c++17 代码你能看懂吗?

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#include <vector>
#include <algorithm>
#include <random>

int main()
{
    std::vector<int> a{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    std::vector<int> b(5);

    std::sample(a.begin(), a.end(), 
                b.begin(), b.size(),
                std::mt19937{std::random_device{}()});
    return 0;
}
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#include <iostream>
#include <string>

int main()
{
    const std::string myString = "Hello World";

    // C++17 with init if:
    if (const auto it = myString.find("Hello"); it != std::string::npos)
        std::cout << it << " Hello
";

    if (const auto it = myString.find("World"); it != std::string::npos)
        std::cout << it << " World
";
}
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#include <iostream>
#include <string>

using namespace std;
 
template<typename ...Args> auto sum(Args ...args) 
{ 
    return (args + ... + 0); 
}

template<typename ...Args> auto sum2(Args ...args) 
{ 
    return (args + ...);
}

int main()
{
    cout << sum(1, 2, 3, 4, 5, 6, 7) << "
";
    cout << sum2(1, 2, 3, 4, 5, 6, 7) << "
";
}
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#include <utility>
#include <tuple>
#include <iostream>

int main() {
    std::pair d(0, 0.0);
    std::tuple t(1, 2, 3);

    std::cout << std::get<0>(t) << ", " << std::get<1>(t) << ", " << std::get<2>(t) << "
";
}
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#include <iostream>
#include <string>

struct S 
{
    int n;
    std::string s;
    float d;
};

template <std::size_t I>
auto& get(S& s)
{
    if constexpr (I == 0)
        return s.n;
    else if constexpr (I == 1)
        return s.s;
    else if constexpr (I == 2)
        return s.d;
}

int main()
{
    S obj { 0, "hello", 10.0f };
    std::cout << get<0>(obj) << ", " << get<1>(obj) << "
";
}
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https://www.codingame.com/playgrounds/2205/7-features-of-c17-that-will-simplify-your-code/introduction
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