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//! This crate provides set and relational operations for all iterators in the standard library that are known //! at compile time to be sorted. //! //! # Set operations //! ``` //! # extern crate maplit; //! # use maplit::*; //! # extern crate sorted_iter; //! use sorted_iter::SortedIterator; //! //! let primes = btreeset! { 2, 3, 5, 7, 11, 13u64 }.into_iter(); //! let fibs = btreeset! { 1, 2, 3, 5, 8, 13u64 }.into_iter(); //! let fib_primes = primes.intersection(fibs); //! ``` //! //! It is possible to efficiently define set operations on sorted iterators. Sorted iterators are //! very common in the standard library. E.g. the elements of a [BTreeSet] or the keys of a [BTreeMap] //! are guaranteed to be sorted according to the element order, as are iterable ranges like `0..100`. //! //! There are also a number of operations on iterators that preserve the sort order. E.g. if an //! iterator is sorted, [take], [take_while] etc. are going to result in a sorted iterator as well. //! //! Since the complete types of iterators are typically visible in rust, it is possible to encode these //! rules at type level. This is what this crate does. //! //! For available set operations, see [SortedIterator]. //! For sorted iterators in the std lib, see instances the for [SortedByItem] marker trait. //! //! # Relational operations //! ``` //! # extern crate maplit; //! # use maplit::*; //! # extern crate sorted_iter; //! use sorted_iter::SortedPairIterator; //! //! let cities = btreemap! { //! 1 => "New York", //! 2 => "Tokyo", //! 3u8 => "Berlin" //! }.into_iter(); //! let countries = btreemap! { //! 1 => "USA", //! 2 => "Japan", //! 3u8 => "Germany" //! }.into_iter(); //! let cities_and_countries = cities.join(countries); //! ``` //! //! Iterators of pairs that are sorted according to the first element / key are also very common in //! the standard library and elsewhere. E.g. the elements of a [BTreeMap] are guaranteed to be sorted //! according to the key order. //! //! The same rules as for sorted iterators apply for preservation of the sort order, except that there //! are some additional operations that preserve sort order. Anything that only operates on the value, //! like e.g. map or filter_map on the value, is guaranteed to preserve the sort order. //! //! The operations that can be defined on sorted pair operations are the relational operations known //! from relational algebra / SQL, namely join, left_join, right_join and outer_join. //! //! For available relational operations, see [SortedPairIterator]. //! For sorted iterators in the std lib, see instances the for [SortedByKey] marker trait. //! //! # Transformations that retain order are allowed //! ``` //! # extern crate sorted_iter; //! use sorted_iter::*; //! //! let odd = (1..31).step_by(2); //! let multiples_of_3 = (3..30).step_by(3); //! let either = odd.union(multiples_of_3); //! ``` //! //! # Transformations that can change the order lose the sorted property //! ```compile_fail //! # extern crate sorted_iter; //! use sorted_iter::*; //! //! // we have no idea what map does to the order. could be anything! //! let a = (1..31).map(|x| -x); //! let b = (3..30).step_by(3); //! let either = a.union(b); // does not compile! //! ``` //! //! # Assuming sort ordering //! //! For most std lib iterators, this library already provides instances. But there will occasionally be an iterator //! from a third party library where you *know* that it is properly sorted. //! //! For this case, there is an escape hatch: //! //! ``` //! // the assume_ extensions have to be implicitly imported //! use sorted_iter::*; //! use sorted_iter::assume::*; //! let odd = vec![1,3,5,7u8].into_iter().assume_sorted_by_item(); //! let even = vec![2,4,6,8u8].into_iter().assume_sorted_by_item(); //! let all = odd.union(even); //! //! let cities = vec![(1u8, "New York")].into_iter().assume_sorted_by_key(); //! let countries = vec![(1u8, "USA")].into_iter().assume_sorted_by_key(); //! let cities_and_countries = cities.join(countries); //! ``` //! //! # Marking your own iterators //! //! If you have a library and want to mark some iterators as sorted, this is possible by implementing the //! appropriate marker trait, [SortedByItem] or [SortedByKey]. //! //! ``` //! # extern crate sorted_iter; //! // marker traits are not at top level, since usually you don't need them //! use sorted_iter::sorted_iterator::SortedByItem; //! use sorted_iter::sorted_pair_iterator::SortedByKey; //! //! pub struct MySortedIter<T> { whatever: T } //! pub struct MySortedPairIter<K, V> { whatever: (K, V) } //! //! impl<T> SortedByItem for MySortedIter<T> {} //! impl<K, V> SortedByKey for MySortedPairIter<K, V> {} //! ``` //! //! By reexporting the extension traits, you get a seamless experience for people using your library. //! //! ``` //! extern crate sorted_iter; //! pub use sorted_iter::{SortedIterator, SortedPairIterator}; //! ``` //! //! ## Tests //! //! Tests are done using the fantastic [quickcheck] crate, by comparing against the operations defined on //! [BTreeSet] and [BTreeMap]. //! //! [SortedIterator]: trait.SortedIterator.html //! [SortedPairIterator]: trait.SortedPairIterator.html //! [SortedByItem]: sorted_iterator/trait.SortedByItem.html //! [SortedByKey]: sorted_pair_iterator/trait.SortedByKey.html //! [quickcheck]: https://github.com/BurntSushi/quickcheck //! [BTreeSet]: https://doc.rust-lang.org/std/collections/struct.BTreeSet.html //! [BTreeMap]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html //! [take]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.take //! [take_while]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.take_while //! [Ord]: https://doc.rust-lang.org/std/cmp/trait.Ord.html #[cfg(test)] extern crate quickcheck; #[cfg(test)] #[macro_use(quickcheck)] extern crate quickcheck_macros; pub mod sorted_iterator; pub mod sorted_pair_iterator; use crate::sorted_iterator::*; use crate::sorted_pair_iterator::*; #[deny(missing_docs)] /// set operations for iterators where the items are sorted according to the natural order pub trait SortedIterator: Iterator + Sized { /// union with another sorted iterator fn union<J>(self, that: J) -> Union<Self, J> where J: SortedIterator<Item = Self::Item>, { Union { a: self.peekable(), b: that.peekable(), } } /// intersection with another sorted iterator fn intersection<J>(self, that: J) -> Intersection<Self, J> where J: SortedIterator<Item = Self::Item>, { Intersection { a: self.peekable(), b: that.peekable(), } } /// difference with another sorted iterator fn difference<J>(self, that: J) -> Difference<Self, J> where J: SortedIterator<Item = Self::Item>, { Difference { a: self.peekable(), b: that.peekable(), } } /// symmetric difference with another sorted iterator fn symmetric_difference<J>(self, that: J) -> SymmetricDifference<Self, J> where J: SortedIterator<Item = Self::Item>, { SymmetricDifference { a: self.peekable(), b: that.peekable(), } } /// pairs with unit value fn pairs(self) -> Pairs<Self> { Pairs { i: self } } } impl<I> SortedIterator for I where I: Iterator + SortedByItem {} /// Union of multiple sorted iterators. /// /// An advantage of this function over multiple calls to `SortedIterator::union` /// is that the number of merged sequences does not need to be known at the /// compile time. The drawback lies in the fact that all iterators have to be /// of the same type. /// /// The algorithmic complexity of fully consuming the resulting iterator is /// *O(N log(K))* where *N* is the total number of items that the input iterators /// yield and *K* is the number of input iterators. /// /// # Examples /// /// ``` /// # extern crate maplit; /// # use maplit::*; /// # extern crate sorted_iter; /// # use std::collections::BTreeSet; /// use sorted_iter::multiway_union; /// /// let sequences = vec![ /// btreeset! { 0, 5, 10, 15, 20, 25 }.into_iter(), /// btreeset! { 0, 1, 4, 9, 16, 25, 36 }.into_iter(), /// btreeset! { 4, 7, 11, 15, 18 }.into_iter(), /// ]; /// /// assert_eq!( /// multiway_union(sequences).collect::<BTreeSet<u64>>(), /// btreeset! { 0, 1, 4, 5, 7, 9, 10, 11, 15, 16, 18, 20, 25, 36 } /// ); /// ``` pub fn multiway_union<T, I>(iters: T) -> MultiwayUnion<I> where I: SortedIterator, T: IntoIterator<Item = I>, I::Item: Ord, { MultiwayUnion::from_iter(iters) } /// relational operations for iterators of pairs where the items are sorted according to the key pub trait SortedPairIterator<K, V>: Iterator + Sized { fn join<W, J: SortedPairIterator<K, W>>(self, that: J) -> Join<Self, J> { Join { a: self.peekable(), b: that.peekable(), } } fn left_join<W, J: SortedPairIterator<K, W>>(self, that: J) -> LeftJoin<Self, J> { LeftJoin { a: self.peekable(), b: that.peekable(), } } fn right_join<W, J: SortedPairIterator<K, W>>(self, that: J) -> RightJoin<Self, J> { RightJoin { a: self.peekable(), b: that.peekable(), } } fn outer_join<W, J: SortedPairIterator<K, W>>(self, that: J) -> OuterJoin<Self, J> { OuterJoin { a: self.peekable(), b: that.peekable(), } } fn map_values<W, F: (FnMut(V) -> W)>(self, f: F) -> MapValues<Self, F> { MapValues { i: self, f } } fn filter_map_values<W, F: (FnMut(V) -> W)>(self, f: F) -> FilterMapValues<Self, F> { FilterMapValues { i: self, f } } fn keys(self) -> Keys<Self> { Keys { i: self } } } impl<K, V, I> SortedPairIterator<K, V> for I where I: Iterator<Item = (K, V)> + SortedByKey {} pub mod assume { //! extension traits for unchecked conversions from iterators to sorted iterators use super::*; /// extension trait for any iterator to add a assume_sorted_by_item method pub trait AssumeSortedByItemExt: Iterator + Sized { /// assume that the iterator is sorted by its item order fn assume_sorted_by_item(self) -> AssumeSortedByItem<Self> { AssumeSortedByItem { i: self } } } impl<I: Iterator + Sized> AssumeSortedByItemExt for I {} /// extension trait for any iterator of pairs to add a assume_sorted_by_key method pub trait AssumeSortedByKeyExt: Iterator + Sized { fn assume_sorted_by_key(self) -> AssumeSortedByKey<Self> { AssumeSortedByKey { i: self } } } impl<K, V, I: Iterator<Item = (K, V)> + Sized> AssumeSortedByKeyExt for I {} }