Macro raml::caml

macro_rules! caml {
    ($name:ident, |$($param:ident),*|, <$($local:ident),*>, $code:block -> $retval:ident) => { ... };
    ($name:ident, |$($param:ident),*|, $code:block) => { ... };
    ($name:ident, |$($param:ident),*|, $code:block -> $retval:ident) => { ... };
}

Defines an external Rust function for FFI use by an OCaml program, with automatic CAMLparam, CAMLlocal, and CAMLreturn inserted for you.