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

Mark Brown mark at mercurylang.org
Thu Sep 11 19:54:13 AEST 2014

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.


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