Re: [boost] Iterator Range and operator==

Subject: Re: [boost] Iterator Range and operator==
From: Daryle Walker (darylew_at_[hidden])
Date: 2012-04-23 10:02:59

> From: mostafa_working_away_at_[hidden]
> Date: Sat, 21 Apr 2012 17:42:26 -0700
> 
> On Fri, 20 Apr 2012 05:15:50 -0700, Olaf van der Spek <ml_at_[hidden]>  
> wrote:
> 
> > What do you expect this code to do? Is b true or false? And why?
> > Is this expected behaviour?
> >
> > [1]  #include <boost/range/iterator_range.hpp>
> > [2]  #include <string>
> > [3][4]  int main()
> > [5]  {
> > [6]      std::string s = "Olaf";
> > [7]      boost::iterator_range<std::string::iterator> r(s);
> > [8]      bool a = r == s;
> > [9]      bool b = r == "Olaf";
> > [10]     assert(a);
> > [11]     assert(b);
> > [12]     return 0;
> > [14] }
> >
> 
> I would expect both lines 8 and 9 to cause compilation failure.  To  
> someone unfamiliar with the library, it's not /immediately/ clear what the  
> intent of either line is.  If one wants to treat "s" as a range for the  
> purpose of comparison, then one should explicitly adapt it to such.  Ditto  
> for line 9.  It just makes the maintaining code that much easier.  In the  
> case of line 9, this has the additional benefit of forcing newcomers to  
> ask what does make_iterator_range("Olaf") mean?, leading to a  
> documentation look up that will preempt any potential surprises associated  
> with char arrays and the library.
[TRUNCATE]
I'm guessing that Boost.Range handles the range traversal method that's acounter to the iterator traversal method.  If so, I was thinking the samething Mostafa did when reading this thread: the comparisons should causecompiler errors because the types shouldn't be conceptually directlycompatible.
Daryle W.