Re: [Boost-users] Range_iterator - char* - reverse

Subject: Re: [Boost-users] Range_iterator - char* - reverse
From: Rao, Anant (Anant.Rao_at_[hidden])
Date: 2010-12-10 13:23:40

Hi Kris,
Thanks for a quick response!
This is part of a larger issue that I'm addressing.

So, there's absolutely no way to use the same ptr to traverse backwards? I tried the options based on my limited knowledge, but if there're other options, please let me know (using the same ptr).
It's ironic a simple pointer could go fwd, but not back.
Anant

From: boost-users-bounces_at_[hidden] [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Krzysztof Czainski
Sent: Friday, December 10, 2010 9:00 AM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] Range_iterator - char* - reverse

2010/12/10 Rao, Anant <Anant.Rao_at_[hidden]><mailto:Anant.Rao_at_[hidden]>>

      char *s = "abcdefg";

      iterator_range<char*> ir( &s[0], &s[ strlen(s) ] );
      char *cp;

      boost::range_reverse_iterator< char*>::type irb = boost::rbegin( ir );
      boost::range_reverse_iterator< char*>::type ire = boost::rend( ir );

      for (; irb != ire; ++irb)
      {
            cout << "reverse cp [" << *irb << "]\n";
      }

This works like a charm - both in fwd and reverse traversal.

However, what I want is - in reverse traversal also, I want to use the same pointer ("cp" in this case). In other words, I want to use the same pointer to traverse in both directions.
Here's what I want to be able to write, but get a compile error with both attempts and I was wondering if you could help.

Option  1:
for (cp = boost::rbegin(ir); cp != boost::rend(ir); ++cp)
{
      cout << "cp reverse in ri [" << *cp << "]\n";
}

Option 2:
while( cp != ire )
{
  //Do something
  cp++
}

I think You can't do neither. Why do You want to do that?

Regards, Kris

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