0
我學習C++。在我的簡單代碼下方,但我在下一個代碼行遇到問題:爲什麼我在我的ifstream中有一個無限循環?
while(is >> p) vp.push_back(p); // TODO: here I have a problem...
在指定的行中,我收到無限循環。爲什麼會發生?我期望得到'eof'(即!)並退出循環。
/*
main.cpp
© AB, 10/06/2013
Chapter 10, Exercise 1.
*/
//-------------------------------------------------------------------------------------------------
#include <exception>
#include <iostream>
#include <string>
#include <vector>
#include<fstream>
using namespace std;
// Some structure...
struct Point{
int x, y;
Point(int xx, int yy): x(xx), y(yy){}
Point(): x(0), y(0) {}
};
ostream& operator << (ostream& os, const Point& p){
os << p.x << ',' << p.y;
return os;
}
istream& operator >> (istream& is, Point& p){
char ch;
int x,y;
if((cin >> x >> ch >> y) && ch == ',') p = Point(x,y);
return is;
}
//=================================================================================================
int main()
try{
vector<Point> vp;
Point p;
while(cin){
// Get some data...
cout << "x,y: ";
cin >> p;
if(cin) vp.push_back(p);
}
// print
for(int i = 0; i < vp.size(); ++i) cout << vp[i] << ' ';
cin.clear();
string s;
// save to file
cout << endl << "Output file name: ";
if(!(cin >> s)) throw runtime_error("Invalid output file name.");
{ // create output stream
ofstream os(s.c_str());
if(!os) throw runtime_error("Can't open file: " + s);
for(int i = 0; i < vp.size(); ++i) os << vp[i] << ' ';
} // here ofstream erased
cout << "Read back..." << endl;
vp.clear();
ifstream is(s.c_str()); // create input stream
if(!is) throw runtime_error("Can't open file: " + s);
while(is >> p) vp.push_back(p); // TODO: here I have a problem...
for(int i = 0; i < vp.size(); ++i) cout << vp[i] << ' '; // print
}
catch(exception& e){
cerr << e.what() << endl;
return 1;
}
catch(...){
cerr << "Unknown exception." << endl;
return 2;
}
謝謝。
因爲在你的'operator >>(istream&is,Point&p)'你正在使用'cin'而不是'is'。 – dyp
@DyP這應該是一個答案。 – Angew
@DyP,謝謝!我是一隻盲驢.... :))) –