平日小问题 (2)：[Error] 'setprecision' is not a member of 'std'

#include <iostream>

template <typename t>
t sum(t x,t y)
{
    return x+y;
}

int main()
{
    int a,b;
    double c,d;

    std::cin>>a>>b>>c>>d;

    std::cout<<sum(a,b)<<std::endl;
    std::cout<<std::fixed<<std::setprecision(3)<<sum(c,d)<<std::endl;
}

报错：[Error] ‘setprecision’ is not a member of ‘std’

需要加上头文件 便可通过编译

修改后：

#include <iostream>
#include <iomanip>
template <typename t>
t sum(t x,t y)
{
    return x+y;
}

int main()
{
    int a,b;
    double c,d;

    std::cin>>a>>b>>c>>d;

    std::cout<<sum(a,b)<<std::endl;
    std::cout<<std::fixed<<std::setprecision(3)<<sum(c,d)<<std::endl;
}