STL Basics tutorial

[nathacof]

I'm just wondering how the program presented at the end of the tutorial knows when to stop accepting words from the standard input.

    // This vector of strings will be holding the words as the user
    // enters them.
    vector<string> words;

    // std::ostream_iterator's evil twin, std::istream_iterator, can
    // be used for doing the opposite: turn an input stream into an
    // iterator. Here we keep copy all strings from cin to the back of
    // the words vector:
    copy (istream_iterator<string> (cin), 
          istream_iterator<string> (),    // "end"
          back_inserter (words));

This is the code that I don't really understand. When I compile the program and run it I can enter an infinite number of words without the program printing the list of words.

Maybe I just don't understand iterators enough.

istream_iterator();
     Construct an end-of-stream iterator.  This iterator can be used to
     compare against an end-of-stream condition. Use it to provide end
     iterators to algorithms

This is from http://h30097.www3.hp.com/cplus/istr...or_3c__std.htm
It seems that I just don't know how to close the stream?

[redhead]

I'm just wondering how the program presented at the end of the tutorial knows when to stop accepting words from the standard input.

It reads till it reads EOS (End Of Stream) that beeing the end of file if it's a file you're reading from or a termination of your input stream when you read from stdin.

It seems that I just don't know how to close the stream?

Terminate the tranmission, on *nix thats <ctrl>+D in DOS it's <ctrl>+S, it all depends on what system you're running.

A small example:

#include <iterator>
#include <vector>
#include <numeric>
#include <iostream>

using namespace std;

int main ()
{
  vector<int> d;
  int total = 0;
  //
  // Collect values from cin until end of file
  // Note use of default constructor to get ending iterator
  //
  cout << "Enter a sequence of integers (eof to quit): " ;
  copy(istream_iterator<int,char>(cin),
       istream_iterator<int,char>(),
       inserter(d,d.begin()));
  //
  // stream the whole vector and the sum to cout
  //
  copy(d.begin(),d.end()-1,
       ostream_iterator<int,char>(cout," + "));
  if (d.size())
    cout << *(d.end()-1) << " = " <<
      accumulate(d.begin(),d.end(),total) << endl;
  return 0;
}

Since this reads anything of type int then anything which isn't an int, like a char.

[nathacof]

Ah thank you for the help! ctrl-D causes the programs execution to continue right along, I had actually tried ctrl-x ctrl-c and even a couple random letters.

OK so iterators are just used to traverse over multiple objects in a container?

[redhead]

OK so iterators are just used to traverse over multiple objects in a container?

Yes, in a way, you can think of them as beeing the equivalent of something like

for(int i=0; i < container.length(); i++)
    // Do stuff with container[i];