c++ - boost::array of boost::reference_wrapper not compiling -


i have class boost::array type stores references std::vector. want construct array of references (i'm trying di, or think), haven't succeeded far.

class refholder {  public:      boost::array<boost::reference_wrapper<std::vector<int> >, 3> sumsarray;  };  class originalholder {  public:      originalholder(boost::array<boost::reference_wrapper<std::vector<int> >, 3> & psumsarray)     {         sumsarray[0] = boost::ref(_sums);     }  private:      std::vector<int> _sums;  }  int main() {     refholder ref;      originalholder original(ref.sumsarray);      return 0; }

i don't compiler telling me. array work reference_wrapper?

c:/ide-4.6-workspace/chunkybacon/boost/boost/array.hpp:60: error: no matching function call 'boost::reference_wrapper<std::vector<int, std::allocator<int> > >::reference_wrapper()' c:/ide-4.6-workspace/chunkybacon/boost/boost/ref.hpp:43: note: candidates are: boost::reference_wrapper<t>::reference_wrapper(t&) [with t = std::vector<int, std::allocator<int> >] c:/ide-4.6-workspace/chunkybacon/boost/boost/ref.hpp:33: note:                 boost::reference_wrapper<std::vector<int, std::allocator<int> > >::reference_wrapper(const boost::reference_wrapper<std::vector<int, std::allocator<int> > >&) c:/ide-4.6-workspace/chunkybacon/test/test.cc: in constructor 'refholder::refholder()': c:/ide-4.6-workspace/chunkybacon/test/test.cc:6: note: synthesized method 'boost::array<boost::reference_wrapper<std::vector<int, std::allocator<int> > >, 3u>::array()' first required here  c:/ide-4.6-workspace/chunkybacon/test/test.cc: in function 'int main()': c:/ide-4.6-workspace/chunkybacon/test/test.cc:32: note: synthesized method 'refholder::refholder()' first required here cc: c:/qnx641/host/win32/x86/usr/lib/gcc/i386-pc-nto-qnx6.4.0/4.3.3/cc1plus caught signal 1

of course use plain pointers, , works, still have doubt and, if can fix it, i'd rather use references.

i'm working qnx 6.4.1 , gcc 4.3.3.

thank in advance =)

when create array have "empty" entries. reference cannot empty (ok, be, it's bad idea), references not work array entries.

consider using boost::smart_ptr<vectorint> > instead. realize that's not want (pointer vs reference) works big point in favor.

------------response question in comments---------

the difference vector of references must referencing objects exist somewhere else -- somewhere manages lifetime of these objects , ensures live longer references them do.

a vector of smart pointers must pointing heap-allocated objects, , manages lifetime of objects.

both of these approaches have valid uses.


Comments

Post a Comment

Popular posts from this blog

javascript - jquery or ashx not working -

i using ajax file upload control. it creating html: <form action="/pages/handlers/asyncfileuploadhandler.ashx" method="post" enctype="multipart/form-data" target="ajaxuploader-iframe-1397144545"> <input type="hidden" name="type" value="mindvoice"> <input type="file" id="imagefile" style="display: block; width: 80%; margin-right: auto; margin-left: auto;"> </form> and target is: <iframe width="0" height="0" style="display:none;" name="ajaxuploader-iframe-1397144545" id="ajaxuploader-iframe-1397144545"></iframe> the form submitted using .submit() . my ashx handler: <%@ webhandler language="c#" class="asyncfileuploadhandler" %> using system; using system.web; using nettpals.core; public class asyncfileuploadhandler : ihttphandler { public void processre...
Read more

opencv - DataType<cv::detail::deriv_type>::depth what is it used for -

i wondering why line used in lucas kanade tracker in opencv: datatype<cv::detail::deriv_type>::depth can explain me? in opencv, depth of mat refers type of data contained in mat 's data buffer. represented integer values correspond given data type. these integers commonly abstracted appropriate macro definition (e.g. uchar data represented macro cv_8u ). cv::datatype type-traits class provides method obtain corresponding integer value without having memorize macro means data type. there few cases user code needs use datatype::depth . more common datatype::type . a simple example shows 1 possible use of datatype::depth : cv::mat uchar_data = cv::mat::ones(3, 3, cv_8uc1); cv::mat float_data; uchar_data.convertto(float_data, cv::datatype<float>::depth); // ^^ equivalently replaced // cv_32f macro float_data.at<float>(0,1) += 0.5f; std::cout << float_data << std::endl;...
Read more

python 3.x - Mapping specific letters onto a list of words -

can please suggest approach write piece of codes automatically maps letter in letter_str onto dic_key (a dict key string type contains dashes match length of words in word_lst)? so, mapping occurs if letter appears in every words in list @ same position no matter how many words in list. if no letter appears @ position words in word list new_dic_key '----'. please see examples below thanks word_lst = ['ague', 'bute', 'byre', 'came', 'case', 'doze'] dic_key = '----' letters_str ='abcdefghijklmnopqrstuvwxyz' new_dic_key = '---e' if word_list = ['bute', 'byre'] new_dic_key = 'b--e' or word_list = ['drek', 'drew', 'dyes'] new_dic_key = 'd-e-' if words in word_list of same length code give want: word_list = ['drek', 'drew', 'dyes'] cols = [] in range(len(word_list[0])): cols.append([]) word in ...
Read more