Fixing const arrays

[Andrei Alexandrescu]

On 12/11/11 4:19 PM, Jonathan M Davis wrote:
> On Sunday, December 11, 2011 23:13:39 Timon Gehr wrote:
>> On 12/11/2011 10:34 PM, Jonathan M Davis wrote:
>>> On Sunday, December 11, 2011 10:34:40 Andrei Alexandrescu wrote:
>>>> On 12/11/11 9:46 AM, dsimcha wrote:
>>>>> On 12/10/2011 4:47 PM, Andrei Alexandrescu wrote:
>>>>>> We decided to fix this issue by automatically shedding the
>>>>>> top-level
>>>>>> const when passing an array or a pointer by value into a function.
>>>>>
>>>>> Really silly question: Why not do the same for primitives (int,
>>>>> float,
>>>>> char, etc.) or even structs without indirection? I've seen plenty of
>>>>> code that blows up when passed an immutable double because it tries
>>>>> to
>>>>> mutate its arguments. About 1.5 years ago I fixed a bug like this in
>>>>> std.math.pow().
>>>>
>>>> Yes, that would be good to do as well.
>>>
>>> Actually, that could be a problem for some stuff. It might be an
>>> acceptable problem, but it creates a problem nonetheless. What about
>>> containers? You can have arrays with immutable elements, but if you
>>> made it so that immutable int and int were the same as far as templates
>>> were concerned,  then it would be impossible to have a container which
>>> held immutable elements. How big of a problem that is, I don't know,
>>> but I'd be concerned about some of the side effects.
>>
>> Those issues are inexistent. int and immutable(int) are implicitly
>> convertible to each other.
>
> They may be implicitly convertible, but if you just outright stripped const
> and immutable from primitives, it would become impossible to instantiate a
> container which held const or immutable elements which were primitive.

Timon is right, there's no issue. Top-level qualifier would be stripped 
ONLY when passing by-value into a function.

Andrei