Extended Type Design.

[Bruno Medeiros]

Andrei Alexandrescu (See Website For Email) wrote:
> Derek Parnell wrote:
>> On Mon, 19 Mar 2007 22:34:13 -0700, Andrei Alexandrescu (See Website For
>> Email) wrote:
>>
>>> Tyler Knott wrote:
>>>> *const and invariant only make sense when applied to references, 
>>>> otherwise they are ignored or (preferably) errors.
>>> Correct.
>>
>> Can 'const' and 'invariant' apply to structs, especially ones that 
>> contain
>> references.
>>
>>   struct Foo
>>   {
>>       char[] s;
>>       char c;
>>   }
>>
>>   const Foo f;  // Is this a mistake then?
> 
> That code is fine. I should have said "const and invariant make sense 
> only when applied to types that are, or contain, references". Sorry.
> 
>>   f.s[0] = 'a'; // okay???
> 
> No.
> 
>>   f.s = "xyz";  // okay???
> 
> Yes.
> 
>>   f.s = "def".dup; // okay ???
> 
> Yes.
> 
>>   f.s.length = 1;  // okay?
> 
> Yes.
> 
>>   f.s ~= 'a'; // okay??
> 
> Yes.
> 
>>   f.c = 'a';   // okay???
> 
> Yes.
> 
>>   const Foo somefunc();
>>   f = somefunc; // okay??
> 
> Yes.
> 
>>   Foo someotherfunc();
>>   f = someotherfunc; // okay??
> 
> Yes. Non-const transforms into const no problem.
> 
> 
> Andrei

What?? If f is 'const', how are any of those "f.s =" assignments allowed?


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