What is the difference between...

[Bruno Medeiros]

Sean Kelly wrote:
> Bruno Medeiros wrote:
>> Janice Caron wrote:
>>> -----Original Message-----
>>> From: digitalmars-d-bounces at puremagic.com 
>>> [mailto:digitalmars-d-bounces at puremagic.com] On Behalf Of Daniel919
>>> Sent: 07 September 2007 12:39
>>> To: digitalmars-d at puremagic.com
>>> Subject: Re: What is the difference between...
>>>
>>>> > (2) void f(const(int) x)
>>>> Useless, like all: const/invariant(simplestoragetype)
>>>
>>> It is? Why? Why doesn't it mean x is a const int?
>>>
>>> So f(const(int)* x) means x is a pointer to const int, but 
>>> f(const(int) x) does not mean x is a const int? Now I'm very, very 
>>> confused.
>>>
>>> Why am I not getting this?
>>>
>>
>> const(...) makes everything inside the parenthesis const. But there is 
>> one exception: If that const is part of a declaration, then the 
>> top-level value/type is not const. (the top-level value is the one 
>> that changes with assignments) So:
>>
>> const(int)* x;  // mutable pointer to const int
>> const(int)  x;  // mutable int;
>> const(int*) x;  // mutable pointer to const int
>> const(int**) x;  // mutable pointer to const pointer to const int;
>> const(int*)* x;  // mutable pointer to const pointer to const int;
> 
> Wouldn't this be "mutable pointer to mutable pointer to const int?"
> 
> 
> Sean

The last one :
   const(int*)* x;
?

Nope, it's like I said. It can be verified with this:

   x = null;   // Ok
   *x = null;  // Error
   **x = null; // Error

If people were thinking that const(<X>) would *allways* only apply 
immutability to the referenced value of <X> (if X is a reference), then 
that's wrong. It only does that when const(<X>) is the top-level type.

(BTW, naturally, the same is true for invariant)


-- 
Bruno Medeiros - MSc in CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D