# savvy-bindgen
Parse Rust functions, and generate C and R code.
For the full details, please read [savvy's crate
documentation](https://docs.rs/savvy/latest/).
``` rust
/// 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() {
// Set the i-th element to NA
out.set_na(i)?;
continue;
}
let e_upper = e.to_uppercase();
out.set_elt(i, e_upper.as_str())?;
}
out.into()
}
```