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Question #375 Difficulty: 2

According to the C++23 standard, what is the output of this program? 

    #include <iostream>
#include <utility>

struct A {
  A() = default;
  A(const A &a) { std::cout << '1'; }
  A(A &&a) { std::cout << '2'; }
};

A a;

int main() {
  [a = std::move(a)]() {
    [a = std::move(a)]() {};
  }();
}

Hint:

The outer lambda captures the global a. The inner lambda captures the a of the outer lambda. That lambda is not declared mutable, so its function call operator is const.

Answer:

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