std

问题 We are given some int el_position number which is a position of wanted by us element in flatened representation of our 2d vector ( std::vector< std::vector<int> > matrix(5, std::vector<int>(4)) ). Meaning if we had such matrix 11 21 31 41 51 61 71 81 91 101 and we were given el_position == 7 we would need to get second element of second row. Is it possible to do such thing withstd stl 2d vector? How to get value of element by given its position in flattened array? 回答1: Sure this is possible:

问题 I was experimenting with assembly code and the GTK+ 3 libraries when I discovered that my application turns into a zombie if I don't link the object file with gcc against the standard library. Here is my code for the stdlib -free application %include "gtk.inc" %include "glib.inc" global _start SECTION .data destroy db "destroy", 0 ; const gchar* strWindow db "Window", 0 ; const gchar* SECTION .bss window resq 1 ; GtkWindow * SECTION .text _start: ; gtk_init (&argc, &argv); xor rdi, rdi xor

问题 I'm referring to Refbase.h, Refbase.cpp and StrongPointer.h In the Android implementation of strong pointer, any strong-pointer based object must inherit refbase i.e. sp<TheClass> theObj // TheClass must inherit from class RefBase This requirement can be seen in the code for one of sp 's methods: template<typename T> sp<T>& sp<T>::operator =(T* other) { if (other != NULL) { other->incStrong(this); } if (mPtr != NULL) { mPtr->decStrong(this); } mPtr = other; return *this; } In order for call

问题 I have a simple application in qt and I'm trying to link some code that I have to it. However, when I'm merging the files in the project, it compiles, but I get an error at startup. When I try to debug it, I get a pop up message telling me Executable error : During startup program exited with code 0xc0000139. I searched in google and I found that it's probably a dll error. I've got to admit, I don't really know how libraries work so I'm a bit confused. I trying to import the code functions by

问题 I encounter an issue while using the noexcept specifier on derived classes, more precisely when the parent is an abstract class (has protected constructors). Hereafter is an example of the way I declare my classes. With a public constructor in the base class: Everything is ok. Same code with protected and the derived class is no more "nothrow movable". Do I miss something? Is std::is_nothrow_move_constructible the correct traits to use in derived class declarations or should I use something

问题 Exploring a valgrind report in search of a huge memleak, it seems that the following line produces the biggest threat over lots of calls: std::remove_copy_if(raw_word.begin(), raw_word.end(), std::back_inserter(word), std::ptr_fun<int, int>(&std::ispunct)); CODE char * payload = /* acquire somehow */ int whitespace; char * p_word = NULL; for(whitespace = 0; whitespace < payload_len; whitespace ++) { if(isspace(payload[whitespace])) { payload[whitespace] = 0; if(p_word != NULL) { std::string

问题 I'm a newcomer to C++ and Qt. I've been messing around with Qt Creator for a few days, and what really struck me was how the GUI components only accepted a const QString& rather than a string or an std::wstring . To stay consistent with this, I've been trying to accept and return QString from most of my function calls, however I find myself converting to and from std::string a lot to use most of the standard library facilities. My question here is, what's the purpose of QString if std::string

问题 I've seen similar questions on here but I can't seem to apply the solutions to my problem. I have a variable called $results which I got from an API. I'll change the proper nouns so as to protect my work's customers: stdClass Object ( [out] => stdClass Object ( [count] => 2 [transactions] => stdClass Object ( [RealTimeCommissionDataV2] => Array ( [0] => stdClass Object ( [adId] => 12345678 [advertiserId] => 123456789 [advertiserName] => Chuck E. Cheese, inc. [commissionAmount] => 50 [country]

问题 I have the following code -: int main() { set<string> s; s.insert( "asas" ); s.insert( "abab" ); for ( auto item : s ) { cout << item << "\n"; reverse( item.begin(), item.end() ); } cout << "\n"; for ( auto item : s ) { cout << item << "\n"; } } Output -: abab asas abab asas The elements of the set are not being modified at all by the reverse() function. I suspect that the elements inside a set cannot be modified at all. But, if this is the case, why doesn't the compiler give an error in the

问题 Even after reading many online resources and other questions, including template argument type deduction from std::function return type with lambda and Argument type auto deduction and anonymous lambda functions, I am struggling with clearly expressing the following in c++. I would like to avoid duplicate template arguments, which seem unnecessary. For example, container 'H' of generic type 'A' has a generic method 'M' for generic type 'B'. This expresses my intent for 'H' and method 'M':