c++ - 如何使用条件语句返回指针？

Question

以下代码输出第二个数字作为最大值。如果您需要任何其他信息，请告诉我。

#include <iostream>                                                     
#include <cstdlib>
using namespace std;
double *ComputeMaximum(const double *Max, const double *Min);

double *ComputeMaximum(const double *Max, const double *Min)
{
    return ((double *)((&Max > &Min) ? Max : Min));
}

int main(void)
{
    double *max;
    double Initial, Secondary;


    cout << "Enter the number followed by space then another number: ";
    cin >> Initial;
    cout << "\nIn-" << Initial;
    cin >> Secondary;
    cout << "\nSe-" << Secondary;
    //cout >> "Of " >> Inital >> "and " >> Secondary;
    //cout >> "the maximum is " >>
    max = ComputeMaximum((double*)&Initial,(double*)&Secondary);
    cout << "\nmax" << *max;
    return 0;
}

下一段代码输出第一个数字作为最大值

#include <iostream>                                                     
#include <cstdlib>
using namespace std;
double *ComputeMaximum(const double *Max, const double *Min);

double *ComputeMaximum(const double *Max, const double *Min)
{
    return ((double *)((Max > Min) ? Max : Min));  // Here is the difference(& missing)
}

int main(void)
{
    double *max;
    double Initial, Secondary;


    cout << "Enter the number followed by space then another number: ";
    cin >> Initial;
    cout << "\nIn-" << Initial;
    cin >> Secondary;
    cout << "\nSe-" << Secondary;
    //cout >> "Of " >> Inital >> "and " >> Secondary;
    //cout >> "the maximum is " >>
    max = ComputeMaximum((double*)&Initial,(double*)&Secondary);
    cout << "\nmax" << *max;
    return 0;
}

哪里做错了？我只需要最大值，不需要第二个或第一个输入。我得到了答案。谢谢大家。

这里是:

#include <iostream>                                                     
#include <cstdlib>
using namespace std;
double *ComputeMaximum(const double *Max, const double *Min);

double *ComputeMaximum(const double *Max, const double *Min)
{
    return (double*)((*Max > *Min) ? Max : Min);
}

int main(void)
{
    double *max;
    double Initial, Secondary;


    cout << "Enter the number followed by space then another number: ";
    cin >> Initial;
    cout << "\nIn-" << Initial;
    cin >> Secondary;
    cout << "\nSe-" << Secondary;
    //cout >> "Of " >> Inital >> "and " >> Secondary;
    //cout >> "the maximum is " >>
    max = ComputeMaximum(&Initial, &Secondary);
    cout << "\nmax" << *max;
    return 0;
}

Answer 1

double *ComputeMaximum(const double *Max, const double *Min)
{
    return *Max > *Min ? Max : Min;
}

请注意，我使用了 *Max 和 *Min 而不是 &Max 和 &Min，即取消引用，而不是地址!另请注意，对于已经是所需类型的表达式，您有很多不必要的转换为 double* 。一个例子是您的 ComputeMaximum 函数体。另一个例子

max = ComputeMaximum((double*)&Initial,(double*)&Secondary);

因为Initial和Secondary是double类型，&Initial和&Secondary属于 double* 类型，因此绝对不需要丑陋的不必要的转换。只需使用

max = ComputeMaximum(&Initial,&Secondary);

其他地方也类似。

我强烈推荐你阅读a good book on C++ .