As the author of that post, I must respond... # ----- first comment -------
Ducan: "The article that Henrik cited gives a reasonable description up until near the end" Suraj: Given the complexity of the topics at hand, the many accolades I've received for the post, and how thoroughly I've approached the topic and carefully navigated the user through rough terrain, I feel that characterizing my description as "reasonable" substantially shortchanges it. I wrote the post because the available descriptions (including those from well-established R community members) were confusing and filled with holes. # ----- next comment ------- Duncan: "...up until near the end, where (in my opinion) it makes things unnecessarily complicated" Suraj: I think Duncan is confusing iterative teaching, repetition, and thoroughness with complexity. These topics ARE complex. The need for a resource such as mine is a testament to that. My approach to complex topics is to break them down fully; to be diligent in the explanation so there are no leaps in logic. It's far more difficult to do that than to assume a reader can connect the dots and default to brevity. # ----- next comment ------- Duncan: "I'd recommend that you stop reading around where he tries to explain the dotted lines." Suraj: It's a disservice to yourself to stop here. This section provides a "light bulb" moment on the path to understanding the search/find mechanism. As stated in the blog post "Function execution is the most complex piece of the puzzle." I specifically encourage readers to re-read that section. Other resources will provide the same understanding, but it's likely a cumbersome process for the average reader. I synthesized these insights after laboring over words in books and articles, tinkering in R, and asking lots of questions. # ----- next comment ------- Duncan: "In particular, ignore the second version of the "Map of the World"; the first one is accurate, the second is just misleading" Suraj: A reader that doesn't understand the second Map cannot fully grasp the search/find mechanism. Everything in the post builds up to the second map. The second map encompasses function execution. I challenge anyone (in a friendly way) to create a better visualization of enclosing environments and function execution that allows a reader to easily navigate environment-space and figure out how R searches for symbols and where it finds them. I'll replace my map with yours if you can do that - we will all be better off for it! # ----- last comment ------- Duncan: "Gupta's article misses the possibility of packages that are loaded but not in the search path..." Suraj: I'm pretty sure I discuss all of this in "Imports v Depends" section. I have a diagram that shows package PLYR as loaded but not in the search path and I discuss it. On Wed, Mar 19, 2014 at 1:12 PM, Mark Leeds <marklee...@gmail.com> wrote: > Hi Everyone: Suraj will respond to Duncan's comments below promptly. Suraj > doesn't have the original thread so I am just helping out by commenting > here so that he can respond and the thread can be kept continuous. > > Mark > > > > > > On Sun, Mar 9, 2014 at 9:09 AM, Duncan Murdoch <murdoch.dun...@gmail.com > >wrote: > > > On 14-03-08 6:42 PM, Benjamin Tyner wrote: > > > >> Duncan, > >> > >> Thank you for the informative link. So, do the loaded namespaces have an > >> "ordering" akin to the package search path that determines that > >> functions in the base namespace can see objects in the utils namespace? > >> (I noticed that loadedNamespaces() just comes back in alphabetical > order.) > >> > > > > No. The article that Henrik cited gives a reasonable description up > until > > near the end, where (in my opinion) it makes things unnecessarily > > complicated. I'd recommend that you stop reading around where he tries > to > > explain the dotted lines. In particular, ignore the second version of > the > > "Map of the World"; the first one is accurate, the second is just > > misleading. > > > > In answer to your question: Gupta's article misses the possibility of > > packages that are loaded but not in the search path. In the notation of > > the first part of that article, loading a namespace just puts it in the > > middle two columns (i.e. creates the namespace and imports environments) > > without putting it in the search list. That happens when you import or > > load a package without attaching it. The search path imposes an > ordering, > > things that aren't in it aren't ordered. > > > > Duncan Murdoch > > > > > > > >> Regards > >> Ben > >> > >> On 03/07/2014 11:46 AM, Duncan Murdoch wrote: > >> > >>> On 07/03/2014 10:16 AM, Benjamin Tyner wrote: > >>> > >>>> Hello, > >>>> > >>>> I realize that a function in <environment: base> (for example, > function > >>>> "head1" below) is unable to see (without resorting to "::", anyway) > >>>> objects in utils (for example, "head" below), since package:base is > >>>> after package:utils on the search path. > >>>> > >>> > >>> > >>>> However, I'm wondering what is the machinery that allows a function in > >>>> <environment: namespace:base> (for example, function "head2" below) to > >>>> be able to see "head" just fine, without needing to resort to "::". > >>>> > >>> > >>> > >>> See Luke Tierney's article in R News, > >>> > >>> Name space management for R. Luke Tierney, R News, 3(1):2-6, June 2003 > >>> <http://cran.r-project.org/doc/Rnews/Rnews_2003-1.pdf> > >>> > >>> There's a link to it from the R help system. Run help.start(), then > >>> look at "Technical papers" in the Miscellaneous Material section. > >>> > >>> I believe most of what it says is still current; the only thing I can > >>> see at a glance that is no longer correct is that in those days > >>> namespaces were optional in packages. Now all packages have > namespaces. > >>> > >>> Duncan Murdoch > >>> > >>> > >>>> I'm also wondering more generally, why there is a need (practically > >>>> speaking) for a distinction between the environment associated with a > >>>> package and the environment associated with the namespace. > >>>> > >>>> $ export R_PROFILE=/home/btyner/Rprofile.site > >>>> > >>>> $ cat /home/btyner/Rprofile.site > >>>> sys.source("/home/btyner/head1.R", envir = baseenv()) > >>>> sys.source("/home/btyner/head2.R", envir = .BaseNamespaceEnv) > >>>> > >>>> $ cat /home/btyner/head1.R > >>>> head1 <- function(x) head(x) > >>>> > >>>> $ cat /home/btyner/head2.R > >>>> head2 <- function(x) head(x) > >>>> > >>>> $ Rscript -e "head1(letters)" > >>>> Error in head1(letters) : could not find function "head" > >>>> Execution halted > >>>> > >>>> $ Rscript -e "head2(letters)" > >>>> [1] "a" "b" "c" "d" "e" "f" > >>>> > >>>> $ Rscript -e "sessionInfo()" > >>>> R version 3.0.1 (2013-05-16) > >>>> Platform: x86_64-pc-linux-gnu (64-bit) > >>>> > >>>> locale: > >>>> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C > >>>> [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 > >>>> [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 > >>>> [7] LC_PAPER=C LC_NAME=C > >>>> [9] LC_ADDRESS=C LC_TELEPHONE=C > >>>> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C > >>>> > >>>> attached base packages: > >>>> [1] stats graphics grDevices utils datasets base > >>>> > >>>> Regards > >>>> Ben > >>>> > >>>> > >>>> > >>>> ______________________________________________ > >>>> R-help@r-project.org mailing list > >>>> https://stat.ethz.ch/mailman/listinfo/r-help > >>>> PLEASE do read the posting guide > >>>> http://www.R-project.org/posting-guide.html > >>>> and provide commented, minimal, self-contained, reproducible code. > >>>> > >>> > >>> > >> > >> -- > >> // > >> > > > > ______________________________________________ > > R-help@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/ > > posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Best Regards, Suraj http://obeautifulcode.com/ [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
