extendr - A safe and user friendly R extension interface using Rust.

Installation - Rust

Extendr is available on crates.io.

Simply add this line to the [dependencies] section of a rust crate. You will then be able to call R code from Rust.

[dependencies]
extendr-api = "0.2"

There are two ways you can use the extendr API from R. First, you can use the rextendr package to call individual Rust functions from an R session. Second, you can write an R package that uses compiled Rust code, see the helloextendr repo for a minimal example.

Overview

Extendr is a Rust extension mechanism for R

It is intended to be easier to use than the C interface and Rcpp as Rust gives type safety and freedom from segfaults.

The following code illustrates a simple structure trait which is written in Rust. The data is defined in the struct declaration and the methods in the impl.

use extendr_api::prelude::*;

struct Person {
    pub name: String,
}

#[extendr]
impl Person {
    fn new() -> Self {
        Self { name: "".to_string() }
    }

    fn set_name(&mut self, name: &str) {
        self.name = name.to_string();
    }

    fn name(&self) -> &str {
        self.name.as_str()
    }
}

#[extendr]
fn aux_func() {
}


// Macro to generate exports
extendr_module! {
    mod classes;
    impl Person;
    fn aux_func;
}

The #[extendr] attribute causes the compiler to generate wrapper and registration functions for R which are called when the package is loaded.

The extendr_module! macro lists the module name and exported functions and interfaces.

This library aims to provide an interface that will be familiar to first-time users of Rust or indeed any compiled language.

Anyone who knows the R library should be able to write R extensions.

Goals of the project

Instead of wrapping R objects, we convert to Rust native objects on entry to a function. This makes the wrapped code clean and dependency free. The ultimate goal is to allow the wrapping of existing Rust libraries without markup, but in the meantime, the markup is as light as possible.

#[extendr]
pub fn my_sum(v: &[f64]) -> f64 {
    v.iter().sum()
}

You can interact in more detail with R objects using the RObj type which wraps the native R object type. This supports a large subset of the R internals functions, but wrapped to prevent accidental segfaults and failures.