Re: [Boost-users] Counting matches with Regex V4

From: john.wismar_at_[hidden]
Date: 2004-02-20 16:54:00

Earlier, I wrote:
>
> <Using VC7.0>
>
> I'm converting to V4 of Regex, and I thought I might be able to
> count regex matches using this snippet:

<snip>

> boost::sregex_iterator itBegin(first, last, e);
> boost::sregex_iterator itEnd;
> ptrdiff_t pd = std::distance(itBegin, itEnd);
>
> I get these errors:
>
> xutility(312) : error C2665: 'std::_Iter_cat' : none of the 12 overloads
> can convert parameter 1 from type 'boost::sregex_iterator'

<snip different _Iter_cat overloads taking integral types>

> Anyone have any thoughts?  Is it a VC7.0 issue?  Is there a better or
> different way of doing the same thing?

I should have mentioned that I'm using boost 1.31.0.

After some further research, I found that this DOES appear to be a
VC7.0-only problem.  It doesn't happen in VC7.1, notably.

The problem seems to be with VC7.0's implementation of the standard
library. In particular, there's another overload of std::_Iter_cat that
takes a std::iterator as a parameter; this overload wasn't considered by
the compiler when it generated the error message above.

It looks like instead of relying on iterators to define typedefs for
iterator_category, value_type, et al., the library assumes that an iterator
must actually derive from std::iterator.  This assumption has been removed
from the library implementation in VC7.1.

Given all of this, it seems like my options are to modify my copy of
regex_iterator.hpp, modify my copy of <xutility>, or hope that someone has
a third option.  (Upgrading to vc7.1 is not an option this week.  :-)

--------------------------------
John Wismar
jwismar_at_[hidden]

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