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  • How do I get characters common to two vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • How can I tell if an ADODB::_RecordsetPtr has already been created?

    - by scottm
    I am trying to write a class that uses ADO to retrieve SQL records. The intent is for the class to maintain one private recordset an other methods move forward, retrieve fields, etc. This is a basic example of my class: class SqlADO { private: ADODB::_RecordsetPtr m_recordset; public: void Open(); //open the connection void Execute(const char* sql); // creates or replaces current recordset void Next(); //moves recordset cursor forward void Field(const char* fieldName); //retrieves field name from current record of the recordset }; My Questions: In the Execute method, how can I check to see that the recordset instance has been created (or do I need to) so that I can close it first? Do you know of any good ADO COM Interop references?

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  • Dereferencing deleted pointers always result in an Access Violation ??

    - by m3rLinEz
    I have a very simple C++ code here: char *s = new char[100]; strcpy(s, "HELLO"); delete [] s; int n = strlen(s); If I run this code from Visual C++ 2008 by pressing F5 (Start Debugging,) this always result in crash (Access Violation.) However, starting this executable outside the IDE, or using the IDE's Ctrl+F5 (Start without Debugging) doesn't result in any crash. What could be the difference? I also want to know if it's possible to stably reproduce the Access Violation crash caused from accessing deleted area? Is this kind of crash rare in real-life?

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  • Passing arguments to UILabel [ 2 ] *

    - by DesperateLearner
    I'm trying to call a method of the below (Scroll animation class) type from a viewcontroller class. -(void)CreateLabel:(CGRect )frame andLabel:(UILabel *[NUM_LABELS])label andview:(UIView *)view; I got some errors when I tried passing the argument. Any suggestion on how to call this? This is how I called that method ScrollAnimation *newAnimation = [[ScrollAnimation alloc] init]; [newAnimation CreateLabel:CGRectMake(0, 50, 300,30) andLabel:animateLabel[NUM_LABELS] andview:self.view]; I have the error /Volumes/Red Drive/CarTransition/CarTransition/ViewController.m:120:66: Implicit conversion of an Objective-C pointer to 'UILabel **' is disallowed with ARC /Volumes/Red Drive/CarTransition/CarTransition/ViewController.m:120:66: Incompatible pointer types sending 'UILabel *__strong' to parameter of type 'UILabel **'

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  • Loading Unmanaged C++ in C#. Error Attempted to read or write protected memory

    - by Thatoneguy
    I have a C++ function that looks like this __declspec(dllexport) int ___stdcall RegisterPerson(char const * const szName) { std::string copyName( szName ); // Assign name to a google protocol buffer object // Psuedo code follows.. Protobuf::Person person; person->set_name(copyName); // Error Occurs here... std::cerr << person->DebugString() << std::endl; } The corresponding C# code looks like this... [DllImport(@"MyLibrary.dll", SetLastError = true)] public static unsafe extern int RegisterPerson([MarshalAs(UnmanagedType.LPTStr)]string szName) Not sure why this is not working. My C++ library is compiled as Multi Threaded DLL with MultiByte encoding. Any help would be appreciated. I saw this is a common problem online but no answers lead me to a solution for my problem.

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  • How to check total cache size using a program

    - by user1888541
    so I'm having some trouble creating a program to measure cache size in C. I understand the basic concept of going about this but I'm still having trouble figuring out exactly what I am doing wrong. Basically, I create an array of varying length (going by power of 2s) and access each element in the array and put it in a dummy variable. I go through the array and do this around 1000 times to negate the "noise" that would otherwise occur if I only did it once to get an accurate measurement for time. Then, I look for the size that causes a big jump in access time. Unfortunately, this is where I am having my problem, I don't see this jump using my code and clearly I am doing something wrong. Another thing is that I used /proc/cpuinfo to check the cache and it said the size was 6114 but that was not a power of 2. I was told to go by powers of 2 to figure out the cache can anyone explain why this is? Here is the just of my code...I will post the rest if need be { struct timeval start; struct timeval end; // int n = 1; // change this to test different sizes int array_size = 1048576*n; // I'm trying to check the time "manually" first before creating a loop for the program to do it by itself this is why I have a separate "n" variable to increase the size char x = 0; int i =0, j=0; char *a; a =malloc(sizeof(char) * (array_size)); gettimeofday(&start,NULL); for(i=0; i<1000; i++) { for(j=0; j < array_size; j += 1) { x = a[j]; } } gettimeofday(&end,NULL); int timeTaken = (end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec *1000000 + start.tv_usec); printf("Time Taken: %d \n", timeTaken); printf("Average: %f \n", (double)timeTaken/((double)array_size); }

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  • Why isn't my IO executed in order?

    - by HaskellElephant
    Hi, I'm having some fun learning about the haskell IO. However in my recent exploration of it I have encountered some problems with IO not executing in order, even inside a do construct. In the following code I am just keeping track of what cards are left, where the card is a tuple of chars (one for suit and one for value) then the user is continously asked for wich cards have been played. I want the putStr to be executed between each input, and not at the very end like it is now. module Main where main = doLoop cards doLoop xs = do putStr $ show xs s <- getChar n <- getChar doLoop $ remove (s,n) xs suits = "SCDH" vals = "A23456789JQK" cards = [(s,n) | s <- suits, n <- vals] type Card = (Char,Char) remove :: Card -> [Card] -> [Card] remove card xs = filter (/= card) xs

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  • Is there a simple script to convert C++ enum to string?

    - by Edu Felipe
    Suppose we have some named enums: enum MyEnum { FOO, BAR = 0x50 }; What I googled for is a script (any language) that scans all the headers in my project and generates a header with one function per enum. char* enum_to_string(MyEnum t); And a implementation with something like this: char* enum_to_string(MyEnum t){ switch(t){ case FOO: return "FOO"; case BAR: return "BAR"; default: return "INVALID ENUM"; } } The gotcha is really with typedefed enums, and unnamed C style enums. Does anybody know something for this? EDIT: The solution should not modify my source, except for the generated functions. The enums are in an API, so using the solutions proposed until now is just not an option.

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  • Need MYSQL query for finding lowest score per game player

    - by Chris Barnhill
    I have a game on Facebook called Rails Across Europe. I have a Best Scores page where I show the players with the best 20 scores, which in game terms refers to the lowest winning turn. The problem is that there are a small number of players who play frequently, and their scores dominate the page. I'd like to make the scores page open to more players. So I thought that I could display the single lowest winning turn for each player instead of displaying all of the lowest winning turns for all players. The problem is that the query for this eludes me. So I hope that one of you brilliant StackOverflow folks can help me with this. I have included the relevant MYSQL table schemas below. Here are the the table relationships: player_stats contains statistics for either a game in progress or a completed game. If a game is in progress, winning_turn is zero (which means that games with a winning_turn of zero should not be included in the query). player_stats has a game_player table id reference. game_player contains data describing games currently in progress. game_player has a player table id reference. player contains data describing a person who plays the game. Here's the query I'm currently using: 'SELECT p.fb_user_id, ps.winning_turn, gp.difficulty_level, c.name as city_name, g.name as goods_name, d.cost FROM game_player as gp, player as p, player_stats as ps, demand as d, city as c, goods as g WHERE p.status = "ACTIVE" AND gp.player_id = p.id AND ps.game_player_id = gp.id AND d.id = ps.highest_demand_id AND c.id = d.city_id AND g.id = d.goods_id AND ps.winning_turn > 0 ORDER BY ps.winning_turn ASC, d.cost DESC LIMIT '.$limit.';'; Here are the relevant table schemas: -- -- Table structure for table `player_stats` -- CREATE TABLE IF NOT EXISTS `player_stats` ( `id` int(11) NOT NULL auto_increment, `game_player_id` int(11) NOT NULL, `winning_turn` int(11) NOT NULL, `highest_demand_id` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `game_player_id` (`game_player_id`,`highest_demand_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=3814 ; -- -- Table structure for table `game_player` -- CREATE TABLE IF NOT EXISTS `game_player` ( `id` int(10) unsigned NOT NULL auto_increment, `game_id` int(10) unsigned NOT NULL, `player_id` int(10) unsigned NOT NULL, `player_number` int(11) NOT NULL, `funds` int(10) unsigned NOT NULL, `turn` int(10) unsigned NOT NULL, `difficulty_level` enum('STANDARD','ADVANCED','MASTER','ULTIMATE') NOT NULL, `date_last_used` datetime NOT NULL, PRIMARY KEY (`id`), KEY `game_id` (`game_id`,`player_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=3814 ; -- -- Table structure for table `player` -- CREATE TABLE IF NOT EXISTS `player` ( `id` int(11) NOT NULL auto_increment, `fb_user_id` char(255) NOT NULL, `fb_proxied_email` text NOT NULL, `first_name` char(255) NOT NULL, `last_name` char(255) NOT NULL, `birthdate` date NOT NULL, `date_registered` datetime NOT NULL, `date_last_logged_in` datetime NOT NULL, `status` enum('ACTIVE','SUSPENDED','CLOSED') NOT NULL, PRIMARY KEY (`id`), KEY `fb_user_id` (`fb_user_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1646 ;

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  • Same loop giving different output. Java IO

    - by Nitesh Panchal
    Hi, I am facing a very strange problem where the same loop keeps giving me different different output on change of value of BUFFER final int BUFFER = 100; char[] charArr = new char[BUFFER]; StringBuffer objStringBuffer = new StringBuffer(); while (objBufferedReader.read(charArr, 0,BUFFER) != -1) { objStringBuffer.append(charArr); } objFileWriter.write(objStringBuffer.toString()); When i change BUFFER size to 500 it gives me a file of 7 kb when i change BUFFER size to 100000 it gives a file of 400 kb where the contents are repeated again and again. Please help. What should i do to prevent this?

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  • Use C function in C++ program; "multiply-defined" error

    - by eom
    I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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  • Basic C++ code for multiplication of 2 matrix or vectors (C++ beginner)

    - by Ice
    I am a new C++ user and I am also doing a major in Maths so thought I would try implement a simple calculator. I got some code off the internet and now I just need help to multiply elements of 2 matrices or vectors. Matrixf multiply(Matrixf const& left, Matrixf const& right) { // error check if (left.ncols() != right.nrows()) { throw std::runtime_error("Unable to multiply: matrix dimensions not agree."); } /* I have all the other part of the code for matrix*/ /** Now I am not sure how to implement multiplication of vector or matrix.**/ Matrixf ret(1, 1); return ret; }

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  • Preprocessor directive to test if this is C or C++

    - by Collin
    I'm trying to find a standard macro which will test whether a header file is being compiled as C or as C++. The purpose of this is that the header may be included by either C or C++ code, and must behave slightly differently depending on which. Specifically: In C, I need this to be the code: extern size_t insert (const char*); In C++, I need this to be the code: extern "C" size_t insert (const char*); Additionally, is there a way to avoid putting #ifdef's around every declaration in the header?

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • java decmail string to AS 3.0 conversion procedure

    - by Jack Smith
    Hello, I have a problem with conversion java code to action script 3. Anyone can help with code translation? Thanks. public static short[] decmail_str_to_binary_data(String s) { short[] data = new short[s.length()/2]; for (int i = 0; i < s.length(); i += 2) { char c1 = s.charAt(i); char c2 = s.charAt(i + 1); int comb = Character.digit(c1, 16) & 0xff; comb <<= 4; comb += Character.digit(c2, 16) & 0xff; data[i/2] = (short)comb; } return data; }

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  • Why this works (Templates, SFINAE). C++

    - by atch
    Hi guys, reffering to yesterday's post, this woke me up this morning. Why this actually works? As long as the fnc test is concerned this fnc has no body so how can perform anything? Why and how this works? I'm REALLY interested to see your answers. template<typename T> class IsClassT { private: typedef char One; typedef struct { char a[2]; } Two; template<typename C> static One test(int C::*); //NO BODY HERE template<typename C> static Two test(…); //NOR HERE public: enum { Yes = sizeof(IsClassT<T>::test<T>(0)) == 1 }; enum { No = !Yes }; }; Thanks in advance with help to understand this very interesting fenomena.

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  • parsing command option with default values and range constrains in C

    - by agramfort
    Hi, I need to parse command line arguments in C. My arguments are basically int or float with default values and range constrains. I've started to implement something that look like this: option_float(float* out, int argc, char* argv, char* name, description, float default_val, int is_optional, float min_value, float max_value) which I call for example with: float* pct; option_float(pct, argc, argv, "pct", "My super percentage option", 50, 1, FALSE, 0, 100) however I don't want to reinvent the wheel ! My objective is to have error checking of range constrains, throw an error when the option is not optional and is not set. And generate the help message usually given by usage() function. The usage text would look like this: --pct My super percentage option (default : 50). Should be in [0, 100] I've started with getopt but it is too limited for what I want to do and I feel it still requires me to write too much code for a simple usecase like this. thanks

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  • Casting a Calculated Column in a MySQL view.

    - by Chris Brent
    I have a view that contains a calculated column. Is there are a way to cast it as a CHAR or VARCHAR rather than a VARBINARY ? Obviously, I have tried using CAST(... as CHAR) but it gives an error. Here is a simple replicable example. CREATE VIEW view_example AS SELECT concat_ws('_', lpad(9, 3,'0'), lpad(1,3,'0'), date_format(now(),'%Y%m%d%H%i%S')) AS calculated_field_id; This is how my view is created: describe view_example; +---------------------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------------------+---------------+------+-----+---------+-------+ | calculated_field_id | varbinary(27) | YES | | NULL | | +---------------------+---------------+------+-----+---------+-------+ select version(); +-----------------------+ | version() | +-----------------------+ | 5.0.51a-community-log | +-----------------------+

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  • Is it good practice to initialize array in C/C++?

    - by sand
    I recently encountered a case where I need to compare two files (golden and expected) for verification of test results and even though the data written to both the files were same, the files does not match. On further investigation, I found that there is a structure which contains some integers and a char array of 64 bytes, and not all the bytes of char array were getting used in most of the cases and unused fields from the array contain random data and that was causing the mismatch. This brought me ask the question whether it is good practice to initialize the array in C/C++ as well, as it is done in Java?

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  • What object called a method in Obj-C

    - by Loz
    Hi, I am looking to write a plugin controller in Cocoa that loads bundles, and exposes a specific set of methods for the plugins to call. My question is this: is it possible to know (any) info about the object that called a method in the controller. When an instantiated plugin calls a method in my plugin controller, I would like to know which of the plugin instances called the method, without having to rely on the plugin sending a pointer to itself as a parameter (I could always validate the pointer they send, but I want to keep the API methods as simple as possible). There may be no perfect solution (and there are simple workarounds), but it's always good to learn some new tricks if possible (or the reasons why it's impossible). Thanks in advance.

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  • strenge exception phenomenon in win7

    - by Level 2
    Hello all, I spot some interesting artcles about exception handle in codeproject http://www.codeproject.com/KB/cpp/seexception.aspx after reading, I decided to do some experiment. The first time I try to excute the following code char *p; p[0] = 0; The program died without question. But After serveral time I execute the same problem binary code. It magically did fine. even the following code is doing well. any clue or explain? char *p p[1000] = 'd'; cout<<p[1000]<<endl; my os is windows 7 64bit and compiler is vs2008 rc1.

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  • How can I remove the head of a main function?

    - by Nathan McDavitt-Van Fleet
    I am trying to move some code from a seperate binary and have it inside my main program. Unfortunately I can't mimic the initialization variables for the main function. How can I create argc and argv by hand? Can someone give me some example assignments. since it looks like this: int main(int argc, char *argv[]) I figured I could assign them like this: int argc=1; char *argv[0]="Example"; But it doesn't work. Can anyone tell me how this might be done?

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  • allocator with no template

    - by Merni
    Every stl container take an allocator as a second object, template < class T, class Allocator = allocator<T> > class vector; If you write your own class It is possible to use your own allocator. But is it possible to write your own allocator without using templates? For example, writing this function is not easy if you are not allowed to use templates pointer allocate(size_type n, const_pointer = 0) { void* p = std::malloc(n * sizeof(T)); if (!p) throw std::bad_alloc(); return static_cast<pointer>(p); } Because how could you know the size of T?

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  • How can I obtain the IPv4 address of the client?

    - by Dr Dork
    Hello! I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code setup to listen for incoming TCP connection requests from clients after the parent socket has been created and is set to listen... int sockfd, newfd; unsigned int len; socklen_t sin_size; char msg[]="Test message sent"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char ip[INET6_ADDRSTRLEN]; . . //parent socket creation and listen code omitted for simplicity . //wait for connection requests from clients while(1) { //Returns the socketID and address of client connecting to socket if( ( newfd = accept(sockfd, (struct sockaddr *)&client, &len) ) == -1 ){ perror("Accept"); exit(-1); } if( (rv = recv(newfd, buf, MAXLEN-1, 0 )) == -1) { perror("Recv"); exit(-1); } struct sockaddr_in *clientAddr = ( struct sockaddr_in *) get_in_addr((struct sockaddr *)&client); inet_ntop(client.ss_family, clientAddr, ip, sizeof ip); printf("Receive from %s: query type is %s\n", ip, buf); if( ( st = send(newfd, msg, strlen(msg), 0)) == -1 ) { perror("Send"); exit(-1); } //ntohs is used to avoid big-endian and little endian compatibility issues printf("Send %d byte to port %d\n", ntohs(clientAddr->sin_port) ); close(newfd); } } I found the get_in_addr function online and placed it at the top of my code and use it to obtain the IP address of the client connecting... // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } but the function always returns the IPv6 IP address since thats what the sa_family property is set as. My question is, is the IPv4 IP address stored anywhere in the data I'm using and, if so, how can I access it? Thanks so much in advance for all your help!

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