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// build-pass
#![allow(incomplete_features)]
#![feature(generic_const_exprs)]
use std::{marker::PhantomData, ops::Mul};
pub enum Nil {}
pub struct Cons<T, L> {
_phantom: PhantomData<(T, L)>,
}
pub trait Indices<const N: usize> {
const RANK: usize;
const NUM_ELEMS: usize;
}
impl<const N: usize> Indices<N> for Nil {
const RANK: usize = 0;
const NUM_ELEMS: usize = 1;
}
impl<T, I: Indices<N>, const N: usize> Indices<N> for Cons<T, I> {
const RANK: usize = I::RANK + 1;
const NUM_ELEMS: usize = I::NUM_ELEMS * N;
}
pub trait Concat<J> {
type Output;
}
impl<J> Concat<J> for Nil {
type Output = J;
}
impl<T, I, J> Concat<J> for Cons<T, I>
where
I: Concat<J>,
{
type Output = Cons<T, <I as Concat<J>>::Output>;
}
pub struct Tensor<I: Indices<N>, const N: usize>
where
[u8; I::NUM_ELEMS]: Sized,
{
pub data: [u8; I::NUM_ELEMS],
_phantom: PhantomData<I>,
}
impl<I: Indices<N>, J: Indices<N>, const N: usize> Mul<Tensor<J, N>> for Tensor<I, N>
where
I: Concat<J>,
<I as Concat<J>>::Output: Indices<N>,
[u8; I::NUM_ELEMS]: Sized,
[u8; J::NUM_ELEMS]: Sized,
[u8; <I as Concat<J>>::Output::NUM_ELEMS]: Sized,
{
type Output = Tensor<<I as Concat<J>>::Output, N>;
fn mul(self, _rhs: Tensor<J, N>) -> Self::Output {
Tensor {
data: [0u8; <I as Concat<J>>::Output::NUM_ELEMS],
_phantom: PhantomData,
}
}
}
fn main() {}
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