[Boost-users] is_range / is_range_of metafunctions

Subject: [Boost-users] is_range / is_range_of metafunctions
From: Duncan Smith (duncanphilipnorman_at_[hidden])
Date: 2010-06-24 14:12:08

I'm using the Boost.Range 2.0 library (Boost version 1.43.0), and I
was looking for metafunctions to use in conjunction with
boost::enable_if.  I wasn't able to find anything akin to "is_range"
and/or "is_range_of" in Boost.Range or in Boost.TypeTraits.

Here is a demonstrative example that uses "is_range_of":

class Y, Z;
class X
{
 struct enabler {};

public:
  // Construct from a range of Y.
  template <class Range>
X(const Range &r,
 typename boost::enable_if
< typename boost::is_range_of<Range, Y>::type
, enabler
>::type = enabler())
{ /* ... */ }

  // Construct from a range of Z.
  template <class Range>
X(const Range &r,
 typename boost::enable_if
< typename boost::is_range_of<Range, Z>::type
, enabler
>::type = enabler())
{ /* ... */ }
};

Did I overlook something?  Is there an easy way to get this effect?

I did find an email in the archives with an implementation of this
functionality:
 http://lists.boost.org/Archives/boost/2007/08/125851.php
That implementation works for me.  Is there a reason they have not
been included?

Thanks for any guidance,
Duncan