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Auto merge of #14747 - oxalica:feat/arena-idx-range, r=HKalbasi
More APIs for `la_arena::IdxRange`
```rust
impl<T> ExactSizeIterator for IdxRange<T>;
impl<T> Arena<T> {
pub fn alloc_many<II: IntoIterator<Item = T>>(&mut self, iter: II) -> IdxRange<T>;
}
```
1. There are no currently ways to get `IdxRange` without manually offseting `Idx`. Providing a method for multiple-allocation simplifies this process and makes it less error-prone.
2. `IdxRange: ExactSizeIterator` makes `iter.zip(range).rev()` possible. Since `Zip: DoubleEndedIterator` requires all its arguments to be `ExactSizeIterator`. It also ease the usage for, eg. `len()`.
3. Fixed a typo.
I noticed that `IdxRange::end` may be invalid. Is it good to return `Idx` instead of `RawIdx`?
| -rw-r--r-- | lib/la-arena/src/lib.rs | 46 |
1 files changed, 44 insertions, 2 deletions
diff --git a/lib/la-arena/src/lib.rs b/lib/la-arena/src/lib.rs index b03fa5b61d..1f8ef01a5b 100644 --- a/lib/la-arena/src/lib.rs +++ b/lib/la-arena/src/lib.rs @@ -6,7 +6,7 @@ use std::{ cmp, fmt, hash::{Hash, Hasher}, - iter::Enumerate, + iter::{Enumerate, FusedIterator}, marker::PhantomData, ops::{Index, IndexMut, Range, RangeInclusive}, }; @@ -168,7 +168,7 @@ impl<T> IdxRange<T> { Idx::from_raw(RawIdx::from(self.range.start)) } - /// Returns the start of the index range. + /// Returns the end of the index range. pub fn end(&self) -> Idx<T> { Idx::from_raw(RawIdx::from(self.range.end)) } @@ -176,9 +176,32 @@ impl<T> IdxRange<T> { impl<T> Iterator for IdxRange<T> { type Item = Idx<T>; + fn next(&mut self) -> Option<Self::Item> { self.range.next().map(|raw| Idx::from_raw(raw.into())) } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.range.size_hint() + } + + fn count(self) -> usize + where + Self: Sized, + { + self.range.count() + } + + fn last(self) -> Option<Self::Item> + where + Self: Sized, + { + self.range.last().map(|raw| Idx::from_raw(raw.into())) + } + + fn nth(&mut self, n: usize) -> Option<Self::Item> { + self.range.nth(n).map(|raw| Idx::from_raw(raw.into())) + } } impl<T> DoubleEndedIterator for IdxRange<T> { @@ -187,6 +210,10 @@ impl<T> DoubleEndedIterator for IdxRange<T> { } } +impl<T> ExactSizeIterator for IdxRange<T> {} + +impl<T> FusedIterator for IdxRange<T> {} + impl<T> fmt::Debug for IdxRange<T> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple(&format!("IdxRange::<{}>", std::any::type_name::<T>())) @@ -305,6 +332,21 @@ impl<T> Arena<T> { idx } + /// Densely allocates multiple values, returning the values’ index range. + /// + /// ``` + /// let mut arena = la_arena::Arena::new(); + /// let range = arena.alloc_many(0..4); + /// + /// assert_eq!(arena[range], [0, 1, 2, 3]); + /// ``` + pub fn alloc_many<II: IntoIterator<Item = T>>(&mut self, iter: II) -> IdxRange<T> { + let start = self.next_idx(); + self.extend(iter); + let end = self.next_idx(); + IdxRange::new(start..end) + } + /// Returns an iterator over the arena’s elements. /// /// ``` |