Given a struct which has a vector member, I would like to extract all of them and then flatten them, without creating new vectors on the heap
I'm using c++17 and librange-v3-dev(0.11.0-2), ubuntu22.10
#include <range/v3/all.hpp>
#include <vector>
#include <iostream>
struct A {
std::vector<int> vv;
};
int main()
{
using namespace ranges;
std::vector<A> As = { A{{1,2,3,4}}, A{{5,6,7}} };
auto getter = [](const auto&r) { return r.vv; };
auto flattened_range = As | view::transform(getter)| view::join;
for (auto i : flattened_range){
std::cout << i << " ";
}
return 0;
}
I would expect it prints
1 2 3 4 5 6 7
I can't figure out how to compile it,
compiled with
c++ --std=c++17 range.cpp
here is the compiling error:
range.cpp: In function 'int main()':
range.cpp:16:56: error: no match for 'operator|' (operand types are 'ranges::transform_view<ranges::ref_view<std::vector<A> >, main()::<lambda(const auto:10&)> >' and 'const ranges::views::view_closure<ran
ges::views::join_fn>') 16 | auto flattened_range = As | view::transform(getter)| view::join;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ ~~~~~~~~~~
| | |
| | const ranges::views::view_closure<ranges::views::join_fn>
| ranges::transform_view<ranges::ref_view<std::vector<A> >, main()::<lambda(const auto:10&)> >
In file included from /usr/include/c++/11/regex:39,
This is a limitation in ranges-v3 v0.11. In v0.12 your code works with a slight adjustment: You need to replace ranges::view with ranges::views, like this:
#include <range/v3/all.hpp>
#include <iostream>
#include <vector>
struct A {
std::vector<int> vv;
};
int main() {
std::vector<A> As = {A{{1, 2, 3, 4}}, A{{5, 6, 7}}};
auto getter = [](const auto& r) { return r.vv; };
auto flattened_range = As
| ranges::views::transform(getter)
| ranges::views::join;
for (auto i : flattened_range) {
std::cout << i << " ";
}
}