[Bioc-devel] GenomicFiles reducer and iterate argument

[Martin Morgan]

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
>
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>
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