[LC++]The behavior of istream_iterator<string> as a pointer.

[Roberto Diaz]

On Thu, Dec 27, 2001 at 01:48:49PM +0200, Shaul Karl wrote:
> Aren't the increment operator and comparison work with 
> istream_iterator<string>?

Yes.. it works..

> The following program tries to copy part of its own source file 
> (main.cc) to cout.
> 
> $ cat main.cc
> 
> #include <algorithm>
> #include <fstream>
> #include <iostream>
> #include <iterator>
> #include <string>
> 
> using namespace std;
> 
> int main() 
> {
>     ifstream input("main.cc");
>     istream_iterator<string> iter1(input), iter2, eof;
>     iter1 = find(iter1, eof, "main()");
>     iter2 = find(iter1, eof, "}");
	  ^^^^^^
      Since you are repositioning your stream iter1 is not valid anymore..

>     for (; iter1 != iter2; iter1++) cout << *iter1;
>     cout << "\n";
> }
> 

see this code, it works:

#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <string>

using namespace std;

int 
main()
{
  ifstream input("input_iterator.cc");
 
  istream_iterator<string> in(input), it1, eof;
  
  it1 = find (in, eof, "main()");

  // now you have your stream pointer positioned!! if you make a second
  // find like this:
  // it2 = find (int, eof, "}");
  // then it1 will not be valid anymore.. and you only could to use ++it2 not
  // ++it1

  for (; *it1 != "}"; it1++) cout <<  *it1 << endl;
  return 0;
}

It would be usefull to have a rewind()/seek() method to use in the ifstream.. 

Yes these iterators are not working as expected... 

Stroustrup's book is so badly written!!! aggggggggggg!! it is not that C++ is
bad!!! 

-- 
Saludos

Roberto Díaz <roberto at vivaldi.dhis.org>

PLEASE HELP SAVE faqs.org!
http://www.faqs.org/save_faqs-org.html