[cs13001] Pointers question

[Mikhail Nesterenko]

> Professor, what would happen if you have three pointers and a
> variable.    The first pointer points to the variable, and second
> pointer points to the first variable, and the third pointer is a
> constant pointer that points to the second pointer. What would
> happen?   So if I am thinking this correctly, it would be like
>
>
> Int * const p3 = p2 = p1 = Int i 
> 
> So if the const points to a pointer pointing to a pointer pointing
> to an i variable, would the const point only to the p2 memory
> location, or would it point to the variable? 
> 


A good way to figure out complicated C++ declarations is to read them
from right to left. For example:

	const int* i; // pointer to an int that is const
	int* const j; // constant pointer to a (non-const) int
	int const* k; // pointer to a const int, less popular but correct form

If you want to declare a constant pointer that points to a pointer
that points to another pointer that points to an int; and then
initialize the declared pointer, it might look like this:

	int i, *p, **pp;
	int ***const cppp = &pp; // initializes a constant pointer to a
	    	     	         // pointer to a pointer to int
	p = &i;  // assigns p the address of i
	pp = &p; // assigns pp the address of p
	***cppp = 42; // assigns a new value to i
	
Naturally, extended chains of pointers-to-pointers (called "levels of
indirection") make the program difficult to underhand and should be
avoided or used with extreme care.

Thanks,
-- 
Mikhail