Are nested structured bindings possible?

问题

Assume I have an object of type

std::map<std::string, std::tuple<int, float>> data;

Is it possible to access the element types in a nested way (i.e. when used in ranged for loop) like this

for (auto [str, [my_int, my_float]] : data) /* do something */

回答1:

No, it is not possible.

I distinctly remember reading somewhere that nested structured bindings are not allowed for C++17, but they are considering allowing it in a future standard. Can't find the source though.

回答2:

No, they aren't possible; but this is:

for (auto&& [key, value] : data) {
  auto&& [my_int, my_float] = value;
}

which is close at least.

来源：https://stackoverflow.com/questions/49035732/are-nested-structured-bindings-possible