我有两段代码。它们在 main()
中单独使用时可以正常工作。
vector<int> v;
cout << "Enter sequance of integers "<< "(press q to quit) : ";
istream_iterator<int> start_cin(cin);
istream_iterator<int> end_of_cin;
copy(start_cin,end_of_cin,back_inserter(v));
for ( vector<int>::iterator It = v.begin();It != v.end(); It++ )
cout << *It << "\t";
cout << endl;
和
vector<string> vS;
cout << "Enter three strings : ";
for ( int i = 0; i < 3; i++ )
vS.push_back(*istream_iterator<string>(cin));
ostream_iterator<string> sIt(cout,", ");
copy(vS.begin(),vS.end(),sIt);
cout << endl;
当这两部分一起使用时,即
#include <iostream>
#include <algorithm>
#include <vector>
#include <iterator>
#include <string>
using namespace std;
int main ()
{
// first part
vector<int> v;
cout << "Enter sequance of integers "<< "(press q to quit) : ";
istream_iterator<int> start_cin(cin);
istream_iterator<int> end_of_cin;
copy(start_cin,end_of_cin,back_inserter(v));
for ( vector<int>::iterator It = v.begin();It != v.end(); It++ )
cout << *It << " \t";
cout << endl;
vector<string> vS;
cout << "Enter three strings : ";
for ( int i = 0; i < 3; i++ )
vS.push_back(*istream_iterator<string>(cin));
ostream_iterator<string> sIt(cout,", ");
copy(vS.begin(),vS.end(),sIt);
cout << endl;
return 0;
}
此处第一部分有效,但第二部分给出输出:Enter Three Strings : , , ,
。
我想知道这种行为背后的原因是什么?
谢谢。
最佳答案
copy()
完成后,cin
会处于不可读状态(!cin.good()
),由于读取“整数”q
失败。这意味着后续的 for
循环将无法读取任何内容。
添加:
cin.clear();
cin.ignore(); // To skip the unread "q"
在 for
循环之前。
编辑:
正如 James Kanze 评论的那样, 检查以确保 "q"
是 copy()
终止的原因:
...
cin.clear();
string int_read_terminator;
cin >> int_read_terminator;
if ("q" != int_read_terminator)
{
cerr << "Integer copy() failure: " << int_read_terminator << "\n";
}
else
{
...
关于c++ - istream_iterator 行为,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10171511/