stdvector

问题 In one of my projects it is necessary to remove certain elements from a std::vector<double> values . The indices I have to remove are given as a vector of intervals. For example {1,3} means, that I have to remove indices from 1 to 3 inclusive from values . I can assume that the intervals given are mutually exclusive. The code shown below illustrates, what the desired behavior should look like. #include <iostream> #include <vector> int main(int argc, char** args) { // Intervals of indices I

问题 I'm currently working on a graph library for C++ and now got stuck at a point where I get an assertion error in debug mode during runtime. I also had a look an some other question here on SO but none of the questions and answers lead me to a solution. After reading in some forums I have the impression that this error happens because iterators become invalid as soon as the vector content is changed. (for example when using erase() ) But as you can see in my code, I'm not modifying the vector,

问题 Look at this code. #include <vector> template<class ...Args> using other_vector = std::vector<Args...>; template<class T> void f(std::vector<T>& ) {} template<class T> void f(other_vector<T>& ) {} int main() { other_vector<int> b; f(b); return 0; } It does not compile, because f is being redeclared. I totally understand the error. However, I need a second class that behaves like std::vector<T> , but will be seen as a different type, so that overloading, like in the above example, would be

问题 I'm wondering if there is prettier syntax for this to get a normal pointer (not an iterator) to the last element in a C++ vector std::vector<int> vec; int* ptrToLastOne = &(*(vec.end() - 1)) ; // the other way I could see was int* ptrToLastOne2 = &vec[ vec.size()-1 ] ; But these are both not very nice looking! 回答1: int* ptrToLastOne = &vec.back(); // precondition: !vec.empty() 回答2: int* ptrToLast = &(vec.back()); // Assuming the vector is not empty. 回答3: Some more options: int* ptrToLast = &

问题 I have a class with parse(int argc, char* argv[]) function which I have to use to set a desired state of an object. I'm taking the parameters from the gui using stringstream and then I'm trying to convert them to char** to pass them to the function. Here's what I've got: std::stringstream sstream; sstream << "-clip" << " " << min_x_entry.get_text() << " " << max_x_entry.get_text(); // etc. std::cout << sstream.str(); // All looks good here std::vector<std::string> args; std::vector<char*>

问题 I've been trying to write a Finite State Machine in VHDL code for a simple 16-bit processor I'm implementing on an Altera DE1 board. In the Finite State Machine, I have a CASE statement that handles the different 16-bit instructions, which are brought into the FSM by a 16-bit STD_LOGIC_VECTOR. However, I'm having a little trouble in the decode state where the Finite State Machine decodes the instruction. One of the instructions is an ADD which takes two registers as operands and a third as

问题 I have a std::vector as part of a class, that contains a custom type. Its contents seems to be mysteriously changed from somewhere in the program. I am having trouble trying to figure out where this is happening. Is there a way to "watch" the contents (or size) of a std::vector from gdb? Thanks. 回答1: Is there a way to "watch" the contents (or size) of a std::vector from gdb? Assuming you are using GCC, set watchpoints on theVector->_M_impl._M_start and _M_finish . If you are using some other

问题 I wish to store a large vector of d-dimensional points (d fixed and small: <10). If I define a Point as vector<int> , I think a vector<Point> would store in each position a pointer to a Point. But if define a Point as a fixed-size object like: std::tuple<int,int,...,int> or std::array<int, d> , will the program store all points in contiguous memory or will the additional level of indirection remain? In case the answer is that arrays avoid the additional indirection, could this have a large

问题 I'm compiling a C++ library which defines a single function that randomly samples from a set of data points. The data points are stored in a std::vector . There are 126,272 std::vector push_back statements, where the vector in question is of type double . It is taking a long time to compile. Why would this take so long? (All the code other than the std::vector push_back statements would take less than 1 second to compile, because there's very little other code.) 回答1: There is the -ftime

问题 I need to copy std::set to std::vector : std::set <double> input; input.insert(5); input.insert(6); std::vector <double> output; std::copy(input.begin(), input.end(), output.begin()); //Error: Vector iterator not dereferencable Where is the problem? 回答1: You need to use a back_inserter : std::copy(input.begin(), input.end(), std::back_inserter(output)); std::copy doesn't add elements to the container into which you are inserting: it can't; it only has an iterator into the container. Because