On 13/09/2013 8:31 AM, Michael Friendly wrote:
On 9/12/2013 1:37 PM, Duncan Murdoch wrote:
>
> I think this one would be fine if you had library(MASS) or
> require(MASS) or (probably best) used MASS::loglm explicitly. It may
> be that in the past some other package put MASS on the search list,
> and that's why it worked before.
>
> The distinction is between "loading" and "attaching" a package.
> Loading it (which would be done if you had MASS::loglm, or imported
> it) guarantees that the package is initialized and in memory, but
> doesn't make it visible to the user without the explicit MASS::
> prefix. Attaching it first loads it, then modifies the user's search
> list so the user can see it.
>
> Loading is less intrusive, so it's preferred over attaching. Both
> library() and require() would attach it.
>
Thanks for this explanation, but I'm still confused about how to avoid
the wrath of the CRAN-devel
daemon, whose appetite for new morsels of developer flesh seems ever
increasing and makes
keeping even a stable package up-to-date a moving target. Perhaps such
changes in R devel
should be announced on this list for public comment before they are
enforced in R CMD check.
Changes are generally announced in the NEWS.Rd file long before release,
but R-devel is an unreleased version, so you won't see the news until it
is there. Announcing things that nobody can try leads to fewer useful
comments than putting them into R-devel where at least people can see
what is really happening.
In vcdExtra, I use MASS::loglm in ~ 6 .Rd examples, a vignette, and also
provide R code that
extends *.loglm methods. All of this previously worked by including
Suggests: MASS, ...
Changing this to Imports: MASS seems rather heavy-handed; I don't really
want/need all of MASS
in my namespace, and using MASS::loglm in examples seems ugly. For now,
I'll use
require(MASS) in each example.
If you need a small number of things from MASS in your package code,
then importing them explicitly is definitely the way to go, e.g.
importFrom(MASS, loglm). If you only use them in examples, I wouldn't
do that, I'd recommend Suggests and use the MASS:: prefix. Whether that
is ugly is a matter of taste: it makes it clear to a user where that
function came from, and doesn't potentially hide objects from other
packages later in the search path.
On the other hand, require(pkg) is really simple; we have no equivalent
function that only does the loading, without attaching.
So it's hard to write
if (requireLoadable(MASS)) {
MASS::loglm( ... )
}
> Attaching it first loads it, then modifies the user's search list so
> the user can see it.
Which directive does this?
library() and require() both do it.
Duncan Murdoch
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