Macro nano_ecs::system_ids

macro_rules! system_ids {
    ($world:ident,
     $(?|$filter_id:ident| $filter:expr ;)*
     $id:ident,
     |$($n:ident: $x:ty),* $(,)?| $e:expr) => { ... };
}

Same as system!, but with entity ids.

Example: system_ids!(world, ?|n| ...; id, |&Position| {...});