C++17 STL Cookbook

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A lot of fundamental data structures from the STL are immediately accessible using structured bindings without us having to change anything. Consider, for example, a loop that prints all the items of an std::map:

std::map<std::string, size_t> animal_population {    {"humans",   7000000000},    {"chickens", 17863376000},    {"camels",   24246291},    {"sheep",    1086881528},    /* … */};for (const auto &[species, count] : animal_population) {    std::cout << "There are " << count << " " << species               << " on this planet.\n";}

This particular example works because when we iterate over an std::map container, we get the std::pair<const key_type, value_type> nodes on every iteration step. Exactly these nodes are unpacked using the structured bindings ...