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  • Template class implicit copy constructor issues

    - by Nate
    Stepping through my program in gdb, line 108 returns right back to the calling function, and doesn't call the copy constructor in class A, like (I thought) it should: template <class S> class A{ //etc... A( const A & old ){ //do stuff... } //etc... }; template <class T> class B{ //etc... A<T> ReturnsAnA(){ A<T> result; // do some stuff with result return result; //line 108 } //etc... }; Any hints? I've banged my head against the wall about this for 4 hours now, and can't seem to come up with what's happening here.

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  • Table character encoding - exception in application

    - by zgnilec
    I have a code: CREATE TABLE IF NOT EXISTS Person ( name varchar(24) ... ) CHARACTER SET utf8 COLLATE utf8_polish_ci; This works OK in my application, but I read if someone put in name field a string that contains character wchich code is greater than 127, database will use 2 bytes (or more) to store this character. So i think, i will change character set to utf16: CHARACTER SET utf16 COLLATE utf16_polish_ci; But now when I run my application, exception apears: KeyNotFoundException. It apears exactly at these instructions: MySqlCommand komenda = baza.Polaczenie.CreateCommand (); komenda.CommandText = zapytanie; MySqlDataReader dr = komenda.ExecuteReader (); // HERE, at execute reader method if (dr.Read ()) ... 1) Anyone had similar problem? 2) Any idea how to use always 2 bytes/char in database field?

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  • Android internet connectivity check problem

    - by Chaoz
    Hello, I'm new to Android development and working on an Android application that requires the phone to be connected to the internet, through either Wifi, EDGE or 3G. This is the code that I'm using: public static boolean isConnected() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); return cm.getActiveNetworkInfo().isConnectedOrConnecting(); } I've also set these permissions in the manifest file: <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> This works fine in the emulator running version 1.5 of Android when 3G is enabled, but it crashes when I disable the 3G connection. My application throws a null pointer exception when I call isConnectedOrConnecting(). Hope that anyone knows the solution to this. Thanks in advance!

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  • How do I use "this" in a member function?

    - by Peter Stewart
    I've written a member function of class Node to read a tree of Nodes in postfix order. It will be called by the Node instance which is the root node of the tree. So: N.postfix(); these appear to be illeagal: *this->left.postfix(); *this->right.postfix(); What is the proper way to do this? class Node { public: const char *cargo; int depth; Node *left; Node *right void Node::postfix() { if (this==__nullptr) { return; } else { *this->left.postfix(); *this->right.postfix(); out<<*this->cargo<<"\n"; return; } };

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  • From my code, I can't trace the out of bounds exception.

    - by Matt
    public override Models.CalculationNode Parse(string expression) { var calNode = new Models.CalculationNode(); int i = expression.Length; char[] x = expression.ToCharArray(); string temp = ""; //Backwards assembly of the tree //Right Node while (!IsOperator(x[i]) && i > 0) { if (!x[i].Equals(' ')) temp = x[i] + temp; i--; } } It has been a while since I've used trees and I'm getting an out of bounds exception in the while loop.

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  • QList as a function parameter - Linking Error - LNK2019

    - by user2445136
    I have an issue with QList as a function parameter and I'll be glad if you can assist me. I have this code for example: void SpinBoxList_Enable(QList spinBoxList) { foreach(QWidget mWidget,*spinBoxList) mWidget-setEnabled(false); } and in the implemantation file I use the QList variable as a pointer: SpinBoxList_Enable(&controlBoardSpinBoxList); ( controlBoardSpinBoxList is a variable of QList ). The Function ToggleBoards_Slot(bool) is a slot that uses When I compile, I get this error message: 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Disable(class QList *)" (?SpinBoxList_Disable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "public: void __cdecl CMosaixSerialNumber::ToggleBoards_Slot(bool)" (?ToggleBoards_Slot@CMosaixSerialNumber@@QEAAX_N@Z) 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Enable(class QList *)" (?SpinBoxList_Enable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "private: void __cdecl CMosaixSerialNumber::on_ControlBoardCheckBox_StateChanged(int)" (?on_ControlBoardCheckBox_StateChanged@CMosaixSerialNumber@@AEAAXH@Z) How can I fix this ? Thanks, EVH671

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  • Why would I get a bus error or segmentation fault when calling free() normally?

    - by chucknelson
    I have a very simple test program, running on Solaris 5.8: #include <stdio.h> #include <stdlib.h> int main(void) { char *paths; paths = getenv("PATH"); printf("Paths: %s\n", paths); free(paths); // this causes a bus error return 0; } If I don't call free() at the end, it displays the message fine and exits. If I include the free() call, it crashes with a bus error. I've had other calls to free(), in other programs, cause segmentation faults as well. Even if I allocate the memory for *paths myself, free() will cause a bus error. Is there some reason trying to free up the memory is causing a crash?

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  • How to build up a lookup table in microcontroller?

    - by GiGi
    Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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  • Glib hash table replace

    - by Robert
    I'm using GLib Hash Table. I'm trying to get the current value of the key that I found and then increment its value. I'm not quite sure how can I replace the existing value. typedef struct { gchar *key; guint my_int; } my_struct; char *v; v = g_hash_table_lookup(table, my_struct.key); if (v == NULL) g_hash_table_insert(table, g_strdup(my_struct.key), (gpointer)(my_struct.my_int)); else g_hash_table_replace() // here I'd like to do something like current_val+1 Any ideas will be appreciate it.

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  • How can I require an attribute on a class definition?

    - by spoulson
    Is there a way to enforce a compile requirement for certain attributes on a class or interface implementation? For example, let's say my application uses a series of static classes that contain const int resource values. I'd like to decorate the class in a Description attribute to describe its contents. In concept, I'd like to apply this attribute requirement to an interface, then each static class would implement it with its required Description. I could write a run-time check or a unit test to check compliance. But really a compile-time check would be best. Is there such a thing?

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  • Does a static object within a function introduce a potential race condition?

    - by Jeremy Friesner
    I'm curious about the following code: class MyClass { public: MyClass() : _myArray(new int[1024]) {} ~MyClass() {delete [] _myArray;} private: int * _myArray; }; // This function may be called by different threads in an unsynchronized manner void MyFunction() { static const MyClass _myClassObject; [...] } Is there a possible race condition in the above code? Specifically, is the compiler likely to generate code equivalent to the following, "behind the scenes"? void MyFunction() { static bool _myClassObjectInitialized = false; if (_myClassObjectInitialized == false) { _myClassObjectInitialized = true; _myClassObject.MyClass(); // call constructor to set up object } [...] } ... in which case, if two threads were to call MyFunction() nearly-simultaneously, then _myArray might get allocated twice, causing a memory leak? Or is this handled correctly somehow?

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  • how to parse from command line arguements in yacc ?

    - by user205688
    how to parse from command line arguements in yacc ? of course i undefined input in both lex & yacc and then wrote int input(void) { printf("in input\n:"); char c; if(target > limit) return 0; if((c = target[0][offset++]) != '\0') return (c); target++; offset =0; return (' '); } where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.

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  • not able to select hidden link - selenium

    - by Maddy
    I have to select web link when i mouse hover to particular frame in the webpage, the button(link to next page) will be visible. WebElement mainElement = driver.findElement(By.xpath(<frame xpath >)); Actions builder = new Actions(driver); builder.moveToElement(mainElement); WebElement button1 = driver.findElement(By.xpath("//*[@id='currentSkills']/div[1]/div/a")); builder.moveToElement(button1).click().perform(); I am still unable to select the particular link when i execute, the following error am getting org.openqa.selenium.ElementNotVisibleException: Element is not currently visible and so may not be interacted with (WARNING: The server did not provide any stacktrace information) Command duration or timeout: 131 milliseconds But when i hover mouse pointer to the particular frame during AUT(just to move to particular frame without clicking anything), then test is executing sucessfully. I know this can be handled by JS. But i want to find out is there any solution within selenium webdriver Your help is much appreciated... Thanks Madan

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  • reading a file that doesn't exist

    - by John
    Hi, I have got a small program that prints the contents of files using the system call - read. unsigned char buffer[8]; size_t offset=0; size_t bytes_read; int i; int fd = open(argv[1], O_RDONLY); do{ bytes_read = read(fd, buffer, sizeof(buffer)); printf("0x%06x : ", offset); for(i=0; i<bytes_read; ++i) { printf("%c ", buffer[i]); } printf("\n"); offset = offset + bytes_read; }while(bytes_read == sizeof(buffer)); Now while running I give a file name that doesn't exist. It prints some kind of data mixed with environment variables and a segmentation fault at the end. How is this possible? What is the program printing? Thanks, John

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  • A question on vectors, pointers and iterators

    - by xbonez
    Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated. Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions: what type is p? what type is *p? what code provides the address of the actual Thingie? what code provides the actual Thingie?

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  • How can I highlight the line of text that is closest to the mouse?

    - by Aaron Digulla
    I have a long text and I'd like to offer the user a reading help: The current line should be highlighted. To make it easier, I'll just use the Y coordinate of the mouse (this way, the mouse pointer isn't going to get in the way). I have a big DIV with the id content which fills the whole width and a small DIV with the class content for the text (see here for an example). I'm using jQuery 1.4. How can I highlight the line of text that is closest to the current mouse position?

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  • How to get this to compile?

    - by ShaChris23
    I have this code which compiles and works as expected: class Right {}; class Left { public: Left& operator = (Right const&) { //... Do something ... return *this; } }; int main() { Right right; Left left; // Assign individual object -- this works left = right; } But now, this one surprises me, I thought the template would work itself out since I already provided the = operator() to the Left class. int main() { ... std::list<Right> rightLst; std::list<Left> leftLst; // Assign a list of objects -- this doesn't compile leftLst = rightLst; } What can I do so that I could convert the rightLst to leftLst conversion in a single line?

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  • Why does a delegate with no parameters compile?

    - by Ryan
    I'm confused why this compiles: private delegate int MyDelegate(int p1, int p2); private void testDelegate() { MyDelegate imp = delegate { return 1; }; } MyDelegate should be a pointer to a method that takes two int parameters and returns another int, right? Why am I allowed to assign a method that takes no parameters? Interestingly, these doesn't compile (it complains about the signature mismatches, as I'd expect) private void testDelegate() { // Missing param MyDelegate imp = delegate(int p1) { return 1; }; // Wrong return type MyDelegate imp2 = delegate(int p1, int p2) { return "String"; }; } Thanks for any help! Ryan

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  • Double indirection and structures passed into a function

    - by ZPS
    I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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  • C++0x, How do I expand a tuple into variadic template function arguments?

    - by Gustaf
    Consider the case of a templated function with variadic template arguments: template<typename Tret, typename... T> Tret func(const T&... t); Now, I have a tuple t of values. How do I call func() using the tuple values as arguments? I've read about the bind() function object, with call() function, and also the apply() function in different some now-obsolete documents. The GNU GCC 4.4 implementation seems to have a call() function in the bind() class, but there is very little documentation on the subject. Some people suggest hand-written recursive hacks, but the true value of variadic template arguments is to be able to use them in cases like above. Does anyone have a solution to is, or hint on where to read about it?

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  • Check if a SQL table exists.

    - by Carra
    What's the best way to check if a table exists in a Sql database in a database independant way? I came up with: bool exists; const string sqlStatement = @"SELECT COUNT(*) FROM my_table"; try { using (OdbcCommand cmd = new OdbcCommand(sqlStatement, myOdbcConnection)) { cmd.ExecuteScalar(); exists = true; } } catch (Exception ex) { exists = false; } Is there a better way to do this? This method will not work when the connection to the database fails. I've found ways for Sybase, SQL server, Oracle but nothing that works for all databases.

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  • How to save checkbox checked values in Database

    - by user1298215
    How to save checkbox values in database. Below is my view code. @foreach (var item in Model) { @Html.CheckBox("statecheck", (IEnumerable<SelectListItem>)ViewData["StatesList"]) @Html.DisplayFor(modelItem => item.state_name) </br> } <input class="ASPbutton" type="submit" value="submit"/> Below is My controller. public ActionResult States() { ViewData["StatesList"] = new SelectList(am.FindUpcomingStates().ToList(), "state_id", "state_Name"); return View(); } My model is public IQueryable<state> FindUpcomingStates() { return from state in Adm.states orderby state.state_name select state; } After clicking submit button checked item state_id will be saved into database. I wrote like below in Controller, but i got true or false values, i want state_id [AcceptVerbs(HttpVerbs.Post)] public ActionResult States(string _stateName, char[] statecheck, FormCollection formvalues) { statecheck = Request.Form["statecheck"].ToArray(); ViewData["StatesList"] = new SelectList(am.FindUpcomingStates222().ToList(), "state_id", "state_id", _stateName); }

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  • C optimization breaks algorithm

    - by Halpo
    I am programming an algorithm that contains 4 nested for loops. The problem is at at each level a pointer is updated. The innermost loop only uses 1 of the pointers. The algorithm does a complicated count. When I include a debugging statement that logs the combination of the indexes and the results of the count I get the correct answer. When the debugging statement is omitted, the count is incorrect. The program is compiled with the -O3 option on gcc. Why would this happen?

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  • MySQL : incrementing text id in DB

    - by BarsMonster
    I need to have text IDs in my application. For example, we have acceptable charset azAZ09, and allowed range of IDs [aaa] - [cZ9]. First generated id would be aaa, then aab, aac, aad e.t.c. How one can return ID & increment lower bound in transaction-fashion? (provided that there are hundreds of concurrent requests and all should have correct result) To lower the load I guess it's possible to define say 20 separate ranges, and return id from random range - this should reduce contention, but it's not clear how to do single operation in the first place. Also, please note that number of IDs in range might exceed 2^32. Another idea is having ranges of 64-bit integers, and converting integer-char id in software code, where it could be done asyncroniously. Any ideas?

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