savvy-bindgen

Parse Rust functions, and generate C and R code.

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: StringSxp) -> savvy::Result<savvy::SEXP> {
    // Use `Owned{type}Sxp` to allocate an R vector for output.
    let mut out = OwnedStringSxp::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());
    }

    // `Owned{type}Sxp` type implements `From` trait for `SEXP`, so you can use `into()`.
    Ok(out.into())
}