What's new in C++17

auto [a, b, c] = tuple('a', 1, 0.5);

map<int, int> mymap = {{1, 2}, {3, 4}};

for (const auto& [key, value] : mymap) {
    // ...
}

for (auto [a, b] = tuple(0, 'a'); a < 5; a++) {
    // ...
}

auto p = pair(2, 4.5);

auto p = pair<int, double>(2, 4.5);

if (auto a = getval(); a < 10) {
    // ...
}

switch (auto ch = getnext(); ch) {
    // ...
}