C++格式输出控制

#include<iostream>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<iterator>
#include<algorithm>
#include<cctype>
int main() {
    using namespace std;
    cout.setf(ios_base::left,ios_base::adjustfield);
    cout.setf(ios_base::showpos);
    cout.setf(ios_base::showpoint);
    cout.precision(3);
    ios_base::fmtflags old = cout.setf(ios_base::scientific,ios_base::floatfield);
    cout << "left just" << endl;
    long n;
    for (n = 1 ; n <= 41 ; n += 10) {
        cout.width(4);
        cout << n << "|";
        cout.width(12);
        cout << sqrt(double(n)) << endl;
    }

    cout.setf(ios_base::right,ios_base::adjustfield);
    cout.setf(ios_base::fixed,ios_base::floatfield);
    for (n = 1 ; n <= 41 ; n += 10) {
        cout.width(4);
        cout << n << "|";
        cout.width(12);
        cout << sqrt(double(n)) << endl;
    }
    return 0;
}