[Question] How do I use keywords in Rust?

[Yappaholic]

I want to provide a way to use keywords in functions when embedding steel in Rust. Something like:

fn foo(fst: Keyword<String>, snd: Keyword<String>) {
  print!("{} {}", fst,snd);
}

And then in Steel:

(foo #:fst "bar" #:snd "baz")

Is this possible to do at the current stage of the project? Thank you

[mattwparas]

Nothing quite that straightforward yet, however you can do something like this:

fn plist_get_impl<'a>(
    mut iter: impl Iterator<Item = &'a SteelVal>,
    key: &SteelVal,
) -> Result<SteelVal> {
    let symbol = iter.find(|x| *x == key);
    let value = iter.next();
    match (symbol, value) {
        (None, _) => stop!(Generic => format!("Key not found: {}", key)),
        (Some(_), None) => stop!(Generic => format!("Missing value for key: {}", key)),
        (Some(_), Some(v)) => Ok(v.clone()),
    }
}

fn foo(args: &[SteelVal]) -> Result<SteelVal, SteelErr> {

    static FST: once_cell::sync::Lazy<SteelVal> =
        once_cell::sync::Lazy::new(|| SteelVal::SymbolV("#:fst".into()));

    let fst = plist_get_impl(args.iter(), &FST);

   // etc
}