[C++-sig] Re: difficulty with has_back_reference example

[Jonathan Brandmeyer]

On Sat, 2004-07-17 at 15:21, David Abrahams wrote:
> David Abrahams <dave at boost-consulting.com> writes:
> > See libs/python/test/back_reference.cpp in your boost distribution,
> > which does compile.  Would you mind posting a patch to correct the
> > documentation (or just checking in the fix once you know what it is
> > if you have checkin privs)?
> 
> The problem is that has_back_reference<T> needs to be a metafunction.

Thanks for the diagnosis.  Rather than raise the requirement of
has_back_reference<T> from being a traits class to a predicate
metafunction, would you accept the following patch?  It basically
performs a metacast from a predicate traits struct to a metafuction.  I
will be happy to apply the right patches in either case.

Thanks,
Jonathan

===================================================================
RCS file: /cvsroot/boost/boost/boost/python/object/select_holder.hpp,v
retrieving revision 1.19
diff -u -r1.19 select_holder.hpp
--- select_holder.hpp   25 Aug 2003 18:41:02 -0000      1.19
+++ select_holder.hpp   18 Jul 2004 14:30:23 -0000
@@ -94,7 +94,7 @@
    private:
       typedef mpl::or_<
           mpl::not_<is_same<T,Held> >
-        , has_back_reference<T>
+        , mpl::bool_<has_back_reference<T>::value>
       > use_back_ref;

    public:
@@ -123,7 +123,7 @@
       typedef typename python::pointee<Ptr>::type wrapper;
       typedef mpl::or_<
           mpl::not_<is_same<T,wrapper> >
-        , has_back_reference<T>
+        , mpl::bool_<has_back_reference<T>::value>
       > use_back_ref;

    public: