保留小数，有效位数

#include<iostream>
#include<cstring>
#include<iomanip>
using namespace std;
int main()
{
    double ce=1.2323;
    cout<<setprecision(4)<<ce<<endl;//1.232
    cout<<setiosflags(ios::fixed)<<setprecision(4)<<ce<<endl;//1.2323
    cout<<setiosflags(ios::fixed)<<setprecision(4)<<ce<<endl;//1.2323
    cout.unsetf(ios::fixed);
    cout<<setprecision(4)<<ce<<endl;//1.232
    return 0;
}