[Rd] FW: [Rcpp-devel] Question on 5.6 Interfacing C++ code

[Duncan Murdoch]

On 11-04-20 11:33 AM, Sean Robert McGuffee wrote:
> Hi, apparently I sent my question about using R and C++ to the wrong list,
> ironically seeing as that list was called Rcpp. Anyway, I was directed to
> post my question here. To summarize my current question, I have found two
> commands that I want to be able to put into a package. The commands are 'R
> CMD SHLIB X.cc X_main.cc' and
> 'dyn.load(paste("X",.Platform$dynlib.ext,sep="")),' which I would like to
> run when my package is installed and maybe have the second command run again
> when my package is to be used. I've been trying to figure out the
> documentation and learn through examples, but I'm just not getting it and
> have been trying for weeks.
> Does anyone on this site have any suggestions for me?

Assuming those lines work on their own, just do the following:

1.  Put those *.cc files into the src directory of your package.  (You 
may need to create it.)

2.  Put useDynLib(foo) into the NAMESPACE file of your foo package.

3.  Call those functions using .C("X", args, PACKAGE="foo").

That's it.

Duncan Murdoch

> Thanks, Sean
>
> |On 20 April 2011 at 10:20, Sean Robert McGuffee wrote:
> |
> |
> | Hi, thanks!
> |
> |>On 4/20/11 10:03 AM, "Steve Lianoglou"<mailinglist.honeypot at gmail.com>
> wrote:
> |>  Hi,
> |>
> |>  On Wed, Apr 20, 2011 at 9:49 AM, Sean Robert McGuffee
> |>  <sean.mcguffee at gmail.com>  wrote:
> |>>  Hi, I have a quick couple of questions about some of the documentation
> on
> |>>  the web page:
> |>>
> http://cran.r-project.org/doc/manuals/R-exts.html#Linking-GUIs-and-other-fro
> n
> |>>  t_002dends-to-R
> |>>  under the heading:
> |>>  5.6 Interfacing C++ code
> |>>
> |>>  Question 1:
> |>>  If I¹m at a terminal, I can type the instructions they suggest:
> |>>  R CMD SHLIB X.cc X_main.cc
> |>>  If I wanted a package to do this, how would I tell the package to do
> that
> |>>  same thing?
> |>
> |>  Just to make sure we're all on the same page, you want an R package to
> |>  compile some source code into a shared library/dll from inside R?
> |>
> |>  Not sure if there's a "baked in" way for that to happen, but maybe you
> |>  can invoke `R CMD WHATEVER` from inside R using the `system` function:
> |>
> |>  R>  ?system
> |>
> |
> | ok, so where in the package would I put the system call in the package to
> | have it run when installing the package?
>
>> You don't. As I said, 'R CMD INSTALL' et all do that.
>> Download an existing package with source, install it.  Study its sources,
>> study the 'Writing R Extensions' manual.  Ask on r-devel.
>> Basic R questions are off-topic here.
>
> |>>  Would I use the same command and just include it in a file somewhere in
> the
> |>>  package?
> |>>  If so, which file?
> |>
> |>  Hmm ... I'm curious what you're trying to do, exactly?
> |
> | I'm trying to figure out how take commands such as " R CMD SHLIB X.cc
> | X_main.cc" followed by "dyn.load(paste("X", .Platform$dynlib.ext, sep =
> | ""))," which are commands I can get to work for myself as a human
> | interactively, and put the commands into a package to be automatically run
> | when installing the package. I mean, it's great if I can compile a c++
> file
> | and then use it inside R, but I'm only doing that so I can let other
> people
> | do that via a package. As much as I read this documentation, I keep
> missing
>
>> Again, I like working from an existing, working package. As I said, there are
>> almost 1000 to pick from.
>> Please direct follow-ups that have no bearing on Rcpp to r-devel.
>> Dirk
>
> I've tried to figure this out for weeks by looking at other packages and
> reading the confusing and nonintegrated documentation, but it hasn't taught
> me how to put the two commands into a package so that they are run when the
> package is installed. I'm simply trying to find out where in my package I
> should put the commands 'R CMD SHLIB X.cc X_main.cc' and
> 'dyn.load(paste("X",.Platform$dynlib.ext,sep="")),'
> in order to have them run when my package is installed.
>
>
> | the connections between the different sections. This is a section I am
> | loving because it works very well. Thus, I want to figure out how to take
> | the baby steps I'm doing and combine them into a package. Specifically, I
> | want to take these two commands and insert them into a package so that
> these
> | commands will compile my code and make a dynamic ".so" file where R can
> | access its functions when others install my package.
> |
> |>
> |>>  Question 2:
> |>>  dyn.load(paste("X", .Platform$dynlib.ext, sep = ""))
> |>>
> |>>  Where does .Platform$dynlib.ext come from?
> |>>  What does it mean?
> |>>  What do it¹s components .Platform and $dynlib and .ext mean?
> |>
> |>  .Platform is lust a normal list -- it is defined internally (I guess).
> |>  You can access "named" elements of a list with `$`.
> |>
> |>  .Platform$dynlyb (or .Platform[['dynlib']]) tells you the extension
> |>  your particular system uses for shared libraries:
> |>
> |>  R>  .Platform
> |>  $OS.type
> |>  [1] "unix"
> |>
> |>  $file.sep
> |>  [1] "/"
> |>
> |>  $dynlib.ext
> |>  [1] ".so"
> |>
> |>  $GUI
> |>  [1] "X11"
> |>
> |>  $endian
> |>  [1] "little"
> |>
> |>  $pkgType
> |>  [1] "mac.binary.leopard"
> |>
> |>  $path.sep
> |>  [1] ":"
> |>
> |>  $r_arch
> |>  [1] "x86_64"
> |>
> |>  See ?.Platform for more help.
> |
> | Ah, thanks, that clarifies exactly what .Platform$dynlib.ext is, it's
> ".so"
> | on my system.
> |
> | This, the dyn.load(paste("X", .Platform$dynlib.ext, sep = "")) is
> equivalent
> | to the command dyn.load("X.so) which now makes sense in that context!
> |
> |
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