[m-rev.] for review: Add take_while and drop_while to the list module

[Julien Fischer]

Hi Paul,

On Thu, 21 Apr 2016, Paul Bone wrote:

>>> I noticed that in our YesLogic code we have some utility code that can be
>>> put into the Mercury standard library, including a dropwhile predicate.  So
>>> I named it drop_while and submitted it and an similar take_while predicate.
>>>
>>> I don't really mind what happens, does anyone else have any strong ideas
>>> about these kinds of predicates?
>>
>> I would prefer some consistency in naming for a start ;-)
>>
>> I suggest adding take_while/4, deprecating the existing takewhile/4
>> predicate and adding your new ones as well.  (That said, I think the
>> documentation for drop_while/3 is unclear, so don't commit them
>> until that's been reviewed.)
>
> To clarify, we would be (in the long term) renaming takewhile/4 to
> take_while/4?

Yes.  (The new name is more consistent with your new predicates as
well as take_upto etc.)

Julien.