[Rd] readBin() arg check has unnecessary overhead (patch included)

[Martin Maechler]

>>>>> "JC" == Jon Clayden <jon.clayden at gmail.com>
>>>>>     on Wed, 12 Aug 2009 14:57:10 +0100 writes:

    >>    > Dear all,
    >>    > The version of readBin() in R-devel includes a use of match(), through
    >>    > `%in%`, which can affect its performance significantly. By using
    >>    > primitives instead of the rather expensive call to match(), I reduce
    >>    > the time spent inside readBin() by more than 30% in some of my code
    >>    > (part of the tractor.base package). A simple patch that does this is
    >>    > given below. This passes "make check-devel" fine, and I don't see that
    >>    > it could produce unexpected behaviour -- though I may, of course, be
    >>    > wrong.
    >> 
    >> actually,  %in%  is liked by programmeRs for its inherent
    >> robustness combined with "expressiveness" (<-> readability)
    >> inspite of its potential efficiency loss wrt to  '=='

    JC> Oh, absolutely. I like it and use it widely. But my feeling was that
    JC> in core code, a small loss in expressiveness for a significant
    JC> performance improvement is a trade worth making.

Yes, I agree, and hence the following ...

    >> and indeed, your patch fails in one case where the original code works:
    >> 
    >>  readBin(., NA_character_, ...)
    >> 
    >> However that case can also be checked explicitly,
    >> and I will implement the corresponding patch.

now in R-devel, revision 49187.

    JC> Many thanks.
    JC> Regards,
    JC> Jon

Thank *you* ! {I forgot to say the first time ..}
Martin