On 17/10/12 04:28, Jeffrey Lee Hellrung, Jr. wrote:
On Tue, Oct 16, 2012 at 10:06 AM, "Claas H. Köhler" <claas.koehler@dlr.de>wrote:
On Tue, Oct 16, 2012 at 4:21 AM, "Claas H. Köhler" <claas.koehler@dlr.de wrote:
On 16/10/12 12:01, Giovanni Piero Deretta wrote:
On Tue, Oct 16, 2012 at 9:06 AM, "Claas H. Köhler" <
claas.koehler@dlr.de>
wrote:
Hi!
I would like to use the boost::zip_iterator with std::pair. Unfortunately this does not work out of the box, but there exists a namespace boost::detail::tuple_impl_specific, which apparently needs to be specialised for each tuple type.
Hmmm...I guess it makes sense you might have to specialize something if zip_iterator doesn't specifically know about your desired tuple type.
I managed to re-implement tuple_meta_transform and tuple_meta_accumulate for std::tuple, which seems to be straightforward. However, there are functions of the form
template<typename Tuple, typename Fun> complex_result_type tuple_transform(const Tuple&, Fun)
which have to be overloaded as well, if I am not mistaken. However, overloading this with something like template<typename... Args, typename Fun> complex_result_type tuple_transform(const std::tuple<Args...>&, Fun)
is probably not going to work, since this would be a partial template specialisation of a function.
That's an overload actually and should work fine. Did you try it?
HTH,
Thanks for the hint. I have to admit I did not try it yet. I have just created a similar simple test case, which indeed compiles/works fine. Shame on me for not trying it out. For me this was always a classical example of template function specialisation. I guess I should take a look at template basics again :-)
Sorry for that and thanks for the quick response.
I'm glad you got it working, but ideally, I think, zip_iterator should work out of the box for std::pair and std::tuple. Could I trouble you to
On 16/10/12 14:27, Jeffrey Lee Hellrung, Jr. wrote: provide
patches based on what you needed to get this to work?
- Jeff
Unfortunately things are not working yet. As far as I can judge, the problem is that some of the functions are called from within the zip_iterator.hpp header file, which is before I can actually define the overloaded functions. As a result the overloaded functions are not called.
Should I get this working, however, I am glad to share the wisdom.
Well, I'd consider it fair game to edit the zip_iterator.hpp header file directly :)
- Jeff
Looks like I found a working solution. I transformed the tuple_xxx template functions into template structs, for which overloading seemingly works fine. Since I am not familiar with boost::mpl I used my own versions of the meta transformations based on C++11. For tuple this may not be an issue, since its a C++11 feature, but for std::pair it could be. Furthermore I would suggest to implement these functions exclusively for boost::tuple and leave the general template unimplemented. This may ease specialisations of other classes. Using C++11 for example the specialisations for std::pair and std::tuple are almost identical, but have to be specialised individually. Just my 0.02$ . Shall I post the modified code directly to the mailing list or somewhere else? Regards Claas