c++ - 使用 istream_iterator 范围构造时无法访问 vector

Question

我试图编译此代码片段，但出现编译器错误 :( !使用 Visual Studio 2010 编译

#include <vector>
#include <string>
#include <sstream>
#include <iterator>
#include <iostream>

using namespace std;

int main() {
    string s( "Well well on" );
    istringstream in( s );
    vector<string> v( istream_iterator<string>( in ), istream_iterator<string>() );
    copy( v.begin(), v.end(), ostream_iterator<string>( cout, "\n" ) );
}

错误:

Error   1   error C2228: left of '.begin' must have class/struct/union  c:\visual studio 2008 projects\vector test\vector test\main.cpp 13  vector test
Error   2   error C2228: left of '.end' must have class/struct/union    c:\visual studio 2008 projects\vector test\vector test\main.cpp 13  vector test

发生了什么事？ vector构造正确，怎么会调用不了呢？

最好的问候，

Answer 1

我觉得是

vector<string> v( istream_iterator<string>( in ), istream_iterator<string>() );

被解析为函数声明:

vector<string> v( istream_iterator<string> in, istream_iterator<string> );

这通常称为 "C++' most-vexing parse" .

我认为一些额外的括号可以解决这个问题:

vector<string> v( (istream_iterator<string>(in)), (istream_iterator<string>()) );