On Tue, Jun 17, 2014 at 7:00 AM, Valerie Obenchain <voben...@fhcrc.org>
wrote:
> Hi Michael, Ryan,
>
> Yes, it would be ideal to have a single signature for both cases of
> 'iterate'. We went over the pros/cons again and at the end of the day
> decided to keep things as they are. No perfect solution here.
>
> These were the primary points:
>
> - Disadvantages of defining REDUCER with only '...' is that '...' can
> represent variables other than just the output from MAPPER.
>
>
Do you mean that "..." will capture additional arguments? From where?
> - The unappealing aspect of the variadic approach is introducing a new
> check each time REDUCER is called.
>
>
What is this check?
> - Going the other direction, considering a single arg for REDUCER instead
> two, requires coercing 'last' and 'current' to a list before pulling them
> apart again.
>
>
What is the problem with constructing this list? Isn't that one extremely
fast line of code?
It seems to me simpler to settle on one signature, and my preference would
be for the single list argument, just because the call is smaller and
simpler. Then have a convenient adaptor to handle the variadic case.
>
> Valerie
>
>
>
> On 06/15/14 16:36, Michael Lawrence wrote:
>
>> I kind of prefer the adaptor solution, just for the sake of API
>> cleanliness
>> (the MAPPER/REDUCER pair has some elegance), but I think we agree that the
>> iterate switch introduces undesirable coupling.
>>
>>
>>
>>
>> On Sun, Jun 15, 2014 at 3:07 PM, Ryan <r...@thompsonclan.org> wrote:
>>
>> What about having two separate reducer arguments, one for a reducer that
>>> takes two elements at a time and combines them, and the other for a
>>> reducer
>>> that takes a list and combines all the elements of the list? Specifying
>>> both at once would be an error. I think it makes more sense to say "these
>>> two arguments expect different things" than "this one argument expects a
>>> different thing depending on the value of another argument".
>>>
>>> -Ryan
>>>
>>>
>>> On Sun Jun 15 11:17:59 2014, Michael Lawrence wrote:
>>>
>>> I just thought there is some benefit for the callback to be the same,
>>>> regardless of the iterate setting. This would allow generalization
>>>> across
>>>> different data scales. Perhaps all that is needed is a constructor for
>>>> an
>>>> adapter closure, one for each direction.
>>>>
>>>> For example, the variadic adapter would look like:
>>>>
>>>> Variadic <- function(FUN) {
>>>> function(x, y) {
>>>> if (missing(y)) {
>>>> do.call(FUN, x)
>>>> } else {
>>>> FUN(x, y)
>>>> }
>>>> }
>>>> }
>>>>
>>>> That would make it easy to e.g. adapt rbind into the framework. I wonder
>>>> if
>>>> there is precedent and better terminology from the functional
>>>> programming
>>>> domain?
>>>>
>>>> Michael
>>>>
>>>>
>>>>
>>>> On Sun, Jun 15, 2014 at 8:38 AM, Martin Morgan <mtmor...@fhcrc.org>
>>>> wrote:
>>>>
>>>> On 06/15/2014 07:34 AM, Michael Lawrence wrote:
>>>>
>>>>>
>>>>> Hi guys,
>>>>>
>>>>>>
>>>>>> Was just checking out GenomicFiles and was a little surprised that the
>>>>>> arguments to the REDUCER are different depending on iterate=TRUE vs.
>>>>>> iterate=FALSE. In my often flawed opinion, iteration should not be a
>>>>>> concern of the REDUCER. It should be oblivious to the iteration mode.
>>>>>> In
>>>>>> other words, when iterate=TRUE, it is a special case of having two
>>>>>> objects
>>>>>> to combine, instead of multiple.
>>>>>>
>>>>>>
>>>>>> My 'rationale' was that one would choose iterate=FALSE when one
>>>>> required
>>>>> all elements to perform the reduction. I thought of the list (rather
>>>>> than
>>>>> ...) as the general R data structure for representing N elements, with
>>>>> a
>>>>> special case (consistent with Reduce) made for the pairwise reduction
>>>>> of
>>>>> iterate=TRUE. Either way, the two cases (x, y vs. list(), x, y vs. ...)
>>>>> seem to require some explaining to the user. Is there a clear better
>>>>> choice? You're the second person to trip over this, so I guess there's
>>>>> a
>>>>> crack in the sidewalk...
>>>>>
>>>>> Martin
>>>>>
>>>>>
>>>>> What would be convenient (but unnecessary) is to detect from the
>>>>> formal
>>>>>
>>>>>> arguments whether REDUCER is variadic or list-based. In other words,
>>>>>> if
>>>>>> REDUCER is defined like function(...) { } it is called via do.call(),
>>>>>> otherwise it is passed the list.
>>>>>>
>>>>>> Thoughts? Maybe I'm totally confused?
>>>>>>
>>>>>> Michael
>>>>>>
>>>>>> [[alternative HTML version deleted]]
>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>> Computational Biology / Fred Hutchinson Cancer Research Center
>>>>> 1100 Fairview Ave. N.
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>>>>>
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>>>>> Phone: (206) 667-2793
>>>>>
>>>>>
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>
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