Lambda Capture Improvements

#include <iostream>
#include <vector>
#include <algorithm>
struct Widget {
    int id;
    std::string name;
};
int main() {
    // C++20: Capture structured bindings
    std::pair<int, std::string> pair{42, "answer"};
    auto [num, str] = pair;
    
    auto lambda1 = [num, str]() {
        std::cout << str << ": " << num << std::endl;
    };
    lambda1();  // answer: 42
    
    // C++20: Template lambdas
    auto print_all = []<typename T>(const std::vector<T>& vec) {
        for (const auto& item : vec) {
            std::cout << item << " ";
        }
        std::cout << std::endl;
    };
    
    std::vector<int> nums = {1, 2, 3};
    std::vector<std::string> words = {"hello", "world"};
    print_all(nums);    // 1 2 3
    print_all(words);   // hello world
    
    // C++20: Lambdas in unevaluated contexts
    using Comparator = decltype([](int a, int b) { return a < b; });
    
    // C++20: Default-constructible stateless lambdas
    auto cmp = []<typename T>(const T& a, const T& b) { return a < b; };
    decltype(cmp) another_cmp;  // Default construct!
    
    std::cout << another_cmp(1, 2) << std::endl;  // 1 (true)
    
    return 0;
}