cfunction {inline} | R Documentation |
Functionality to dynamically define R functions and S4 methods with in-lined C, C++ or Fortran code supporting .C and .Call calling conventions.
cfunction(sig=character(), body=character(), includes=character(), otherdefs=character(), language=c("C++", "C", "Fortran", "F95", "ObjectiveC", "ObjectiveC++"), verbose=FALSE, convention=c(".Call", ".C", ".Fortran") ) ## S4 methods for signatures # f='character', sig='list', body='list' # f='character', sig='character', body='character' setCMethod(f, sig, body, ...) ## Further arguments: # setCMethod(f, sig, body, includes="", otherdefs="", cpp=TRUE, verbose=FALSE, where=topenv(.GlobalEnv), ...)
f |
A single character value if sig and body are character vectors
or a character vector of the same length and the length of sig or
body with the name(s) of methods to create. |
sig |
A match of formal argument names for the function with the character-string names of corresponding classes. Alternatively, a list of such character vectors. |
body |
A character vector with C, C++ or Fortran code omitting function
declaration (only the body, i.e. in case of C starting after the function
opening curly bracket and ending before the closing curly bracket,
brackets excluded). In case of setCMethod with signature
list – a list of such character vectors. |
includes |
A character vector of additional includes and preprocessor statements etc that will be put between the R includes and the user function(s). |
otherdefs |
A characted vector with the code for any further definitions of
functions, classes, types, forward declarations, namespace usage clauses etc
which is inserted between the includes and the declarations of the functions
defined in sig . |
language |
A character value that specifies the source language of the
inline code. The possible values for language include all those
supported by R CMD SHLIB on any platform, which are currently C,
C++, Fortran, F95, ObjectiveC and ObjectiveC++; they may not all be supported
on your platform. One can specify the language either in full as above, or
using any of the following case insensitive shortened forms: c, cpp,
c++, f, f95, objc, objcpp, objc++ . Defaults to C++ . |
verbose |
If TRUE prints the compilation output, the source
code of the resulting program and the definitions of all declared
methods. If FALSE , the function is silent, but it prints compiler
warning and error messages and the source code if compilation fails. |
convention |
Which calling convention to use? See the Details section. |
... |
Reserved. |
To declare multiple functions in the same library one can use setCMethod
supplying lists of signatures and implementations. In this case, provide as
many method names in f
as you define methods. Avoid clashes when selecting
names of the methods to declare, i.e. if you provide the same name several times
you must ensure that signatures are different but can share the same generic!
The source code in the body
should not include the header or
"front-matter" of the function or the close, e.g. in C or C++ it
must start after the C-function opening curly bracket and end before
the C-function closing curly bracket, brackets should not be
included. The header will be automatically generated from the R-signature
argument. Arguments will will carry the same name as used in the signature,
so avoid variable names that are not legal in the target language
(e.g. names with dots).
C/C++: If convention == ".Call"
(the default), the .Call
mechanism
is used and its result is returned directly as the result of the call of the
generated function. As the last line of the generated C/C++ code a
return R_NilValue;
is added in this case and a warning is generated
in case the user has forgotten to provide a return value. To suppress the
warning and still return NULL, add return R_NilValue;
explicitly.
Special care is needed with types, memory allocation and protection
– exactly the same as if the code was not inline: see the
Writing R Extension manual for information on .Call
.
If convention == ".C"
or convention == ".Fortran"
, the
.C
or .Fortran
mechanism respectively is
used, and the return value is a list containing all arguments.
Attached R includes include R.h
for ".C"
, and
additionally Rdefines.h
and R_ext\Error.h
for
".Call"
.
If sig
is a single character vector, cfunction
returns a single
function
; if it is a list, it returns a list of functions.
setCMethod
declares new methods with given names and signatures and
returns invisible NULL
.
Oleg Sklyar <osklyar@ebi.ac.uk> Duncan Murdoch Mike Smith
Foreign Function Interface
## A simple Fortran example code <- " integer i do 1 i=1, n(1) 1 x(i) = x(i)**3 " cubefn <- cfunction(signature(n="integer", x="numeric"), code, convention=".Fortran") x <- as.numeric(1:10) n <- as.integer(10) cubefn(n, x)$x ## Use of .C convention with C code ## Defining two functions, one of which calls the other sigSq <- signature(n="integer", x="numeric") codeSq <- " for (int i=0; i < *n; i++) { x[i] = x[i]*x[i]; }" sigQd <- signature(n="integer", x="numeric") codeQd <- " squarefn(n, x); squarefn(n, x); " fns <- cfunction( list(squarefn=sigSq, quadfn=sigQd), list(codeSq, codeQd), convention=".C") squarefn <- fns[["squarefn"]] quadfn <- fns[["quadfn"]] squarefn(n, x)$x quadfn(n, x)$x ## Alternative declaration using 'setCMethod' setCMethod(c("squarefn", "quadfn"), list(sigSq, sigQd), list(codeSq, codeQd), convention=".C") squarefn(n, x)$x quadfn(n, x)$x ## Use of .Call convention with C code ## Multyplying each image in a stack with a 2D Gaussian at a given position code <- " SEXP res; int nprotect = 0, nx, ny, nz, x, y; PROTECT(res = Rf_duplicate(a)); nprotect++; nx = INTEGER(GET_DIM(a))[0]; ny = INTEGER(GET_DIM(a))[1]; nz = INTEGER(GET_DIM(a))[2]; double sigma2 = REAL(s)[0] * REAL(s)[0], d2 ; double cx = REAL(centre)[0], cy = REAL(centre)[1], *data, *rdata; for (int im = 0; im < nz; im++) { data = &(REAL(a)[im*nx*ny]); rdata = &(REAL(res)[im*nx*ny]); for (x = 0; x < nx; x++) for (y = 0; y < ny; y++) { d2 = (x-cx)*(x-cx) + (y-cy)*(y-cy); rdata[x + y*nx] = data[x + y*nx] * exp(-d2/sigma2); } } UNPROTECT(nprotect); return res; " funx <- cfunction(signature(a="array", s="numeric", centre="numeric"), code) x <- array(runif(50*50), c(50,50,1)) res <- funx(a=x, s=10, centre=c(25,15)) if (interactive()) image(res[,,1]) ## Same but done by registering an S4 method setCMethod("funy", signature(a="array", s="numeric", centre="numeric"), code, verbose=TRUE) res <- funy(x, 10, c(35,35)) if (interactive()) { x11(); image(res[,,1]) }