The problem about a function as a functor - whyglinux @Wiki

下面的程序为什么要这样修改才可以呢？

<cstdlib>

<ctime>

<cmath>

<iostream>

<vector>

<iterator>

<algorithm>
using namespace std;

int main()
{

 vector<double> v1;
 for ( int i = 0; i < 10; ++i ) {
   v1.push_back( i );
 }
 vector<double> v2( v1.size() );

 // transform( v1.begin(), v1.end(), v2.begin(), exp );
 transform( v1.begin(), v1.end(), v2.begin(), ::exp );

 copy( v2.begin(), v2.end(), ostream_iterator<double>( cout, " " ) );
 cout << endl;

}