| //! Implementation for `arr!` macro. |
| |
| use super::ArrayLength; |
| use core::ops::Add; |
| use typenum::U1; |
| |
| /// Helper trait for `arr!` macro |
| pub trait AddLength<T, N: ArrayLength<T>>: ArrayLength<T> { |
| /// Resulting length |
| type Output: ArrayLength<T>; |
| } |
| |
| impl<T, N1, N2> AddLength<T, N2> for N1 |
| where |
| N1: ArrayLength<T> + Add<N2>, |
| N2: ArrayLength<T>, |
| <N1 as Add<N2>>::Output: ArrayLength<T>, |
| { |
| type Output = <N1 as Add<N2>>::Output; |
| } |
| |
| /// Helper type for `arr!` macro |
| pub type Inc<T, U> = <U as AddLength<T, U1>>::Output; |
| |
| #[doc(hidden)] |
| #[macro_export] |
| macro_rules! arr_impl { |
| ($T:ty; $N:ty, [$($x:expr),*], []) => ({ |
| unsafe { $crate::transmute::<_, $crate::GenericArray<$T, $N>>([$($x),*]) } |
| }); |
| ($T:ty; $N:ty, [], [$x1:expr]) => ( |
| arr_impl!($T; $crate::arr::Inc<$T, $N>, [$x1 as $T], []) |
| ); |
| ($T:ty; $N:ty, [], [$x1:expr, $($x:expr),+]) => ( |
| arr_impl!($T; $crate::arr::Inc<$T, $N>, [$x1 as $T], [$($x),*]) |
| ); |
| ($T:ty; $N:ty, [$($y:expr),+], [$x1:expr]) => ( |
| arr_impl!($T; $crate::arr::Inc<$T, $N>, [$($y),*, $x1 as $T], []) |
| ); |
| ($T:ty; $N:ty, [$($y:expr),+], [$x1:expr, $($x:expr),+]) => ( |
| arr_impl!($T; $crate::arr::Inc<$T, $N>, [$($y),*, $x1 as $T], [$($x),*]) |
| ); |
| } |
| |
| /// Macro allowing for easy generation of Generic Arrays. |
| /// Example: `let test = arr![u32; 1, 2, 3];` |
| #[macro_export] |
| macro_rules! arr { |
| ($T:ty;) => ({ |
| unsafe { $crate::transmute::<[$T; 0], $crate::GenericArray<$T, $crate::typenum::U0>>([]) } |
| }); |
| ($T:ty; $($x:expr),*) => ( |
| arr_impl!($T; $crate::typenum::U0, [], [$($x),*]) |
| ); |
| ($($x:expr,)+) => (arr![$($x),*]); |
| () => ("""Macro requires a type, e.g. `let array = arr![u32; 1, 2, 3];`") |
| } |