istringstream

问题 I am trying to read a .txt file line by line: vector<vector<int>> iVecGrid; vector<int> iVecRow; ifstream text; text.open("grid.txt", ios::in); if (!text) { cout << "Error!\n"; return EXIT_FAILURE; } istringstream isLine; string sLine; while (getline(text, sLine)) { isLine.str(sLine); int iNumber; while (isLine >> iNumber) { cout << iNumber << " "; iVecRow.push_back(iNumber); } cout << endl; iVecGrid.push_back(iVecRow); iVecRow.clear(); } When I put isLine inside the while (getline(text,

问题 I have some code that utilizes fork, execlp, and wait to make two processes. The objective is to be able to repeatedly print a prompt and have the user enter a command with up to 4 arguments/options to the command. int main() { string command, argument; istringstream iss(argument); do { //prompt user for command to run cout << "Enter command: "; cin >> command >> argument; int pid, rs, status; //fork will make 2 processes pid = fork(); if(pid == -1) { perror("fork"); exit(EXIT_FAILURE); } if

问题 So istringstream copies the contents of a string when initialised, e.g string moo("one two three four"); istringstream iss(moo.c_str()); I was wondering if there's a way to make std::istringstream use the given c_str as its buffer without copying things. This way, it won't have to copy large bits of memory before passing the std::istringstream& to functions that take istream& as an argument. What I've been trying to do is convert some functions which only take std::ifstream& arguments (they

问题 Data saved in my file is (white spaces added at both beginning and end on purpose for this test): 1 2 3 Loading the data using the code below with or without "std::ws" does not cause any difference. So I am confused by the role of "std::ws" as I have seen code using it. Can someone explain a little bit? Thanks! void main () { ifstream inf; inf.open ("test.txt"); double x=0, y=0, z=0; string line; getline(inf, line); istringstream iss(line); //Using "std::ws" here does NOT cause any difference

问题 I am coding in Eclipse and have something like the following: #include <ftream> #include <iostream> void read_file(){ char buffer[1025]; std::istringstream iss(buffer); } However, when I try to build, I get the following error: variable 'std::istringstream iss' has initializer but incomplete type Any quick thoughts? I have googled around and it seems like most people with this problem simply did not include the right header files which I believe I am doing correctly. 回答1: You need this

问题 I'm trying to set the internal buffer of an input stream, but my implementation in C++17 doesn't implement pubsetbuf() for istringstream. I've tried some other techniques, but they are slow or copy the original buffer. I'm looking for a fast method that doesn't do any copying. It's closely related to this question about an output stream: Setting the internal buffer used by a standard stream (pubsetbuf) I've followed it closely, but the buffer for the input stream remains uninitialised/empty.

问题 I have a question about the following code that tokenizes a string (separates the tokens by space). #include <iostream> #include <iterator> #include <sstream> #include <string> #include <vector> using namespace std; int main() { string s="And I feel fine ..."; istringstream ss(s); vector<string> tokens{istream_iterator<string>(ss),{}}; for(auto& elem: tokens) cout << elem << endl; } This works perfectly fine. On the other hand, if I try to pass a temporary istringstream object to istream

问题 Why does my program not output: 10 1.546 ,Apple 1 instead of 10 1 <empty space> here's my program: #include <iostream> #include <string> #include <sstream> using namespace std; int main () { string str = "10,1.546,Apple 1"; istringstream stream (str); int a; double b; string c, dummy; stream >> a >> dummy >> b >> dummy >> c; cout << a << endl; cout << b << endl; cout << c << endl; return 0; } Basically I am trying to parse the comma-separated strings, any smoother way to do this would help me

问题 I am currently trying to read in characters into a class that looks like this struct data { string segment; string name; double length; double radius; double wall_thickness; double young_modulus; double compliance; }; I also have a vector that contains the following elements: 2A Aorta_Ascendens 2 1.47 .164 4 53.4 2B Aorta_Ascendens 2 1.44 .161 4 51.0 3A I want to read in the text file into each part, and currently this is my algorithm to continuously read through the text file and add each

问题 In the following function, I try to see if a string s is convertible to type T by seeing if I can read a type T , and if the input is completely consumed afterwards. I want template <class T> bool can_be_converted_to(const std::string& s, T& t) { std::istringstream i(s); i>>std::boolalpha; i>>t; if (i and i.eof()) return true; else return false; } However, can_be_converted_to<bool>("true") evaluates to false, because i.eof() is false at the end of the function. This is correct, even though