Re: [Rd] Identical copy of base function

From: Jeffrey Ryan <jeffrey.ryan_at_lemnica.com>
Date: Mon, 27 Feb 2012 07:39:32 -0600

Doesn't this also mean that if Matrix is loaded first, det() will be calling Matrix::determinant, which could be quite surprising change in behavior from expectation?

This seems rather dangerous and 'untrustworthy' to me - unless I am missing some other hidden mechanism involved here.

I haven't read the code yet, and I am sure Matrix will "do the right thing", but I have strong reservations about this behavior when applied to the general universe of R and CRAN.

Jeff

On Mon, Feb 27, 2012 at 6:03 AM, Martin Maechler <maechler_at_stat.math.ethz.ch> wrote:
>>>>>> Matthew Dowle <mdowle@mdowle.plus.com>
>>>>>>     on Mon, 27 Feb 2012 09:59:43 +0000 writes:
>
>    > Hello,
>
>    > Regarding this in R-devel/NEWS/New features :
>
>    > o 'library(pkg)' no longer warns about a conflict with a
>    > function from 'package:base' if the function is an
>    > identical copy of the base one but with a different
>    > environment.
>
>    > Why would one want an identical copy in a different
>    > environment? I'm thinking I may be missing out on a trick
>    > here.
>
> Yes, you are ;-)   The trick is called ``namespace'' :
>
> One example which lead me to implement the above:
>
> The Matrix package has had an identical copy of 'det' for a
> while now, but of course  in the Matrix namespace.
> Because of that, the call to determinant() inside det() will
> correctly dispatch Matrix methods for determinant(), whereas
> base::det() would not.
>
> Martin
>
> ______________________________________________
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-- 
Jeffrey Ryan
jeffrey.ryan_at_lemnica.com

www.lemnica.com
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