【C++】A trick I learned：put boilerplate code into constructor of a struct

I learned this trick from hitonanode's submission on AtCoder.

The trick is like

struct fast_ios {

      fast_ios(){

            cin.tie(0);

            ios::sync_with_stdio(false);

            cout << fixed << setprecision(20);

      }

} fast_ios_;

What I used to do is like

#define FAST_READ ios::sync_with_stdio(false); cin.tie(nullptr);

int main() {

    FAST_READ

    cout << fixed << setprecision(10);

    // ...

}

using this trick, the code becomes

struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(10); } } fast_ios_;

int main() {

    // ...

}

I think macros are better avoided when alternatives are available.

Update 2020/5/21

There is another way to achieve the same function:

int fast_io = []() {

            cin.tie(0);

            ios::sync_with_stdio(false);

            cout << fixed << setprecision(20);

            return 0;

}();

巴特西

【C++】A trick I learned：put boilerplate code into constructor of a struct

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