istringstream evaluating to boolean ?

My common convention when I want to take a string and tokenize it is as follows

Code:

---

string str = "hello world";
vector<string> vs;
istringstream iss(str);
while(iss)
{
  string t;
  iss >> t;
  vs.push_back(t);
}
cout << vs.size();

---

the vectors size is 3 in this case because the last string pushed into the vector is empty..

what does iss evaluate to when its 'empty' that causes this last iteration of an empty string being pushed?

thanks

iss does not enter a bad state (which is what your conversion to bool is checking) until a read has failed. This is the same sort of thing as the FAQ about "why shouldn't I use feof to run a while loop". You should have

Code:

---

while (iss >> t)

---

because you don't care about the state of iss (necessarily) -- you care whether the reading into t was successful.

thank tapstop for once again solving my problems!

:)