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[教育经济学基本知识] C++ Prime Plus 学习笔记020 [推广有奖]

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海棠未眠666 发表于 2025-11-27 20:17:17 |AI写论文

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参考书籍：C++ Primer Plus（第六版）中文版本

开发工具：Dev-C++ 5.11

设备配置：Intel(R) Xeon(R) CPU E5-2603 v3 @ 1.60GHz

系统信息：Windows 10 专业版，64位操作系统，基于X64架构的处理器

第8章 函数探幽

8.5 函数模板

以下为实例8.11的代码实现，文件名为 funtemp.cpp：

#include <iostream>
template <class T>
void Swap(T &a, T &b);

int main()
{
    using namespace std;
    int i = 10;
    int j = 20;
    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler generated in swapper:\n";
    Swap(i, j);
    cout << "Now i,j=" << i << ", " << j << ".\n";

    double x = 24.5;
    double y = 81.7;
    cout << "x,y= " << x << ", " << y << ".\n";
    cout << "Using compiler generated double swapper:\n";
    Swap(x, y);
    cout << "Now x,y =" << x << ", " << y << ".\n";

    return 0;
}

template <class T>
void Swap(T &a, T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

程序执行后的输出结果如下：

i,j = 10, 20.
Using compiler generated in swapper:
Now i,j=20, 10.
x,y= 24.5, 81.7.
Using compiler generated double swapper:
Now x,y =81.7, 24.5.
--------------------------------
Process exited after 0.3397 seconds with return value 0
请按任意键继续. . .
[此处为图片1]

接下来是另一个版本的示例代码，即实例8.11a，同样命名为 funtemp.cpp，其功能一致，仅在语法细节上略有不同：

#include <iostream>
template <typename T>
void Swap(T &a, T &b);

int main()
{
    using namespace std;
    int i = 10;
    int j = 20;
    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler generated in swapper:\n";
    Swap(i, j);
    cout << "Now i,j=" << i << ", " << j << ".\n";

    double x = 24.5;
    double y = 81.7;
    cout << "x,y= " << x << ", " << y << ".\n";
    cout << "Using compiler generated double swapper:\n";
    Swap(x, y);
    cout << "Now x,y =" << x << ", " << y << ".\n";

    return 0;
}

template <typename T>
void Swap(T &a, T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

该版本的运行结果与前一版本完全相同：

i,j = 10, 20.
Using compiler generated in swapper:
Now i,j=20, 10.
x,y= 24.5, 81.7.
Using compiler generated double swapper:
Now x,y =81.7, 24.5.
--------------------------------
[此处为图片2]

实例8.12 twotemps.cpp

#include <iostream>
template <typename T>
void swap(T &a, T &b);
template <typename T>
void swap(T *a, T *b, int n);
void show(int a[]);

const int Lim = 8;

int main()
{
    using namespace std;
    int i = 10;
    int j = 20;
    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler generated in swapper:\n";
    ::swap(i, j);
    cout << "Now i,j=" << i << ", " << j << ".\n";

    int d1[Lim] = {0, 7, 0, 4, 1, 7, 7, 6};
    int d2[Lim] = {0, 7, 2, 0, 1, 9, 6, 9};

    cout << "original arraya:\n";
    show(d1);
    show(d2);

    ::swap(d1, d2, Lim);
    cout << "swapped arrays:\n";
    show(d1);
    show(d2);

    return 0;
}

template <typename T>
void swap(T &a, T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

template <typename T>
void swap(T a[], T b[], int n)
{
    T temp;
    for (int i = 0; i < n; i++)
    {
        temp = a[i];
        a[i] = b[i];
        b[i] = temp;
    }
}

void show(int a[])
{
    using namespace std;
    cout << a[0] << a[1] << "/";
    cout << a[2] << a[3] << "/";
    for (int i = 4; i < Lim; i++)
        cout << a[i];
    cout << endl;
}

程序运行输出结果如下：

i,j = 10, 20.
Using compiler generated in swapper:
Now i,j=20, 10.
original arraya:
07/04/1776
07/20/1969
swapped arrays:
07/20/1969
07/04/1776

执行过程结束，返回值为0。

请按任意键继续...

[此处为图片1]

另一个相似实现版本（实例8.12a）中，函数名由swap改为Swap，并去除了作用域解析符::的显式调用，其余结构保持一致。该版本同样实现了对基本类型变量和数组元素的交换功能。

#include <iostream>
template <typename T>
void Swap(T &a, T &b);
template <typename T>
void Swap(T *a, T *b, int n);

void show(int a[]);
const int Lim = 8;

int main()
{
    using namespace std;
    int i = 10;
    int j = 20;

    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler generated in swapper:\n";
    Swap(i, j);
    cout << "Now i,j=" << i << ", " << j << ".\n";

    int d1[Lim] = {0, 7, 0, 4, 1, 7, 7, 6};
    int d2[Lim] = {0, 7, 2, 0, 1, 9, 6, 9};

    cout << "original arraya:\n";
    show(d1);
    show(d2);

    Swap(d1, d2, Lim);
    cout << "swapped arrays:\n";
    show(d1);
    show(d2);

    return 0;
}

template <typename T>
void Swap(T &a, T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

此版本中的模板函数通过重载支持两种操作：引用类型的单个变量交换与指针形式的数组批量交换。函数show()用于格式化输出日期样式的整型数组，前四位表示月日，后四位表示年份信息。

两次运行均正常退出，耗时分别为0.2825秒和0.1926秒，系统返回值均为0，表明程序无异常终止。

#include <iostream>
template <typename T>
void Swap(T &a, T &b)
{
    T temp = a;
    a = b;
    b = temp;
}

struct job
{
    char name[40];
    double salary;
    int floor;
};

template <> void Swap<job>(job &j1, job &j2);
void show(job &j);

int main()
{
    using namespace std;
    cout.precision(2);
    cout.setf(ios::fixed, ios::floatfield);

    int i = 10;
    int j = 20;

    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler generated in swapper:\n";
    Swap(i, j);
    cout << "Now i,j=" << i << ", " << j << ".\n";

    job sue = {"Susan yaffee", 73000.60, 7};
    job sidney = {"Sidney Taffee", 78090.67, 9};

    cout << "Before job swapping:\n";
    cout << "original arraya:\n";
    show(sue);
    show(sidney);

    Swap(sue, sidney);

    cout << "After job swapping:\n";
    show(sue);
    show(sidney);

    return 0;
}

template <typename T>
void Swap(T &a, T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

template <> void Swap<job>(job &j1, job &j2)
{
    double t1 = j1.salary;
    j1.salary = j2.salary;
    j2.salary = t1;

    int t2 = j1.floor;
    j1.floor = j2.floor;
    j2.floor = t2;
}

void show(job &j)
{
    using namespace std;
    cout << j.name << ": $" << j.salary << " on floor " << j.floor << endl;
}
编译运行结果： i,j = 10, 20. Using compiler generated in swapper: Now i,j=20, 10. Before job swapping: original arraya: Susan yaffee: $73000.60 on floor 7 Sidney Taffee: $78090.67 on floor 9 After job swapping: Susan yaffee: $78090.67 on floor 9 Sidney Taffee: $73000.60 on floor 7 -------------------------------- Process exited after 0.2238 seconds with return value 0 请按任意键继续. . . [此处为图片1] 
template <typename T>
void Swap(T a[], T b[], int n)
{
    T temp;
    for (int i = 0; i < n; ++i)
    {
        temp = a[i];
        a[i] = b[i];
        b[i] = temp;
    }
}
[此处为图片2] 
void show(int a[])
{
    using namespace std;
    cout << a[0] << a[1] << "/";
    cout << a[2] << a[3] << "/";
    for (int i = 4; i < Lim; ++i)
        cout << a[i];
    cout << endl;
}
[此处为图片3]
实例8.14 temptempover.cpp

#include <iostream>
template <typename T>
void ShowArray(T arr[], int n);
template <typename T>
void ShowArray(T *arr[], int n);

struct debts
{
    char name[50];
    double amount;
};

int main()
{
    using namespace std;

    int things[6] = {13, 31, 103, 301, 310, 130};

    struct debts mr_E[3] =
    {
        {"Ima wolfe", 2400.0},
        {"Ura Foxe", 1300.0},
        {"Iby Stout", 1800.0}
    };

    double *pd[3];
    for (int i = 0; i < 3; i++)
        pd[i] = &mr_E[i].amount;

    cout << "Listing Mr. E's counts of things:\n";
    ShowArray(things, 6);

    cout << "Listing Mr. E's counts of debts:\n";
    ShowArray(pd, 3);

    return 0;
}

template <typename T>
void ShowArray(T arr[], int n)
{
    using namespace std;
    cout << "template A\n";
    for (int i = 0; i < n; i++)
        cout << arr[i] << ' ';
    cout << endl;
}

template <typename T>
void ShowArray(T *arr[], int n)
{
    using namespace std;
    cout << "template B\n";
    for (int i = 0; i < n; i++)
        cout << *arr[i] << ' ';
    cout << endl;
}

编译运行结果：
Listing Mr. E's counts of things:
template A
13 31 103 301 310 130
Listing Mr. E's counts of debts:
template B
2400 1300 1800

实例8.15 choices.cpp

#include <iostream>
template <class T>
T lesser(T a, T b)
{
    return a < b ? a : b;
}

int lesser(int a, int b)
{
    a = a < 0 ? -a : a;
    b = b < 0 ? -b : b;
    return a < b ? a : b;
}

int main()
{
    using namespace std;

    int m = 20;
    int n = -30;
    double x = 15.5;
    double y = 25.9;

    cout << lesser(m, n) << endl;
    cout << lesser(x, y) << endl;
    cout << lesser<>(m, n) << endl;
    cout << lesser<int>(x, y) << endl;

    return 0;
}

编译运行结果：
20
15.5
-30
15
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