Re: No match for 'operator<<' in '((HttpRequest*

Dear advanced c/g++ programers:

   I have a simple program from book C++ cookbook, page 291, 8.3, Using
Constructors and Destructors to manage
resources (or RAII), but it can not get compiled in my g++
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// Example 8-3. Using constructors and destructors
#include<iostream>
#include<string>
using namespace std;
class Socket {
public:
    Socket(const string& hostname) {}
};
class HttpRequest {
public:
   HttpRequest (const string& hostname) :
      sock_(new Socket(hostname)) {}
   void send(string soapMsg) {sock_<< soapMsg; }
   ~HttpRequest () {delete sock_;}
private:
    Socket* sock_;
};
void sendMyData(string soapMsg, string host) {
    HttpRequest req(host);
    req.send(soapMsg);
    // Nothing to do here, because when req goes out of scope
    // everything is cleaned up.
}
int main() {
    string s = "xml";
    sendMyData(s, "www.oreilly.com");
}
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my test compile fail as
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eric@eric-laptop:~/cppcookbook/ch8$ g++ Example8-3.cpp
Example8-3.cpp: In member function ?void
HttpRequest::send(std::string)?:
Example8-3.cpp:13:39: error: no match for ?operator<<? in
?((HttpRequest*)this)->HttpRequest::sock_<< soapMsg?
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