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  • When are temporaries created as part of a function call destroyed?

    - by Michael Mrozek
    Is a temporary created as part of an argument to a function call guaranteed to stay around until the called function ends, even if the temporary isn't passed directly to the function? There's virtually no chance that was coherent, so here's an example: class A { public: A(int x) : x(x) {printf("Constructed A(%d)\n", x);} ~A() {printf("Destroyed A\n");} int x; int* y() {return &x;} }; void foo(int* bar) { printf("foo(): %d\n", *bar); } int main(int argc, char** argv) { foo(A(4).y()); } If A(4) were passed directly to foo it would definitely not be destroyed until after the foo call ended, but instead I'm calling a method on the temporary and losing any reference to it. I would instinctively think the temporary A would be destroyed before foo even starts, but testing with GCC 4.3.4 shows it isn't; the output is: Constructed A(4) foo(): 4 Destroyed A The question is, is GCC's behavior guaranteed by the spec? Or is a compiler allowed to destroy the temporary A before the call to foo, invaliding the pointer to its member I'm using?

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  • multiple dependent android projects in eclipse

    - by lope
    Hi there! I just started to play with android dev and java+eclipse is pretty new to me. I managed to create simple project and run it on my device. Now I want to create simple game (more of them actually) and I would love to use shared code base for all of them (game loop, initialization, etc..). Problem is that I have no idea how to correctly do this. I created android project called engine with all basic stuff that I need and made it work on device. Now I tried to create another project in same workspace called mygame. Main class (activity) of mygame is MyGameApp which inherits from EngineApp (main activity of my engine project) which inherits from Activity. I added engine project into required projects in mygame build path tab in properties. Problem is that when I try to run this project it crashes on ClassNotFoundException trying to find my MyGameApp class. Any help (or pointer to some articles that explain how this is done) is greatly appreciated. few hours of googling didn't help much :/

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  • Why does this CSS button mess with <a> tags?

    - by Ian McCullough
    Here is my CSS button { border: 0 none; cursor: pointer; padding: 0 15px 0 0; text-align: center; height: 30px; line-height: 30px; width: auto; } button a { color:white; text-decoration:none; } button.rounded { background: transparent url(/images/button/btn_right.png) no-repeat scroll right top; clear: left; font-size: 0.8em; } button span { display: block; padding: 0 0 0 15px; position: relative; white-space: nowrap; height: 30px; line-height: 30px; } button.rounded span { background: transparent url(/images/button/btn_left.png) no-repeat scroll left top; color: #FFFFFF; } button.rounded:hover { background-position: 100% -30px; } button.rounded:hover span { background-position: 0% -30px; } button::-moz-focus-inner { border: none; } Here is the code for my "button" with a link in it. <button class="rounded"><span><a href="profile.php">Profile</a></span></button> The issue is it does not link to the href when i click on it. Anyone know why?

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  • Parsing string based on initial format

    - by Kayla
    I'm trying to parse a set of lines and extract certain parts of the string based on an initial format (reading a configuration file). A little more explanation: the format can contain up to 4 parts to be formatted. This case, %S will skip the part, %a-%c will extract the part and will be treated as a string, %d as int. What I am trying to do now is to come up with some clever way to parse it. So far I came up with the following prototype. However, my pointer arithmetic still needs some work to skip/extract the parts. Ultimately each part will be stored on an array of structs. Such as: struct st_temp { char *parta; char *partb; char *partc; char *partd; }; ... #include <stdio.h> #include <string.h> #define DIM(x) (sizeof(x)/sizeof(*(x))) void process (const char *fmt, const char *line) { char c; const char *src = fmt; while ((c = *src++) != '\0') { if (c == 'S'); // skip part else if (c == 'a'); // extract %a else if (c == 'b'); // extract %b else if (c == 'c'); // extract %c else if (c == 'd'); // extract %d (int) else { printf("Unknown format\n"); exit(1); } } } static const char *input[] = { "bar 200.1 / / (zaz) - \"bon 10\"", "foo 100.1 / / (baz) - \"apt 20\"", }; int main (void) { const char *fmt = "%S %a / / (%b) - \"%c %d\""; size_t i; for(i = 0; i < DIM (input); i++) { process (fmt, input[i]); } return (0); }

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  • Is this an error in "More Effective C++" in Item28?

    - by particle128
    I encountered a question when I was reading the item28 in More Effective C++ .In this item, the author shows to us that we can use member template in SmartPtr such that the SmartPtr<Cassette> can be converted to SmartPtr<MusicProduct>. The following code is not the same as in the book,but has the same effect. #include <iostream> class Base{}; class Derived:public Base{}; template<typename T> class smart{ public: smart(T* ptr):ptr(ptr){} template<typename U> operator smart<U>() { return smart<U>(ptr); } ~smart(){delete ptr;} private: T* ptr; }; void test(const smart<Base>& ) {} int main() { smart<Derived> sd(new Derived); test(sd); return 0; } It indeed can be compiled without compilation error. But when I ran the executable file, I got a core dump. I think that's because the member function of the conversion operator makes a temporary smart, which has a pointer to the same ptr in sd (its type is smart<Derived>). So the delete directive operates twice. What's more, after calling test, we can never use sd any more, since ptr in sd has already been delete. Now my questions are : Is my thought right? Or my code is not the same as the original code in the book? If my thought is right, is there any method to do this? Thanks very much for your help.

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  • pass parameter from $.post() callback to outer variable

    - by Nazmin
    basically i want to hold a parameter that retrieve value from $.post() call like this: init = function(){ var lastpage = getLastPage(); } function getLastPage(){ $.post("getInfo.php",{ last: "yes" }, function(data){ setLast(data.last); },'json'); return function setLast(data){ return data; } } so when reach at last post (last page) i should check with lastpage variable that has a value returned from getLastPage() function. I'm pretty blur with javascript pointer and all. Please help guys. update (20/4/2010): I've done the other way around, like this: init = function(){ getLastPage(); if((page+1) == $("#lastpage").val()){ alert("this is last post"); }else{ page++; //get info and display to the page here } } function getLastPage(){ $.post("getInfo.php",{ last: "yes" }, function(data){ $("#lastpage").val(data.last); },'json'); } first run the function to temporarily store the value in hidden input tag (lastpage) and then grab the value again to check it whenever i click forward button. if you all have more appropriate way please tell me.

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  • C++: getting the address of the start of an std::vector ?

    - by shoosh
    Sometimes it is useful to use the starting address of an std::vector and temporarily treat that address as the address of a regularly allocated buffer. For instance replace this: char* buf = new char[size]; fillTheBuffer(buf, size); useTheBuffer(buf, size); delete[] buf; With This: vector<char> buf(size); fillTheBuffer(&buf[0], size); useTheBuffer(&buf[0], size); The advantage of this is of course that the buffer is deallocated automatically and I don't have to worry about the delete[]. The problem I'm having with this is when size == 0. In that case the first version works ok. An empty buffer is "allocated" and the subsequent functions do nothing size they get size == 0. The second version however fails if size == 0 since calling buf[0] may rightly contain an assertion that 0 < size. So is there an alternative to the idiom &buf[0] that returns the address of the start of the vector even if the vector is empty? I've also considered using buf.begin() but according to the standard it isn't even guaranteed to return a pointer.

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  • Program using read() entering into an infinite loop

    - by Soham
    1oid ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 100000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) < 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; Message* newMessage; while(i!=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; //--------------------------------------------------- newMessage = (Message*)parser(message); MessageProcess(newMessage,AssetMap); //-------------------------------------------------- //printf("idNUM %e\n",newMessage->idNum); free(newMessage); i++; counter=0; ch =data[i]; } free(data); } Here, I have allocated 100MB of data with malloc, and passed a file big enough(not 500MB) size of 926KB about. When I pass small files, it reads and exits like a charm, but when I pass a big enough file, the program executes till some point after which it just hangs. I suspect it either entered an infinite loop, or there is memory leak. EDIT For better understanding I stripped away all unnecessary function calls, and checked what happens, when given a large file as input. I have attached the modified code void ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 500000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) < 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; while(i<=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; i++; printf("idNUM \n"); counter=0; ch =data[i]; } free(data); } What looks like is, it prints a whole lot of idNUM's and then poof segmentation fault I think this is an interesting behaviour, and to me it looks like there is some problem with memory FURTHER EDIT I changed back the i!=bytes_read it gives no segmentation fault. When I check for i<=bytes_read it blows past the limits in the innerloop.(courtesy gdb)

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  • Determining difference in timestamps for two values in the same MySQL table

    - by JayRizzo03
    I am relatively new to programming in PHP, so I apologize if this is a rather simple question. I have a MySQL database table called MachineReports that contains the following values: ReportNum(primary key, auto increment), MachineID and Timestamp Here is some example data: |ReportNum | MachineID | Timestamp | |1 | AD3203 | 2012-11-18 06:32:28| |2 | AD3203 | 2012-11-19 04:00:15| |3 | BC4300 | 2012-11-19 04:00:15| What I am attempting to do is find the difference in timestamps in seconds for each machine ID by iterating over each row set. I am getting stuck on the best way to do this, however. Here is the code I've written so far: <?php include '../dbconnect/dbconnect.php'; $machineID=[]; //Get a list of all MachineIDs in the database foreach($dbh->query('SELECT DISTINCT(MachineID) FROM MachineReports') as $row) { array_push($machineID, $row[0]); } for($i=0;$i<count($machineID);$i++){ foreach($dbh->query("SELECT MachineID FROM MachineReports WHERE MachineID='$machineID[$i]' ORDER BY MachineID") as $row) { //code to associate each machineID with two time stamps goes here } } ? This code just lists out the contents of the table row by row. My ultimate goal is to find the difference in timestamps for a certain MachineID. One of the things I've considered is using a multidimensional array in php - using the $machineID as the key and then storing the timestamp inside the array the key points to. However, I'm uncertain how to do that since my query parses row by row. I have quite a few questions. 1) Is this the most efficient way to be doing this? I suspect my database table design may not be the best. 2)What would be the best way to determine the difference in timestamps for a certain machineID? Even just a pointer to a topic that would prompt me to think about this in a different way would be helpful - I'm not afraid to do research. Thanks!

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  • geb StaleElementReferenceException

    - by Brian Mortenson
    I have just started using geb with webdriver for automating testing. As I understand it, when I define content on a page, the page element should be looked up each time I invoke a content definition. //In the content block of SomeModule, which is part of a moduleList on the page: itemLoaded { waitFor{ !loading.displayed } } loading { $('.loading') } //in the page definition moduleItems {index -> moduleList SomeModule, $("#module-list > .item"), index} //in a test on this page def item = moduleItems(someIndex) assert item.itemLoaded So in this code, I think $('.loading') should be called repeatedly, to find the element on the page by its selector, within the context of the module's base element. Yet I sometimes get a StaleElementReference exception at this point. As far as I can tell, the element does not get removed from the page, but even if it does, that should not produce this exception unless $ is doing some caching behind the scenes, but if that were the case it would cause all sorts of other problems. Can someone help me understand what's happening here? Why is it possible to get a StaleElementReferenceException while looking up an element? A pointer to relevant documentation or geb source code would be useful as well.

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  • about getadrrinfo() C++?

    - by Isavel
    I'm reading this book called beej's guide to network programming and there's a part in the book were it provide a sample code which illustrate the use of getaddrinfo(); the book state that the code below "will print the IP addresses for whatever host you specify on the command line" - beej's guide to network programming. now I'm curious and want to try it out and run the code, but I guess the code was develop in UNIX environment and I'm using visual studio 2012 windows 7 OS, and most of the headers was not supported so I did a bit of research and find out that I need to include the winsock.h and ws2_32.lib for windows, for it to get working, fortunately everything compiled no errors, but when I run it using the debugger and put in 'www.google.com' as command argument I was disappointed that it did not print any ipaddress, the output that I got from the console is "getaddrinfo: E" what does the letter E mean? Do I need to configure something out of the debugger? Interestingly I left the command argument blank and the output changed to "usage: showip hostname" Any help would be appreciated. #ifdef _WIN32 #endif #include <sys/types.h> #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> using namespace std; #include <stdio.h> #include <string.h> #include <sys/types.h> #include <winsock.h> #pragma comment(lib, "ws2_32.lib") int main(int argc, char *argv[]) { struct addrinfo hints, *res, *p; int status; char ipstr[INET6_ADDRSTRLEN]; if (argc != 2) { fprintf(stderr,"usage: showip hostname\n"); system("PAUSE"); return 1; } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version hints.ai_socktype = SOCK_STREAM; if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); system("PAUSE"); return 2; } printf("IP addresses for %s:\n\n", argv[1]); for(p = res;p != NULL; p = p->ai_next) { void *addr; char *ipver; // get the pointer to the address itself, // different fields in IPv4 and IPv6: if (p->ai_family == AF_INET) { // IPv4 struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr; addr = &(ipv4->sin_addr); ipver = "IPv4"; } else { // IPv6 struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr; addr = &(ipv6->sin6_addr); ipver = "IPv6"; } // convert the IP to a string and print it: inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr); printf(" %s: %s\n", ipver, ipstr); } freeaddrinfo(res); // free the linked list system("PAUSE"); return 0; }

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  • Accessing multiple view controllers in page controller

    - by Apple Delegates
    I am showing view in ipad like a book, single view shows two view. I want to add more views so that when view flipped third and fourth view appears and further. I am using the code below to do so. I am adding ViewControllers to array it got kill at orientation method at this line " ContentViewController *currentViewController = [self.pageViewController.viewControllers objectAtIndex:0];". - (void)viewDidLoad { [super viewDidLoad]; //Instantiate the model array self.modelArray = [[NSMutableArray alloc] init]; for (int index = 1; index <= 12 ; index++) { [self.modelArray addObject:[NSString stringWithFormat:@"Page %d",index]]; } //Step 1 //Instantiate the UIPageViewController. self.pageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil]; //Step 2: //Assign the delegate and datasource as self. self.pageViewController.delegate = self; self.pageViewController.dataSource = self; //Step 3: //Set the initial view controllers. ViewOne *one = [[ViewOne alloc]initWithNibName:@"ViewOne" bundle:nil]; viewTwo *two = [[viewTwo alloc]initWithNibName:@"ViewTwo" bundle:nil]; ContentViewController *contentViewController = [[ContentViewController alloc] initWithNibName:@"ContentViewController" bundle:nil]; contentViewController.labelContents = [self.modelArray objectAtIndex:0]; // NSArray *viewControllers = [NSArray arrayWithObject:contentViewController]; viewControllers = [NSArray arrayWithObjects:contentViewController,one,two,nil]; [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil]; //Step 4: //ViewController containment steps //Add the pageViewController as the childViewController [self addChildViewController:self.pageViewController]; //Add the view of the pageViewController to the current view [self.view addSubview:self.pageViewController.view]; //Call didMoveToParentViewController: of the childViewController, the UIPageViewController instance in our case. [self.pageViewController didMoveToParentViewController:self]; //Step 5: // set the pageViewController's frame as an inset rect. CGRect pageViewRect = self.view.bounds; pageViewRect = CGRectInset(pageViewRect, 40.0, 40.0); self.pageViewController.view.frame = pageViewRect; //Step 6: //Assign the gestureRecognizers property of our pageViewController to our view's gestureRecognizers property. self.view.gestureRecognizers = self.pageViewController.gestureRecognizers; } - (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation { if(UIInterfaceOrientationIsPortrait(orientation)) { //Set the array with only 1 view controller UIViewController *currentViewController = [self.pageViewController.viewControllers objectAtIndex:0]; NSArray *viewControllers = [NSArray arrayWithObject:currentViewController]; [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:NULL]; //Important- Set the doubleSided property to NO. self.pageViewController.doubleSided = NO; //Return the spine location return UIPageViewControllerSpineLocationMin; } else { // NSArray *viewControllers = nil; ContentViewController *currentViewController = [self.pageViewController.viewControllers objectAtIndex:0]; NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentViewController *)currentViewController labelContents]]; if(currentIndex == 0 || currentIndex %2 == 0) { UIViewController *nextViewController = [self pageViewController:self.pageViewController viewControllerAfterViewController:currentViewController]; viewControllers = [NSArray arrayWithObjects:currentViewController, nextViewController, nil]; } else { UIViewController *previousViewController = [self pageViewController:self.pageViewController viewControllerBeforeViewController:currentViewController]; viewControllers = [NSArray arrayWithObjects:previousViewController, currentViewController, nil]; } //Now, set the viewControllers property of UIPageViewController [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:NULL]; return UIPageViewControllerSpineLocationMid; } }

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  • Zend models and database relathionships

    - by user608341
    Hi people, i'm starting with Zend Framework and I'm a little bit confused with models and relathionships (one-to-many, many-to-many etc). The "Zend Framework Quick Start" says to create a Zend_Db_Table, a Data Mapper and finally our model class Suppose we have a database like this: table A ( id integer primary key, name varchar(50) ); table B ( id integer primary key, a_id integer references A ); then, i'll create: Application_Model_DbTable_A extends Zend_Db_Table_Abstract, Application_Model_AMapper, Application_Model_A, Application_Model_DbTable_B extends Zend_Db_Table_Abstract, Application_Model_BMapper, Application_Model_B, if I understood, i've to store the references informations in Application_Model_DbTable_A: protected $_dependentTables = array('B'); and Application_Model_DbTable_B: protected $_referenceMap = array( 'A' => array( 'columns' => array('a_id'), 'refTableClass' => 'A', 'refColums' => array('id') ) ); and my models class: class Application_Model_A { protected $_id; protected $_name; public function __construct(array $options = null) { if(is_array($options)) { $this->setOptions($options); } } public function __set($name, $value) { $method = 'set' . $name; if (('mapper' == $name) || !method_exists($this, $method)) { throw new Exception('Invalid property'); } $this->$method($value); } public function __get($name) { $method = 'get' . $name; if (('mapper' == $name) || !method_exists($this, $method)) { throw new Exception('Invalid property'); } return $this->$method(); } public function setOptions(array $options) { $methods = get_class_methods($this); foreach ($options as $key => $value) { $method = 'set' . ucfirst($key); if (in_array($method, $methods)) { $this->$method($value); } } return $this; } public function setName($name) { $this->_name = (string) $name; return $this; } public function getName() { return $this->_name; } public function setId($id) { $this->_id = (int) $id; return $this; } public function getId() { return $this->_id; } class Application_Model_B { protected $_id; protected $_a_id; public function __construct(array $options = null) { if(is_array($options)) { $this->setOptions($options); } } public function __set($name, $value) { $method = 'set' . $name; if (('mapper' == $name) || !method_exists($this, $method)) { throw new Exception('Invalid property'); } $this->$method($value); } public function __get($name) { $method = 'get' . $name; if (('mapper' == $name) || !method_exists($this, $method)) { throw new Exception('Invalid property'); } return $this->$method(); } public function setOptions(array $options) { $methods = get_class_methods($this); foreach ($options as $key => $value) { $method = 'set' . ucfirst($key); if (in_array($method, $methods)) { $this->$method($value); } } return $this; } public function setA_id($a_id) { $this->_a_id = (int) $a_id; return $this; } public function getA_id() { return $this->_a_id; } public function setId($id) { $this->_id = (int) $id; return $this; } public function getId() { return $this->_id; } it's that right?

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  • Another C++ question, delete not working?

    - by kyeana
    New to c++, and am having a problem with delete and destructor (I am sure i am making a stupid mistake here, but haven't been able to figure it out as of yet). When i step through into the destructor, and attepmt to call delete on a pointer, the message shows up "Cannot access memory at address some address." The relevant code is: /* * Removes the front item of the linked list and returns the value stored * in that node. * * TODO - Throws an exception if the list is empty */ std::string LinkedList::RemoveFront() { LinkedListNode *n = pHead->GetNext(); // the node we are removing std::string rtnData = n->GetData(); // the data to return // un-hook the node from the linked list pHead->SetNext(n->GetNext()); n->GetNext()->SetPrev(pHead); // delete the node delete n; n=0; size--; return rtnData; } and /* * Destructor for a linked node. * * Deletes all the dynamically allocated memory, and sets those pointers to 0. */ LinkedListNode::~LinkedListNode() { delete pNext; // This is where the error pops up delete pPrev; pNext=0; pPrev=0; }

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  • Why is the operation address incremented by two?

    - by Gavin Jones
    I am looking at a Javascript emulator of a NES to try and understand how it works. On this line: addr = this.load(opaddr+2); The opcode is incremented by two. However, the documentation (see appendix E) I'm reading says: Zero page addressing uses a single operand which serves as a pointer to an address in zero page ($0000-$00FF) where the data to be operated on can be found. By using zero page addressing, only one byte is needed for the operand, so the instruction is shorter and, therefore, faster to execute than with addressing modes which take two operands. An example of a zero page instruction is AND $12. So if the operand's argument is only one byte, shouldn't it appear directly after it, and be + 1 instead of + 2? Why +2? This is how I think it works, which may be incorrect. Suppose our memory looks like: ------------------------- | 0 | 1 | 2 | 3 | 4 | 5 | <- index ------------------------- | a | b | c | d | e | f | <- memory ------------------------- ^ \ PC and our PC is 0, pointing to a. For this cycle, we say that the opcode: var pc= 0; //for example's sake var opcode= memory[pc]; //a So shouldn't the first operand be the next slot, i.e. b? var first_operand = memory[pc + 1]; //b

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  • Internal typedef and circular dependency

    - by bcr
    I have two classes whose functions take typedefed pointers to eachother as return values and parameters. I.e.: class Segment; class Location : public Fwk::NamedInterface { public: // ===== Class Typedefs ===== typedef Fwk::Ptr<Location const> PtrConst; typedef Fwk::Ptr<Location> Ptr; // ===== Class Typedefs End ===== void segmentIs(Segment::Ptr seg); /* ... */ } and class Location; class Segment : public Fwk::NamedInterface { public: // ===== Class Typedefs ===== typedef Fwk::Ptr<Segment const> PtrConst; typedef Fwk::Ptr<Segment> Ptr; // ===== Class Typedefs End ===== void locationIs(Location::Ptr seg); /* ... */ } This understandably generated linker errors...which the forward declarations of the respective classes don't fix. How can I forward declare the Ptr and PtrConst typedefs while keeping these typedefs internal to the class (i.e. I would like to write Location::Ptr to refer to the location pointer type)? Thanks folks!

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  • Sending a message to nil?

    - by Ryan Delucchi
    As a Java developer who is reading Apple's Objective-C 2.0 documentation: I wonder as to what sending a message to nil means - let alone how it is actually useful. Taking an excerpt from the documentation: There are several patterns in Cocoa that take advantage of this fact. The value returned from a message to nil may also be valid: If the method returns an object, any pointer type, any integer scalar of size less than or equal to sizeof(void*), a float, a double, a long double, or a long long, then a message sent to nil returns 0. If the method returns a struct, as defined by the Mac OS X ABI Function Call Guide to be returned in registers, then a message sent to nil returns 0.0 for every field in the data structure. Other struct data types will not be filled with zeros. If the method returns anything other than the aforementioned value types the return value of a message sent to nil is undefined. Has Java rendered my brain incapable of grokking the explanation above? Or is there something that I am missing that would make this as clear as glass? Note: Yes, I do get the idea of messages/receivers in Objective-C, I am simply confused about a receiver that happens to be nil.

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  • php parsing csv with ftell

    - by Robert82
    I have a 500mb csv file with over 500,000 lines, each with 80 fields. I am using fget to process the file line by line. $col1 = array(); while (($row = fgetcsv($handle, 1000, ",")) !== FALSE) { $col1[] = $row[0]; } Because of an execution time limit on the PHP file by my hosting provider (120 seconds), I can't process the whole file in one run. I tried using ftell() and fseek() to remember the last position for restart. The trouble is, sometimes the ftell() position is in the middle of a row, and resuming means missing the first half of the row. Is there an elegant way to know the last line successfully processed, and resume from the one after it? I realize I can do a simple counter, and then loop through to that point again, but that would produce diminishing returns on the rows I can process towards the end of the file. Is there something like ftell() and fseek() that would work in my case? Or a way to limit ftell() to return the pointer for the end of the previous line?

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  • How do virtual destructors work?

    - by Jack
    I am using gcc. I am aware how the virtual destructors solve the problem when we destroy a derived class object pointed by a base class pointer. I want to know how do they work? class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; int main() { A * a = new B(); delete a; getch(); return 0; } When I change A's destructor to a virtual function, the problem is solved. What is the inner working for this. Why do I make A's destructor virtual.

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  • I am trying to access the individual bytes in a floating point number and I am getting unexpected results

    - by oweinh
    So I have this so far: #include <iostream> #include <string> #include <typeinfo> using namespace std; int main () { float f = 3.45; // just an example fp# char* ptr = (char*)&f; // a character pointer to the first byte of the fp#? cout << int(ptr[0]) << endl; // these lines are just to see if I get what I cout << int(ptr[1]) << endl; // am looking for... I want ints that I can cout << int(ptr[2]) << endl; // otherwise manipulate. cout << int(ptr[3]) << endl; } the result is: -51 -52 92 64 so obviously -51 and -52 are not in the byte range that I would expect for a char... I have taken information from similar questions to arrive at this code and from all discussions, a conversion from char to int is straightforward. So why negative values? I am trying to look at a four-byte number, therefore I would expect 4 integers, each in the range 0-255. I am using Codeblocks 13.12 with gcc 4.8.1 with option -std=C++11 on a Windows 8.1 device.

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  • save as .txt format

    - by user1180492
    I made a NotePad program. The problem is it doesn't save in .txt format, It save as a file with no format. But it can open .txt files. How can i fix it? Here is my work. import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.Scanner; import java.io.*; public class NotePad extends JFrame { private JTextArea noteArea; public static void main(String[] args) { NotePad p = new NotePad(); p.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); p.setSize(500,300); p.setVisible(true); } public NotePad() { super("Java Notepad"); setLayout(new BorderLayout()); noteArea = new JTextArea("",20,20); noteArea.setWrapStyleWord(true); noteArea.setLineWrap(true); Font font = new Font("sanserif", Font.BOLD,14); noteArea.setFont(font); JScrollPane scroller = new JScrollPane(noteArea); scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS); scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); add(scroller,BorderLayout.CENTER); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenuItem openMenu = new JMenuItem("Open"); openMenu.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent ae) { JFileChooser openFile = new JFileChooser(); openFile.showOpenDialog(new NotePad()); loadFile(openFile.getSelectedFile()); } }); JMenuItem saveMenu = new JMenuItem("Save"); saveMenu.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent ae) { JFileChooser saveFile = new JFileChooser(); saveFile.showSaveDialog(new NotePad()); fileSaved(saveFile.getSelectedFile()); } }); JMenuItem exitMenu = new JMenuItem("Close"); exitMenu.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent ae) { System.exit(0); } }); fileMenu.add(openMenu); fileMenu.add(saveMenu); fileMenu.add(exitMenu); menuBar.add(fileMenu); this.setJMenuBar(menuBar); } public void loadFile(File file) { noteArea.setText(""); try { BufferedReader read = new BufferedReader(new FileReader(file)); String line = null; while((line =read.readLine())!=null) { noteArea.append(line +"\n"); } read.close(); } catch (Exception e) { System.out.println("Error " + e.toString()); } } public void fileSaved(File file) { try { PrintWriter writer = new PrintWriter(file); String[] lines = noteArea.getText().split("\\n"); for (String ) { writer.println(words); } writer.close(); } catch (Exception e) { System.out.println("Error " + e.toString()); } } } btw I can't post my question because of not explaning the scenario according to the site. So there. Thanks for the help

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  • make it simpler and efficient

    - by gcc
    temp1=*tutar[1]; //i hold input in char *tutar[] if(temp1!='x'||temp1!='n') arrays[1]=malloc(sizeof(int)*num_arrays); //if second input is int a=0; n=i; for(i=1;i<n;++i) { temp1=*tutar[i]; if(temp1=='d') { ++i; j=atoi(tutar[i]); free(arrays[j]); continue; } if(temp1=='x') break; if(temp1=='n')//if it is n { a=0; ++j; arrays[j]=malloc(sizeof(int)*num_arrays);//create and allocate continue; } ++a; if(a>num_arrays) //resize the array arrays[j]=realloc(arrays[j],sizeof(int)*(num_arrays+a)); *(arrays[j]+a-1)=atoi(tutar[i]); printf("%d",arrays[1][1]); } arrays is pointer when you see x exit you see n create (old one is new array[a] new one is array[i+1]) you see d delete arrays[i] according to int after d first number is size of max arrays and where is the error in code input is composed from int and n d x i make a program -taking input(first input must be int) -according to input(there is comman in input like n or d or j , i fill array with number and use memory efficiently -j is jumb to array[x] ( x is int coming after j in input)

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  • What encoding does c32rtomb convert to?

    - by R. Martinho Fernandes
    The functions c32rtomb and mbrtoc32 from <cuchar>/<uchar.h> are described in the C Unicode TR (draft) as performing conversions between UTF-321 and "multibyte characters". (...) If s is not a null pointer, the c32rtomb function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by c32 (including any shift sequences), and stores the multibyte character representation in the array whose first element is pointed to by s. (...) What is this "multibyte character representation"? I'm actually interested in the behaviour of the following program: #include <cassert> #include <cuchar> #include <string> int main() { std::u32string u32 = U"this is a wide string"; std::string narrow = "this is a wide string"; std::string converted(1000, '\0'); char* ptr = &converted[0]; std::mbstate_t state {}; for(auto u : u32) { ptr += std::c32rtomb(ptr, u, &state); } converted.resize(ptr - &converted[0]); assert(converted == narrow); } Is the assertion in it guaranteed to hold1? 1 Working under the assumption that __STDC_UTF_32__ is defined.

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  • Returning a dynamically created array from function

    - by informer2000
    I'm trying to create a function that would dynamically allocate an array, sets the values of the elements, and returns the size of the array. The array variable is a pointer that is declared outside the function and passed as a parameter. Here is the code: #include <cstdlib> #include <iostream> using namespace std; int doArray(int *arr) { int sz = 10; arr = (int*) malloc(sizeof(int) * sz); for (int i=0; i<sz; i++) { arr[i] = i * 5; } return sz; } int main(int argc, char *argv[]) { int *arr = NULL; int size = doArray(arr); for (int i=0; i<size; i++) { cout << arr[i] << endl; } return 0; } For some reason, the program terminates on the first iteration of the for loop in main()! Am I doing something wrong?

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  • glTexImage2D + byte[]

    - by miniMe
    How can I upload pixels from a simple byte array to an OpenGl texture ? I'm using glTexImage2D and all I get is a white rectangle instead of a pixelated texture. The 9th parameter (32-bit pointer to the pixel data) is IMO the problem. I tried lots of parameter types there (byte, ref byte, byte[], ref byte[], int & IntPtr + Marshall, out byte, out byte[], byte*). glGetError() always returns GL_NO_ERROR. There must be something I'm doing wrong because it's never some gibberish pixels. It's always white. glGenTextures works correct. The first id has the value 1 like always in OpenGL. And I draw colored lines without any problem. So something is wrong with my texturing. I'm in control of the DllImport. So I can change the parameter types if necessary. GL.glBindTexture(GL.GL_TEXTURE_2D, id); int w = 4; int h = 4; byte[] bytes = new byte[w * h * 4]; for (int i = 0; i < bytes.Length; i++) bytes[i] = (byte)Utils.random(256); GL.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, w, h, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, bytes); [DllImport(GL_LIBRARY)] public static extern void glTexImage2D(uint what, int level, int internalFormat, int width, int height, int border, int format, int type, byte[] bytes);

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