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| <H1><a name="R">37 SWIG and R</a></H1> |
| <!-- INDEX --> |
| <div class="sectiontoc"> |
| <ul> |
| <li><a href="#R_nn2">Bugs</a> |
| <li><a href="#R_nn3">Using R and SWIG</a> |
| <li><a href="#R_nn4">Precompiling large R files</a> |
| <li><a href="#R_nn5">General policy</a> |
| <li><a href="#R_language_conventions">Language conventions</a> |
| <li><a href="#R_nn6">C++ classes</a> |
| <li><a href="#R_nn7">Enumerations</a> |
| </ul> |
| </div> |
| <!-- INDEX --> |
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| |
| <p> |
| R is a GPL'ed open source statistical and plotting environment. |
| Information about R can be found at <a |
| href="http://www.r-project.org/">www.r-project.org</a>. |
| |
| The R bindings are under active development. They have been used to |
| compile and run an R interface to QuantLib running on Mandriva Linux |
| with gcc. The R bindings also work on Microsoft Windows using Visual C++. |
| </p> |
| |
| <H2><a name="R_nn2">37.1 Bugs</a></H2> |
| |
| |
| <p> |
| Currently the following features are not implemented or broken: |
| </p> |
| |
| <ul> |
| <li>Garbage collection of created objects |
| <li>C Array wrappings |
| </ul> |
| |
| <H2><a name="R_nn3">37.2 Using R and SWIG</a></H2> |
| |
| |
| <p> |
| To use R and SWIG in C mode, execute the following commands where |
| example.c is the name of the file with the functions in them |
| </p> |
| |
| <div class="shell"> |
| <pre> |
| swig -r example.i |
| R CMD SHLIB example_wrap.c example.c |
| </pre> |
| </div> |
| |
| <p> |
| The corresponding options for C++ mode are |
| </p> |
| |
| <div class="shell"> |
| <pre> |
| swig -c++ -r -o example_wrap.cpp example.i |
| R CMD SHLIB example_wrap.cpp example.cpp |
| </pre> |
| </div> |
| |
| <p> |
| Note that R is sensitive to the names of the files. |
| The name of the wrapper file must be the |
| name of the library unless you use the -o option to R when building the library, for example: |
| </p> |
| |
| <div class="shell"> |
| <pre> |
| swig -c++ -r -o example_wrap.cpp example.i |
| R CMD SHLIB -o example.so example_wrap.cpp example.cpp |
| </pre> |
| </div> |
| |
| <p> |
| R is also sensitive to the name of the file |
| extension in C and C++ mode. In C++ mode, the file extension must be .cpp |
| rather than .cxx for the R compile command to recognize it. If your C++ code is |
| in a file using something other than a .cpp extension, then it may still work using PKG_LIBS: |
| </p> |
| |
| <div class="shell"> |
| <pre> |
| swig -c++ -r -o example_wrap.cpp example.i |
| PKG_LIBS="example.cxx" R CMD SHLIB -o example example_wrap.cpp |
| </pre> |
| </div> |
| |
| <p> |
| The commands produces two files. A dynamic shared object file called |
| example.so, or example.dll, and an R wrapper file called example.R. To load these |
| files, start up R and type in the following commands |
| </p> |
| |
| <div class="shell"> |
| <pre> |
| dyn.load(paste("example", .Platform$dynlib.ext, sep="")) |
| source("example.R") |
| cacheMetaData(1) |
| </pre> |
| </div> |
| |
| The cacheMetaData(1) will cause R to refresh its object tables. |
| Without it, inheritance of wrapped objects may fail. |
| |
| <p> |
| These two files can be loaded in any order |
| </p> |
| |
| <p> |
| If you are compiling code yourself (not using R itself), there are a few things to watch out for: |
| </p> |
| |
| <ul> |
| <li>The output shared library name (to the left of the file extension) MUST match the module name, or alternatively, you can also set the -package NAME command line argument. See swig -r -help for more information |
| <li>If you do not set the output file name appropriately, you might see errors like |
| <div class="shell"> |
| <pre> |
| > fact(4) |
| Error in .Call("R_swig_fact", s_arg1, as.logical(.copy), PACKAGE = "example") : |
| "R_swig_fact" not available for .Call() for package "example" |
| </pre> |
| </div> |
| <li>Make sure the architecture of the shared library(x64 for instance), matches the architecture of the R program you want to load your shared library into |
| </ul> |
| |
| <H2><a name="R_nn4">37.3 Precompiling large R files</a></H2> |
| |
| |
| In cases where the R file is large, one make save a lot of loading |
| time by precompiling the R wrapper. This can be done by creating the |
| file makeRData.R which contains the following |
| |
| <pre> |
| source('BigFile.R') |
| save(list=ls(all=TRUE), file="BigFile.RData", compress=TRUE) |
| q(save="no") |
| </pre> |
| |
| This will generate a compiled R file called BigFile.RData that |
| will save a large amount of loading time. |
| |
| |
| |
| <H2><a name="R_nn5">37.4 General policy</a></H2> |
| |
| |
| <p> |
| The general policy of the module is to treat the C/C++ as a basic |
| wrapping over the underlying functions and rely on the R type system |
| to provide R syntax. |
| </p> |
| |
| <H2><a name="R_language_conventions">37.5 Language conventions</a></H2> |
| |
| |
| <p> |
| getitem and setitem use C++ conventions (i.e. zero based indices). [<- |
| and [ are overloaded to allow for R syntax (one based indices and |
| slices) |
| </p> |
| |
| <H2><a name="R_nn6">37.6 C++ classes</a></H2> |
| |
| |
| <p> |
| C++ objects are implemented as external pointer objects with the class |
| being the mangled name of the class. The C++ classes are encapsulated |
| as an SEXP with an external pointer type. The class is the mangled |
| name of the class. The nice thing about R is that is allows you to |
| keep track of the pointer object which removes the necessity for a lot |
| of the proxy class baggage you see in other languages. |
| </p> |
| |
| <H2><a name="R_nn7">37.7 Enumerations</a></H2> |
| |
| |
| <p> |
| enumerations are characters which are then converted back and forth to |
| ints before calling the C routines. All of the enumeration code is |
| done in R. |
| </p> |
| |
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