writable zip ranges are not possible?

Question

The following is failing:

#include <range/v3/view.hpp>
#include <range/v3/view/zip.hpp>
#include <range/v3/utility/iterator.hpp>

// ...

std::vector< std::tuple<int, std::string> > const data{
   {1,"a"},
   {2,"b"},
   {3,"c"}
};
std::vector<int> vi(data.size());
std::vector<std::string> vs(data.size());

using namespace ranges;
copy(data,  view::zip(vi,vs) ); // error

clang says

No matching function for call to object of type 'const 
ranges::v3::with_braced_init_args<ranges::v3::copy_fn>'

Assuming this is by design, why?

And, how can I do this obvious thing with ranges?

Answer 1

1. copy takes an output iterator , not an output range . So you need to call begin on the zip view and turn it into an iterator.
2. With that fixed, you run into a separate problem. zip ping two ranges produce a pair (well, a common_pair ), but while tuples of two elements are assignable from pairs, pairs are not assignable from tuples of two elements. As a result, we can't do the equivalent of *zip_iterator = *data.begin() , and the concept check fails. If you make data a vector of pair s, then it would work.