Macro ocaml_interop::ocaml

macro_rules! ocaml {
    () => { ... };
    ($vis : vis fn $name : ident($arg : ident : $typ : ty $(,) ?) $(-> $rtyp : ty)
 ? ; $($t : tt) *) => { ... };
    ($vis : vis fn $name :
 ident($arg1 : ident : $typ1 : ty, $arg2 : ident : $typ2 : ty $(,) ?)
 $(-> $rtyp : ty) ? ; $($t : tt) *) => { ... };
    ($vis : vis fn $name :
 ident($arg1 : ident : $typ1 : ty, $arg2 : ident : $typ2 : ty, $arg3 : ident :
       $typ3 : ty $(,) ?) $(-> $rtyp : ty) ? ; $($t : tt) *) => { ... };
    ($vis : vis fn $name : ident($($arg : ident : $typ : ty), + $(,) ?)
 $(-> $rtyp : ty) ? ; $($t : tt) *) => { ... };
}

Declares OCaml functions.

ocaml! { pub fn registered_name(arg1: ArgT, ...) -> Ret_typ; ... } declares a function that has been defined in OCaml code and registered with Callback.register "registered_name" ocaml_function.

Visibility and return value type can be omitted. The return type defaults to () when omitted.

When invoking one of these functions, the first argument must be a &mut OCamlRuntime, and the remaining arguments OCamlRef<ArgT>.

The return value is a BoxRoot<RetType>.

Calls that raise an OCaml exception will panic!. Care must be taken on the OCaml side to avoid exceptions and return ('a, 'err) Result.t values to signal errors, which can then be converted into Rust’s Result<A, Err> and Result<OCaml<A>, OCaml<Err>>.

Examples

ocaml! {
    // Declares `print_endline`, with a single `String` (`OCamlRef<String>` when invoked)
    // argument and `BoxRoot<()>` return type (default when omitted).
    pub fn print_endline(s: String);

    // Declares `bytes_concat`, with two arguments, an OCaml `bytes` separator,
    // and an OCaml list of segments to concatenate. Return value is an OCaml `bytes`
    // value.
    fn bytes_concat(sep: OCamlBytes, segments: OCamlList<OCamlBytes>) -> OCamlBytes;
}