Hello,
I am confused about why two certain lamba expressions work (on VC8)
while two others do not. I do not profess to be any sort of expert in
boost lambda expressions. This code is being executed in a function
which is a friend of a template "takostack". Basically, this function
deals with a member "contents_" that is a scoped_array of scoped_ptrs.
It is supposed to iteratively call the << operator for the elements of
contents_ scoped_array.
template<typename O>
std::ostream& operator<< (std::ostream& os, const
takostack& s)
{
/* Works, not sure why */
for (int i(0); i < s.top_; ++i)
{
os << *(&boost::scoped_ptr<O>::get,
boost::lambda::_1)(s.contents_[i]) << " ";
}
/* Works, not sure why */
std::for_each(&s.contents_[0], &s.contents_[0] + s.top_,
os << *(&boost::scoped_ptr<O>::get,
boost::lambda::_1)(boost::lambda::_1)
<< " ");
/* Does not work, don't know why
std::for_each(&s.contents_[0], &s.contents_[0] + s.top_,
os << *(boost::lambda::_1 ->*
&boost::scoped_ptr<O>::get)(boost::lambda::_1)
<< " ");
*/
/* Does not work, don't know why
std::for_each(&s.contents_[0], &s.contents_[0] + s.top_,
os << *(boost::bind(&boost::scoped_ptr<O>::get,
boost::lambda::_1)(boost::lambda::_1))
<< " ");
*/
}
Basically, I would like to understand why compilation succeeds without
using bind, and fails when bind or the member pointer operator is used.
The first failed example fails with:
Error 131 error C2784: 'const
boost::lambda::lambda_functor>>
boost::lambda::operator *(const boost::lambda::lambda_functor<T> &)' :
could not deduce template argument for 'const
boost::lambda::lambda_functor<T> &' from
'boost::lambda::detail::member_pointer_caller'
d:\source\c\takostack\takostack\takostack.h 135
Error 132 error C2100: illegal indirection
d:\source\c\takostack\takostack\takostack.h 135
Error 133 error C2679: binary '<<' : no operator found which takes
a right-hand operand of type
'boost::lambda::detail::member_pointer_caller' (or there is no
acceptable conversion) d:\source\c\takostack\takostack\takostack.h
135
The second failed example fails with:
Error 131 error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios'
: cannot access private member declared in class
'std::basic_ios<_Elem,_Traits>' D:\Microsoft Visual Studio
8\VC\include\ostream 581
Thanks,
Matt
