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  • C++ Segmentation fault in binary_function

    - by noryb009
    I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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  • Operator Overloading for Queue C++

    - by Josh
    I was trying to use the overload operator method to copy the entries of one queue into another, but I am going wrong with my function. I don't know how else to access the values of the queue "original" any other way than what I have below: struct Node { int item; Node* next; }; class Queue { public: [...] //Extra code here void operator = (const Queue &original); protected: Node *front, *end; } void Queue::operator=(const Queue &original) { //THIS IS WHERE IM GOING WRONG while(original.front->next != NULL) { front->item = original.front->item; front->next = new Node; front = front->next; original.front = original.front->next; } }

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  • Appropriate data structure for a buffer of the packets

    - by psihodelia
    How to implement a buffer of the packets where each packet is of the form: typedef struct{ int32 IP; //4-byte IP-address int16 ID; //unique sequence id }t_Packet; What should be the most appropriate data structure which: (1) allows to collect at least 8000 such packets (fast Insert and Delete operations) (2) allows very fast filtering using IP address, so that only packets with given IP will be selected (3) allows very fast find operation using ID as a key (4) allows very fast (2), then (3) within filtered results ? RAM size does matter, e.g. no huge lookup table is possible to use.

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  • Write to a binary file?

    - by rick irby
    Here is data structure w/ variables: struct Part_record { char id_no[3]; int qoh; string desc; double price: }; --- (Using "cin" to input data) --- Part_record null_part = {" ", 0," ",0.0}; --- --- file.seekg( -(long)sizeof(Part_record), ios::cur); file.write( ( char *)&part, sizeof(Part_record) ); The three variables, qoh, Id_no & price, write out correctly, but the "desc" variable is not right. Do I need to initialize Part_record some other way? It should be 20 characters in length. If you have enough info here, pls share your advice,thanks.

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  • Initialising structs in C++

    - by Neil Butterworth
    As an addendum to this question, what is going on here: #include <string> using namespace std; struct A { string s; }; int main() { A a = {0}; } Obviously, you can't set a std::string to zero. Can someone provide an explanation (backed with references to the C++ Standard, please) about what is actually supposed to happen here? And then explain for example): int main() { A a = {42}; } Are either of these well-defined? Once again an embarrassing question for me - I always give my structs constructors, so the issue has never arisen before.

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  • timer_getoverrun() doesn't behave as expected when using sleep()

    - by dlp
    Here is a program that uses a POSIX per-process timer alongside the sleep subroutine. The signal used by the timer has been set to SIGUSR1 rather than SIGALRM, since SIGALRM may be used internally by sleep, but it still doesn't seem to work. I have run the program using the command line timer-overruns -d 1 -n 10000000 (1 cs interval) so, in theory, we should expect 100 overruns between calls to sigwaitinfo. However, timer_getoverrun returns 0. I have also tried a version using a time-consuming for loop to introduce the delay. In this case, overruns are recorded. Does anyone know why this happens? I am running a 3.4 Linux kernel. Program source /* * timer-overruns.c */ #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <signal.h> #include <time.h> // Signal to be used for timer expirations #define TIMER_SIGNAL SIGUSR1 int main(int argc, char **argv) { int opt; int d = 0; int r = 0; // Repeat indefinitely struct itimerspec its; its.it_interval.tv_sec = 0; its.it_interval.tv_nsec = 0; // Parse arguments while ((opt = getopt(argc, argv, "d:r:s:n:")) != -1) { switch (opt) { case 'd': // Delay before calling sigwaitinfo() d = atoi(optarg); break; case 'r': // Number of times to call sigwaitinfo() r = atoi(optarg); break; case 's': // Timer interval (seconds) its.it_interval.tv_sec = its.it_value.tv_sec = atoi(optarg); break; case 'n': // Timer interval (nanoseconds) its.it_interval.tv_nsec = its.it_value.tv_nsec = atoi(optarg); break; default: /* '?' */ fprintf(stderr, "Usage: %s [-d signal_accept_delay] [-r repetitions] [-s interval_seconds] [-n interval_nanoseconds]\n", argv[0]); exit(EXIT_FAILURE); } } // Check sanity of command line arguments short e = 0; if (d < 0) { fprintf(stderr, "Delay (-d) cannot be negative!\n"); e++; } if (r < 0) { fprintf(stderr, "Number of repetitions (-r) cannot be negative!\n"); e++; } if (its.it_interval.tv_sec < 0) { fprintf(stderr, "Interval seconds value (-s) cannot be negative!\n"); e++; } if (its.it_interval.tv_nsec < 0) { fprintf(stderr, "Interval nanoseconds value (-n) cannot be negative!\n"); e++; } if (its.it_interval.tv_nsec > 999999999) { fprintf(stderr, "Interval nanoseconds value (-n) must be < 1 second.\n"); e++; } if (e > 0) exit(EXIT_FAILURE); // Set default values if not specified if (its.it_interval.tv_sec == 0 && its.it_interval.tv_nsec == 0) { its.it_interval.tv_sec = its.it_value.tv_sec = 1; its.it_value.tv_nsec = 0; } printf("Running with timer delay %d.%09d seconds\n", (int) its.it_interval.tv_sec, (int) its.it_interval.tv_nsec); // Will be waiting for signals synchronously, so block the one in use. sigset_t sigset; sigemptyset(&sigset); sigaddset(&sigset, TIMER_SIGNAL); sigprocmask(SIG_BLOCK, &sigset, NULL ); // Create and arm the timer struct sigevent sev; timer_t timer; sev.sigev_notify = SIGEV_SIGNAL; sev.sigev_signo = TIMER_SIGNAL; sev.sigev_value.sival_ptr = timer; timer_create(CLOCK_REALTIME, &sev, &timer); timer_settime(timer, TIMER_ABSTIME, &its, NULL ); // Signal handling loop int overruns; siginfo_t si; // Make the loop infinite if r = 0 if (r == 0) r = -1; while (r != 0) { // Sleeping should cause overruns if (d > 0) sleep(d); sigwaitinfo(&sigset, &si); // Check that the signal is from the timer if (si.si_code != SI_TIMER) continue; overruns = timer_getoverrun(timer); if (overruns > 0) { printf("Timer overrun occurred for %d expirations.\n", overruns); } // Decrement r if not repeating indefinitely if (r > 0) r--; } return EXIT_SUCCESS; }

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  • iOS get file size on disk

    - by F2_CMD
    I'm trying to get the size on disk of a file in iOS using Objective C. As of now I've been able to get the actual size of the file and other file information using NSFileManager and then getting the attributes attributesOfItemAtPath:error but not the size on disk. I also tried getting the file size from struct stat but again it doesn't give me size on disk.I tried using NSTask to make a call to du -h but iOS didn't allow me to fork other processes. Any ideas are welcome :) I know this questions is similar to many others but the difference is that I'm trying to do this in iOS and most of the methods used in other systems don't work here. Thanks

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  • pointer to const member function typedef

    - by oldcig
    I know it's possible to separate to create a pointer to member function like this struct K { void func() {} }; typedef void FuncType(); typedef FuncType K::* MemFuncType; MemFuncType pF = &K::func; Is there similar way to construct a pointer to a const function? I've tried adding const in various places with no success. I've played around with gcc some and if you do template deduction on something like template <typename Sig, typename Klass> void deduce(Sig Klass::*); It will show Sig with as a function signature with const just tacked on the end. If to do this in code it will complain that you can't have qualifiers on a function type. Seems like it should be possible somehow because the deduction works.

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  • Statically initialize anonymous union in C++

    - by wpfwannabe
    I am trying to statically initialize the following structure in Visual Studio 2010: struct Data { int x; union { char ch; const Data* data; }; }; The following is fails with error C2440: 'initializing' : cannot convert from 'Data *' to 'char'. static Data d1; static Data d = {1, &d1}; I have found references to some ways this can be initialized properly but none of them work in VS2010. Any ideas?

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  • C/C++ memory usage API in Linux/Windows

    - by minjang
    I'd like to obtain memory usage information for both per process and system wide. In Windows, it's pretty easy. GetProcessMemoryInfo and GlobalMemoryStatusEx do these jobs greatly and very easily. For example, GetProcessMemoryInfo gives "PeakWorkingSetSize" of the given process. GlobalMemoryStatusEx returns system wide available memory. However, I need to do it on Linux. I'm trying to find Linux system APIs that are equivalent GetProcessMemoryInfo and GlobalMemoryStatusEx. I found 'getrusage'. However, max 'ru_maxrss' (resident set size) in struct rusage is just zero, which is not implemented. Also, I have no idea to get system-wide free memory. Current workaround for it, I'm using "system("ps -p %my_pid -o vsz,rsz");". Manually logging to the file. But, it's dirty and not convenient to process the data. I'd like to know some fancy Linux APIs for this purpose.

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  • [C#] How to share a variable between two classes?

    - by Altefquatre
    Hello, How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it? Thanks Altefquatre

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  • How to force a deep copy when copying structs with arrays?

    - by Danvil
    If have a struct A { public double[] Data; public int X; } How can I force a deep copy when using operator= or adding instances of A to a container? The problem is for example: A a = new A(); var list = new List<A>(); list.Add(a); // does not make a deep copy of Data A b = a; // does not make a deep copy of Data Do I really have to implement my own DeepClone method and call it every time? This would be extremly error-prone ...

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  • Global list in C/gtk+

    - by sterh
    Hello, I need in global list in my gtk+ application, i use for it GList: For example: I have structure: typedef struct _data { Glist list; }Data; I want to use one copy of the list in the whole program: I have a function bulid my list: gboolean build_list() { Data->list = g_list_append(mw->a, "First "); Data->list = g_list_append(mw->a, "Second "); Data->list = g_list_append(mw->a, "Third "); g_list_foreach(Data->list, (GFunc)printf, NULL); } After calling this function to display all items in the list. zbut when i try to make it in another function - for example: void foreach() { g_list_foreach(Data->list, (GFunc)printf, NULL); } I see error in gdb: *Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0xb7335700 (LWP 5364)] 0xb765a7d7 in strchrnul () from /lib/i686/cmov/libc.so.6 * How can i create global list in my application? Thank you.

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  • Where does output of print in kernel go?

    - by apoorv020
    I am debugging a driver for linux (specifically ubuntu server 9.04), and there are several printf statements in the code. Where can I view the output of these statements? EDIT1: What i'm trying to do is write to kernel using the proc file-system. The print code is static int proc_fractel_config_write(struct file *file, const char *argbuf, unsigned long count, void *data) { printk(KERN_DEBUG "writing fractel config\n"); ... In kern.log when I see the following message when i try to overwrite the file /proc/net/madwifi/ath1/fractel_config (with varying time of course). [ 8671.924873] proc write [ 8671.924919] Any explainations?

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  • Working with Form Array's in Coldfusion?

    - by Jakub
    I have no idea how to handle this in coldfusion 9, I have a form being submitted (POST) with element checkboxes, called items[]. When I do a <cfdump var="#form#" /> no-problem, I get all the items shown with the proper names like items[] eg: struct ITEMS[] 13,14 FIELDNAMES ITEMS[] however doing a <cfdump var="#form.items[]#" /> results in an error. How do I access the CF9 field values? Somehow loop through it? I cannot seem to do anything with the array to get the id's out of it? Thoughts, I'm kindof stumped and coldfusion isn't the easiest language to find examples / references on the net ;) Is there a correct way to deal with this? I need to get the ID's out of there so I can referenc what lines were checked in the form, so I can follow up with an action. Thanks!

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  • How to get proper alignment when printing to file

    - by user1067334
    I have this Structure the elements of which that I need to write in a text file struct Stage3ADisplay { int nSlot; char *Item; char *Type; int nIndex; unsigned char attributesMD[17]; //the last character is \0 unsigned char contentsMD[17]; //only for regular files - //the last character is \0 }; buffer = malloc(sizeof(Stage3ADisplayVar[nIterator]->nSlot) + sizeof(Stage3ADisplayVar[nIterator]->Item) + sizeof(Stage3ADisplayVar[nIterator]->Type) + sizeof(Stage3ADisplayVar[nIterator]->nIndex) + sizeof(Stage3ADisplayVar[nIterator]->attributesMD) + sizeof(Stage3ADisplayVar[nIterator]->contentsMD) + 1); sprintf (buffer,"%d %s %s %d %x %x",Stage3ADisplayVar[nIterator]->nSlot, Stage3ADisplayVar[nIterator]->Item,Stage3ADisplayVar[nIterator]->Type,Stage3ADisplayVar[nIterator]->nIndex,Stage3ADisplayVar[nIterator]->attributesMD,Stage3ADisplayVar[nIterator]->contentsMD); How do I make sure the rows in the file are properly aligned. Thank you.

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  • measuring uncertainty in matlabs svmclassify

    - by Mark
    I'm doing contextual object recognition and I need a prior for my observations. e.g. this space was labeled "dog", what's the probability that it was labeled correctly? Do you know if matlabs svmclassify has an argument to return this level of certainty with it's classification? If not, matlabs svm has the following structures in it: SVM = SupportVectors: [11x124 single] Alpha: [11x1 double] Bias: 0.0915 KernelFunction: @linear_kernel KernelFunctionArgs: {} GroupNames: {11x1 cell} SupportVectorIndices: [11x1 double] ScaleData: [1x1 struct] FigureHandles: [] Can you think of any ways to compute a good measure of uncertainty from these? (Which support vector to use?) Papers/articles explaining uncertainty in SVMs welcome. More in depth explanations of matlabs SVM are also welcome. If you can't do it this way, can you think of any other libraries with SVMs that have this measure of uncertainty?

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  • Go - Concurrent method

    - by nevalu
    How to get a concurrent method? In my case, the library would be called from a program to get a value to each argument str --in method Get()--. When it's used Get() then it assigns a variable from type bytes.Buffer which it will have the value to return. The returned values --when it been concurrently called-- will be stored into a database or a file and it doesn't matter that its output been of FIFO way (from method). type test struct { foo uint8 bar uint8 } func NewTest(arg1 string) (*test, os.Error) {...} func (self *test) Get(str string) ([]byte, os.Error) { var format bytes.Buffer ... } I think that all code inner of method Get() should be put inner of go func() {...}(), and then to use a channel. Would there be a problem if it's called another method from Get()? Or would it also has to be concurrent?

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  • Using module include in OCaml

    - by Geoff
    In OCaml 3.11, I want to "extend" an existing module using the include directive, like so: module MyString = struct include String let trim s = ... end No problem. But now I want to expose this module's type explicitly (i.e. in a .mli file). I want something like this: module MyString : sig include String val trim : string -> string end But the include syntax is not correct because String refers to a module, not a module type (and the compiler does indeed barf). How can I refer to the module type for String here (without having write it out explicitly in a sig expression)? Thanks!

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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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  • Is there a way to know if std::chrono::monotonic_clock is defined?

    - by Vicente Botet Escriba
    C++0X N3092 states that monotonic_clock is optional. 20.10.5.2 Class monotonic_clock [time.clock.monotonic] 1 Objects of class monotonic_clock represent clocks for which values of time_point never decrease as physical time advances. monotonic_clock may be a synonym for system_clock if system_clock::is_monotonic is true. ** 2 The class monotonic_clock is conditionally supported.** Is there a way using SFINAE or another technique to define a traits class that states if monotonic_clock is defined? struct is_monotonic_clock_defined; If yes, how? If not, shouldn't the standard define macro that gives this information at preprocessing time?

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  • C# GDI - How to check if a Pixel is opaque or not?

    - by rkawano
    I am using a method to get a pixel of the image to check if this point is transparent or not. I am using GetPixel that returns a System.Drawing.Color with a 32bit color info. This struct have the "A" property where I can get the alpha value of pixel, according to this MSDN topic. Code: using (Bitmap bmp = new Bitmap(path)) { Color pixel = bmp.GetPixel(0, 0); if (pixel.A == 0) // This is a fully transparent pixel else // This is not a fully transparent pixel } When I use this method with a fully transparent PNG images it returns 0. When I run with a white semi-transparent images, it will give me other values starting on 1 and up to 86, where 86 are given for images with a 100% alfa (full opaque). But with opaque JPEG images, the "A" property are giving me all sort of values like 56, 71, 86, 129, and others, depending on image. But these pixels are fully opaques! How are the correct way to check if a pixel is opaque or not?

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  • Using C++ is a Linked-List implementation without using pointers possible or not?

    - by sonicoder
    My question is very simply, can one using C++, implment a link-list data structure without using pointers (next nodes)? To further qualify my question, I'm mean can one create a Linked-List data structure using only class instantiations. A common node definition might be like so: template<typename T> struct node { T t; node<T>* next; node<T>* prev; }; I'm aware of std::list etc, I'm just curious to know if its possible or not - and if so how? code examples will be greatly appreciated.

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  • How are value types implemented in .NET

    - by Michael
    Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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