meta_tuple

A statically typed opaque tuple that can contain any type.

Use Cases

This crate is generally used for complicated input and output abstractions. The incompleteness of rust's current trait system makes this crate somewhat tricky to use, so we compiled a few standard usage patterns:

Chaining builder pattern:

pub trait CardComponent {
    fn play(&self, input: impl MetaTuple) -> impl MetaTuple;

    fn join(self, other: impl CardComponent) -> impl CardComponent where Self: Sized{
        Join(self, other)
    }
}

impl CardComponent for Attack {
    fn play(&self, input: impl MetaTuple) -> impl MetaTuple {
        let attacker = input.get::<Attacker>().unwrap();
        let defender = input.get::<Defender>().unwrap();
        let damage_dealt = self.calculate_damage(attacker, defender);
        input.join(DamageDealt(damage_dealt))
    }
}

pub struct Join<A, B>(A, B);

impl<A: CardComponent, B: CardComponent> CardComponent for Join<A, B> {
    fn play(&self, input: impl MetaTuple) -> impl MetaTuple{
        let out = self.0.play(input);
        self.1.play(out)
    }
}

Reference input pattern:

pub trait CardComponent {
    type Out: MetaTuple;
    fn play<T: MetaTuple>(&self, input: &T) -> Self::Out;

    fn join(self, other: impl CardComponent) -> impl CardComponent where Self: Sized{
        Join(self, other)
    }
}

impl<A: CardComponent, B: CardComponent> CardComponent for Join<A, B> {
    type Out = meta_tuple_type!(#A::Out, #B::Out);
    fn play<T: MetaTuple>(&self, input: &T) -> Self::Out {
        let out = self.0.play(input);
        let out_2 = self.1.play(&input.join_tuple(&out));
        meta_tuple!(#out, #out_2)
    }
}

Note: for RPITIT to be used here precise capturing must be stabilized first.

License

License under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.

Contribution

Contributions are welcome!

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.