (index != -1){ my_shelf[index]->add(bp); return true; }else return false; } void Bookcase::print(){ printf("Bookcase #%d\n", my_id); for (int i = 0; i < no_shelf; i++){ printf("--- Shelf (%d mm, %d dg) ---\n", my_shelf[i]->width(), my_shelf[i]->capacity()); my_shelf[i]->print(); } }

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  • Floating point comparison in STL, BOOST

    - by Paul
    Is there in the STL or in Boost a set of generic simple comparison functions? The one I found are always requiring template parameters, and/or instantiation of a struct template. I'm looking for something with a syntax like : if ( is_greater(x,y) ) { ... } Which could be implemented as : template <typename T> bool is_greater(const T& x, const T& y) { return x > y + Precision<T>::eps; }

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  • Can someone explain how pointer to pointer works?

    - by user3549560
    I don't really understand how the pointer to pointer works. Any way to do the same work without using pointer to pointer? struct customer{ char name[20]; char surname[20]; int code; float money; }; typedef struct customer customer; void inserts(customer **tmp) { *tmp = (customer*)malloc(sizeof(customer)); puts("Give me a customer name, surname code and money"); scanf("%s %s %d %f", (*tmp)->name, (*tmp)->surname, &(*tmp)->code,&(*tmp)->money); }

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  • Redirecting one file to another using dub2 and strtok

    - by Sergiy Zakharov
    OK, here goes. I have to write a program, in which I need to use strtok and dup2 to redirect one file to another, but I need to also have the user to actually put the command cat < file1 file2, but not from the shell, but instead by using my program. That's why I need strtok. And the reason my program doesn't work is probably because of that, because I don't really understand how strtok works. I found a similar program on the internet, but they just take the ls command and redirect it to the file. That's it. My program is much more complicated. I mean, it would've been easier just to say in shell cat < file1 file2, but for some reason they want us to do it this way. So, anyways, here is what I have so far (here I just combined what I have found on the internet with what I already had from before. We had to do something similar but then the user would just go ls or ls -l. Very simple stuff. This is much harder, for me, at least.) #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <errno.h> #include <sys/wait.h> #include <string.h> int main() { pid_t pid; char line[256]; char *args[129]; int i; int fd; int status; char *temp; while (1) { printf(">"); if (fgets(line, 256, stdin) == 0) { exit(0); } else { pid = fork(); if (pid == 0) { i = 0; temp = strtok("<",line); while (temp != NULL) { args[i++] = temp; temp = strtok(">",line); args[i] = '\0'; } fd = open("hello", O_RDONLY); dup2(fd, STDIN_FILENO); fd = open("world", O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU); dup2(fd, STDOUT_FILENO ); close(fd); execvp(args[0], args); } else { close(fd); wait(&status); } } } } Any help would be greatly appreciated.

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  • Difference between debug and release.

    - by atch
    Why when I'm debugging in debug mode everything in code below works as suppose to but when I switch to release I'm getting strange result? void say_hello(int argc, char* argv[])//In release mode argc has different values from 124353625 to 36369852 <include iostream> { std::cout << "In say_hello()\n"; } int main(int argc, char* argv[]) { say_hello(3,argv);//when instead of literal I enter "argc" everything is ok. return 0; } Thanks for help.

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  • Sorting array of structs

    - by mrblippy
    Hi, i am having trouble making a method to sort an array of structs. i am tring to sort them in ascending order based on classcode. any help you could give would be appreciated struct unit { char classcode[4]; char *classname; }; void insertion_sort(struct unit u[], int n) { int j, p; struct unit tmp[1]; for(p = 1; p < n; p++) { tmp[0] = u[p]; for(j = p; j > 0 && (strcmp(tmp[j-1].classcode, tmp[p].classcode) > 0); j--) u[j] = u[j-1]; u[j] = tmp[0]; } }

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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • Get current session /process id from inside a mysql query

    - by Indra Ginanjar
    I'm trying to create a table for pseudo array variable. That looks like CREATE TABLE IF NOT EXISTS `MyArray`.`ArrayTable` ( `ID` INT UNSIGNED NOT NULL COMMENT 'Hash value of SessionID + ArrayName' , `SessionID` INT UNSIGNED NOT NULL , `ArrayName` CHAR(26) NOT NULL COMMENT '32 digit char - 6 digit longest process id (assumtion)' , `Index` INT UNSIGNED NOT NULL , `Value` TEXT NOT NULL , PRIMARY KEY (`ID`, `SessionID`) ) ENGINE = MyISAM; The table is not normalized yet, 'hope this will make it a little simpler to understand :) To avoid collission between client, there should be a differentiator between client session. For that reason i think need to know current session/process id (just like "SHOW PROCESSLIST") but really need to know IN WHICH process the query are?

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  • C pointer array scope and function calls

    - by juvenis
    I have this situation: { float foo[10]; for (int i = 0; i < 10; i++) { foo[i] = 1.0f; } object.function1(foo); // stores the float pointer to a const void* member of object } object.function2(); // uses the stored void pointer Are the contents of the float pointer unknown in the second function call? It seems that I get weird results when I run my program. But if I declare the float foo[10] to be const and initialize it in the declaration, I get correct results. Why is this happening?

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