Easy way to iterate over two structures consecutively with a foreach loop

Question

Is there an easy way to achieve this design pattern in c++17?

std::set<uint32_t> first;
std::set<uint32_t> second;

for (uint32_t number : JoinIterator<uint32_t>(first, second)) {
   <DO SOMETHING WITH number>
}

This would replace the following code:

std::set<uint32_t> first;
std::set<uint32_t> second;

for (uint32_t number : first) {
   <DO SOMETHING WITH number>
}

for (uint32_t number : second) {
   <DO SOMETHING WITH number>
}

All of the search results I have found are about looping over both structures in parallel, not looping over the structures consecutively.

Answer 1

Use views::concat from range-v3:

for (uint32_t number : views::concat(first, second)) {
   <DO SOMETHING WITH number>
}

This only works with ranges that have the same underlying type (which is true in this example).

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In Boost (i.e. range-v2), this is spelled boost::range::join(first, second).

Since it's not apparent from the Boost documentation directly, this function is found in boost/range/join.hpp