重置升压累加器 C++

Question

由于没有找到 'boost' 在 C++ 中重置累加器的方法，我遇到了一段似乎可以重置升压累加器的代码。但是不明白它是如何实现的。代码如下-

#include <iostream>
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/mean.hpp>
using namespace boost::accumulators;

template< typename DEFAULT_INITIALIZABLE >
inline void clear( DEFAULT_INITIALIZABLE& object )
{
        object.DEFAULT_INITIALIZABLE::~DEFAULT_INITIALIZABLE() ;
        ::new ( boost::addressof(object) ) DEFAULT_INITIALIZABLE() ;
}

int main()
{
    // Define an accumulator set for calculating the mean 
    accumulator_set<double, stats<tag::mean> > acc;

    float tmp = 1.2;
    // push in some data ...
    acc(tmp);
    acc(2.3);
    acc(3.4);
    acc(4.5);

    // Display the results ...
    std::cout << "Mean:   " << mean(acc) << std::endl;
    // clear the accumulator
    clear(acc);
    std::cout << "Mean:   " << mean(acc) << std::endl;
    // push new elements again
    acc(1.2);
    acc(2.3);
    acc(3.4);
    acc(4.5);
    std::cout << "Mean:   " << mean(acc) << std::endl;

    return 0;
}

第 7 行到第 12 行是做什么的？ 'clear' 如何设法重置累加器？另外，是否有我缺少的标准提升方式以及实现上述代码所完成功能的任何其他方式。

Answer 1

要重新初始化对象，只需执行以下操作：

acc = {};

它所做的是 {} 创建一个默认初始化的临时对象，该对象被分配给 acc。

Answer 2

what do lines 7 to 12 do?

他们调用对象的析构函数，然后在同一存储中默认构造一个新对象（相同类型）。

对于明智的类型，这将与建议的效果相同，即将默认构造的临时对象分配给现有对象。

第三种选择是使用不同的对象

#include <iostream>
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/mean.hpp>
using namespace boost::accumulators;

int main()
{
    {
        // Define an accumulator set for calculating the mean 
        accumulator_set<double, stats<tag::mean> > acc;

        float tmp = 1.2;
        // push in some data ...
        acc(tmp);
        acc(2.3);
        acc(3.4);
        acc(4.5);

        // Display the results ...
        std::cout << "Mean:   " << mean(acc) << std::endl;
    } // acc's lifetime ends here, afterward it doesn't exist

    {
        // Define another accumulator set for calculating the mean
        accumulator_set<double, stats<tag::mean> > acc;

        // Display an empty result
        std::cout << "Mean:   " << mean(acc) << std::endl;

        // push elements again
        acc(1.2);
        acc(2.3);
        acc(3.4);
        acc(4.5);
        std::cout << "Mean:   " << mean(acc) << std::endl;
    }

    return 0;
}

重置升压累加器 C++

reset boost accumulator c++

c++

boost

boost-accumulators