struct vs. class, int vs. char.

[Don]

grauzone wrote:
> Denis Koroskin wrote:
>> On Tue, 28 Apr 2009 22:13:50 +0400, Tomas Lindquist Olsen 
>> <tomas.l.olsen at gmail.com> wrote:
>>
>>> On Tue, Apr 28, 2009 at 6:07 PM, MLT <none at anon.com> wrote:
>>>> 2. char[] vs. int[]
>>>> I think it is strange that
>>>> char[] x = "1234" ;
>>>> x[0] = '4' ;
>>>>
>>>> Produces a run time error, but
>>>> int[] x = [1,2,3,4] ;
>>>> x[0] = 4 ;
>>>> Doesn't. I think that they both should, or both shouldn't - to be  
>>>> consistent (and it would be better if they both didn't). Best would 
>>>> be  again, to allow the programmer to specify where the array (or 
>>>> other  stuff) should be stored.
>>>>
>>> It pretty much boils down to this (mostly said in other replies)
>>>
>>> * string literals are special, they are allocated in a static data
>>> segment, readonly if the platform allows it.
>>>
>>> * arrayliterals as non-static expressions are always heap allocated.
>>> even when there's absolute no need for it... (see
>>> http://d.puremagic.com/issues/show_bug.cgi?id=2356 )
>>>
>>> -Tomas
>>
>> Someone ought to post a feature request to make arrayliterals 
>> immutable by default (D2 only, I don't think this change will go to D1 
>> anyway) and don't heap-allocate them every time they're used:

Definitely. They should go into the initialized data segment.
>>
>> int[] x1 = [1,2,3,4]; // error: can't assign immutable(int)[] to int[]
> 
> Why not auto-allocate? Writing that .dup all the time is going to be 
> annoying. Just implicitly convert it from immutable to mutable by copying.

I think it's pretty unlikely that you'd want to do that. It's far more 
likely that it's a bug, and you meant it to be an immutable(int)[].
Except in the case where the array is empty.
(Likewise, it'd be nice if char [] s=""; were legal in D2. Since a 
mutable "" string has nothing that can be changed anyway, "" can be 
treated in the same way that 'null' is).

> 
>> int[] x2 = [1,2,3,4].dup; // okay, allocates
>>
>> int[4] x3 = [1,2,3,4]; // okay, doesn't allocate
>>
>> foreach (int i; [1,2,3,4]) { // okay, doesn't allocate
>>     // ...
>> }