|
| 1 | +// run-pass |
| 2 | +#![feature(const_generics)] |
| 3 | +#![allow(incomplete_features)] |
| 4 | + |
| 5 | +trait ConstChunksExactTrait<T> { |
| 6 | + fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'_, T, {N}>; |
| 7 | +} |
| 8 | + |
| 9 | +impl <T> ConstChunksExactTrait<T> for [T] { |
| 10 | + fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'_, T, {N}> { |
| 11 | + assert!(N != 0); |
| 12 | + let rem = self.len() % N; |
| 13 | + let len = self.len() - rem; |
| 14 | + let (fst, _) = self.split_at(len); |
| 15 | + ConstChunksExact { v: fst, } |
| 16 | + } |
| 17 | +} |
| 18 | + |
| 19 | +struct ConstChunksExact<'a, T: 'a, const N: usize> { |
| 20 | + v: &'a [T], |
| 21 | +} |
| 22 | + |
| 23 | +impl <'a, T: std::fmt::Debug, const N: usize> Iterator for ConstChunksExact<'a, T, {N}> { |
| 24 | + type Item = &'a [T; N]; |
| 25 | + |
| 26 | + fn next(&mut self) -> Option<Self::Item> { |
| 27 | + if self.v.len() < N { |
| 28 | + None |
| 29 | + } else { |
| 30 | + let (fst, snd) = self.v.split_at(N); |
| 31 | + |
| 32 | + self.v = snd; |
| 33 | + let ptr = fst.as_ptr() as *const _; |
| 34 | + Some(unsafe { &*ptr}) |
| 35 | + } |
| 36 | + } |
| 37 | +} |
| 38 | + |
| 39 | +fn main() { |
| 40 | + let slice = &[1i32, 2, 3, 4, 5, 6, 7, 8, 9, 10]; |
| 41 | + |
| 42 | + let mut iter = [[1, 2, 3], [4, 5, 6], [7, 8, 9]].iter(); |
| 43 | + |
| 44 | + for a in slice.const_chunks_exact::<3>() { |
| 45 | + assert_eq!(a, iter.next().unwrap()); |
| 46 | + } |
| 47 | +} |
0 commit comments