[boost] Boost::lambda::call_xxx, right or wrong?

From: Robin.Hu (huxw_at_[hidden])
Date: 2002-12-09 12:55:14

Hi Boosters:

   In the document of boost::lambda (ar01s05.html#sect:nested_stl_algorithms), 
it says:
------------------>cited begin<-------------------
   Some aid for common special cases can be provided though. The BLL defines two 
   helper function object classes, call_begin and call_end, which wrap a
   call to the begin and, respectively, end functions of a container,
   and return the const_iterator type of the container. With these
   helper templates, the above code becomes: 

   std::for_each(a.begin(), a.end(), 
      bind(ll::for_each(), 
         bind(call_begin(), _1), bind(call_end(), _1),
         protect(sum += _1)));
------------------->cited end<---------------------

   But I failed to compile this example with gcc 3.2 and vc 2003 beta.
I think the problem is, both struct call_begin and struct call_end dont
provide a result_type. 

[lambda/algorithm.hpp]
------------------->cited begin<-------------------
#define CALL_MEMBER(X)                                     \
struct call_##X {                                          \
template <class Args>                                      \
  struct sig {                                             \
    typedef typename boost::remove_const<                  \
        typename boost::tuples::element<1, Args>::type     \
     >::type::const_iterator type;                         \
  };                                                       \
                                                           \
  template<class T>                                        \
  typename T::const_iterator                               \
  operator()(const T& t) const                             \
  {                                                        \
    return t.X();                                          \
  }                                                        \
};
------------------->cited end<---------------------
 
  Is there anything I missed? And is there a possibel way to make these
call_xxx run?

-- 
 <huxw_at_[hidden]>