Joel de Guzman wrote:
shunsuke wrote:
Joel de Guzman wrote:
shunsuke wrote:
Hi,
I'm trying to fix ticket #1396: http://svn.boost.org/trac/boost/ticket/1396 Any hint? I just replied to that in the ticket :-) HTH. Hmm, your `identity` implementation seems wrong. `result<Fun(int)>` invocation means that the argument is rvalue by the definition of result_of behavior. Therefore, you can't return mutable reference to `int`.
Well, it's just for that specific case. Did you intend the transform to be generic? I didn't think so when you had it hard coded to int. I guess, it really depends on what your intent is. A transform cannot, in general, return a reference. What if the input is computed on the fly, like, say:
mpl::vector_c<int, 1, 2, 3>
Here's a more generic identity transform that works for mpl sequences too, FWIW (attached test in the trac ticket): struct identity { template<class FunCall> struct result; template <class Fun, class T> struct result<Fun(T)> { typedef T type; }; template <class T> T& operator()(T& val) const { return val; } template <class T> T const& operator()(T const& val) const { return val; } }; Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net