c++ primer 学习笔记-第六章

习题6.3：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

int fact(int n)
{
if (n == 1 || n==0)
return 1;
return n*fact(n - 1);
}
int main()
{
cout << fact(4) << endl;
getchar();
getchar();
return 0;
}

习题6.4：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

int fact(void)
{
cout << "n=?" << endl;
int n = 0, f = 1;
cin >> n;
for (size_t i = 1; i < n+1; i++)
{
f *= i;
}
return f;
}
int main()
{
cout << fact() << endl;
getchar();
getchar();
return 0;
}

习题6.10：

#include "标头.h"
void exchange(int *a,int *b)
{
*a = (*a) ^ (*b);
*b = (*b) ^ (*a);
*a = (*a) ^ (*b);
}

习题6.12：

#include "标头.h"
void exchange(int &a,int &b)
{
a ^= b;
b ^= a;
a ^= b;
}

习题6.17：

函数cpp：

#include "标头.h"

#include <string>
#include <cctype>//用iostream即可使用isupper()

using std::string;
using std::isupper;

bool find_super(const string &s)//判断string对象中是否含有大写字母
{
for (auto c : s)
if (isupper(c))
return true;
return false;
}
void lower(string &s)//把string对象全都改成小写形式
{
for (auto &c : s)
c = tolower(c);
}

头文件.h：

#ifndef H
#define H
#include <string>
using std::string;
bool find_super(const string &s);
void lower(string &s);
#endif

源文件.cpp：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include "标头.h"
using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

int main()
{
cout << std::boolalpha << find_super("hello,Boy!") << endl;
string s("gagaGGG");
lower(s);
cout << s << endl;
getchar();
getchar();
return 0;
}

习题6.21：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

int compare_int_pointer(const int i, const int *pi)
{
return (i > *pi) ? i : *pi;
}
int main()
{
int i = 8, ii = 10, *pi = ⅈ
cout << compare_int_pointer(i, pi) << endl;
getchar();
getchar();
return 0;
}

习题6.22：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

void swap_pointer(int *&pi1, int *&pi2)
{
int *ptemp = pi1;
pi1 = pi2;
pi2 = ptemp;
}
int main()
{
int i1 = 8, i2 = 10, *pi1 = &i1, *pi2 = &i2;
swap_pointer(pi1, pi2);
cout << *pi1 << " " << *pi2 << endl;
getchar();
getchar();
return 0;
}

习题6.23:

#include <iostream>
#include <string>
#include <vector>
#include <iterator>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;

void print(const int *pi)//显示整型变量
{
if (pi)
cout << *pi << endl;
}
void print(const char *pc)//显示字符数组
{
if (pc)
while (pc)
cout << *pc++;
}
void print(const int *beg, const int *end)//利用标准库函数begin、end来显示整型数组
{
while (beg != end)
cout << *beg++ << endl;
}
void print(const int ia[], size_t size)//显式传递长度显示整型数组
{
for (size_t i = 0; i != size; ++i)
cout << ia[i] << endl;
}
void print(int (&arr)[2])//数组引用形参显示整型数组
{
for (auto i : arr)
cout << i << endl;
}
int main()
{
char ch[5] = "abcd";
int i = 0, j[2] = { 0, 1 };

print(&i);
print(ch);
print(begin(j), end(j));
print(j, end(j) - begin(j));
//print(j);
getchar();
getchar();
return 0;
}

习题6.27：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

int sum_list(initializer_list<int> ini)
{
int sum = 0;
for (auto i : ini)
sum += i;
return sum;
}
int main()
{
initializer_list<int> ini({ 1, 2, 3, 4, 5, 6, 7, 8, 9 });
cout << sum_list(ini) << endl;
getchar();
getchar();
return 0;
}

习题6.33：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

using iter = vector<int>::const_iterator;
void display(iter beg, iter end)
{
if (beg != end)
{
cout << *beg << " ";
return display(++beg, end);
}
cout << endl;
return;
}
int main()
{
vector<int> ivec{ 1, 2, 3, 4, 5 };
display(ivec.cbegin(),ivec.cend());
getchar();
getchar();
return 0;
}

习题6.37：

string(&func1(string(&arrStr)[10]))[10];

using arrS = string(&)[10];
arrS func2(arrS arrStr);

auto func3(string(&arrStr)[10])->string(&)[10];

string arrs[10] = { "a" };
decltype(arrs) &func(arrS arrStr);

习题6.38：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

int odd[] = { 1, 3, 5, 7, 9 };
int even[] = { 0, 2, 4, 6, 8 };
decltype(odd) &arrPtr(int i)
{
return (i % 2) ? odd : even;
}

int main()
{
cout << arrPtr(1)[0] << endl;
getchar();
getchar();
return 0;
}

习题6.42：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

string making_plural(size_t ctr, const string &word, const string &ending = "s")
{
return (ctr > 1) ? word + ending : word;
}
int main()
{
cout << making_plural(1, "success", "es") << endl;
cout << making_plural(2, "success", "es") << endl;
cout << making_plural(1, "failure") << endl;
cout << making_plural(2, "failure") << endl;
getchar();
getchar();
return 0;
}

习题6.44：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

inline bool isShorter(const string &s1, const string &s2)
{
return s1.size() < s2.size();
}
int main()
{
cout << std::boolalpha << isShorter("hhhh", "23333");
getchar();
getchar();
return 0;
}

习题6.54：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

int func(int, int)
{
cout << "calling" << endl;
return 0;
}
using f = int(int, int);
int main()
{
vector<f *> fvec;
fvec.push_back(&func);
fvec[0](1, 2);

getchar();
getchar();
return 0;
}

习题6.55：

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <initializer_list>

using std::cin; using std::cout;
using std::endl;
using std::string; using std::vector;
using std::begin; using std::end;
using std::initializer_list;

int add(int a, int b)
{
return a + b;
}
int minus(int a, int b)
{
return a - b;
}
int multiply (int a, int b)
{
return a * b;
}
int divide(int a, int b)
{
return a / b;
}

using pf = decltype(add) *;//using pf = int (*)(int, int)等都可以

int main()
{
vector<pf> pfvec{ add, minus, multiply, divide };
for (auto f : pfvec)
cout << f(3, 2) << endl;
getchar();
getchar();
return 0;
}