Optional Argument

To represent an optional argument, you can wrap it with Option. Then, the corresponding R function sets the default value of NULL on the argument.

#[savvy]
fn default_value_vec(x: Option<IntegerSexp>) -> savvy::Result<Sexp> {
    if let Some(x) = x {
        x.iter().sum::<i32>().try_into()
    } else {
        (-1).try_into()
    }
}

function(x = NULL) {
  .Call(savvy_default_value_vec__impl, x)
}

This function works with or without the argument.

default_value_vec(1:10)
#> [1] 55

default_value_vec()
#> [1] -1