今天看到了函数指针这一小结，发现自己对指针的认知还是不够深刻，特意贴下来，日后回顾。
《C++ Primer Plus》
第七章 7.19(arfupt.cpp)

#include <iostream>

const double * f1(const double ar[], int n);
const double * f2(const double [], int);
const double * f3(const double *, int);

int main()
{
	using namespace std;
	double av[3] = { 1112.3, 1542.6, 2227.9 };
//p1 指向 f1
	const  double * (*p1)(const double * ,int) = f1;
//自动声明类型
	auto p2 = f2;
	cout << "Using pointers to functions:\n";
	cout << " Address Value\n";
	cout << (*p1)(av,3) << ": " << *(*p1)(av,3) << endl;
	cout << (*p2)(av,3) << ": " << *(*p2)(av,3) << endl;
//注意()优先级大于*，*p2(av,3) == *(p2(av,3))
	cout << p2(av,3) << ": " << *p2(av,3) << endl;

//二级指针
	const double * (*pa[3])(const double * , int) = { f1,f2,f3 };
	auto pb = pa;
	cout << "\nUsing an array of pointers to functions:\n";
	cout << " Address Value\n";
	for (int i = 0;i < 3;i++)
// (*(pa+i))(av,3) == pa[i](av,3) 似乎[]优先级高于()
		cout << (*(pa + i))(av,3) << ": " << *(*(pa+i))(av,3) << endl;

	cout << "\nUsing a pointer to a pointer to a function:\n";
	cout << " Address Value\n";
	for (int i = 0;i < 3; i++)
		cout << pb[i](av,3) << ": " << *pb[i](av,3) << endl;

	cout << "\nUsing pointers to an array of pointers:\n";
	cout << " Address Value\n";
// 三级指针
	const double *(*(*pd)[3])(const double *, int ) = & pa;
	auto pc = &pa;
	const double * pdb = (*pd)[1](av,3);

	cout << (*pc)[0](av,3) << ": " << *(*pc)[0](av,3) << endl;
	cout << pdb << ": " << *pdb << endl;
	cout << (*(*pd)[2])(av,3) << ": " << *(*(*pd)[2])(av,3) << endl;
	return 0;
}

const double * f1 (const double * ar, int n)
{
	return ar;
}
const double * f2 (const double ar[] , int n)
{
	return ar+1;
}
const double * f3 (const double * ar, int n)
{
	return ar+2;
}

第七章 复习题-13

#include <iostream>
#include <cstring>
//声明一个结构体
struct applicant
{
	char name[30];
	int credit_rating[3];
};
using namespace std;

//声明一个show函数
void show(applicant *);

//声明一个empty函数
void empty(const applicant *);

//声明一个函数指针类型
typedef void (*tempty)(const applicant *);

//声明一个指向empty函数的函数指针p1
tempty p1 = empty;

//声明一个函数strscat
const char * strscat(const applicant *, const applicant *);

//声明一个函数指针p2,并指向strscat
const char * (*p2)(const applicant *,const applicant *) = strscat;

//声明一个包含5个函数指针的数组ap
tempty ap [5];

//声明一个包含10个函数指针的数组pb
const char * (*(pb[10]))(const applicant * ,const applicant *);
//同上,声明一个包含10个函数指针的数组pc
const char * (*pc[10])(const applicant * ,const applicant *);

//声明一个指向包含10个函数指针的数组的指针pa
char * (*(*pa[10]))(const applicant * ,const applicant *);

int main()
{
	struct applicant test = { "=-=.",{ 0,1,2 } };
	cout << "Use show function." << endl;
	show(&test);
	cout << "Use strscat function." << endl;
	const char * pstr = strscat(&test,&test);
	cout << pstr << endl;
//忘记添加的delete. =_=!
	delete [] pstr;
	return 0;
}
void show(struct applicant * app)
{
	cout << app->name << endl;
	for (int i = 0; i < 3; i++)
		cout << app->credit_rating[i] << endl;
	return;
}
void empty(const applicant * a)
{
	return;
}
const char * strscat(const applicant * chars1, const applicant * chars2)
{
	char pstr [20];
	strcpy(pstr,chars1->name);
	char * str = new char [40];
	strcpy(str,strcat(pstr,chars2->name));
	return str;
}