Re: [Boost-users] [boost-users] istream_iterator question - need Steven's help

17 May 2009


      AMDG

Max wrote:
...
const _Ty& operator*() const
      {	// return designated value
      return (_Myval);
      }
_Myt& operator++()
      {	// preincrement
      _Getval();
      return (*this);
      }
IMO, it should be modified as:
const _Ty& operator*() //const
      {	// return designated value
      _Getval();
      return (_Myval);
      }
_Myt& operator++()
      {	// preincrement
      return (*this);
      }
The main problem of the current design of istream_iterator is that
it always swallow one extra object, of the template parameter
type, prepared for the coming * or -> operator. This makes the 
coming plain >> operator a distance forward of where it shoud be.
I've tested with this modification and found it works well. Please
note that I've simply commented out the trailing const qualifier 
for the * and -> operator, to make things simpler and more 
straightforward. Obviously, furthur modification is to be made to 
make the code to a product level.
I want to know whether this change makes sense?
Well, it solves your problem, but it creates other problems instead.

For example, what should this do:
std::istream_iterator<int> iter(std::cin);
std::advance(iter, 10);

Or this:
std::istream_iterator<int> iter(std::cin);
if(*iter != 10) {
    std::cout << *iter;
}

In Christ,
Steven Watanabe