[m-rev.] for review: Correct status of partial instantiation support

[Paul Bone]

On Wed, Mar 12, 2014 at 02:18:53PM +1100, Julien Fischer wrote:
>>
>> That it works but there are some caveats or you may run into bugs.  This is
>> my understanding of how well partial instantiation works anyway.
>
> IIRC, the current implementation allows you to construct partially
> instantiated terms, but filling in the holes later on will not work.
> Given that, they are pretty much useless for any pratical purpose at the
> moment.

I'm pretty sure I've used this and it worked in the C backends.  I think the
issue might have been the Erlang backend.

https://github.com/Mercury-Language/mercury/blob/master/mdbcomp/feedback.m#L98

I remember that this piece of code was contentious because it prevented
Mercury from being built in the Erlang grade.  But AFAIK it works in the C,
C# and Java grades.

>>>>  Correcting this statement will confuse users of Mercury
>>>> less.  (It was pointed out to me by 1-2 people that this had confused them.)
>>>
>>> What exactly confused them?  That the compiler appeared to accept some
>>> programs containing partially instantiated terms without complaining
>>> even though the reference manual suggests otherwise?
>>
>> Pretty much yes.
>>
>> That the compiler accepts them, that there is code in list.m which defines
>> then, but doesn't use them.
>
> There is no code in list.m that uses them; there are only a few insts
> that represent partially instantiated lists.

That's what I said.

> Looking at that section, I
> note that some of those insts were marked as deprecated a long time ago,
> so we should just delete them.  I my previous mail I suggested deleting
> the others, although now I think just moving them out of the library
> documentation (i.e. into a "private" interface") section would suffice.
>
> If that's done the documentation for list.m shouldn't need to concern
> itself with partial instanatiation at all.

Okay, since they're unused I don't see a problem with that.  Perhaps they
should be moved to samples/ as an example of how to use partial
instantiation?


-- 
Paul Bone