Macro bevy_utils::all_tuples
source · all_tuples!() { /* proc-macro */ }
Expand description
Helper macro to generate tuple pyramids. Useful to generate scaffolding to work around Rust
lacking variadics. Invoking all_tuples!(impl_foo, start, end, P, Q, ..)
invokes impl_foo
providing ident tuples through arity start..=end
.
§Examples
A single parameter.
use std::marker::PhantomData;
use bevy_utils_proc_macros::all_tuples;
struct Foo<T> {
// ..
_phantom: PhantomData<T>
}
trait WrappedInFoo {
type Tup;
}
macro_rules! impl_wrapped_in_foo {
($($T:ident),*) => {
impl<$($T),*> WrappedInFoo for ($($T,)*) {
type Tup = ($(Foo<$T>,)*);
}
};
}
all_tuples!(impl_wrapped_in_foo, 0, 15, T);
// impl_wrapped_in_foo!();
// impl_wrapped_in_foo!(P0);
// impl_wrapped_in_foo!(P0, P1);
// ..
// impl_wrapped_in_foo!(P0 .. P14);
Multiple parameters.
use bevy_utils_proc_macros::all_tuples;
trait Append {
type Out<Item>;
fn append<Item>(tup: Self, item: Item) -> Self::Out<Item>;
}
impl Append for () {
type Out<Item> = (Item,);
fn append<Item>(_: Self, item: Item) -> Self::Out<Item> {
(item,)
}
}
macro_rules! impl_append {
($(($P:ident, $p:ident)),*) => {
impl<$($P),*> Append for ($($P,)*) {
type Out<Item> = ($($P),*, Item);
fn append<Item>(($($p,)*): Self, item: Item) -> Self::Out<Item> {
($($p),*, item)
}
}
}
}
all_tuples!(impl_append, 1, 15, P, p);
// impl_append!((P0, p0));
// impl_append!((P0, p0), (P1, p1));
// impl_append!((P0, p0), (P1, p1), (P2, p2));
// ..
// impl_append!((P0, p0) .. (P14, p14));