isLoadedNamespace() sounds fine to me..
Thanks for addressing this,
Michael
On Mon, Jan 26, 2015 at 5:51 AM, Martin Maechler <
maech...@lynne.stat.math.ethz.ch> wrote:
> >>>>> Michael Lawrence <lawrence.mich...@gene.com>
> >>>>> on Mon, 26 Jan 2015 05:12:55 -0800 writes:
>
> > A isNamespaceLoaded() function would be a useful thing to
> > have in general if we are interested in readable code. An
> > efficient implementation would be just a bonus.
>
> Good point (readability), and thank you for the support!
>
> Note one slight drawback with your name (which is clearly
> better than mine first proposal):
> We'd have the three functions named
>
> isBaseNamespace(ns)
> isNamespace(ns)
> isNamespaceLoaded(name)
>
> where 'name' is really different from 'ns', namely :
>
> > isNamespace("stats")
> [1] FALSE
> > isNamespace(asNamespace("stats"))
> [1] TRUE
>
> but
>
> > isNamespaceLoaded("stats")
> [1] TRUE
>
> > isNamespaceLoaded(asNamespace("stats"))
> Error in as.vector(x, "symbol") :
> cannot coerce type 'environment' to vector of type 'symbol'
> >
>
> So, from my (non native English view) a slightly more suggestive
> function name may be
>
> isLoadedNamespace(name)
>
> or using Luke's original language, still present in the C code,
>
> isRegisteredNamespace(name)
>
> but I would prefer the former, isLoadedN..S..()
>
> Martin
>
> > On Mon, Jan 26, 2015 at 3:36 AM, Martin Maechler
> > <maech...@lynne.stat.math.ethz.ch> wrote:
> >>>>>>> Winston Chang <winstoncha...@gmail.com> on Fri, 23
> >>>>>>> Jan 2015 10:15:53 -0600 writes:
> >>
> >> > I think you can simplify a little by replacing this:
> >>
> >> > pkg %in% loadedNamespaces() > with this: >
> >> .getNamespace(pkg)
> >>
> >> almost: It would be
> >>
> >> !is.null(.getNamespace(pkg))
> >>
> >> > Whereas getNamespace(pkg) will load the package if it's
> >> not already > loaded, calling .getNamespace(pkg) (note
> >> the leading dot) won't load > the package.
> >>
> >> indeed. And you, Winston, are right that this new code
> >> snippet would be an order of magnitude faster :
> >>
> >>
> ##-----------------------------------------------------------------------------
> >>
> >> f1 <- function(pkg) pkg %in% loadedNamespaces() f2 <-
> >> function(pkg) !is.null(.getNamespace(pkg))
> >>
> >> require(microbenchmark)
> >>
> >> pkg <- "foo"; (mbM <- microbenchmark(r1 <- f1(pkg), r2 <-
> >> f2(pkg))); stopifnot(identical(r1,r2)); r1 ## Unit:
> >> microseconds ## expr min lq mean median uq max neval cld
> >> ## r1 <- f1(pkg) 38.516 40.9790 42.35037 41.7245 42.4060
> >> 82.922 100 b ## r2 <- f2(pkg) 1.331 1.8285 2.13874 2.0855
> >> 2.3365 7.252 100 a ## [1] FALSE
> >>
> >> pkg <- "stats"; (mbM <- microbenchmark(r1 <- f1(pkg), r2
> >> <- f2(pkg))); stopifnot(identical(r1,r2)); r1 ## Unit:
> >> microseconds ## expr min lq mean median uq max neval cld
> >> ## r1 <- f1(pkg) 29.955 31.2575 32.27748 31.6035 32.1215
> >> 62.428 100 b ## r2 <- f2(pkg) 1.067 1.4315 1.71437 1.6335
> >> 1.8460 9.169 100 a ## [1] TRUE loadNamespace("Matrix") ##
> >> <environment: namespace:Matrix> pkg <- "Matrix"; (mbM <-
> >> microbenchmark(r1 <- f1(pkg), r2 <- f2(pkg)));
> >> stopifnot(identical(r1,r2)); r1 ## Unit: microseconds ##
> >> expr min lq mean median uq max neval cld ## r1 <- f1(pkg)
> >> 32.721 33.5205 35.17450 33.9505 34.6050 65.373 100 b ##
> >> r2 <- f2(pkg) 1.010 1.3750 1.93671 1.5615 1.7795 12.128
> >> 100 a ## [1] TRUE
> >>
> >>
> ##-----------------------------------------------------------------------------
> >>
> >> Hence, indeed, !is.null(.getNamespace(pkg))
> >>
> >> seems equivalent to pkg %in% loadedNamespaces()
> >>
> >> --- when 'pkg' is of length 1 (!!!)
> >>
> >> but is 20 times faster.... and we have 11 occurrences of
> >> ' <...> %in% loadedNamespaces() ' in the "base packages"
> >> in the R (devel) sources, 3 in base, 2 in methods, 3 in
> >> stats, 2 in tools, 1 in utils..
> >>
> >> On the other hand, pkg %in% loadedNamespaces()
> >>
> >> is extremely nicely readable code, whereas
> >> !is.null(.getNamespace(pkg)) is pretty much the contrary.
> >> .. and well readable code is so much easier to maintain
> >> etc, such that in many cases, code optimization with the
> >> cost of code obfuscation is *not* desirable.
> >>
> >> Of course we could yet again use a few lines of C and R
> >> code to provide a new R lowlevel function, say
> >>
> >> is.loadedNamespace()
> >>
> >> which would be even faster than
> >> !is.null(.getNamespace(pkg))
> >>
> >> ... ...
> >>
> >> but do we have *any* evidence that this would noticably
> >> speedup any higher level function such as library() ?
> >>
> >>
> >> Thank you, again, Winston; you've opened an interesting
> >> topic!
> >>
> >> --
> >> Martin Maechler, ETH Zurich
> >>
> >> ______________________________________________
> >> R-devel@r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
>
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