On Thu, Oct 18, 2012 at 3:11 AM, "Claas H. Köhler" <claas.koehler@dlr.de>wrote:
On Wed, Oct 17, 2012 at 12:08 AM, "Claas H. Köhler" < claas.koehler@dlr.de>wrote:
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 16/10/12 14:27, Jeffrey Lee Hellrung, Jr. 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 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
On 17/10/12 13:21, Jeffrey Lee Hellrung, Jr. wrote: 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?
Create a trac ticket, attach any patches, and I'll take a look at it when I get a chance.
- Jeff
I just created ticket #7526 with a proposed patch. I am not sure, whether I got the different compiler macros right, though, since I do not have access to the compilers they are intented for. Furthermore you may want to enclose the std::tuple stuff (including namespace helper) into a macro, which enables it if C++11 is used (I presume such a macro does already exist, but I did not know its exact syntax).
Great, thanks! I'll try to get to this before 1.53.0 is released. Did you add a unit test by chance? As for conditioning on the existence of std::tuple, looks like BOOST_NO_CXX11_HDR_TUPLE and BOOST_HAS_TR1_TUPLE would be macros to use. - Jeff