pointer and ampersand position with const in C++ [duplicate]

Question

Possible Duplicate:
Declaring pointers; asterisk on the left or right of the space between the type and name?

I've always been wondering what's the exact correct position to put * and &. it seems that C++ is pretty tolerant about where to put these marks. For example I've seem pointer and ampersand been put on both left and right of a keyword or in the middle of two keywords, but confusingly sometimes they seems to mean the same thing, especially when used together with const

void f1(structure_type const& parameter)
void f2(structure_type const &parameter)

void f2(structure_type  const *sptr);
void f2(structure_type  const* sptr);
void f2(structure_type  const * sptr);

The examples are not exhaustive. I see them everywhere while being declared or been passed to a function. Do they even mean the same thing? But I also see cases while putting * will affect which object being referred as a pointer (likely the case where * is in between two keywords).

EDITED:

int const *Constant
int const * Constant // this above two seem the same to me, both as pointer to a constant value
int const* Constant //  EDIT: this one seems the same as above. instead of a constant pointer

const int * Constant // this is also a pointer to a constant value, but the word order changed while the pointer position stays the same, rather confusing.

int* const Constant
int * const Constant // instead, these two are constant pointers

So I concluded this:

T const* p; // pointer to const T
const T* p  // seems same from above
T* const p; // const pointer to T

Still, this confused the hell out of me. Doesn't the compiler care about position and the spacing required for them?

Edit: I want to know in general of the position matters. If yes in what cases.

Answer 1

White space matters only to the degree that it keeps tokens from running together and (for example) creating a single token, so (for example) int x is obviously different from intx.

When you're dealing with something like: int const*x;, whitespace on either size of the * makes absolutely no difference to the compiler at all.

The difference between a pointer to const int and const pointer to int depends on which side of the * the const is on.

int const *x;    // pointer to const int
int *const x;    // const pointer to int

The primary difference is readability when/if you define/declare multiple objects in the same declaration.

int* x, y;
int *x, y;

In the first, somebody might think that x and y are pointers to int -- but in fact, x is a pointer to an int, and y is an int. To some people's eyes, the second reflects that fact more accurately.

One way to prevent any misinterpretation is to only ever define one object at a time:

int *x;
int y;

For any of these, correct interpretation is fairly easy if you ignore whitespace entirely (except to tell you where one toke ends and another starts, so you know "const int" is two tokens) and read from right to left, reading * as "pointer to". For example: int volatile * const x; is read as "x is a const pointer to a volatile int".

Answer 2

int const *Constant
int const * Constant 
int const* Constant

All of the above intend to declare a non constant pointer to a constant integer.

Simple rule:

If const follows after the * it applies to the pointer if not it applies to the pointed object. The spacing doesn't matter.