问如何逐行读取文件？

struct CoordinatePai

{

    int x;

    int y;

};

std::istream& operator>>(std::istream& is, CoordinatePair& coordinates)

{

    is >> coordinates.x >> coordinates.y;

    return is;

}

#include <fstream>

#include <iterator>

#include <vector>

int main()

{

    char filename[] = "coordinates.txt";

    std::vector<CoordinatePair> v;

    std::ifstream ifs(filename);

    if (ifs) {

        std::copy(std::istream_iterator<CoordinatePair>(ifs), 

                std::istream_iterator<CoordinatePair>(),

                std::back_inserter(v));

    }

    else {

        std::cerr << "Couldn't open " << filename << " for reading\n";

    }

    // Now you can work with the contents of v

}

#include <fstream>

std::ifstream infile("thefile.txt");

int a, b;

while (infile >> a >> b)

{

    // process pair (a,b)

}

基于行的解析，使用字符串流：

#include <sstream>

#include <string>

std::string line;

while (std::getline(infile, line))

{

    std::istringstream iss(line);

    int a, b;

    if (!(iss >> a >> b)) { break; } // erro

    // process pair (a,b)

}