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use core::fmt::Debug;
use core::ops::{Add, AddAssign, RangeBounds, Sub, SubAssign};
pub trait Summarize: Debug {
type Summary: Debug
+ Default
+ Clone
+ for<'a> Add<&'a Self::Summary, Output = Self::Summary>
+ for<'a> Sub<&'a Self::Summary, Output = Self::Summary>
+ for<'a> AddAssign<&'a Self::Summary>
+ for<'a> SubAssign<&'a Self::Summary>
+ PartialEq<Self::Summary>;
fn summarize(&self) -> Self::Summary;
}
pub trait BaseMeasured: Summarize {
type BaseMetric: Metric<Self::Summary>;
}
pub trait AsSlice: Summarize {
type Slice<'a>: Copy + Summarize<Summary = Self::Summary>
where
Self: 'a;
fn as_slice(&self) -> Self::Slice<'_>;
}
pub trait Leaf: Summarize + BaseMeasured + AsSlice {}
impl<T: Summarize + BaseMeasured + AsSlice> Leaf for T {}
pub trait BalancedLeaf: Leaf + for<'a> From<Self::Slice<'a>> {
/// Returns whether the leaf node is too small to be on its own and should
/// be rebalanced with another leaf.
fn is_underfilled(&self, summary: &Self::Summary) -> bool;
/// Balance two leaves.
///
/// The `right` leaf can be left empty if the two leaves can be combined
/// into a single one.
fn balance_leaves(
left: (&mut Self, &mut Self::Summary),
right: (&mut Self, &mut Self::Summary),
);
}
pub trait ReplaceableLeaf<M: Metric<Self::Summary>>: BalancedLeaf {
type Replacement<'a>;
type ExtraLeaves: ExactSizeIterator<Item = Self>;
/// Replace the contents of the leaf in the range with the given
/// replacement.
///
/// If that would cause the leaf to be too big the function can return an
/// iterator over the leaves to insert right after this leaf. Note that in
/// this case both this leaf and all the leaves yielded by the iterator are
/// assumed to not be underfilled.
fn replace<R>(
&mut self,
summary: &mut Self::Summary,
range: R,
replace_with: Self::Replacement<'_>,
) -> Option<Self::ExtraLeaves>
where
R: RangeBounds<M>;
fn remove_up_to(&mut self, summary: &mut Self::Summary, up_to: M);
}
pub trait Metric<Summary: ?Sized>:
Debug
+ Copy
+ Ord
+ Add<Self, Output = Self>
+ Sub<Self, Output = Self>
+ AddAssign<Self>
+ SubAssign<Self>
{
/// The identity element of this metric with respect to addition.
///
/// Given an implementor `M` of this trait, for all instances `m` of `M`
/// it should hold `m == m + M::zero()`.
fn zero() -> Self;
/// The smallest value larger than [`zero`](Self::zero()) this metric can
/// measure.
fn one() -> Self;
/// Returns the measure of the summary according to this metric.
fn measure(summary: &Summary) -> Self;
}
/// Metrics that can be used to slice `Tree`s and `TreeSlice`s.
pub trait SlicingMetric<L: Leaf>: Metric<L::Summary> {
fn slice_up_to<'a>(
slice: L::Slice<'a>,
up_to: Self,
summary: &L::Summary,
) -> (L::Slice<'a>, L::Summary);
fn slice_from<'a>(
slice: L::Slice<'a>,
from: Self,
summary: &L::Summary,
) -> (L::Slice<'a>, L::Summary);
}
/// Allows iterating forward over the units of this metric.
pub trait UnitMetric<L: Leaf>: Metric<L::Summary> {
/// Returns a
/// `(first_slice, first_summary, advance, rest_slice, rest_summary)`
/// tuple, where `advance` is equal to `first_summary` **plus** the summary
/// of any content between the end of `first_slice` and the start of
/// `rest_slice` that's not included in neither of them.
///
/// It follows that if `slice == first_slice ++ rest_slice` (where `++`
/// denotes concatenation) the `first_summary` and the `advance` should be
/// equal.
///
/// In any case it must always hold `summary == advance + rest_summary`.
#[allow(clippy::type_complexity)]
fn first_unit<'a>(
slice: L::Slice<'a>,
summary: &L::Summary,
) -> (L::Slice<'a>, L::Summary, L::Summary, L::Slice<'a>, L::Summary);
}
/// Allows iterating backward over the units of this metric.
pub trait DoubleEndedUnitMetric<L: Leaf>: UnitMetric<L> {
/// Returns a
/// `(rest_slice, rest_summary, last_slice, last_summary, advance)`
/// tuple, where `advance` is equal to `last_summary` **plus** the summary
/// of any content between the end of `last_slice` and the end of the
/// original `slice`.
///
/// It follows that if `slice == rest_slice ++ last_slice` (where `++`
/// denotes concatenation) the `last_summary` and the `advance` should be
/// equal.
///
/// In any case it must always hold `summary == rest_summary + advance`.
#[allow(clippy::type_complexity)]
fn last_unit<'a>(
slice: L::Slice<'a>,
summary: &L::Summary,
) -> (L::Slice<'a>, L::Summary, L::Slice<'a>, L::Summary, L::Summary);
/// It's possible for a leaf slice to contain some content that extends
/// past the end of its last `M`-unit. This is referred to as "the
/// remainder of the leaf divided by `M`".
///
/// Returns a `(rest_slice, rest_summary, remainder, remainder_summary)`
/// tuple. Note that unlike [`last_unit`](Self::last_unit()), this function
/// does not allow an `advance` to be returned. Instead `rest_slice` and
/// `remainder` should always concatenate up the original `slice` and their
/// summaries should sum up to the original `summary`.
///
/// The remainder can be empty if the last `M`-unit coincides with the end
/// of the leaf slice.
#[allow(clippy::type_complexity)]
fn remainder<'a>(
slice: L::Slice<'a>,
summary: &L::Summary,
) -> (L::Slice<'a>, L::Summary, L::Slice<'a>, L::Summary);
}