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  • Why use C typedefs rather than #defines?

    - by me_and
    What advantage (if any) is there to using typedef in place of #define in C code? As an example, is there any advantage to using typedef unsigned char UBYTE over #define UBYTE unsigned char when both can be used as void func() { UBYTE byte_value = 0; /* Do some stuff */ return byte_value; } Obviously the pre-processor will try to expand a #define wherever it sees one, which wouldn't happen with a typedef, but that doesn't seem to me to be any particular advantage or disadvantage; I can't think of a situation where either use wouldn't result in a build error if there was a problem.

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  • Set intersection of two strings

    - by user1785712
    import java.util.*; class set { public static void main(String args[]) { TreeSet<Character> t1 = new TreeSet<Character>(); TreeSet<Character> t2 = new TreeSet<Character>(); String s1 = "Ambitab bachan"; String s2 = "Ranjikanth"; for(char c1:s1.toCharArray()) t1.add(c1); for(char c2:s2.toCharArray()) t2.add(c2); t2.retainAll(t1); System.out.println(t2); } } this program find the common character in two different string. in this program Treeset is used to store the value and retainAll() method is used to find the common characters. can anybody help me reduce the line of coding.thanks in advance

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  • hash table with chaining method program freezing

    - by Justin Carrey
    I am implementing hash table in C using linked list chaining method. The program compiles but when inserting a string in hash table, the program freezes and gets stuck. The program is below: struct llist{ char *s; struct llist *next; }; struct llist *a[100]; void hinsert(char *str){ int strint, hashinp; strint = 0; hashinp = 0; while(*str){ strint = strint+(*str); } hashinp = (strint%100); if(a[hashinp] == NULL){ struct llist *node; node = (struct llist *)malloc(sizeof(struct llist)); node->s = str; node->next = NULL; a[hashinp] = node; } else{ struct llist *node, *ptr; node = (struct llist *)malloc(sizeof(struct llist)); node->s = str; node->next = NULL; ptr = a[hashinp]; while(ptr->next != NULL){ ptr = ptr->next; } ptr->next = node; } } void hsearch(char *strsrch){ int strint1, hashinp1; strint1 = 0; hashinp1 = 0; while(*strsrch){ strint1 = strint1+(*strsrch); } hashinp1 = (strint1%100); struct llist *ptr1; ptr1 = a[hashinp1]; while(ptr1 != NULL){ if(ptr1->s == strsrch){ cout << "Element Found\n"; break; } else{ ptr1 = ptr1->next; } } if(ptr1 == NULL){ cout << "Element Not Found\n"; } } hinsert() is to insert elements into hash and hsearch is to search an element in the hash. Hash function is written inside hinsert() itself. In the main(), what i am initializing all the elements in a[] to be NULL like this: for(int i = 0;i < 100; i++){ a[i] = NULL; } Help is very much appreciated. Thanks !

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  • How to remove an item from a structure array in C++?

    - by Antik
    I have the following array structure (linked list): struct str_pair { char ip [50] ; char uri [50] ; str_pair *next ; } ; str_pair *item; I know to create a new item, I need to use item = new str_pair; However, I need to be able to loop through the array and delete a particular item. I have the looping part sorted. But how do I delete an item from an array of structures?

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  • C++: Throwing shared_ptr of derived and catching shared_ptr of base?

    - by hasvn
    Ok, I've been told this problem: Why can you throw a pointer to a derived class and catch a pointer to its base... but you can't do that with shared_ptrs? Example, this works: class Base {}; class Derived : public Base {}; int main() { try { throw new Derived() ; } catch( const Base2 * b ) { printf("Received a base" ) ; } return 0 ; } But this doesn't int main() { try { throw std::tr1::shared_ptr<Derived>( new Derived() ) ; } catch( const std::tr1::shared_ptr<Base> & b ) { printf("Received a base" ) ; } return 0 ; } Any ideas?

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  • Read options from file

    - by Devel
    I would like to write a function which will read values from a text file and write them to variables. For example my file is: mysql_server localhost mysql_user root mysql_passworg pospaz mysql_database testgenerator log log.txt username admin password abcd and I have the same variables as the first word in the line. So how to make the function read data from file and do sth like this: char *mysql_server = localhost; char *mysql_user = root; ... I have no idea even how to start writing it...

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  • C++ Declaring an uninitialized variable without a null constructor

    - by xbonez
    Consider the DUPoint class, whose declaration appears below. Assume this code appears in a file named DUPoint.h: #include <string> class DUPoint { public: DUPoint (int x, int y); int getX () const; int getY () const; void setX (int x); void setY (int y); void print(); private: int x_; int y_; }; Is it true that you cannot declare an uninitialized DUPoint variable with a statement such as DUPoint P; using this class as currently configured because it has no null constructor?

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  • How to access constant defined in child class from parent class functions?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • Sending a file from memory (rather than disk) over HTTP using libcurl

    - by cinek1lol
    Hi! I would like to send pictures via a program written in C + +. - OK WinExec("C:\\curl\\curl.exe -H Expect: -F \"fileupload=@C:\\curl\\ok.jpg\" -F \"xml=yes\" -# \"http://www.imageshack.us/index.php\" -o data.txt -A \"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1\" -e \"http://www.imageshack.us\"", NULL); It works, but I would like to send the pictures from pre-loaded carrier to a variable char (you know what I mean? First off, I load the pictures into a variable and then send the variable), cause now I have to specify the path of the picture on a disk. I wanted to write this program in c++ by using the curl library, not through exe. extension. I have also found such a program (which has been modified by me a bit) #include <stdio.h> #include <string.h> #include <iostream> #include <curl/curl.h> #include <curl/types.h> #include <curl/easy.h> int main(int argc, char *argv[]) { CURL *curl; CURLcode res; struct curl_httppost *formpost=NULL; struct curl_httppost *lastptr=NULL; struct curl_slist *headerlist=NULL; static const char buf[] = "Expect:"; curl_global_init(CURL_GLOBAL_ALL); /* Fill in the file upload field */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "send", CURLFORM_FILE, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "nowy.jpg", CURLFORM_COPYCONTENTS, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "submit", CURLFORM_COPYCONTENTS, "send", CURLFORM_END); curl = curl_easy_init(); headerlist = curl_slist_append(headerlist, buf); if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "http://www.imageshack.us/index.php"); if ( (argc == 2) && (!strcmp(argv[1], "xml=yes")) ) curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist); curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost); res = curl_easy_perform(curl); curl_easy_cleanup(curl); curl_formfree(formpost); curl_slist_free_all (headerlist); } system("pause"); return 0; }

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  • Is it possible for a parent to use a child's constant or static variables from inside a static metho

    - by ryeguy
    Below is an example of what I'm trying to do. The parent can't access any of the child's variables. It doesn't matter what technique I use (static or constants), I just need some kind of functionality like this. class ParentClass { public static function staticFunc() { //both of these will throw a (static|const) not defined error echo self::$myStatic; echo self::MY_CONSTANT; } } class ChildClass extends ParentClass { const MY_CONSTANT = 1; public static $myStatic = 2; } ChildClass::staticFunc();

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  • C++ how to store integer into a binary file??

    - by blaxc
    i gt a struct with 2 integer, i want to store them in a binary file and read it again... here is my code... struct pw { int a; int b; }; void main(){ pw* p = new pw(); pw* q = new pw(); std::ofstream fout(ADMIN_FILE, ios_base::out | ios_base::binary | ios_base::trunc); std::ifstream fin(ADMIN_FILE, ios_base::in | ios_base::binary); p->a=123; p->b=321; fout.write((const char*)p, sizeof(pw)); fin.write((char*)q, sizeof(pw)); fin.close(); cout<< q->a << endl;} my output is 0. anyone can tell me what is the problem?

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  • Different sizes of same strings - Telnet programming

    - by tommyogp
    Hi all, I have been trying to create an iphone app sending telnet command. However what puzzling me is that the sizes of certain strings are so much different, particularly when they include \n or \r. I listed out a few examples. Please assist. const char *a = "play 25\n"; int sizeBitA1 = sizeof(a); // 8 units int sizeBitA2 = sizeof("play 25\n"); // 9 units const char *b = "\r\n"; int sizeBitB1 = sizeof(b); // 8 units int sizeBitB2 = sizeof("\r\n"); // 3 units

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  • Exception in C#

    - by user1803513
    I am facing null pointer exception in below code as it is happening very rarely and I tried to debug to replicate the issue but no luck. Can anybody help me what can cause null point exception here. private static void MyTaskCompletedCallback(IAsyncResult res) { var worker = (AsyncErrorDelegate)((AsyncResult)res).AsyncDelegate; var async = (AsyncOperation)asyncResult.AsyncState; worker.EndInvoke(res); lock (IsAsyncOpOccuring) { IsBusy = false; } var completedArgs = new AsyncCompletedEventArgs(null, false, null); async.PostOperationCompleted(e => OnTaskCompleted((AsyncCompletedEventArgs)e), completedArgs); } Null Pointer exception is reported at var async = (AsyncOperation)asyncResult.AsyncState;

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  • Second query to SQLite (on iPhone) errors.

    - by Luke
    Hi all, On the iPhone, I am developing a class for a cart that connects directly to a database. To view the cart, all items can be pulled from the database, however, it seems that removing them doesn't work. It is surprising to me because the error occurs during connection to the database, except not the second time I connect even after the DB has been closed. #import "CartDB.h" #import "CartItem.h" @implementation CartDB @synthesize database, databasePath; - (NSMutableArray *) getAllItems { NSMutableArray *items = [[NSMutableArray alloc] init]; if([self openDatabase]) { const char *sqlStatement = "SELECT * FROM items;"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(cartDatabase, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { while(sqlite3_step(compiledStatement) == SQLITE_ROW) { int rowId = sqlite3_column_int(compiledStatement, 0); int productId = sqlite3_column_int(compiledStatement, 1); NSString *features = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; int quantity = sqlite3_column_int(compiledStatement, 3); CartItem *cartItem = [[CartItem alloc] initWithRowId:rowId productId:productId features:features quantity:quantity]; [items addObject:cartItem]; [cartItem release]; } } sqlite3_finalize(compiledStatement); } [self closeDatabase]; return items; } - (BOOL) removeCartItem:(CartItem *)item { sqlite3_stmt *deleteStatement; [self openDatabase]; const char *sql = "DELETE FROM items WHERE id = ?"; if(sqlite3_prepare_v2(cartDatabase, sql, -1, &deleteStatement, NULL) != SQLITE_OK) { return NO; } sqlite3_bind_int(deleteStatement, 1, item.rowId); if(SQLITE_DONE != sqlite3_step(deleteStatement)) { sqlite3_reset(deleteStatement); [self closeDatabase]; return NO; } else { sqlite3_reset(deleteStatement); [self closeDatabase]; return YES; } } - (BOOL) openDatabase { if(sqlite3_open([databasePath UTF8String], &cartDatabase) == SQLITE_OK) { return YES; } else { return NO; } } - (void) closeDatabase { sqlite3_close(cartDatabase); } The error occurs on the line where the connection is opened in openDatabase. Any ideas? Need to flush something? Something gets autoreleased? I really can't figure it out. --Edit-- The error that I receive is GDB: Program received signal "EXC_BAD_ACCESS". --Edit-- I ended up just connecting in the init and closing in the free methods, which might not be the proper way, but that's another question altogether so it's effectively persistent instead of connecting multiple times. Still would be nice to know what was up with this for future reference.

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  • Sqlite insertion problem

    - by Devi
    Hi, I had sqlite database for my application I am able to retrieve values from my sqlite table and inserting values with no sql error but unable to find in sqlite table....please do needful help for this problem. I just stucked up at this point plz help me here is my code NSMutableString *registrationquery=[NSMutableString stringWithFormat:@"insert into tbl_kicks values ('%@','%@','%@')",[totalkicks text],[sessionstart text],[sessionstart text],@"0"]; //NSString *sqlNSString = [NSString stringWithFormat:@"INSERT INTO 'tbl_kicks' VALUES('%d','%@','%@');", // 4,sessionstart.text, appDelegate.note]; const char *sqlString = [registrationquery UTF8String]; char *sqlError; sqlite3_exec( appDelegate.database, sqlString, NULL, NULL, &sqlError );

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  • What's the simplest way of defining lexicographic comparison for elements of a class?

    - by the_mandrill
    If I have a class that I want to be able to sort (ie support a less-than concept), and it has several data items such that I need to do lexicographic ordering then I need something like this: struct MyData { string surname; string forename; bool operator<(const MyData& other) const { return surname < other.surname || (surname==other.surname && forename < other.forename); } }; This becomes pretty unmanageable for anything with more than 2 data members. Are there any simpler ways of achieving it? The data members may be any Comparable class.

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  • Reading line by line from a file in C

    - by mh234
    What I am trying to do is print out the contents of a file line by line. I run the program in terminal by doing: ./test testText.txt. When I do this, random characters are printed out but not what is in the file. The text file is located in the same folder as the makefile. What's wrong? #include <stdio.h> FILE *fp; int main(int argc, char *argv[]) { char line[15]; fp = fopen(*argv, "r"); while((fgets(line, 15, fp)) != NULL) { printf(line); printf("\n"); } }

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  • Any idea why this query always returns duplicate items?

    - by Kardo
    I want to get all Images not used by current ItemID. The this subquery but it also always returns duplicate Images: EDITED select Images.ImageID, Images.ItemStatus, Images.UserName, Images.Url, Image_Item.ItemID, Image_Item.ItemID from Images left join (select ImageID, ItemID, MAX(DateCreated) x from Image_Item where ItemID != '5a0077fe-cf86-434d-9f3b-7ff3030a1b6e' group by ImageID, ItemID having count(*) = 1) image_item on Images.imageid = image_item.imageid where ItemID is not null I guess the problem is with the subquery which I can't avoid duplicate rows: select ImageID, ItemID, MAX(DateCreated) x from Image_Item where ItemID != '5a0077fe-cf86-434d-9f3b-7ff3030a1b6e' group by ImageID, ItemID having count(*) = 1 Result: F2EECBDC-963D-42A7-90B1-4F82F89A64C7 0578AC61-3C32-4A1D-812C-60A09A661E71 F2EECBDC-963D-42A7-90B1-4F82F89A64C7 9A4EC913-5AD6-4F9E-AF6D-CF4455D81C10 42BC8B1A-7430-4915-9CDA-C907CBC76D6A CB298EB9-A105-4797-985E-A370013B684F 16371C34-B861-477C-9A7C-DEB27C8F333D 44E6349B-7EBF-4C7E-B3B0-1C6E2F19992C Table: Images ImageID uniqueidentifier UserName nvarchar(100) DateCreated smalldatetime Url nvarchar(250) ItemStatus char(1) Table: Image_Item ImageID uniqueidentifier ItemID uniqueidentifier UserName nvarchar(100) ItemStatus char(1) DateCreated smalldatetime Any kind help is highly appreciated.

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  • How to remove [^a-z\s] in C++

    - by Steven
    So far I have: int SimplifyText(char chars[], int length) { //To lower for(int i=0; i<length; i++) { chars[i] = tolower(chars[i]); } This function simplifies the text in the first argument which is an array containing the number of characters as given in the second argument The requirements are: tolower all remove all non-alpha characters replace multiple whitespace by one blank. Any leading whitespace at the beginning of the array should be removed completely. The resulting number of characters should be returned as the value of the function. And the annoying part: Another array cannot appear in the function Cannot use strings, only char arrays. Cannot using G++'s extension for setting an array size using a variable. Oh and can't use regex :) I'm stuck with this, any help would be great. :)

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  • Reading from a file into an array in c

    - by NaNa21
    My file contains a series of numbers (integer, float, integer, float ....), each written on a separate line. The numbers of columns are different from one line to another i.e. 1 2.45 3 1.75 5 3.45 7 2.55 9 3.25 6 1.75 4 3.55 6 2.55 9 2.45 The program should read the contents of the entire file and place the data into an array of type float with an entry for each line. Here is my basic solution, but this is only suitable if I have fixed no of columns. float Read(FILE *pFile) { char line[50]; char letter[5]; fi = fopen("file.txt", "r"); while (fgets(line,200,fi)!=NULL) { sscanf(line,"%f %f %f",&a[i], &a2[i],&a3[i]); printf("%2.0f %2.5f %2.0f\n",a[i],a2[i],a3[i]); } fclose(fi); return a[i]; } Please HELP.

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  • Getting MATLAB variable (string) from C

    - by Hamming
    Hi! I'm writing a small C application that launchs a Matlab script (.m file). I need to exchange some variables and I don't know how to get an array of chars that exists in Matlab. I'm doing something like this: enter code here result = engGetVariable(ep,"X"); if (!result) { printf ("Error..."); exit -1; } int n = mxGetN(result); char *varx = NULL; memcpy(varx, mxGetData(result),n*sizeof(char)); It doesn't work. Does someone know how to get a Matlab string in C? I've read Matlab documentation about engGetVariable() and the provided example but any of this things clarify me.

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  • extracting string occurrence in c

    - by David78
    I have a string from a text file that look something like this: long_str = "returns between paragraphs 20102/34.23" - 9203 1232 "test" "basic HTML" Note: Quotes are part of the string. int match(char *long_str){ char * str; if ((str = strchr(long_str, '"')) != NULL) str++; // last " ? else return 1; return 0; } Using strstr I'm trying to get the whole substring between the last two quotes: "basic HTML". I'm just not quite sure what would be a good and efficient way of getting that match. I'm open to any other ideas on how to approach this. Thanks

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  • C++: Could Polymorphic Copy Constructors work?

    - by 0xC0DEFACE
    Consider: class A { public: A( int val ) : m_ValA( val ) {} A( const A& rhs ) {} int m_ValA; }; class B : public A { public: B( int val4A, int val4B ) : A( val4A ), m_ValB( val4B ) {} B( const B& rhs ) : A( rhs ), m_ValB( rhs.m_ValB ) {} int m_ValB; }; int main() { A* b1 = new B( 1, 2 ); A* b2 = new A( *b1 ); // ERROR...but what if it could work? return 0; } Would C++ be broken if "new A( b1 )" was able to resolve to creating a new B copy and returning an A? Would this even be useful?

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  • Adding characters to string

    - by Jamza
    I am currently trying to build a very basic serial shell with my arduino. I am able to get an output from the device using Serial.read() and can get the character it has outputted, but I cannot work out how to then add that character to a longer to form the full command. I tried the logical thing but it doesn't work: char Command[]; void loop(){ if(Serial.available() > 0){ int clinput = Serial.read(); Command = Command + char(clinput); } Can anybody help? Thank You.

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