In krlmlr/bindrcpp: An 'Rcpp' Interface to Active Bindings

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bindrcpp

It's easy to create active bindings in R via makeActiveBinding(). This package faciliates the creation of active bindings that link back to C++ code. It provides an interface that allows binding several identifiers in an environment to the same C++ function, which is then called with the name (and a payload) as argument.

It is recommended to use the newer _wrapped functions that support passing an arbitrary Rcpp::List as payload. This allows to store an Rcpp::XPtr to a C++ object in that list. The XPtr then will be released when the payload is garbage-collected, and the C++ object will be destroyed.

Installation

You can install bindrcpp from github with:

# install.packages("devtools")
devtools::install_github("krlmlr/bindrcpp")

Example

The following C++ module exports a function test_tolower_bindings() that creates active bindings that return the binding name in lowercase.

```{Rcpp module, cache = TRUE}

include

// [[Rcpp::depends(bindrcpp)]]

include

include

include

using namespace Rcpp;

using namespace bindrcpp;

SEXP tolower_callback(const String& name, PAYLOAD) { std::string name_string = name; std::transform(name_string.begin(), name_string.end(), name_string.begin(), ::tolower); return CharacterVector(name_string); }

// [[Rcpp::export]] SEXP test_tolower_bindings(CharacterVector names, Environment parent) { // We don't pass any payload here return bindrcpp::create_env_string( names, &tolower_callback, PAYLOAD(NULL), parent); }

This function can be called from R:

```r
env <- test_tolower_bindings(c("Converting", "to", "LOWERCASE"), .GlobalEnv)
ls(env)
env$Converting
env$to
env$LOWERCASE
env$y

The bindings are read-only:

env$Converting <- "CONVERTING"

krlmlr/bindrcpp documentation built on Feb. 4, 2024, 9:22 a.m.