The speed difference is largely due to the iostream I/O functions maintaining synchronization with the C I/O functions. We can turn this off with a call to std::ios::sync_with_stdio(false); By default standard C++ streams are synchronized to the standard C stream after each input/output operation. Once synchronization is turned off, the C++ standard streams are allowed … Read more
push_back might cause a reallocation of the data contained in the vector. And that reallocation will make all iterators to the vector invalid. Dereferencing invalid iterators leads to undefined behavior. Indexes into the vector will continue to stay valid, unless you remove elements from the vector. 2 solved Vector iterators incompatible error for a vector … Read more
It appears that what you want is for your Derived class to support the following interface: someInfo si; someMoreInfo smi; Base* pB = new Derived; // Setting info pB->setInfo(si); // Set the `Base::c` member of `*pB` pB->setInfo(smi); // Set the `Derived::g` member of `*pB` // Getting info someInfo pB_si = pB->getInfo(); // Get `Base::c` from … Read more
Your code looks like a weird mixture of C and C++. You are using malloc to allocate dynamic memory, which does not invoke C++ objects’ constructors. You should use new/delete (or even better, smart pointers) if you want to dynamically allocate memory. Any idea why this would be? The reason why your code doesn’t work … Read more
It seems that you don’t have a main function defined. 0 solved Compilation on Linux – In function ‘_start’: (.text+0x20): undefined reference to ‘main’ [closed]
You cannot declare a member variable of a class like that. Declare it as: typedef std::pair <int, int> MyMove; static const MyMove my_no_move; And then define it outside the class as: // The typedef MyMove is also scoped const ConnectFourState::MyMove ConnectFourState::my_no_move(-1, -1); 3 solved not able to compile code with “std::pair” [closed]
Option #1 #include <cstddef> #include <type_traits> #include <utility> #include <tuple> template <typename A, typename B> struct merge_tuples { static_assert(std::tuple_size<A>::value == std::tuple_size<B>::value, “!”); template <std::size_t… Is> static auto merge(std::index_sequence<Is…>) noexcept -> std::tuple<typename std::decay<decltype(std::declval<typename std::tuple_element<Is, A>::type>() + std::declval<typename std::tuple_element<Is, B>::type>()) >::type…>; using type = decltype(merge(std::make_index_sequence<std::tuple_size<A>::value>{})); }; DEMO Option #2 #include <type_traits> #include <utility> template <typename A, typename … Read more
You are expecting the cast from int to unsigned int to simply change the sign of a negative value while maintaining its magnitude. But that isn’t how it works in C or C++. when it comes to overflow, unsigned integers follow modular arithmetic, meaning that assigning or initializing from negatives values such as -1 or … Read more
A binary operator member should only take one parameter, the right-hand argument – the left-hand argument is *this. template<int NMAX> typename FastOut<NMAX>::Flags FastOut<NMAX>::operator&(Flags rhs) const { // Return *this & rhs } solved I can’t get enum class operators to work
This is not standard C++ program. Zero size arrays are not allowed in C & C++. You should use -pedantic-errors command line option if you are using g++ & clang++ compiler to strictly confirm to the standard & disable any compiler extensions. See live demo here. Clang++ says source_file.cpp:7:14: error: zero size arrays are an … Read more
Why sscanf is not handling or ignoring spaces in c++? How else should sscanf seperate words/tokens? From its documentation: [“%s”] matches a sequence of non-whitespace characters (a string) I don’t think you can handle this with sscanf or in a one-liner at all. You could do this with std::string::find_first_of and std::string::substr Edit: std::regex_match might be … Read more
&& students[i].grupa = gr Blockquote in above code, = is an assignment operator you need == for a comparison operator 2 solved C++: Cannot compare double from an array of structures to another double in if function [closed]
Use ONE of the file-handling routines in C++ or C. Mixing FILE and ifstream is certain to cause problems. ifstream input; input.open(“time.in”); input>> hrs; input.get(); … should do the trick. If you want to be picky: if (input.get() != ‘:’) … complain about bad input … 0 solved How can I double a time value … Read more
This was (apparently) changed in C11. C99§6.7/3: If an identifier has no linkage, there shall be no more than one declaration of the identifier (in a declarator or type specifier) with the same scope and in the same name space, except for tags as specified in 6.7.2.3. C11§6.7/3: If an identifier has no linkage, there … Read more
You don’t show this in the code posted, but it appears you have two different definitions for black_screen, one global and one inside the main function. The one inside main has been initialized properly, but the global one is a bad pointer. The segmentation fault is the result of undefined behavior from dereferencing the bad … Read more