从Rcpp C ++函数获取R函数args [英] Getting r function args from Rcpp c++ function
问题描述
我已经在R端定义了一个函数,如下所示:
I have defined a function on the R-side like this:
foo <- function(arg1, arg2, arg3) {
...
}
和c ++中使用Rcpp的函数,该函数获取全局环境并实例化R函数以从该函数执行它.这是代码:
and a function in c++ using Rcpp that gets the global environment and instantiates the R function to execute it from that function. Here is the code:
namespace Rcpp;
void myFunction() {
...
Environment env = Environment::global_env();
Function funct = env["foo"];
...
}
它工作正常,但我想检查一下R函数是否恰好具有3个args.如何在c ++方法中获取R函数的args数量?
It works fine, but I would like to check that the R function has exactly 3 args. How can I get the number of args of the R function in the c++ method?
推荐答案
您可以使用 PreserveStorage
成员函数 get __()
( Rcpp::Function
是 Rcpp :: PreserveStorage
)的派生类,用于获取形式,然后获取其元素数量:
You can use the closure access macro FORMALS
and the PreserveStorage
member function get__()
(Rcpp::Function
is a derived class of Rcpp::PreserveStorage
) to get the formals, then get its number of elements:
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
int n_formals() {
Environment env = Environment::global_env();
Function funct = env["foo"];
SEXP sexp_funct = funct.get__();
SEXP funct_formals = FORMALS(sexp_funct);
return Rf_length(funct_formals);
}
/*** R
foo <- function(x, y) x + y
n_formals()
foo <- function(x, y, z) x + y + z
n_formals()
*/
# > foo <- function(x, y) x + y
#
# > n_formals()
# [1] 2
#
# > foo <- function(x, y, z) x + y + z
#
# > n_formals()
# [1] 3
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