2010/10/8 Thomas Heller <thom.heller@googlemail.com>
alfC wrote:
On Oct 7, 5:13 pm, OvermindDL1 <overmind...@gmail.com> wrote:
On Thu, Oct 7, 2010 at 5:42 PM, Alfredo Correa <
alfredo.cor...@gmail.com>
wrote:
On Thu, Oct 7, 2010 at 3:33 PM, OvermindDL1 <overmind...@gmail.com> wrote:
You do know that based on this:
http://www.boost.org/doc/libs/1_44_0/libs/fusion/doc/html/fusion/adap...
boost::array is already adapted as a fusion container and can be used directly, as soon as you include the proper hpp that is?
yes, thank you, that what I wrote in my last post . I can make this work
#include <boost/fusion/adapted/boost_array.hpp> #include <boost/fusion/include/boost_array.hpp> ... boost::array<double, 3> boostarr={{1.0, 2.1, 3.2}}; vector<double, double, double> fusionvec(boostarr); //now works
Ah, heh, got lost in the noise and I missed it.
On Thu, Oct 7, 2010 at 5:42 PM, Alfredo Correa < alfredo.cor...@gmail.com> wrote:
I still can't do the other way around:
boost::array<double, 3> boostarr2(fusionvec); //doesn't work ideas?
I know that would not work because that is still a 'custom' type as far as fusion is concerned, and only free functions can work on it, a constructor is obviously not a free function, so you need to write a free function to do it (probably called 'copy', probably using fusion's foreach to copy each element one to the other, should be pretty well optimized out thanks to the template-magic).
no luck. I can't make it work. First I tried with "for_each" and didn't manage to put together the code because I need to copy one sequence from the other and the for_each doesn't keep track of the index. So I tried with "transform", the code compiles but does nothing to the array.
boost::array<double, 3> ba0; boost::fusion::transform(ba0, bfv1, copy());
where struct copy{ typedef void result_type; void operator()(double& lhs, double const& rhs) const{ lhs = rhs; } };
ba0 is still undefined after running this.
Obviously I am getting Boost.Fusion wrong.
Thanks, Alfredo
You will find a version using fold attached. What it does, is that it increases the size of the boost::array passed in as state by one for every element in the fusion sequence and copies over the elements. There could be a more elegant solution to the problem ;)
Thomas, thanks so much for the code. Unfortunately it doesn't work (maybe it is my compiler?) $ c++ -v gcc 4.4.3 $ c++ fusion_test.cpp $ ./a.out terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::out_of_range>
' what(): attempt to access element of an empty array Aborted
Thanks, Alfredo
Cheers
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