这段代码有问题吗?为什么8warnings?
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>
using namespace std;
int main()
{
istream_iterator<string> is(cin);
istream_iterator<string> eof;
vector<string> text;
copy(is, eof, back_inserter(text));
sort(text.begin(), text.end());
ostream_iterator<string> os(cout, “ ”);
copy(text.begin(), text.end(), os);
return 0;
}