[Rd] names function for environments?

[Martin Maechler]

>>>>> Peter Haverty <haverty.peter at gene.com>
>>>>>     on Sun, 25 Jan 2015 12:21:04 -0800 writes:

    > Hi all,
    > The "ls" function wears two hats. It allows users to inspect an
    > environment interactively and also serves deeper in code as the
    > accessor for an environment's names/keys. I propose that we separate
    > these two conflicting goals, keeping ls for interactive use and adding
    > names for a quick listing of the hash keys. This involves adding two
    > lines to do_names in attrib.c.

    > The 'ls' function and its 'objects' synonym appear very frequently in
    > performance-critical code like base/R/namespace.R and throughout the
    > methods package. These functions are currently among the major
    > contributors to execution time in package loading.

    > This two-line addition to attrib.c gives a significant speedup for
    > listing an environment's names/keys (2-60X depending on the 'sorted'
    > argument). It also simplifies the environment API by making it more
    > like the other basic types. We already have $ and [[ after all.

    > Rather than sprinkling sorted=FALSE throughout the methods and base
    > code, let's use names.

as for list()s and other (generalized) vectors.

This sounds appealing at first, and I have heard/seen others propose
it.  I see one good reason *not* to allow it (and you mention the
reason by mentioning 'sorted') :

The contents of an environment are inherently unordered, and
even if the order stays fixed for a while, no code should rely
on the ordering of the objects, and for that reason,
 <env>[1]  etc do not make sense and are not allowed.

    > Would you be open to this change?

I'm undecided currently:
 "-": reason above; 
 "+": convenience, compacter R code using it;
      very simple and natural change to src/main/attrib.c

and waiting for other comments, not the least from other members of R core ..

Martin Maechler, ETH Zurich


    > I have submitted a patch and some timings to the bug tracker as
    > https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=16170

    > Regards,
    > Pete

    > ____________________
    > Peter M. Haverty, Ph.D.
    > Genentech, Inc.
    > phaverty at gene.com

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