c++ array and pointer

pointer to const object and const pointer，

1.指向常量对象的指针，意思是指针所指向的 对象内容不能变(不能够通过指针赋值)。

2.常量指针，意思是指针内容不能变，指向对象a就不能改为指向对象b(指针不能指向别处)。
(简单来说就是const挨着哪个近，哪个就不能变。)

pointer to const object:
const double *cptr; // cptr may point to a double that is const


const double pi = 3.14;
double *ptr = π // error: ptr is a plain pointer
const double *cptr = π // ok: cptr is a pointer to const

const int universe = 42;
const void *cpv = &universe; // ok: cpv is const
void *pv = &universe; // error: universe is const

const pointer:
int errNumb = 0;
int *const curErr = &errNumb; // curErr is a constant pointer
curErr = curErr; // error: curErr is const

还有个更恶心的，const pointer to a const object

指向常量对象的常量指针，尼玛两个（pointer and object）都不能变，都是const.

const double pi = 3.14159;
// pi_ptr is const and points to a const object
const double *const pi_ptr = π