savvy

Savvy is a simple R extension interface using Rust.

This is nothing but my personal challenge to re-invent the wheel in order to get better understanding about what extendr does. While this is usable, ergonomics is not included. If you prefer friendliness, please use extendr.

For the full details, please read savvy's crate documentation.

/// Convert to Upper-case
/// 
/// @param x A character vector.
/// @export
#[savvy]
fn to_upper(x: StringSexp) -> savvy::Result<savvy::Sexp> {
    // Use `Owned{type}Sexp` to allocate an R vector for output.
    let mut out = OwnedStringSexp::new(x.len())?;

    for (i, e) in x.iter().enumerate() {
        // To Rust, missing value is an ordinary value. In `&str`'s case, it's just "NA".
        // You have to use `.is_na()` method to distinguish the missing value.
        if e.is_na() {
            // Values need to be set by `set_elt()` one by one.
            out.set_elt(i, <&str>::na())?;
            continue;
        }

        let e_upper = e.to_uppercase();
        out.set_elt(i, e_upper.as_str())?;
    }

    out.into()
}

Getting Started

Prerequisite

Before starting, install a helper R package for savvy.

install.packages(
    "savvy",
    repos = c("https://yutannihilation.r-universe.dev", "https://cloud.r-project.org")
)

Note that, under the hood, this is just a simple wrapper around savvy-cli. So, if you prefer shell, you can directly use the CLI instead, which is available on the releases.

Create a new R package

First, create a new package. usethis::create_package() is convenient for this.

usethis::create_package("path/to/foo")

Then, move to the package directory and generate necessary files like Makevars and Cargo.toml, as well as generating C and R wrapper code corresponding to the Rust code. savvy::savvy_init() does this all (under the hood, this simply runs savvy-cli init).

Lastly, run devtools::document() to generate NAMESPACE and documents.

savvy::savvy_init()
devtools::document()

Now, this package is ready to install!

Update wrapper files

After modifying or adding some Rust code, you can update the C and R wrapper files by running savvy::savvy_update() (under the hood, this simply runs savvy-cli update).

savvy::savvy_update()
devtools::document()