《C++ Primer Plus（第六版）》（11）（第八章 函数探幽 复习题答案）

8.7 复习题

1.经常被调用，逻辑简单，代码少，一般要求没有递归，没有循环。

2.

void song(const char * name, int times);

a.void song(const char * name, int times = 1);

b.加默认值只改原型就行了

c.void song( char * name = "oh, my god", int times = 1);

3.
void iquote(int x)
{
cout << "\"" << x << "\""<<endl;
}

void iquote(double x)
{
cout << "\"" << x << "\"" << endl;
}

void iquote(string x)
{
cout << "\"" << x.c_str() << "\"" << endl;
}

int main()
{
iquote(1);
iquote(2.123456);
iquote("FableGame,http://blog.csdn.net/u012175089");

cin.get();
return 0;
}

4.

结构：

struct box
{
char maker[40];
float height;
float width;
float length;
float volume;
};

//显示
void show(box& b)
{
cout << "maker:" << b.maker << " height:" << b.height << " width:"<<b.width
<< " length:" << b.length << " volume:"<< b.volume;
}

//计算体积
void computeVolume(box& b)
{
b.volume = b.height * b.width * b.length;
}

//main函数
int main()
{
box b{ "FableGame", 1, 2, 3, 0 };
computeVolume(b);
show(b);

cin.get();
return 0;
}

5.
//原来的代码
#include <array>
#include <string>
#include <set>
using namespace std;

const int Seasons = 4;
const array<string, Seasons> Snames = { "Spring", "Summer", "Fall", "Winter" };
void fill(array<double, Seasons> * pa);
void show(array<double, Seasons> da);

int main()
{
array<double, Seasons> expenses;
fill(&expenses);
show(expenses);

cin.get();
cin.get();
return 0;
}

void fill(array<double, Seasons> * pa)
{
for (int i = 0; i < Seasons; i++)
{
cout << "Enter" << Snames[i] << " expenses: ";
cin >> (*pa)[i];
}
}

void show(array<double, Seasons> da)
{
double total = 0.0;
cout << "\nEXPENSES\n";
for (int i = 0; i < Seasons; i++)
{
cout << Snames[i] << ":$" << da[i] << endl;
total += da[i];
}
cout << "Total Expenses: $" << total << endl;
}

//修改后的代码
#include <iostream>
#include <array>
#include <string>
#include <set>
using namespace std;

const int Seasons = 4;
const array<string, Seasons> Snames = { "Spring", "Summer", "Fall", "Winter" };
void fill(array<double, Seasons>&pa);
void show(array<double, Seasons>& da);

int main()
{
array<double, Seasons> expenses;
fill(expenses);
show(expenses);

cin.get();
cin.get();
return 0;
}

void fill(array<double, Seasons>& pa)
{
for (int i = 0; i < Seasons; i++)
{
cout << "Enter" << Snames[i] << " expenses: ";
cin >> pa[i];
}
}

void show(array<double, Seasons>& da)
{
double total = 0.0;
cout << "\nEXPENSES\n";
for (int i = 0; i < Seasons; i++)
{
cout << Snames[i] << ":$" << da[i] << endl;
total += da[i];
}
cout << "Total Expenses: $" << total << endl;
}

区别不是很大，不过原理是不同的。

6.

//a
double mass(double density, double volume = 1.0);//或者重载

double mass(double density, double volume);
double mass(double density);

//b.默认函数只能放在后边,所以只能重载

void repeat(int times, const char* str);
void repeat(const char* str);

//c.可以使用模板函数

template< typename T> T average(T a, T b);

//也可以使用重载函数

int average(int a, int b);
double average(double a, double b);

//d.不能根据返回类型来决定函数的选择,两个版本的特征标相同。

7.

template<typename T> T getMax(T a, T b)
{
return a > b ? a : b;
}

int main()
{
cout << getMax(1, 2) << endl;
cout << getMax(12.323, 3.333) << endl;

cin.get();
cin.get();
return 0;
}

8.书上印错了，是复习题7的模板
#include <iostream>
#include <array>
#include <string>
#include <set>
using namespace std;

struct box
{
char maker[40];
float height;
float width;
float length;
float volume;
};

//显示
void show(box& b)
{
cout << "maker:" << b.maker << " height:" << b.height << " width:" << b.width
<< " length:" << b.length << " volume:" << b.volume<< endl;
}

//计算体积
void computeVolume(box& b)
{
b.volume = b.height * b.width * b.length;
}

//函数模板
template<typename T> T getMax(T a, T b)
{
return a > b ? a : b;
}

//模板的具体化
template<> box getMax(box a, box b)
{
return a.volume > b.volume ? a : b;
}

//main
int main()
{
cout << getMax(1, 2) << endl;
cout << getMax(12.323, 3.333) << endl;
box a{ "FableGame A", 12, 23, 33, 0 };
computeVolume(a);
show(a);
box b{ "FableGame B", 41, 12, 13, 0 };
computeVolume(b);
show(b);
box c = getMax(a, b);
show(c);

cin.get();
cin.get();
return 0;
}

9.对于变量加（），就是引用
int g(int x)
{
return x;
}

int main()
{
float m = 5.5f;
float& rm = m;
decltype(m) v1 = m;//float
decltype(rm) v2 = m;//float&
decltype((m)) v3 = m;//float&
decltype(g(100)) v4 = g(12345);//int
decltype(2.0 * m) v5 = 2.0 * m;//double

cout << v1 << "\t" << v2 << "\t" << v3 << "\t" << v4 << "\t" << v5 << "\t" << endl;
m = 123.123f;
cout << v1 << "\t" << v2 << "\t" << v3 << "\t" << v4 << "\t" << v5 << "\t" << endl;
cin.get();
cin.get();
return 0;
}