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  • why this signal handler is called infinitely

    - by lz_prgmr
    I am using Mac OS 10.6.5, g++ 4.2.1. And meet problem with following code: #include <iostream> #include <sys/signal.h> using namespace std; void segfault_handler(int signum) { cout << "segfault caught!!!\n"; } int main() { signal(SIGSEGV, segfault_handler); int* p = 0; *p = 100; return 1; } It seems the segfault_handler is called infinitely and keep on print: segfault caught!!! segfault caught!!! segfault caught!!! ... I am new to Mac development, do you have any idea on what happened?

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  • Strange error that I've never encounter in c++ before, anyone know what it means?

    - by Silmaril89
    Hi, I won't post any code, because there is too much that could be relevant. But When I run my program it prints Internal Bad Op Name! : Success Anybody even know what that means? I'm using g++ to compile my code and nowhere in my code do I cout anything even remotely close to something like that. I don't know where it's coming from. Also, any suggestions as to figure out where in the code it's coming from, maybe using gdb somehow to do that? Thanks!

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  • Problem with basic program using Boost Threads in c++

    - by Eternal Learner
    I have a simple program which creates and executes as thread using boost threads in c++. #include<boost/thread/thread.hpp> #include<iostream> void hello() { std::cout<<"Hello, i am a thread"<<std::endl; } int main() { boost::thread th1(&hello); th1.join(); } The compiler throws an error against the th1.join() line. It says " Multiple markers at this line - undefined reference to `boost::thread::join()' - undefined reference to `boost::thread::~thread()' "

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  • What's the bug in the following code ?

    - by Johannes
    #include <iostream> #include <algorithm> #include <vector> #include <boost/array.hpp> #include <boost/bind.hpp> int main() { boost::array<int, 4> a = {45, 11, 67, 23}; std::vector<int> v(a.begin(), a.end()); std::vector<int> v2; std::transform(v.begin(), v.end(), v2.begin(), boost::bind(std::multiplies<int>(), _1, 2)); std::copy(v2.begin(), v2.end(), std::ostream_iterator<int>(std::cout, " ")); } When run, this gives a creepy segmentation fault. Please tell me where I'm going wrong.

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  • String vectors not working as expected with newline and iterators? (C++)

    - by kevin
    I have a text file made of 3 lines: Line 1 Line 3 (Line 1, a blank line, and Line 3) vector<string> text; vector<string>::iterator it; ifstream file("test.txt"); string str; while (getline(file, str)) { if (str.length() == 0) str = "\n"; // since getline discards the newline character, replacing blank strings with newline text.push_back(str); } // while for (it=text.begin(); it < text.end(); it++) cout << (*it); Prints out: Line 1 Line 3 I'm not sure why the string with only a newline was not printed out. Any help would be appreciated. Thanks.

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  • Using pow() for large number

    - by g4ur4v
    I am trying to solve a problem, a part of which requires me to calculate (2^n)%1000000007 , where n<=10^9. But my following code gives me output "0" even for input like n=99. Is there anyway other than having a loop which multilplies the output by 2 every time and finding the modulo every time (this is not I am looking for as this will be very slow for large numbers). #include<stdio.h> #include<math.h> #include<iostream> using namespace std; int main() { unsigned long long gaps,total; while(1) { cin>>gaps; total=(unsigned long long)powf(2,gaps)%1000000007; cout<<total<<endl; } }

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  • Why isn't the copy constructor elided here?

    - by Jesse Beder
    (I'm using gcc with -O2.) This seems like a straightforward opportunity to elide the copy constructor, since there are no side-effects to accessing the value of a field in a bar's copy of a foo; but the copy constructor is called, since I get the output meep meep!. #include <iostream> struct foo { foo(): a(5) { } foo(const foo& f): a(f.a) { std::cout << "meep meep!\n"; } int a; }; struct bar { foo F() const { return f; } foo f; }; int main() { bar b; int a = b.F().a; return 0; }

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  • C++ Interpreter: How to emit error messages?

    - by Rawr
    I want to emit dynamic error messages like all interpreters do nowadays, for example: Name error: Undefined variable would be constant, however what I want to reach is: Name error: Undefined variable 'X', in line 1 Okay. The line number was really no problem: Every error message must have a line number, so I added it to the error emitter function: Error( ErrType type, string msg, int line ); So where is my problem? How do I get the 'X' into Undefined variable *? I can't use sprintf as it doesn't support strings yet I use them everywhere I can't simply use cout and connect everything as I want error messages to be supressable I'd like to get everything into one function like above, Error() How do I put together dynamic error messages? For example: Error( Name, sprintf("Undefined variable %s", myVariableName ), lineNum ); (But myVariableName is a string and sprintf will mess things up)

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  • c++ lists question

    - by mousey
    I want put a value from front of the list into an another list but I am getting an error. for exmaple List<int> li; List<int> li2; ............. ............. li2.push_back(li.front()); // this statement doesnt work for me. Can someone please help me. example code: list li; list li2; li.push_back(1); li.push_back(2); li.push_back(3); for(int i=0;i<3;i++) { cout<<li.front()<<endl; li2.push_back(li.pop_front()); }

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  • Simple 'database' in c++

    - by DevAno1
    Hello. My task was to create pseudodatabase in c++. There are 3 tables given, that store name(char*), age(int), and sex (bool). Write a program allowing to : - add new data to the tables - show all records - sort tables with criteria : - name increasing/decreasing - age increasing/decreasing - sex Using function templates is a must. Also size of arrays must be variable, depending on the amount of records. I have some code but there are still problems there. Here's what I have: Function tabSize() for returning size of array. But currently it returns size of pointer I guess : #include <iostream> using namespace std; template<typename TYPE> int tabSize(TYPE *T) { int size = 0; size = sizeof(T) / sizeof(T[0]); return size; } How to make it return size of array, not its pointer ? Next the most important : add() for adding new elements. Inside first I get the size of array (but hence it returns value of pointer, and not size it's of no use now :/). Then I think I must check if TYPE of data is char. Or am I wrong ? // add(newElement, table) template<typename TYPE> TYPE add(TYPE L, TYPE *T) { int s = tabSize(T); //here check if TYPE = char. If yes, get the length of the new name int len = 0; while (L[len] != '\0') { len++; } //current length of table int tabLen = 0; while (T[tabLen] != '\0') { tabLen++; } //if TYPE is char //if current length of table + length of new element exceeds table size create new table if(len + tabLen > s) { int newLen = len + tabLen; TYPE newTab = new [newLen]; for(int j=0; j < newLen; j++ ){ if(j == tabLen -1){ for(int k = 0; k < len; k++){ newTab[k] = } } else { newTab[j] = T[j]; } } } //else check if tabLen + 1 is greater than s. If yes enlarge table by 1. } Am I thinking correct here ? Last functions show() is correct I guess : template<typename TYPE> TYPE show(TYPE *L) { int len = 0; while (L[len] == '\0') { len++; } for(int i=0; i<len; i++) { cout << L[i] << endl; } } and problem with sort() is as follows : Ho can I influence if sorting is decreasing or increasing ? I'm using bubble sort here. template<typename TYPE> TYPE sort(TYPE *L, int sort) { int s = tabSize(L); int len = 0; while (L[len] == '\0') { len++; } //add control increasing/decreasing sort int i,j; for(i=0;i<len;i++) { for(j=0;j<i;j++) { if(L[i]>L[j]) { int temp=L[i]; L[i]=L[j]; L[j]=temp; } } } } And main function to run it : int main() { int sort=0; //0 increasing, 1 decreasing char * name[100]; int age[10]; bool sex[10]; char c[] = "Tom"; name[0] = "John"; name[1] = "Mike"; cout << add(c, name) << endl; system("pause"); return 0; }

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  • Floating point innacuracies

    - by Greg
    While writing a function which will perform some operation with each number in a range I ran into some problems with floating point inaccuracies. The problem can be seen in the code below: #include <iostream> using namespace std; int main() { double start = .99999, end = 1.00001, inc = .000001; int steps = (end - start) / inc; for(int i = 0; i <= steps; ++i) { cout << (start + (inc * i)) << endl; } } The problem is that the numbers the above program outputs look like this: 0.99999 0.999991 0.999992 0.999993 0.999994 0.999995 0.999996 0.999997 0.999998 0.999999 1 1 1 1 1 1.00001 1.00001 1.00001 1.00001 1.00001 1.00001 They only appear to be correct up to the first 1. What is the proper way to solve this problem?

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  • an error "variable of field declared void"

    - by lego69
    I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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  • C++ - defining static const integer members in class definition

    - by HighCommander4
    My understanding is that C++ allows static const members to be defined inside a class so long as it's an integer type. Why, then, does the following code give me a linker error? #include <algorithm> #include <iostream> class test { public: static const int N = 10; }; int main() { std::cout << test::N << "\n"; std::min(9, test::N); } The error I get is: test.cpp:(.text+0x130): undefined reference to `test::N' collect2: ld returned 1 exit status Interestingly, if I comment out the call to std::min, the code compiles and links just fine (even though test::N is also referenced on the previous line). Any idea as to what's going on? My compiler is gcc 4.4 on Linux.

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  • Overloaded function print

    - by Olga Shirokova
    For one of the assignments I need to create an overloaded function print that prints an element or all elements of an array. I have no problem with printing the entire array: for( int i = 0; i < size; i++) cout << list [ i ] <<endl; But how do I make the same function to print only one particular element? The way I see it is to ask a user what to print, either one element or all numbers. Or am I missing something here?

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  • Why won't this static_cast in C++ work?

    - by samoz
    When I try to use a static_cast to cast a double* to an int*, I get the following error: invalid static_cast from type ‘double*’ to type ‘int*’ Here is the code: #include <iostream> int main() { double* p = new double(2); int* r; r=static_cast<int*>(p); std::cout << *r << std::endl; } I understand that there would be problems converting between a double and an int, but why is there a problem converting between a double* and an int*?

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  • How do I insert format str and don't remove the matched regular expression in input string in boost:

    - by Yadollah
    I want to put space between punctuations and other words in a sentence. But boost::regex_replace() replaces the punctuation with space, and I want to keep a punctuation in the sentence! for example in this code the output should be "Hello . hi , " regex e1("[.,]"); std::basic_string<char> str = "Hello.hi,"; std::basic_string<char> fmt = " "; cout<<regex_replace(str, e1, fmt)<<endl; Can you help me?

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  • What is a cross-platform way to get the current directory?

    - by rubenvb
    I need a cross-platform way to get the current working directory (yes, getcwd does what I want). I thought this might do the trick: #ifdef _WIN32 #include <direct.h> #define getcwd _getcwd // stupid MSFT "deprecation" warning #elif #include <unistd.h> #endif #include <string> #include <iostream> using namespace std; int main() { string s_cwd(getcwd(NULL,0)); cout << "CWD is: " << s_cwd << endl; } I got this reading: _getcwd at MSDN getcwd at Kernel.org getcwd at Apple.com There should be no memory leaks, and is should work on a Mac as well, correct?

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  • Why is 'using namespace std;' considered a bad practice in C++?

    - by Mana
    Okay, sorry for the simplistic question, but this has been bugging me ever since I finished high school C++ last year. I've been told by others on numerous occasions that my teacher was wrong in saying that we should have "using namespace std;" in our programs, and that std::cout and std::cin are more proper. However, they would always be vague as to why this is a bad practice. So, I'm asking now: Why is "using namespace std;" considered bad? Is it really that inefficient, or risk declaring ambiguous vars(variables that share the same name as a function in std namespace) that much? Or does this impact program performance noticeably as you get into writing larger applications? I'm sorry if this is something I should have googled to solve; I figured it would be nice to have this question on here regardless in case anyone else was wondering.

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  • arrays declaration and addressing

    - by avinash
    I have a few straightforward questions:- Is the following correct according to a normal c++ compiler? int arr[3][4]; void func(int *a, int m, int n) { int i,j; cin>>i>>j; cout<< a[i*n + j]; //is this way of addressing correct provided 0<=i<m and 0<=j<n } int main() { func((int*)arr, 3,4); } If the bounds of an array strictly has to be a constant expression, why doesn't the following generate compiler errors? int func(int m, int n) { int arr[m][n]; //m and n are not known until run time }

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  • strenge exception phenomenon in win7

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

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  • Using Boost statechart, how can I transition to a state unconditionally?

    - by nickb
    I have a state A that I would like to transition to its next state B unconditionally, once the constructor of A has completed. Is this possible? I tried posting an event from the constructor, which does not work, even though it compiles. Thanks. Edit: Here is what I've tried so far: struct A : sc::simple_state< A, Active > { public: typedef sc::custom_reaction< EventDoneA > reactions; A() { std::cout << "Inside of A()" << std::endl; post_event( EventDoneA() ); } sc::result react( const EventDoneA & ) { return transit< B >(); } }; This yields the following runtime assertion failure: Assertion failed: get_pointer( pContext_ ) != 0, file /includ e/boost/statechart/simple_state.hpp, line 459

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  • Correct Exceptions in C++

    - by Dr.Ackula
    I am just learning how to handle errors in my C++ code. I wrote this example that looks for a text file called some file, and if its not found will throw an exception. #include <iostream> #include <fstream> using namespace std; int main() { int array[90]; try { ifstream file; file.open("somefile.txt"); if(!file.good()) throw 56; } catch(int e) { cout<<"Error number "<<e<<endl; } return 0; } Now I have two questions. First I would like to know if I am using Exceptions correctly. Second, (assuming the first is true) what is the benefit to using them vs an If else statement?

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  • Could someone tell me if my C++ indent style is named? (example given)

    - by Maulrus
    I'm learning C++. For me, my programming style is just what looks the best; it doesn't seem to follow the rules of any one particular style. Here's an example void f(int x){ //no space between close-paren and bracket if (!x){ cout << "x is non-zero\n"; } //closing bracket indented to the same level as the original statement } It's only slightly different for something like a class or a namespace: class myClass {}; //space between class name and bracket, otherwise the same as functions K&R style does uses that kind of bracketing for statements, but my style uses it for everything. I'd like to know if there's a name for it so I can say simply what my indent style is without having to explain using examples like these.

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  • I serialized a C++ object, how to allocate memory for it without knowing what type it is?

    - by Neo_b
    Hello, I have serialized a C++ object and I wish to allocate space for it, although I can't use the "new" operator, because I do not know the object's class. I tried using malloc(sizeof(object)), although trying to typecast the pointer to the type the serialized object is of, the program shut down. Where is the information about the object class stored? class object { public: virtual void somefunc(); int someint; }; class objectchild:public object { } object *o=(object*)malloc(sizeof(objectchild)); cout << int(dynamic_cast<objectchild*>(o)) << endl; This causes a program shutdown. Thank you 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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