Fixing const arrays

[kenji hara]

OK. I agree to the suggestion.

I've been afraid that increasing IFTI rule is making the language
learning difficult.
It comes from the experience from implementing inout deduction for
template function.

But also it is useful that removing top const when passing arguments by value.
C++ precedent convinced me.

Thanks.

Kenji Hara

2011/12/11 kenji hara <k.hara.pg at gmail.com>:
> 2011/12/11 Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org>:
>> On 12/10/11 4:31 PM, kenji hara wrote:
>>>
>>> Treating whole constant arrays as ranges by automatically shedding the
>>> top-level const is good.
>>> But realizing it by language semantic change is definitely bad.It
>>> breaks IFTI rule, and adding special case will make difficult to learn
>>> language.
>>>
>>> Instead of language change, we can add specializations that receive
>>> non-ranges and convert them to ranges by removing top-level const.
>>> I believe that it is Phobos issue and is never the issue of language.
>>
>>
>> I should add there is precedent. C++ also removes top-level const when
>> passing objects by value to templates. Deducing top-level const with
>> pass-by-value is inherently nonsensical.
>>
>> Andrei
>>
>
> Hmm, it's for sure.
> ----
> void print_type(int){}
>
> template <typename T>
> void f(T p)
> {
>    int n;
>    p = &n;     // OK, head is mutable
>    //*p = 10;  // NG, tail is const
>    print_type(p);
>                // Error: need explicit cast from int const * to int
>                // T is deduced as int const * == top const is removed
> }
> int main()
> {
>    int n;
>    int const * const p = &n;
>    f(p);
>    return 0;
> }
>
> Kenji