C++ Primer Plus 8章源码

记录我看C++ Primer Plus(第六版)第八章源代码

8.1

#include<iostream>
inline double square(double x) { return x * x; }
int main()
{
    using namespace std;
    double a, b;
    double c = 13.0;
    a = square(5.0);
    b = square(4.5 + 7.5);
    cout << "a = " << a << ",b = " << b << "\n";
    cout << "c = " << c;
    cout << ", c squared = " << square(c++) << "\n";
    cout << "Now c = " << c << "\n";
    return 0;
}

8.2

#include<iostream>
int main()
{
    using namespace std;
    int rats = 101;
    int &rodents = rats;
    cout << "rats = " << rats;
    cout << ", rodents = " << rodents << endl;
    rodents++;
    cout << "rats = " << rats;
    cout << ", rodents = " << rodents << endl;
    cout << "rats address = " << &rats;
    cout << ",rodents address = " << &rodents << endl;
    return 0;
}

8.3

#include<iostream>
int main()
{
    using namespace std;
    int rats = 101;
    int &rodents = rats;
    cout << "rats = " << rats;
    cout << ",rodents = " << rodents << endl;
    cout << "rats address = " << &rats;
    cout << ", rodents address = " << &rodents << endl;
    int bunnies = 50;
    rodents = bunnies;
    cout << "bunnies = " << bunnies;
    cout << ",rats = " << rats;
    cout << ",rodents = " << rodents << endl;
    cout << "bunnies address = " << &bunnies;
    cout << ",rodents address = " << &rodents << endl;
    return 0;
}

8.4

#include<iostream>
void swapr(int &a, int &b);
void swapp(int *p, int *q);
void swapv(int a, int b);
int main()
{
    using namespace std;
    int wallet1 = 300;
    int wallet2 = 350;
    cout << "wallet1 = $" << wallet1;
    cout << "wallet2 = $" << wallet2 << endl;

    cout << "Using references to swap contents:\n";
    swapr(wallet1, wallet2);
    cout << "wallet1 = $" << wallet1;
    cout << "wallet2 = $" << wallet2 << endl;

    cout << "Using pointers to swap contents again:\n";
    swapp(&wallet1, &wallet2);
    cout << "wallet1 = $" << wallet1;
    cout << "wallet2 = $" << wallet2 << endl;

    cout << "Trying to use passing by value:\n";
    swapv(wallet1, wallet2);
    cout << "wallet1 = $" << wallet1;
    cout << "wallet2 = $" << wallet2 << endl;
    return 0;
}
void swapr(int & a,int & b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}
void swapp(int * p,int *q)
{
    int temp;
    temp = *p;
    *p = *q;
    *q = temp;
}
void swapv(int a, int b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}

8.5

#include<iostream>
double cube(double a);
double refcube(double &ra);
int main()
{
    using namespace std;
    double x = 3.0;
    cout << cube(x);
    cout << " = cube of " << x << endl;
    cout << refcube(x);
    cout << " = cube of " << x << endl;
    return 0;
}
double cube(double a)
{
    a *= a * a;
    return a;
}
double refcube(double &ra)
{
    ra *= ra * ra;
    return ra;
}

8.6

#include<iostream>
#include<string>
struct free_throws
{
    std::string name;
    int made;
    int attempts;
    float percent;
};
void display(const free_throws &ft);
void set_pc(free_throws &ft);
free_throws &accumulate(free_throws &target, const free_throws &source);
int main()
{
    free_throws one = {"Ifelsa Branch", 13, 14};
    free_throws two = {"Andor Knott", 10, 16};
    free_throws three = {"Minnie Max", 7, 9};
    free_throws four = {"Whily Looper", 5, 9};
    free_throws five = {"Long Long",6, 14};
    free_throws team = {"Throwgoods", 0, 0};
    free_throws dup;
    set_pc(one);
    display(one);
    accumulate(team, one);
    display(team);

    display(accumulate(team, two));
    accumulate(accumulate(team, three), four);
    display(team);

    dup = accumulate(team, five);
    std::cout << "Displaying team:\n";
    display(team);
    std::cout << "Displaying dup after assignment:\n";
    display(dup);
    set_pc(four);
    accumulate(dup, five) = four;
    std::cout << "Displaying dup after ill-advised assignment:\n";
    display(dup);
    return 0;
}
void display(const free_throws &ft)
{
    using std::cout;
    cout << "Name: " << ft.name << "\n";
    cout << " Made: " << ft.made << "\t";
    cout <<"Attempts: " << ft.attempts << "\t";
    cout << "Percent: " << ft.percent << "\n";
}
void set_pc(free_throws & ft)
{
    if(ft.attempts!=0)
        ft.percent = 100.0f * float(ft.made) / float(ft.attempts);
    else
        ft.percent = 0;
}
free_throws &accumulate(free_throws &target, const free_throws &source)
{
    target.attempts += source.attempts;
    target.made += source.made;
    set_pc(target);
    return target;
}

8.7

#include<iostream>
#include<string>
using namespace std;
string version1(const string &s1, const string &s2);
const string &version2(string &s1, const string &s2);
const string &version3(string &s1, const string &s2);
int main()
{
    string input;
    string copy;
    string result;
    cout << "Enter a string: ";
    getline(cin, input);
    copy = input;
    cout << "Your string as entered: " << input << endl;
    result = version1(input, "***");
    cout << "Your strng enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;

    result = version2(input, "###");
    cout << "Your string enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;

    cout << "Resetting original string .\n";
    input = copy;
    result = version3(input, "@@@");
    cout << "Your string enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;
    return 0;
}
string version1(const string &s1, const string &s2)
{
    string temp;
    temp = s2 + s1 + s2;
    return temp;
}
const string &version2(string &s1, const string &s2)
{
    s1 = s2 + s1 + s2;
    return s1;
}
const string &version3(string &s1, const string &s2)
{
    string temp;
    temp = s2 + s1 + s2;
    return temp;
}

8.8

#include<iostream>
#include<fstream>
#include<cstdlib>
using namespace std;

void file_it(ostream &os, double fo, const double fe[], int n);
const int LIMIT = 5;
int main()
{
    ofstream fout;
    const char *fn = "ep-data.txt";
    fout.open(fn);
    if(!fout.is_open())
    {
        cout << "Can't open " << fn << ".Bye.\n";
        exit(EXIT_FAILURE);
    }
    double objective;
    cout << "Enter the fical lenght of your "
            "telescope objective in mm: ";
    cin >> objective;
    double eps[LIMIT];
    cout << "Enter the focal lengths,in mm, of " << LIMIT << " eyepieces:\n";
    for (int i = 0; i < LIMIT;i++)
    {
        cout << "Eyepiece #" << i + 1 << ": ";
        cin >> eps[i];
    }
    file_it(fout, objective, eps, LIMIT);
    file_it(cout, objective, eps, LIMIT);
    cout << "Done\n";
    return 0;
}
void file_it(ostream &os, double fo, const double fe[], int n)
{
    ios_base::fmtflags initial;
    initial = os.setf(ios_base::fixed);
    os.precision(0);
    os << "Focal length of objective: " << fo<< " mm\n";
    os.setf(ios:: showpoint);//小数部分为0
    os.precision(1);//显示多少位小数
    os.width(12);//设置输入字段的宽度
    os << "f.l. eyeiece";
    os.width(15);
    os << "magnification" << endl;
    for (int i = 0; i < n;i++)
    {
        os.width(12);
        os << fe[i];
        os.width(15);
        os << int(fo / fe[i] + 0.5) << endl;
    }
    os.setf(initial);//恢复之前的格式
}

8.9

#include<iostream>
const int ArSize = 80;
char *left(const char *str, int n = 1);
int main()
{
    using namespace std;
    char sample[ArSize];
    cout << "Enter a string:\n";
    cin.get(sample, ArSize);
    char *ps = left(sample, 4);
    cout << ps << endl;
    delete[] ps;
    ps = left(sample);
    cout << ps << endl;
    delete[] ps;
    return 0;
}
char * left(const char *str ,int n)
{
    if(n<0)
        n = 0;
    char *p = new char[n + 1];
    int i;
    for (i = 0; i < n && str[i];i++)
        p[i] = str[i];
    while(i<=n)
        p[i++] = '\0';
    return p;
}

8.10

#include<iostream>
unsigned long left(unsigned long num, unsigned ct);
char *left(const char *str, int n = 1);
int main()
{
    using namespace std;
    char * trip = "Hawaii!!";
    unsigned long n = 12345678;
    int i;
    char *temp;
    for (i = 1; i <10;i++)
    {
        cout << left(n, i) << endl;
        temp = left(trip, i);
        cout << temp << endl;
        delete[] temp;
    }
    return 0;
}
unsigned long left(unsigned long num,unsigned ct)
{
    unsigned digits = 1;
    unsigned long n = num;
    if(ct==0||num==0)
        return 0;
    while(n/=10)
        digits++;
    if(digits>ct)
    {
        ct = digits - ct;
        while(ct--)
            num /= 10;
        return num;
    }
    else
        return num;
}
char *left(const char *str ,int n)
{
    if(n<0)
        n = 0;
    char *p = new char[n + 1];
    int i;
    for (i = 0; i < n && str[i];i++)
        p[i] = str[i];
    while(i<=n)
        p[i++] = '\0';
    return p;
}

8.11

#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 int 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  swapper:\n";
    Swap(x, y);
    cout << "Now x,y = " << x << ", " << y << ".\n";
    cin.get();
    return 0;
}
template<typename T>
void Swap( T &a,T &b)
{
    T temp;
    temp = a;
    a = b;
    b = temp;
}

8.12

#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, j = 20;
    cout << "i,j= " << i << ", " << j << ".\n";
    cout << "Using compiler-generated int 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 arrays:\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;
}

8.13

#include<iostream>
template <typename T>
void Swap(T &a, T &b);
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, j = 20;
    cout << "i,j = " << i << ", " << j << ".\n";
    cout << "Using compiler-generated int swapper:\n";
    Swap(i, j);
    cout << "Now i,j = " << i << ", " << j << ".\n";
    job sue = {"Susan Yaffee", 7300.60, 7};
    job sidney = {"Sidney Taffee", 780660.72, 9};
    cout << "Before job swapping:\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;
    int t2;
    t1 = j1.salary;
    j1.salary = j2.salary;
    j2.salary = t1;
    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;
}

8.14

#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 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;
}

8.15

#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;
}