C++Primer Plus（第六版）第九章编程练习：

第一题
知识点

• 在code::block中，不能直接用""来比较确认空字符串，不用string类的情况下还是最好用cstring函数确定长度来确定空串
• 字符串数组单个元素赋值的时候末尾的\0要自己赋值，不然不会自动填充

golf.h

#ifndef GOLF_H_INCLUDED
#define GOLF_H_INCLUDED
const int Len = 40;
struct golf
{
char fullname[Len];
int handicap;
};
void setgolf(golf & g, const char * name, int hc);
int setgolf(golf & g);
void handicap(golf & g, int hc);
void showgolf(const golf & g);

#endif // GOLF_H_INCLUDED

main

#include <iostream>
#include "golf.h"

using namespace std;
int main()
{
golf test[5];
setgolf(test[0], "happy time", 20);
showgolf(test[0]);
while(1)
{
int i = 1;
if(setgolf(test[i]) && i < 5)
{
showgolf(test[i]);
i++;
}
else
break;
}
cout << "byebye";
return 0;
}

define

// contain function called in file1
#include <iostream>
#include "golf.h"
#include <cstring>
void setgolf(golf & g, const char* name, int hc)
{
for(int i = 0; i <= strlen(name); i++) //我尝试用for(int i = 0; name[i] != '\0'; i++)来做循环
g.fullname[i] = name[i];           //这样可以不用使用cstring的函数，结果也是发现name指针末尾的\0不会赋值到数组，会多比较一段乱码出来
g.handicap = hc;
}
int setgolf(golf & g)
{
using namespace std;
cout << "Enter the name and the value:"<< endl;
cin.getline(g.fullname,Len);
cin >> g.handicap;
cin.get();
if(strlen(g.fullname) == 0)         //我试过直接用q.fullname == ''来比较，但是无法触发分支，感觉是编译器的原因，应该用vs studio可以做到
return 0;
else
return 1;
}
void handicap(golf & g, int hc)
{
g.handicap = hc;
}

void showgolf(const golf & g)
{
std::cout << g.fullname << std::endl;
std::cout << g.handicap << std::endl;
}

一道题做尼玛半天。

第二题
知识点

• 就是string为参数的getline记住别在前面加个cin.，而且格式getline(cin,str);

#include <iostream>
#include <string>

using namespace std;
void strcount(const string str);

int main()
{
string input;
cout << "input the line:\n";
getline(cin,input);
while(!input.empty())
{
strcount(input);
cout << "enter next line (empty line to quit):\n";
getline(cin,input);
}
return 0;
}

void strcount(const string str)
{
static int total = 0;
int count = 0;
cout << "\"" << str << "\"contains" ;
count = str.length();
total += count;
cout << count << " characters\n";
cout << total << " characters total\n";
}

第三题：
知识点

• 没什么好说的，就是分配空间的事情，分配缓冲区

#include <iostream>
#include <new>
#include <cstring>

using namespace std;
const int BUF = 10;
struct chaff
{
char dross[20];
int slag;
};

chaff buffer[BUF];

int main()
{
chaff * pd = new (buffer) chaff[2];
strcpy(pd[0].dross, "Bigdaddy");
strcpy(pd[1].dross, "asskicker");
pd[0].slag = 10;
pd[1].slag = 20;
for(int i = 0; i < 2; i++)
{
cout << pd[i].dross <<endl;
cout << pd[i].slag << endl;
}
delete []pd;
return 0;
}

第四题
知识点：

• 在源代码中定义名称空间中函数时，要像声明的时候一样的格式，不能用using来定义，是不行的

head

#ifndef GOLF_H_INCLUDED
#define GOLF_H_INCLUDED
namespace SALES
{
const int QUARTERS = 4;
struct Sales
{
double sales[QUARTERS];
double average;
double max;
double min;
};
void setSales(Sales & s, const double ar[], int n);
void setSales(Sales & s);
void showSales(const Sales & s);
}

#endif // GOLF_H_INCLUDED

definition

// contain function called in file1
#include <iostream>
#include "golf.h"

namespace SALES
{

void setSales(Sales &  s, const double ar[], int n)
{

if(n < 4)
{
double temp = 0;
double max = -100;
double min = 100;
for(int i = 0; i < n; i++)
{
s.sales[i] = ar[i];
temp += s.sales[i];
if(max < s.sales[i])
max = s.sales[i];
if(min > s.sales[i])
min = s.sales[i];
}
s.average = temp / n;
s.max = max;
s.min = min;
for(n; n < 4; n++)
s.sales
 = 0;
}
else
{
double temp = 0;
double max = -100;
double min = 100;
for(int i = 0; i < n; i++)
{
s.sales[i] = ar[i];
temp += s.sales[i];
if(max < s.sales[i])
max = s.sales[i];
if(min > s.sales[i])
min = s.sales[i];
}
s.average = temp / n;
s.max = max;
s.min = min;
}

}
void setSales(Sales &  s)
{
std::cout << "input the sales of 4 quarters:"<<std::endl;
double ar[4];
double temp = 0;
double max = -100;
double min = 100;
for(int i = 0; i < 4; i++)
std::cin >> ar[i];
for(int i = 0; i < 4; i++)
{
s.sales[i] = ar[i];
temp += s.sales[i];
if(max < s.sales[i])
max = s.sales[i];
if(min > s.sales[i])
min = s.sales[i];
}
s.average = temp / 4;
s.max = max;
s.min = min;
}
void showSales(const Sales & s)
{
for(int i = 0; i < 4; i++)
std::cout << "\n"<<s.sales[i]<< "\t";
std::cout << "\n" << "average = " << s.average;
std::cout << "\n" << "max = " <<s.max;
std::cout << "\n" << "min = " <<s.min;
}

}

main

#include <iostream>
#include "golf.h"

using namespace std;
using namespace SALES;

int main()
{
Sales test1,test2;
double ar[4] = {15.25, 25.22, 50.22, 90.44};
setSales(test1,ar,4);
setSales(test2);
showSales(test1);
showSales(test2);
return 0;
}