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  • How to call operator<< on "this" in a descendant of std::stringstream?

    - by romkyns
    class mystream : public std::stringstream { public: void write_something() { this << "something"; } }; This results in the following two compile errors on VC++10: error C2297: '<<' : illegal, right operand has type 'const char [10]' error C2296: '<<' : illegal, left operand has type 'mystream *const ' Judging from the second one, this is because what this points at can't be changed, but the << operator does (or at least is declared as if it does). Correct? Is there some other way I can still use the << and >> operators on this?

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  • c++: strange syntax in what() method of std::exception

    - by Patrick Oscity
    When i am inheriting from std::exception in order to define my own exception type, i need to override the what() method, which has the following signature: virtual const char* what() const throw(); This definitely looks strange to me, like if there were two method names in the signature. Is this some very specific syntax, like with pure virtual methods, e.g.: virtual int method() const = 0; or is this a feature, that could somehow be used in another context, too? And if so, for what could it be used?

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  • How to check whether iterators form a contiguous memory zone?

    - by Vincent
    I currently have the following function to read an array or a vector of raw data (_readStream is a std::ifstream) : template<typename IteratorType> inline bool MyClass::readRawData( const IteratorType& first, const IteratorType& last, typename std::iterator_traits<IteratorType>::iterator_category* = nullptr ) { _readStream.read(reinterpret_cast<char*>(&*first), (last-first)*sizeof(*first)); return _readStream.good(); } First question : does this function seem ok for you ? As we read directly a block of memory, it will only work if the memory block from first to last is contiguous in memory. How to check that ?

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  • another file_exists with special chars problem

    - by Camran
    I have some folders with special characters in their names. I run currently at a test-computer with Windows OS, but later I will use LINUX. My problem is that the folders with special chars in their names cannot be recognized somehow. ex: file_exists('../Bilar/27733691_1.jpg') // TRUE file_exists('../Båtar/27733691_1.jpg') // FALSE because of the special char in folder name... How should I solve this? I plan to run LINUX in the future when website is online... would that matter? Please explain thoroughly because I am a newb at this Thanks

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  • quick sort problem

    - by farka
    I use qsort from C libary and I have datatype Element_type **pElement and Element_type is struct typedef element_type {int ,char ....} example, and i call quicksor function with qsort(*pElement,iCountElement,(size_t)sizeof(Element_type),compare); and callback function static int compare(const void *p1, const void *p2) { Element_type *a1 = (Element_type *)p1; Element_type *a2 = (Element_type *)p2; return ( (a2)->iServiceId < (a1)->iServiceId ); } but I always get segmentation fault. Why?

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  • game currency convert: math efficient

    - by Comradsky
    For variables:4 text views named diamondText, goldText, silverText, and bronzeText;money variable unsigned int money;and an NSTimer, every .1 sec,runs function: -(void)updateMoney{ money++; bronzeText.text = [NSString stringWithFormat:@"%d",money]; silverText.text = [NSString stringWithFormat:@"%d",money%10]; goldText.text = [NSString stringWithFormat:@"%d",money%100]; diamondText.text= [NSString stringWithFormat:@"%d",money%1000]; } Given that my currency is diamond = 10 gold = 10 silver = 10 bronze = 1; What would be most efficient way to calculate and display the money labels? How would you store this variable, with GameCenter and NSDictionary or GameCenter and something else? More details are below if you don't understand. To clarify: bronze has the last 2 numbers, silver has the next 2 numbers, and so on. I understand I could use 4 ints or an array, but i would rather try to use this method, unless theres a much more efficient way. Example: When money = 1000;bronzeText = nothing, silverText = 10,goldText = nothing, diamondText = nothing; What other ways would you do this that you think would be more efficient? I will be calling a function (void)collisionDetector that detects if my player.frame crosses with a flyingObject.frame, and if that object is a coin it gives an added value to money and then calls (void)updateMoney. Im just using the timer to test this and spawn these flying objects.

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  • how to represent negative number to array of integers ?

    - by stdnoit
    I must convert string of 1324312321 to array of integers in java this is fine. I could use integer parseint and string substring method but how do I repesent -12312312 to my original array of integer.. the fact that - is a char / string and convert to array of integer would alter the value ( even though I convert - to integer-equivalent , it would change the rest of 12312312) it must be an array of integers and how should I convert negative numbers and still keeep the same value somehow reminding me of two complements trick but i dont think i need to go down to binary level in my program.. any other trick for doing this? thanks!

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  • SQL SELECT using in() but excluding others.

    - by Pickledegg
    I have a table called 'countries' linked to another table 'networks' with a many to many relationship: countries countries_networks networks +-------------+----------+ +-------------+----------+ +-------------+---------------+ | Field | Type | | Field | Type | | Field | Type | +-------------+----------+ +-------------+----------+ +-------------+---------------+ | id | int(11) | | id | int(11) | | id | int(11) | | countryName | char(35) | | country_id | int(11) | | name | varchar(100) | +-------------+----------+ | network_id | int(11) | | description | varchar(255) | To retrieve all countries that have a network_id of 6 & 7, I just do the following: ( I could go further to use the networks.name but I know the countries_networks.network_id so i just use those to reduce SQL.) SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (6,7) This is fine, but I then want to retrieve the countries with a network_id of JUST 8, and no others. I'ver tried the following but its still returning networks with 6 & 7 in. Is it something to do with my JOIN? SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (8) AND n.network_id not IN(6,7) Thanks.

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  • why it is up to the compiler to decide what value to assign when assigning an out-of-range value to

    - by Allopen
    in C++ Primer 4th edition 2.1.1, it says "when assigning an out-of-range value to a signed type, it is up to the compiler to decide what value to assign". I can't understand it. I mean, if you have code like "char 5 = 299", certainly the compiler will generate asm code like "mov BYTE PTR _sc$[ebp], 43"(VC) or "movb $43, -2(%ebp)"(gcc+mingw), it IS decided by the compiler. but what if we assign a value that is given by the user input? like, via command line? and the asm code generated will be "movb %al, -1(%ebp)"(gcc+mingw) and " mov cl, BYTE PTR _i$[ebp] mov BYTE PTR _sc$[ebp], cl "(VC), so now how can compiler decide what will happen? I think now it is decided by the CPU. Can you give me a clear explanation?

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  • C++, WCHAR[] to std::cout and comparision

    - by michal
    Hi, I need to put WCHAR[] to std::cout ... It is a part of PWLAN_CONNECTION_NOTIFICATION_DATA passed from Native Wifi API callback. I tried simply std::cout << var; but it prints out the numeric address of first char. the comparision (var == L"some text") doesn't work either. The debugger returns the expected value, however the comparision returns 0. How can I convert this array to a standard string(std::string)? Thanks in advance

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  • Iterating through std queue

    - by Ockonal
    Hi, I'm trying to use BOOST_FOREACH for iterating through the std::queue. But there isn't iterators in that class cause I have an error: std::queue<std::string> someList; BOOST_FOREACH(std::string temp, someList) { std::cout << temp; } >no matching function for call to begin(...) >no type named ‘iterator’ in ‘class std::queue<std::basic_string<char> >’ I need in structure like: the first comes, the first goes away.

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  • C pointer initialization and dereferencing, what's wrong here?

    - by randombits
    This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from integer without a cast I just want to print the value that the pointer n references. I'm dereferencing it in the printf() statement and I get a segmentation fault. Compiling this with gcc -o foo foo.c.

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  • DataSet binding problem

    - by Shaine
    I've got in-memory dataset with some table defined and I populate this table in a following way: for(...) ds.Fields.AddFieldsRow(++j, 0, heading, "Char", "", "", "Input", 0, "","",""); On the GUI I've got DataGridView bound to that table inside TabControl (bound through BindingSource). Very strange thing is happening: if I open tab pane with this grid and populate table with some data then I see changes in grid. On the other side if I'm at other tab, populate table, and then switch to tab with grid I've got following exception: "DataMember property 'Fields' cannot be found on the DataSource". In similar way I've got 2 tab panes with grid in each that are bound to the same datatable using different datasources and I open one of them, populate, see the changes, then switch to second tab and get crash. What am I missing?

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  • Looking at the C++ new[] cookie. How portable is this code?

    - by carleeto
    I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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  • Best way to get a date in .NET?

    - by frenchie
    I'm getting a string back from my page and I want to make sure it's a date. This is what I have so far (it works) and I just want to know if this is the "best" way to do it. I'm using .NET 4. int TheMonth =0; int TheDay = 0; int TheYear = 0; DateTime NewDate; var TheIncomingParam = Request.Params.Get("__EVENTARGUMENT").ToString(); char[] TheBreak = { '/' }; string[] TheOutput = TheIncomingParam.Split(TheBreak); try { TheMonth = Convert.ToInt32(TheOutput[0]); } catch { } try { TheDay = Convert.ToInt32(TheOutput[1]); } catch { } try { TheYear = Convert.ToInt32(TheOutput[2]); } catch { } if (TheMonth!=0 && TheDay!=0 && TheYear!=0) { try { NewDate = new DateTime(TheYear, TheMonth, TheDay); } catch { var NoDate = true; } }

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  • const ready only local copies

    - by robUK
    Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a ready-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on ready-only local copies, as it confirms to anyone reading my code that it is a ready-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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  • Single C++/CLI method to wrap many type specific C functions

    - by T33C
    I am wrapping a C library using C++/CLI so that the C library can be used easily from C# in a C#'ish way. Some of the functions in this library are for putting a value into a container. There are no generics in C so there exists a function per type CLIB_SetBool(BOOL value), CLIB_SetInt(int value), CLIB_SetString(char* string) and so on. To make it easier to use from C#, I have created a single Set function which takes a System::Object. I have two related questions: With my method how would you use a switch statement on the type of System::Object to call the correct CLIB_Setxxxx function. [typeid is only for unmanaged code and I can't seem to use GetType.] Is there a better way to wrap these functions like using a Generic? [I started using template specialisation but then realised that C# doesn't see templates.] Thanks.

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  • Resolve circular typedef dependency?

    - by Nick
    What is the best way to resolve the following circular dependency in typedef-ing these structs? Note the C language tag - I'm looking for a solution in standard gcc C. typedef struct { char* name; int age; int lefthanded; People* friends; } Person; typedef struct { int count; int max; Person* data; } People;

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  • How to call a function from a shared library?

    - by Frank
    What is the easiest and safest way to call a function from a shared library / dll? I am mostly interested in doing this on linux, but it would be better if there were a platform-independent way. Could someone provide example code to show how to make the following work, where the user has compiled his own version of foo into a shared library? // function prototype, implementation loaded at runtime: std::string foo(const std::string); int main(int argc, char** argv) { LoadLibrary(argv[1]); // loads library implementing foo std::cout << "Result: " << foo("test"); return 0; } BTW, I know how to compile the shared lib (foo.so), I just need to know an easy way to load it at runtime.

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  • SQL tables using VARCHAR with UTF8 (with respect to multi byte character length)

    - by Elius
    Like in Oracle VARCHAR( 60 CHAR ) I would like to specify a varchar field with variable length depending on the inserted characters. for example: create table X (text varchar(3)) insert into X (text) VALUES ('äöü') Should be possible (with UTF8 as the default charset of the database). On DB2 I got this Error: DB2 SQL Error: SQLCODE=-302, SQLSTATE=22001 (Character data, right truncation occurred; for example, an update or insert value is a string that is too long for the column, or a datetime value cannot be assigned to a host variable, because it is too small.) I'm looking for solutions for DB2, MsSql, MySql, Hypersonic.

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  • MySQLi String comparisons using keys

    - by asdasd
    I have a table with lets say 2 columns. id number, and value. Value is a string (var char). Lets say i have a number x, and a list of numbers a1, a2, a3, a4, a5..... where x is not in the list. All of these numbers correspond to a unique row in the table. I want to know if the string value for x in the table is contained in one of the string values for any table entry for a1, a2, a3, a4... Lets say i have these rows: x, aaa a1, bbb a2, ccc a3, ddd a4, aaabbbcc then i want somehow a confirmation that yes, the value for x is included in one of the values in my list of numbers (a4 contains x). I know i can do this in a couple queries and shove it down some PHP and get my answer. But can i do this with one query?

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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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  • Oracle spatial search within distance

    - by KA_lin
    I have the following table Cities: ID(int),City(char),latitude(float),longitude(float). Now based on a user`s longitude(ex:44.8) and latitude(ex:46.3) I want to search for all the cities near him within 100 miles/KM. I have found some examples but don`t know how to adapt them to my case select * from GEO.Cities a where SDO_WITHIN_DISTANCE([I don`t know], MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(44.8,46.3, NULL) ,NULL, NULL), 'distance = 1000') = 'TRUE'; Any help would be appreciated. P.S: If it is possible to have the distance and to be sorted P.P.S: I want to do it in this way due to performance issues, I have done this in this way http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL but it takes too long...

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  • Reading long lines from text file

    - by sonofdelphi
    I am using the following code for reading lines from a text-file. What is the best method for handling the case where the line is greater than the limit SIZE_MAX_LINE? void TextFileReader::read(string inFilename) { ifstream xInFile(inFilename.c_str()); if(!xInFile){ return; } char acLine[SIZE_MAX_LINE + 1]; while(xInFile){ xInFile.getline(acLine, SIZE_MAX_LINE); if(xInFile){ m_sStream.append(acLine); //Appending read line to string } } xInFile.close(); }

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  • Create 2nd tables and add data

    - by Tyler Matema
    I have this task from school, and I am confuse and lost on how I got to do this. So basically I have to create 2 tables to the database but I have to created from php. I have created the first table, but not the second one for some reason. And then, I have to populate first and second tables with 10 and 20 sample records respectively, populate, does it mean like adding more fake users? if so is it like the code shown below? *I got error on the populating second part as well Thank you so much for the help. <?php $host = "host"; $user = "me"; $pswd = "password"; $dbnm = "db"; $conn = @mysqli_connect($host, $user, $pswd, $dbnm); if (!$conn) die ("<p>Couldn't connect to the server!<p>"); $selectData = @mysqli_select_db ($conn, $dbnm); if(!$selectData) { die ("<p>Database Not Selected</p>"); } //1st table $sql = "CREATE TABLE IF NOT EXISTS `friends` ( `friend_id` INT NOT NULL auto_increment, `friend_email` VARCHAR(20) NOT NULL, `password` VARCHAR(20) NOT NULL, `profile_name` VARCHAR(30) NOT NULL, `date_started` DATE NOT NULL, `num_of_friends` INT unsigned, PRIMARY KEY (`friend_id`) )"; //2nd table $sqlMyfriends = "CREATE TABLE `myfriends` ( `friend_id1` INT NOT NULL, `friend_id2` INT NOT NULL, )"; $query_result1 = @mysqli_query($conn, $sql); $query_result2 = @mysqli_query($conn, $sqlMyfriends); //populating 1st table $sqlSt3="INSERT INTO friends (friend_id, friend_email, password, profile_name, date_started, num_of_friends) VALUES('NULL','[email protected]','123','abc','2012-10-25', 5)"; $queryResult3 = @mysqli_query($dbConnect,$sqlSt3) //populating 2nd table $sqlSt13="INSERT INTO myfriends VALUES(1,2)"; $queryResult13=@mysqli_query($dbConnect,$sqlSt13); mysqli_close($conn); ?>

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