[m-dev.] proposal: extension to pragma obsolete

[Julien Fischer]

On Thu, 11 Sep 2014, Mark Brown wrote:

> On Thu, Sep 11, 2014 at 12:35 PM, Zoltan Somogyi
> <zoltan.somogyi at runbox.com> wrote:
>> On Wed, 10 Sep 2014 23:31:47 +1000, Mark Brown <mark at mercurylang.org> wrote:
>>> If the more general case is really wanted, 'comment' and
>>> 'verbose_comment' attributes could be added. For example:
>>>
>>> :- pragma obsolete(string.substring/3, [
>>>         superseded_by(string.between/3),
>>>         comment("The new string operations were introduced to help
>>> provide better Unicode support."),
>>>         verbose_comment("If Start + Count = End then substring(String,
>>> Start, Count) = between(String, Start, End).")
>>>     ]).
>>
>> I like this, but I would prefer one change. As you argue, I think
>> there should be a second argument that expresses one of three things:
>>
>> (a) there is no replacement for the obsolete entity
>> (b) there is a direct, semantically identical replacement for the obsolete entity
>> (c) there is a direct, but semantically different replacement
>>
>> (b) and (c) would be accompanied by the name of the replacement.
>
> Note also that the user may wish to list more than one potential
> replacement, for (c) at least.

That is precisely the situation that is now present in the standard
library's char module (after commit 696829e6c1cafe86ece8091e36f54f60bcb63076).

Cheers,
Julien.