Larry Evans wrote: On 05/03/2006 01:54 PM, dan marsden wrote:
In boost/fusion/tuple/tuple.hpp there's this: [snip] I don't see any use of the at_meta typedef. What's the purpose of this typedef?
This appears to be the result of a bit of cut and paste from the at and at_c implementations, which also have the redundant typedef. The get implementations should be calling at_c directly, rather than implementing more tag_dispatching to the at_impl type themselves. I've tidied things up, removing the redundant typedefs in both get and at, and modifying get to call at_c directly.
Could you post the location of the revised code?
Its under the spirit parser library cvs: http://tinyurl.com/s7qdw On the branch FUSION_V2
There may be a similar cut and paste problem in /sequence/intrinsic/begin.hpp which has:
template <typename Sequence> inline typename result_of::begin<Sequence>::type begin(Sequence& seq) { typedef result_of::begin<Sequence> begin_meta; return extension::begin_impl <typename traits::tag_of<Sequence>::type>:: template apply<Sequence>::call(seq); }
You seem to have hit a bit of a rich seam here! I suspect this may recur in some of the other intrinsics, I'll do a pass through and tidy this up. We may need to do a bit of work on these anyway based on the MPL style comments made by Dave A about calling the _impl functions.
Also, the docs in notes.html under "Tag Dispatching" at the 2nd item 3 has:
3. result_of::begin is the template which is specialized to provide an implementation for each tag type
yet, in the above begin.hpp, it's not specialized, and a grep of all the .hpp file turned up no likely candidates; however, a grep for 'struct begin_impl' did show several specializations. Is the aforementioned correct?
Yes, that is another typo, the correct structure is metafunction XXX tag dispatching to implementation XXX_impl. Now fixed. Thanks again! Dan