Itertools

Extra iterator adaptors, functions and macros.

Please read the API documentation here

How to use with cargo:

[dependencies]
itertools = "0.8"

How to use in your crate:

#[macro_use] extern crate itertools;

use itertools::Itertools;

How to contribute

• Fix a bug or implement a new thing
• Include tests for your new feature, preferably a quickcheck test
• Make a Pull Request

For new features, please first consider filing a PR to rust-lang/rust, adding your new feature to the Iterator trait of the standard library, if you believe it is reasonable. If it isn't accepted there, proposing it for inclusion in itertools is a good idea. The reason for doing is this is so that we avoid future breakage as with .flatten(). However, if your feature involves heap allocation, such as storing elements in a Vec<T>, then it can't be accepted into libcore, and you should propose it for itertools directly instead.

Recent Changes

• 0.8.0
  • Added new adaptor .map_into() for conversions using Into by @vorner
  • Improved Itertools docs by @JohnHeitmann
  • The return type of .sorted/_by/_by_key() is now an iterator, not a Vec.
  • The return type of the izip!(x, y) macro with exactly two arguments is now the usual Iterator::zip.
  • Remove .flatten() in favour of std's .flatten()
  • Deprecate .foreach() in favour of std's .for_each()
  • Deprecate .step() in favour of std's .step_by()
  • Deprecate repeat_call in favour of std's repeat_with
  • Deprecate .fold_while() in favour of std's .try_fold()
  • Require Rust 1.24 as minimal version.
• 0.7.11
  • Add convenience methods to EitherOrBoth, making it more similar to Option and Either by @jethrogb
• 0.7.10
  • No changes.
• 0.7.9
  • New inclusion policy: See the readme about suggesting features for std before accepting them in itertools.
  • The FoldWhile type now implements Eq and PartialEq by @jturner314
• 0.7.8
  • Add new iterator method .tree_fold1() which is like .fold1() except items are combined in a tree structure (see its docs). By @scottmcm
  • Add more Debug impls by @phimuemue: KMerge, KMergeBy, MergeJoinBy, ConsTuples, Intersperse, ProcessResults, RcIter, Tee, TupleWindows, Tee, ZipLongest, ZipEq, Zip.
• 0.7.7
  • Add new iterator method .into_group_map() -> HashMap<K, Vec<V>> which turns an iterator of (K, V) elements into such a hash table, where values are grouped by key. By @tobz1000
  • Add new free function flatten for the .flatten() adaptor. NOTE: recent Rust nightlies have Iterator::flatten and thus a clash with our flatten adaptor. One workaround is to use the itertools flatten free function.
• 0.7.6
  • Add new adaptor .multi_cartesian_product() which is an n-ary product iterator by @tobz1000
  • Add new method .sorted_by_key() by @Xion
  • Provide simpler and faster .count() for .unique() and .unique_by()
• 0.7.5
  • .multipeek() now implements PeekingNext, by @nicopap.
• 0.7.4
  • Add new adaptor .update() by @lucasem; this adaptor is used to modify an element before passing it on in an iterator chain.
• 0.7.3
  • Add new method .collect_tuple() by @matklad; it makes a tuple out of the iterator's elements if the number of them matches exactly.
  • Implement fold and collect for .map_results() which means it reuses the code of the standard .map() for these methods.
• 0.7.2
  • Add new adaptor .merge_join_by by @srijs; a heterogeneous merge join for two ordered sequences.
• 0.7.1
  • Iterator adaptors and iterators in itertools now use the same must_use reminder that the standard library adaptors do, by @matematikaedit and @bluss “iterator adaptors are lazy and do nothing unless consumed”.
• 0.7.0
  • Faster izip!() by @krdln
    • izip!() is now a wrapper for repeated regular .zip() and a single .map(). This means it optimizes as well as the standard library .zip() it uses. Note: multizip and izip!() are now different! The former has a named type but the latter optimizes better.
  • Faster .unique()
  • no_std support, which is opt-in!
    • Many lovable features are still there without std, like izip!() or .format() or .merge(), but not those that use collections.
  • Trait bounds were required up front instead of just on the type: group_by's PartialEq by @Phlosioneer and repeat_call's FnMut.
  • Removed deprecated constructor Zip::new — use izip!() or multizip()
• 0.6.5
  • Fix bug in .cartesian_product()'s fold (which only was visible for unfused iterators).
• 0.6.4
  • Add specific fold implementations for .cartesian_product() and cons_tuples(), which improves their performance in fold, foreach, and iterator consumers derived from them.
• 0.6.3
  • Add iterator adaptor .positions(predicate) by @tmccombs
• 0.6.2
  • Add function process_results which can “lift” a function of the regular values of an iterator so that it can process the Ok values from an iterator of Results instead, by @shepmaster
  • Add iterator method .concat() which combines all iterator elements into a single collection using the Extend trait, by @srijs
• 0.6.1
  • Better size hint testing and subsequent size hint bugfixes by @rkarp. Fixes bugs in product, interleave_shortest size hints.
  • New iterator method .all_equal() by @phimuemue
• 0.6.0
  • Deprecated names were removed in favour of their replacements
  • .flatten() does not implement double ended iteration anymore
  • .fold_while() uses &mut self and returns FoldWhile<T>, for composability (#168)
  • .foreach() and .fold1() use self, like .fold() does.
  • .combinations(0) now produces a single empty vector. (#174)
• 0.5.10
  • Add itertools method .kmerge_by() (and corresponding free function)
  • Relaxed trait requirement of .kmerge() and .minmax() to PartialOrd.
• 0.5.9
  • Add multipeek method .reset_peek()
  • Add categories
• 0.5.8
  • Add iterator adaptor .peeking_take_while() and its trait PeekingNext.
• 0.5.7
  • Add iterator adaptor .with_position()
  • Fix multipeek's performance for long peeks by using VecDeque.
• 0.5.6
  • Add .map_results()
• 0.5.5
  • Many more adaptors now implement Debug
  • Add free function constructor repeat_n. RepeatN::new is now deprecated.
• 0.5.4
  • Add infinite generator function iterate, that takes a seed and a closure.
• 0.5.3
  • Special-cased .fold() for flatten and put back. .foreach() now uses fold on the iterator, to pick up any iterator specific loop implementation.
  • .combinations(n) asserts up front that n != 0, instead of running into an error on the second iterator element.
• 0.5.2
  • Add .tuples::<T>() that iterates by two, three or four elements at a time (where T is a tuple type).
  • Add .tuple_windows::<T>() that iterates using a window of the two, three or four most recent elements.
  • Add .next_tuple::<T>() method, that picks the next two, three or four elements in one go.
  • .interleave() now has an accurate size hint.
• 0.5.1
  • Workaround module/function name clash that made racer crash on completing itertools. Only internal changes needed.
• 0.5.0
  • Release announcement
  • Renamed:
    • combinations is now tuple_combinations
    • combinations_n to combinations
    • group_by_lazy, chunks_lazy to group_by, chunks
    • Unfold::new to unfold()
    • RepeatCall::new to repeat_call()
    • Zip::new to multizip
    • PutBack::new, PutBackN::new to put_back, put_back_n
    • PutBack::with_value is now a builder setter, not a constructor
    • MultiPeek::new, .multipeek() to multipeek()
    • format to format_with and format_default to format
    • .into_rc() to rciter
    • Partition enum is now Either
  • Module reorganization:
    • All iterator structs are under itertools::structs but also reexported to the top level, for backwards compatibility
    • All free functions are reexported at the root, itertools::free will be removed in the next version
  • Removed:
    • ZipSlices, use .zip() instead
    • .enumerate_from(), ZipTrusted, due to being unstable
    • .mend_slices(), moved to crate odds
    • Stride, StrideMut, moved to crate odds
    • linspace(), moved to crate itertools-num
    • .sort_by(), use .sorted_by()
    • .is_empty_hint(), use .size_hint()
    • .dropn(), use .dropping()
    • .map_fn(), use .map()
    • .slice(), use .take() / .skip()
    • helper traits in misc
    • new constructors on iterator structs, use Itertools trait or free functions instead
    • itertools::size_hint is now private
  • Behaviour changes:
    • format and format_with helpers now panic if you try to format them more than once.
    • repeat_call is not double ended anymore
  • New features:
    • tuple flattening iterator is constructible with cons_tuples
    • itertools reexports Either from the either crate. Either<L, R> is an iterator when L, R are.
    • MinMaxResult now implements Copy and Clone
    • tuple_combinations supports 1-4 tuples of combinations (previously just 2)
• 0.4.19
  • Add .minmax_by()
  • Add itertools::free::cloned
  • Add itertools::free::rciter
  • Improve .step(n) slightly to take advantage of specialized Fuse better.
• 0.4.18
  • Only changes related to the "unstable" crate feature. This feature is more or less deprecated.
    • Use deprecated warnings when unstable is enabled. .enumerate_from() will be removed imminently since it's using a deprecated libstd trait.
• 0.4.17
  • Fix bug in .kmerge() that caused it to often produce the wrong order (#134)
• 0.4.16
  • Improve precision of the interleave_shortest adaptor's size hint (it is now computed exactly when possible).
• 0.4.15
  • Fixup on top of the workaround in 0.4.14. A function in itertools::free was removed by mistake and now it is added back again.
• 0.4.14
  • Workaround an upstream regression in a rust nightly build that broke compilation of of itertools::free::{interleave, merge}
• 0.4.13
  • Add .minmax() and .minmax_by_key(), iterator methods for finding both minimum and maximum in one scan.
  • Add .format_default(), a simpler version of .format() (lazy formatting for iterators).
• 0.4.12
  • Add .zip_eq(), an adaptor like .zip() except it ensures iterators of inequal length don't pass silently (instead it panics).
  • Add .fold_while(), an iterator method that is a fold that can short-circuit.
  • Add .partition_map(), an iterator method that can separate elements into two collections.
• 0.4.11
  • Add .get() for Stride{,Mut} and .get_mut() for StrideMut
• 0.4.10
  • Improve performance of .kmerge()
• 0.4.9
  • Add k-ary merge adaptor .kmerge()
  • Fix a bug in .islice() with ranges a..b where a > b.
• 0.4.8
  • Implement Clone, Debug for Linspace
• 0.4.7
  • Add function diff_with() that compares two iterators
  • Add .combinations_n(), an n-ary combinations iterator
  • Add methods PutBack::with_value and PutBack::into_parts.
• 0.4.6
  • Add method .sorted()
  • Add module itertools::free with free function variants of common iterator adaptors and methods. For example enumerate(iterable), rev(iterable), and so on.
• 0.4.5
  • Add .flatten()
• 0.4.4
  • Allow composing ZipSlices with itself
• 0.4.3
  • Write iproduct!() as a single expression; this allows temporary values in its arguments.
• 0.4.2
  • Add .fold_options()
  • Require Rust 1.1 or later
• 0.4.1
  • Update .dropping() to take advantage of .nth()
• 0.4.0
  • .merge(), .unique() and .dedup() now perform better due to not using function pointers
  • Add free functions enumerate() and rev()
  • Breaking changes:
    • Return types of .merge() and .merge_by() renamed and changed
    • Method Merge::new removed
    • .merge_by() now takes a closure that returns bool.
    • Return type of .dedup() changed
    • Return type of .mend_slices() changed
    • Return type of .unique() changed
    • Removed function times(), struct Times: use a range instead
    • Removed deprecated macro icompr!()
    • Removed deprecated FnMap and method .fn_map(): use .map_fn()
    • .interleave_shortest() is no longer guaranteed to act like fused
• 0.3.25
  • Rename .sort_by() to .sorted_by(). Old name is deprecated.
  • Fix well-formedness warnings from RFC 1214, no user visible impact
• 0.3.24
  • Improve performance of .merge()'s ordering function slightly
• 0.3.23
  • Added .chunks(), similar to (and based on) .group_by_lazy().
  • Tweak linspace to match numpy.linspace and make it double ended.
• 0.3.22
  • Added ZipSlices, a fast zip for slices
• 0.3.21
  • Remove Debug impl for Format, it will have different use later
• 0.3.20
  • Optimize .group_by_lazy()
• 0.3.19
  • Added .group_by_lazy(), a possibly nonallocating group by
  • Added .format(), a nonallocating formatting helper for iterators
  • Remove uses of RandomAccessIterator since it has been deprecated in rust.
• 0.3.17
  • Added (adopted) Unfold from rust
• 0.3.16
  • Added adaptors .unique(), .unique_by()
• 0.3.15
  • Added method .sort_by()
• 0.3.14
  • Added adaptor .while_some()
• 0.3.13
  • Added adaptor .interleave_shortest()
  • Added adaptor .pad_using()
• 0.3.11
  • Added assert_equal function
• 0.3.10
  • Bugfix .combinations() size_hint.
• 0.3.8
  • Added source RepeatCall
• 0.3.7
  • Added adaptor PutBackN
  • Added adaptor .combinations()
• 0.3.6
  • Added itertools::partition, partition a sequence in place based on a predicate.
  • Deprecate icompr!() with no replacement.
• 0.3.5
  • .map_fn() replaces deprecated .fn_map().
• 0.3.4
  • .take_while_ref() by-ref adaptor
  • .coalesce() adaptor
  • .mend_slices() adaptor
• 0.3.3
  • .dropping_back() method
  • .fold1() method
  • .is_empty_hint() method

License

Dual-licensed to be compatible with the Rust project.

Licensed under the Apache License, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0 or the MIT license http://opensource.org/licenses/MIT, at your option. This file may not be copied, modified, or distributed except according to those terms.