【第四章】 复合类型---4.8 指针、数组和指针算术

/* programNo4.19 */
/***********************************
	2017年9月29日15:18:41
	Athor：xiyuan255
	Course：C++
	Contain：addpntrs.cpp
	Reference: C++ Primer plus		
	知识点：
		1.指针算术：将整数变量加1后，其值将增加1；但将指针变量加1后，
		  增加的量等于它指向的类型的字节数(如指向int类型，如果系统对
		  int使用4个字节，则数值增加4)。
		2.C++将数组名也解释为地址。所以array[i]与array[i+1]的地址相差
		  了数组元素数据类型的字节数个字节。
		3.arrayname[i] becomes *(arrayname + i) 
		  编译器实际上是将arrayname[i]解析为*(arrayname + i)进行操作的
		  所以这两则实际上是等价的；
		4.指针与数组名的区别：
		  (1) 指针可以修改其值，而数组名却是常量；(实际上数组名是一个确
		  定的地址，当他定义完数组时，数组名在内存中就指代该内存区域的首
		  地址；为一确定值，而指针不同，它声明的一块内存区域，只是该内存
		  区域里面只存放指针类型的变量，即地址，至于存放什么地址，可以程
		  序员自己按需要修改。)
		  pointername = pointername + 1; // valid
		  arrayname = arrayname + 1;     // not allowed
		  (2) 对数组应用sizeof运算符得到的数组长度，而对指针应用运算符sizeof
		      得到的是指针的长度，即使此时指针指向的是一个数组。
*************************************/
// addpntrs.cpp -- pointer addition

#include <iostream>

int main(void)
{
	using namespace std;
	double wages[3] = {10000.0, 20000.0, 30000.0};
	short stacks[3] = {3, 2, 1};

  // Here are two ways to get the address of an array
	double * pw = wages;     // name of an array = address
	short * ps = &stacks[0]; // or use address operator
  // with array element
	cout << "pw = " << pw << ", *pw = " << *pw << endl;
	pw = pw + 1;
	cout << "add 1 to the pw pointer: \n";
	cout << "pw = " << pw << ", *pw = " << *pw << endl;

	cout << "ps = " << ps << ", *ps = " << *ps << endl;
	ps = ps + 1;
	cout << "add 1 to the ps pointer: \n";
	cout << "ps = " << ps << ", *ps = " << *ps << endl;

	cout << "access two elements with array notation.\n";
	cout << "stacks[0] = " << stacks[0]
	     << ", stacks[1] = " << stacks[1] << endl;
	cout << "access two elements with pointer notation.\n";
	cout << "*stacks = " << *stacks
		 << ", *(stacks + 1) = " << *(stacks + 1) << endl;

	cout << sizeof(wages) << " = size of wages array.\n";
	cout << sizeof(pw) << " = size of pw pointer.\n";

	return 0;
}

/**
输出结果：
	pw = 0034FBFC, *pw = 10000
	add 1 to the pw pointer:
	pw = 0034FC04, *pw = 20000
	ps = 0034FBEC, *ps = 3
	add 1 to the ps pointer:
	ps = 0034FBEE, *ps = 2
	access two elements with array notation.
	stacks[0] = 3, stacks[1] = 2
	access two elements with pointer notation.
	*stacks = 3, *(stacks + 1) = 2
	24 = size of wages array.
	4 = size of pw pointer.
*/