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//! Collection traits for generic programming. //! //! This crate distinguishes three modes of access to a collection, as determined by marker bounds //! on the methods of each collection trait: //! //! | Marker Bound | Enables | Analogous To | //! |--------------|-------------------------------------|---------------| //! | (none) | Read-only access to items and state | `&[T]` | //! | [`Mut`] | Write access to items | `&mut [T]` | //! | [`Own`] | Insertion and removal of items | `&mut Vec<T>` | //! //! [`Mut`]: trait.Mut.html //! [`Own`]: trait.Own.html //! //! These bounds can be combined with each of the collection traits to enable different operations //! on the collection. For example, [`List`] on its own provides [`len`] and [`get`], while //! `List + Mut` additionally provides [`get_mut`] and [`swap`], and `List + Own` additionally //! provides [`clear`] and [`push`]. //! //! [`List`]: trait.List.html //! [`clear`]: trait.Collection.html#tymethod.clear //! [`get`]: trait.List.html#tymethod.get //! [`get_mut`]: trait.List.html#tymethod.get_mut //! [`push`]: trait.List.html#method.push //! [`swap`]: trait.List.html#tymethod.swap //! [`len`]: trait.Collection.html#tymethod.len //! //! Generic code should specify only those bounds that are needed for its operation, but may //! specify additional bounds for future compatibility. Generic code should also use the collection //! traits with a `?Sized` bound in order to support slices and trait objects whenever possible. //! //! # Examples //! //! Insertion sort: //! //! ``` //! use eclectic::{List, Mut}; //! //! fn insertion_sort<L: ?Sized + List + Mut>(list: &mut L) where L::Item: Ord { //! for i in 1..list.len() { // `len` is defined on `Collection`, a supertrait of `List` //! let mut j = i; //! //! while j > 0 && list.get(j) < list.get(j - 1) { //! list.swap(j, j - 1); // the `Mut` bound on `L` enables the use of `List::swap` //! j -= 1; //! } //! } //! } //! //! use std::collections::VecDeque; //! //! let mut slice = ["c", "b", "a"]; //! insertion_sort(&mut slice as &mut [_]); //! assert_eq!(slice, ["a", "b", "c"]); //! //! let mut vec = vec!['c', 'b', 'a']; //! insertion_sort(&mut vec); //! assert_eq!(vec, ['a', 'b', 'c']); //! //! let mut vec_deque: VecDeque<_> = vec![3, 2, 1].into_iter().collect(); //! insertion_sort(&mut vec_deque); //! assert!(vec_deque.iter().eq(&[1, 2, 3])); //! ``` //! //! # A Note on Trait Objects //! //! A number of trait methods in this crate return a `Box<Iterator>`, which requires unnecessary //! heap allocation and opaqueness (e.g. erasure of traits like `Clone` and `DoubleEndedIterator`). //! This is to make up for the (hopefully temporary) inability to define higher-kinded associated //! types like: //! //! ```ignore //! trait Collection { //! type Drain<'a>: 'a + Iterator<Item = Self::Item>; //! //! fn drain<'a>(&'a mut self) -> Self::Drain<'a> where Self: Own; //! } //! ``` //! //! If Rust acquires such types, the iterator- and entry-returning methods will be changed to use //! them. #![deny(missing_docs)] #![feature(deque_extras)] #![feature(set_recovery)] mod impls; pub use map::Map; pub use set::Set; use std::ops::{Range, RangeFrom, RangeFull, RangeTo}; /// A marker trait that enables write access to a collection's items. pub trait Mut {} /// A marker trait that enables insertion and removal of a collection's items. pub trait Own {} /// A collection. /// /// A collection maintains a finite number of items. pub trait Collection { /// The type of the collection's items. type Item; /// Returns the number of items in the collection. fn len(&self) -> usize; /// Checks if the collection contains no items. fn is_empty(&self) -> bool { self.len() == 0 } /// Drains the given collection and inserts its items into the collection. /// /// The exact behavior of this method is unspecified, but it must be equivalent to /// `self.extend_object(&mut other.drain())`. `other`'s capacity should remain the same, when /// possible. fn append(&mut self, other: &mut Self) where Self: Sized + Own { self.extend_object(&mut other.drain()); } /// Inserts the items yielded by the given iterator into the collection. /// /// This method is provided for use with trait objects, and generic code should prefer /// [`Extend::extend`], which this method must be equivalent to. /// /// The exact behavior of this method is unspecified, but may be refined by subtraits. /// /// Note that this trait cannot extend `Extend` due to object-safety limitations. /// /// [`Extend::extend`]: /// https://doc.rust-lang.org/stable/std/iter/trait.Extend.html#tymethod.extend fn extend_object(&mut self, items: &mut Iterator<Item = Self::Item>) where Self: Own; /// Removes all items from the collection. fn clear(&mut self) where Self: Own { self.drain(); } /// Removes all items from the collection and returns an iterator that yields them. /// /// All items are removed even if the iterator is not exhausted. However, the behavior of /// this method is unspecified if the iterator is leaked (e.g. via [`mem::forget`]). /// /// The iteration order is unspecified, but subtraits may place a requirement on it. /// /// `self`'s capacity should remain the same, when possible. /// /// [`mem::forget`]: https://doc.rust-lang.org/stable/std/mem/fn.forget.html fn drain<'a>(&'a mut self) -> Box<Iterator<Item = Self::Item> + 'a> where Self: Own; /// Reserves capacity for the given number of additional items to be inserted into the /// collection. /// /// This method may do nothing (e.g. for node-based collections). fn reserve(&mut self, additional: usize) where Self: Own; /// Shrinks the collection's capacity as much as possible. /// /// This method may do nothing (e.g. for node-based collections). fn shrink_to_fit(&mut self) where Self: Own; } /// A collection that supports by-reference iteration. /// /// Maps are not expected to implement this interface, because they often provide /// `Iterator<Item = (&Self::Key, &Self::Value)>`. pub trait Iter: Collection { /// Returns an iterator that yields references to the collection's items. /// /// The iteration order is unspecified, but subtraits may place a requirement on it. fn iter<'a>(&'a self) -> Box<Iterator<Item = &'a Self::Item> + 'a>; /// Returns an iterator that yields mutable references to the collection's items. /// /// The iteration order is unspecified, but subtraits may place a requirement on it. fn iter_mut<'a>(&'a mut self) -> Box<Iterator<Item = &'a mut Self::Item> + 'a> where Self: Mut; } /// A collection that supports draining a range of its items. pub trait DrainRange<R>: Collection { /// Removes all items from the collection that lie in the given range and returns an iterator /// that yields them. /// /// All items in the given range are removed even if the iterator is not exhausted. However, /// the behavior of this method is unspecified if the iterator is leaked (e.g. via /// [`mem::forget`]). /// /// The iteration order is unspecified, but subtraits may place a requirement on it. /// /// [`mem::forget`]: https://doc.rust-lang.org/stable/std/mem/fn.forget.html fn drain_range<'a>(&'a mut self, range: R) -> Box<Iterator<Item = Self::Item> + 'a> where Self: Own; } /// A list. /// /// A list is an ordered collection in which each item is located at a corresponding index. The /// indices are non-negative integers and zero-based. pub trait List: Collection + Iter + DrainRange<Range<usize>> + DrainRange<RangeFrom<usize>> + DrainRange<RangeTo<usize>> + DrainRange<RangeFull> { /// Returns a reference to the item at the given index in the list. /// /// Returns `None` if `index >= self.len()`. fn get(&self, index: usize) -> Option<&Self::Item>; /// Returns a mutable reference to the item at the given index in the list. /// /// Returns `None` if `index >= self.len()`. fn get_mut(&mut self, index: usize) -> Option<&mut Self::Item> where Self: Mut; /// Swaps the items at the given indices in the list. /// /// # Panics /// /// Panics if `i >= self.len() || j >= self.len()`. fn swap(&mut self, i: usize, j: usize) where Self: Mut; /// Returns a reference to the first item in the list. /// /// Returns `None` if the list is empty. fn first(&self) -> Option<&Self::Item> { self.get(0) } /// Returns a mutable reference to the first item in the list. /// /// Returns `None` if the list is empty. fn first_mut(&mut self) -> Option<&mut Self::Item> where Self: Mut { self.get_mut(0) } /// Returns a reference to the last item in the list. /// /// Returns `None` if the list is empty. fn last(&self) -> Option<&Self::Item> { self.get(self.len().wrapping_sub(1)) } /// Returns a mutable reference to the last item in the list. /// /// Returns `None` if the list is empty. fn last_mut(&mut self) -> Option<&mut Self::Item> where Self: Mut { let len = self.len(); self.get_mut(len.wrapping_sub(1)) } /// Pushes the given item onto the end of the list. fn push(&mut self, item: Self::Item) where Self: Own { let len = self.len(); self.insert(len, item); } /// Inserts the given item into the list at the given index. /// /// All items after the given index are shifted one index to the right. /// /// # Panics /// /// Panics if `index > self.len()`. fn insert(&mut self, index: usize, item: Self::Item) where Self: Own; /// Removes the last item in the list and returns it. /// /// Returns `None` if the list was empty. fn pop(&mut self) -> Option<Self::Item> where Self: Own { let len = self.len(); self.remove(len.wrapping_sub(1)) } /// Removes the item at the given index in the list and returns it. /// /// Returns `None` if `index >= self.len()`. /// /// All items after the given index are shifted one index to the left. fn remove(&mut self, index: usize) -> Option<Self::Item> where Self: Own; /// Removes the item at the given index in the list and returns it, replacing it with the last /// item in the list. /// /// Returns `None` if `index >= self.len()`. fn swap_remove(&mut self, index: usize) -> Option<Self::Item> where Self: Own; /// Removes all items in the list starting at the given index. /// /// Does nothing if `len >= self.len()`. fn truncate(&mut self, len: usize) where Self: Own { self.drain_range(len..); } /// Splits the list in two at the given index. /// /// Returns a new list that contains the items in the range `index..self.len()`. /// /// After this method returns, `self` contains the items in the range `0..index`. `self`'s /// capacity should remain the same, when possible. /// /// # Panics /// /// Panics if `index > self.len()`. // FIXME(rust-lang/rust#20021): this shouldn't be defaulted fn split_off(&mut self, index: usize) -> Self where Self: Sized + Own { let _ = index; unimplemented!() } } impl<L: ?Sized + List> DrainRange<RangeFrom<usize>> for L { fn drain_range<'a>(&'a mut self, range: RangeFrom<usize>) -> Box<Iterator<Item = L::Item> + 'a> where L: Own { let len = self.len(); self.drain_range(range.start..len) } } impl<L: ?Sized + List> DrainRange<RangeTo<usize>> for L { fn drain_range<'a>(&'a mut self, range: RangeTo<usize>) -> Box<Iterator<Item = L::Item> + 'a> where L: Own { self.drain_range(0..range.end) } } impl<L: ?Sized + List> DrainRange<RangeFull> for L { fn drain_range<'a>(&'a mut self, _range: RangeFull) -> Box<Iterator<Item = L::Item> + 'a> where L: Own { self.drain() } } pub mod map { //! Maps. use super::*; /// Map functionality that is independent of an additional type parameter. /// /// It is unusual to use this trait directly. Consider using [`Map`](trait.Map.html) instead. /// /// This trait exists to prevent compilation errors that would occur due to ambiguous method /// calls if the methods were instead implemented on `Map<Q>`. For example, calling `insert` on /// a `Map<Q>` should not depend on `Q`. pub trait Base: Collection<Item = (<Self as Base>::Key, <Self as Base>::Value)> { /// The type of the map's keys. type Key; /// The type of the map's values. type Value; /// Returns an iterator that yields references to the map's keys and references to their /// values. /// /// The iteration order is unspecified, but subtraits may place a requirement on it. fn iter<'a>(&'a self) -> Box<Iterator<Item = (&'a Self::Key, &'a Self::Value)> + 'a>; /// Returns an iterator that yields references to the map's keys and mutable references to /// their values. /// /// The iteration order is unspecified, but subtraits may place a requirement on it. fn iter_mut<'a>(&'a mut self) -> Box<Iterator<Item = (&'a Self::Key, &'a mut Self::Value)> + 'a> where Self: Mut; /// Inserts the given key and value into the map without replacing an equivalent key. /// /// If the map contains a key that is equivalent to the given key, that key is not replaced /// with the given key. The value is always replaced, however. /// /// Returns the equivalent key's value if the map contained one, `None` otherwise. fn insert(&mut self, key: Self::Key, value: Self::Value) -> Option<Self::Value> where Self: Own; /// Returns the entry in the map for the given key. fn entry<'a>(&'a mut self, key: Self::Key) -> Entry<'a, Self::Key, Self::Value> where Self: Own; } /// A map. /// /// A map is a set of keys, each of which is associated with a value. /// /// The type parameter `Q` represents an "equivalence" type that can be used to look up values /// in the map. For example, given a `Map<Key = String>`, it is usually possible to look up /// items using a `str`. When omitted, `Q` defaults to `Self::Key`. pub trait Map<Q: ?Sized = <Self as Base>::Key>: Base { /// Checks if the map contains a key that is equivalent to the given key. fn contains_key(&self, key: &Q) -> bool { self.get(key).is_some() } /// Returns a reference to the value of the key in the map that is equivalent to the given /// key. /// /// Returns `None` if the map contains no such key. fn get(&self, key: &Q) -> Option<&Self::Value>; /// Returns a mutable reference to the value of the key in the map that is equivalent to /// the given key. /// /// Returns `None` if the map contains no such key. fn get_mut(&mut self, key: &Q) -> Option<&mut Self::Value> where Self: Mut; /// Removes the key in the map that is equivalent to the given key and returns its value. /// /// Returns `None` if the map contained no such key. fn remove(&mut self, key: &Q) -> Option<Self::Value> where Self: Own; } /// A map entry. pub enum Entry<'a, K: 'a, V: 'a> { /// An occupied map entry. Occupied(Box<OccupiedEntry<Key = K, Value = V, MutValue = &'a mut V> + 'a>), /// A vacant map entry. Vacant(Box<VacantEntry<Key = K, Value = V, MutValue = &'a mut V> + 'a>), } impl<'a, K: 'a, V: 'a> Entry<'a, K, V> { /// Ensures that the entry is occupied by inserting it into the map with the given value if /// it is vacant. /// /// Returns a mutable reference to the entry's value with the same lifetime as the map. pub fn or_insert(self, value: V) -> &'a mut V { match self { Entry::Occupied(e) => e.into_mut(), Entry::Vacant(e) => e.insert(value), } } /// Ensures that the entry is occupied by inserting it into the map with the result of the /// given function if it is vacant. /// /// Returns a mutable reference to the entry's value with the same lifetime as the map. pub fn or_insert_with<F: FnOnce() -> V>(self, f: F) -> &'a mut V { match self { Entry::Occupied(e) => e.into_mut(), Entry::Vacant(e) => e.insert(f()), } } } /// An occupied map entry. pub trait OccupiedEntry { /// The type of the entry's key. type Key; /// The type of the entry's value. type Value; /// The type of the mutable reference to the entry's value with the same lifetime as the /// map. type MutValue; /// Returns a reference to the entry's value. fn get(&self) -> &Self::Value; /// Returns a mutable reference to the entry's value. fn get_mut(&mut self) -> &mut Self::Value; /// Returns a mutable reference to the entry's value with the same lifetime as the map. fn into_mut(self: Box<Self>) -> Self::MutValue; /// Removes the entry from the map and returns its value. fn remove(self: Box<Self>) -> Self::Value; } /// A vacant entry. pub trait VacantEntry { /// The type of the entry's key. type Key; /// The type of the entry's value. type Value; /// The type of the mutable reference to the entry's value with the same lifetime as the /// map. type MutValue; /// Inserts the entry into the map with the given value. /// /// Returns a mutable reference to the entry's value with the same lifetime as the map. fn insert(self: Box<Self>, value: Self::Value) -> Self::MutValue; } } pub mod set { //! Sets. use super::*; /// Set functionality that is independent of an additional type parameter. /// /// It is unusual to use this trait directly. Consider using [`Set`](trait.Set.html) instead. /// /// This trait exists to prevent compilation errors that would occur due to ambiguous method /// calls if the methods were instead implemented on `Set<Q>`. For example, calling `insert` on /// a `Set<Q>` should not depend on `Q`. pub trait Base: Collection + Iter { /// Checks if the set is disjoint from the given set. /// /// `self` is disjoint from `other` if `self` contains none of `other`'s items. fn is_disjoint(&self, other: &Self) -> bool where Self: Sized; /// Checks if the set is a subset of the given set. /// /// `self` is a subset of `other` if `other` contains all of `self`'s items. fn is_subset(&self, other: &Self) -> bool where Self: Sized; /// Checks if the set is a superset of the given set. /// /// `self` is a superset of `other` if `self` contains all of `other`'s items. fn is_superset(&self, other: &Self) -> bool where Self: Sized { other.is_subset(self) } /// Inserts the given item into the set without replacement. /// /// If the set contains an item that is equivalent to the given item, that item is not /// replaced with the given item. /// /// Returns `true` if the given item was inserted into the set, `false` otherwise. fn insert(&mut self, item: Self::Item) -> bool where Self: Own; /// Inserts the given item into the set with replacement. /// /// If the set contains an item that is equivalent to the given item, that item is replaced /// with the given item. /// /// Returns the item that was replaced, or `None` if the set did not contain an equivalent /// item. fn replace(&mut self, item: Self::Item) -> Option<Self::Item> where Self: Own; } /// A set. /// /// A set is a collection that prohibits duplicate items according to some criteria. /// /// The type parameter `Q` represents an "equivalence" type that can be used to look up items /// in the set. For example, given a `Set<Item = String>`, it is usually possible to look up /// items using a `str`. When omitted, `Q` defaults to `Self::Item`. pub trait Set<Q: ?Sized = <Self as Collection>::Item>: Base { /// Checks if the set contains an item that is equivalent to the given item. fn contains(&self, item: &Q) -> bool { self.get(item).is_some() } /// Returns a reference to the item in the set that is equivalent to the given item. /// /// Returns `None` if the set contains no such item. fn get(&self, item: &Q) -> Option<&Self::Item>; /// Removes the item in the set that is equivalent to the given item. /// /// Returns `true` if the set contained such an item, `false` otherwise. fn remove(&mut self, item: &Q) -> bool where Self: Own { self.take(item).is_some() } /// Removes the item in the set that is equivalent to the given item and returns it. /// /// Returns `None` if the set contained no such item. fn take(&mut self, item: &Q) -> Option<Self::Item> where Self: Own; } } /// A queue. pub trait Queue: Collection + Iter { /// Pushes the given item onto the queue. /// /// For FIFO queues, this pushes the item onto the back of the queue. For other queues, the /// location of the newly inserted item is unspecified. fn push(&mut self, item: Self::Item) where Self: Own; /// Returns a reference to the item at the front of the queue. /// /// Returns `None` if the queue is empty. fn front(&self) -> Option<&Self::Item>; /// Removes the item at the front of the queue and returns it. /// /// Returns `None` if the queue was empty. fn pop_front(&mut self) -> Option<Self::Item> where Self: Own; } /// A first-in, first-out queue. pub trait FifoQueue: Queue { /// Returns a mutable reference to the item at the front of the queue. /// /// Returns `None` if the queue is empty. fn front_mut(&mut self) -> Option<&mut Self::Item> where Self: Mut; } /// A priority queue. pub trait PrioQueue: Queue { /// Pushes the given item onto the queue, then removes the item at the front of the queue and /// returns it. fn push_pop_front(&mut self, item: Self::Item) -> Self::Item where Self: Own { self.push(item); self.pop_front().expect("queue was empty after a `push`") } /// Removes the item at the front of the queue, then pushes the given item onto the queue. /// /// Returns the item that was removed, or `None` if the queue was empty. fn replace_front(&mut self, item: Self::Item) -> Option<Self::Item> where Self: Own { let front = self.pop_front(); self.push(item); front } } /// A double-ended queue. pub trait Deque: Queue { /// Returns a reference to the item at the back of the deque. /// /// Returns `None` if the deque is empty. fn back(&self) -> Option<&Self::Item>; /// Removes the item at the back of the deque and returns it. /// /// Returns `None` if the deque was empty. fn pop_back(&mut self) -> Option<Self::Item> where Self: Own; } /// A double-ended first-in, first-out queue. pub trait FifoDeque: FifoQueue + Deque { /// Pushes the given item onto the front of the deque. fn push_front(&mut self, item: Self::Item) where Self: Own; /// Returns a mutable reference to the item at the back of the deque. /// /// Returns `None` if the deque is empty. fn back_mut(&mut self) -> Option<&mut Self::Item> where Self: Mut; } /// A double-ended priority queue. pub trait PrioDeque: PrioQueue + Deque { /// Pushes the given item onto the deque, then removes the item at the back of the deque and /// returns it. fn push_pop_back(&mut self, item: Self::Item) -> Self::Item where Self: Own { self.push(item); self.pop_back().expect("deque was empty after a `push`") } /// Removes the item at the back of the deque, then pushes the given item onto the deque. /// /// Returns the item that was removed, or `None` if the deque was empty. fn replace_back(&mut self, item: Self::Item) -> Option<Self::Item> where Self: Own { let back = self.pop_back(); self.push(item); back } } #[allow(dead_code)] fn assert_object_safe() { let _: &Mut; let _: &Own; let _: &Collection<Item = String>; let _: &List<Item = String>; let _: &Map<str, Item = (String, i32), Key = String, Value = i32>; let _: &map::OccupiedEntry<Key = String, Value = i32, MutValue = &mut i32>; let _: &map::VacantEntry<Key = String, Value = i32, MutValue = &mut i32>; let _: &Set<str, Item = String>; let _: &Queue<Item = String>; let _: &Deque<Item = String>; let _: &FifoQueue<Item = String>; let _: &FifoDeque<Item = String>; let _: &PrioQueue<Item = String>; let _: &PrioDeque<Item = String>; }