1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028
#![warn(missing_docs)] #![cfg_attr(feature = "unstable", feature(core, zero_one))] #![crate_name="itertools"] //! Itertools — extra iterator adaptors, functions and macros. //! //! To use the iterator methods in this crate, import the [**Itertools** trait](./trait.Itertools.html): //! //! ```ignore //! use itertools::Itertools; //! ``` //! //! Some iterators or adaptors are used directly like regular structs, for example //! [**PutBack**](./struct.PutBack.html), [**Zip**](./struct.Zip.html), //! [**Stride**](./struct.Stride.html), [**StrideMut**](./struct.StrideMut.html). //! //! To use the macros in this crate, use the `#[macro_use]` attribute: //! //! ```ignore //! #[macro_use] //! extern crate itertools; //! ``` //! //! ## 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. //! //! use std::iter::{self, IntoIterator}; use std::fmt::Write; use std::cmp::Ordering; pub use adaptors::{ Interleave, Product, PutBack, FnMap, Batching, GroupBy, Step, Merge, MultiPeek, TakeWhileRef, Coalesce, CoalesceFn, }; #[cfg(feature = "unstable")] pub use adaptors::EnumerateFrom; pub use intersperse::Intersperse; pub use islice::{ISlice}; pub use repeatn::RepeatN; pub use rciter::RcIter; pub use stride::Stride; pub use stride::StrideMut; pub use tee::Tee; pub use times::Times; pub use times::times; pub use linspace::{linspace, Linspace}; pub use zip_longest::{ZipLongest, EitherOrBoth}; pub use ziptuple::{Zip}; #[cfg(feature = "unstable")] pub use ziptrusted::{ZipTrusted, TrustedIterator}; mod adaptors; mod intersperse; mod islice; mod linspace; pub mod misc; mod rciter; mod repeatn; pub mod size_hint; mod stride; mod tee; mod times; mod zip_longest; mod ziptuple; #[cfg(feature = "unstable")] mod ziptrusted; /// The function pointer map iterator created with *.map_fn()*. pub type MapFn<I, B> where I: Iterator = iter::Map<I, fn(I::Item) -> B>; /// An ascending order merge iterator created with *.merge()*. pub type MergeAscend<I, J> where I: Iterator = Merge<I, J, fn(&I::Item, &I::Item) -> Ordering>; #[macro_export] /// Create an iterator over the “cartesian product” of iterators. /// /// Iterator element type is like **(A, B, ..., E)** if formed /// from iterators **(I, J, ..., M)** with element types **I::Item = A**, **J::Item = B**, etc. /// /// ## Example /// /// ``` /// #[macro_use] /// extern crate itertools; /// # fn main() { /// // Iterate over the coordinates of a 4 x 4 x 4 grid /// // from (0, 0, 0), (0, 0, 1), .., (0, 1, 0), (0, 1, 1), .. etc until (3, 3, 3) /// for (i, j, k) in iproduct!(0..4, 0..4, 0..4) { /// // .. /// } /// # } /// ``` macro_rules! iproduct { ($I:expr) => ( (::std::iter::IntoIterator::into_iter($I)) ); ($I:expr, $J:expr) => ( $crate::Product::new(iproduct!($I), iproduct!($J)) ); ($I:expr, $J:expr, $($K:expr),+) => ( { let it = iproduct!($I, $J); $( let it = $crate::misc::FlatTuples::new(iproduct!(it, $K)); )* it } ); } #[macro_export] /// Create an iterator running multiple iterators in lockstep. /// /// The izip! iterator yields elements until any subiterator /// returns `None`. /// /// Iterator element type is like `(A, B, ..., E)` if formed /// from iterators `(I, J, ..., M)` implementing `I: Iterator<A>`, /// `J: Iterator<B>`, ..., `M: Iterator<E>` /// /// ## Example /// /// ``` /// #[macro_use] /// extern crate itertools; /// # fn main() { /// // Iterate over three sequences side-by-side /// let mut xs = [0, 0, 0]; /// let ys = [72, 73, 74]; /// for (i, a, b) in izip!(0..100, &mut xs, &ys) { /// *a = i ^ *b; /// } /// # } /// ``` macro_rules! izip { ($I:expr) => ( (::std::iter::IntoIterator::into_iter($I)) ); ($($I:expr),*) => ( { $crate::Zip::new(($(izip!($I)),*)) } ); } /// **Deprecated:** Will hopefully be replaced by a dedicated /// syntax extension that can offer real convenient python-like syntax. /// /// **Note:** A Python like syntax of `<expression> for <pattern> in <iterator>` is /// **not possible** with the stable macro rules since Rust 1.0.0-alpha. /// /// `icompr` as in “iterator comprehension” allows creating a /// mapped iterator with simple syntax, similar to set builder notation, /// and directly inspired by Python. Supports an optional filter clause. /// /// Syntax: /// /// `icompr!(<expression>, <pattern>, <iterator>)` /// /// or /// /// `icompr!(<expression>, <pattern>, <iterator>, <expression>)` /// /// Each element from the `<iterator>` expression is pattern matched /// with the `<pattern>`, and the bound names are used to express the /// mapped-to value. /// /// Iterator element type is the type of `<expression>` /// /// ## Example /// /// ```ignore /// let mut squares = icompr!(x * x, x, 1..100); /// ``` #[macro_export] macro_rules! icompr { ($r:expr, $x:pat, $J:expr, $pred:expr) => ( ($J).filter_map(|$x| if $pred { Some($r) } else { None }) ); ($r:expr, $x:pat, $J:expr) => ( ($J).filter_map(|$x| Some($r)) ); } /// The trait **Itertools**: extra iterator adaptors and methods for iterators. /// /// This trait defines a number of methods. They are divided into two groups: /// /// * *Adaptors* take an interator and parameter as input, and return /// a new iterator value. These are listed first in the trait. An example /// of an adaptor is [*.interleave()*](#method.interleave) /// /// * *Regular methods* are those that don't return iterators and instead /// return a regular value of some other kind. [*.find_position()*](#method.find_position) /// is an example and the first regular method in the list. pub trait Itertools : Iterator { // adaptors /// Alternate elements from two iterators until both /// run out. /// /// Iterator element type is **Self::Item**. /// /// This iterator is *fused*. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let it = (0..3).interleave(vec![7, 7]); /// assert!(itertools::equal(it, vec![0, 7, 1, 7, 2])); /// ``` fn interleave<J>(self, other: J) -> Interleave<Self, J::IntoIter> where J: IntoIterator<Item=Self::Item>, Self: Sized { Interleave::new(self, other.into_iter()) } /// An iterator adaptor to insert a particular value /// between each element of the adapted iterator. /// /// Iterator element type is **Self::Item**. /// /// This iterator is *fused*. fn intersperse(self, element: Self::Item) -> Intersperse<Self> where Self: Sized, Self::Item: Clone { Intersperse::new(self, element) } /// Create an iterator which iterates over both this and the specified /// iterator simultaneously, yielding pairs of two optional elements. /// /// This iterator is *fused*. /// /// When both iterators return **None**, all further invocations of *.next()* /// will return **None**. /// /// # Example /// /// ```rust /// use itertools::EitherOrBoth::{Both, Right}; /// use itertools::Itertools; /// let it = (0..1).zip_longest(1..3); /// assert!(itertools::equal(it, vec![Both(0, 1), Right(2)])); /// ``` /// /// Iterator element type is **EitherOrBoth\<Self::Item, J::Item\>**. #[inline] fn zip_longest<J>(self, other: J) -> ZipLongest<Self, J::IntoIter> where J: IntoIterator, Self: Sized, { ZipLongest::new(self, other.into_iter()) } /// A “meta iterator adaptor”. Its closure recives a reference to the iterator /// and may pick off as many elements as it likes, to produce the next iterator element. /// /// Iterator element type is **B**. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// // An adaptor that gathers elements up in pairs /// let pit = (0..4).batching(|mut it| { /// match it.next() { /// None => None, /// Some(x) => match it.next() { /// None => None, /// Some(y) => Some((x, y)), /// } /// } /// }); /// /// assert!(itertools::equal(pit, vec![(0, 1), (2, 3)])); /// ``` /// fn batching<B, F>(self, f: F) -> Batching<Self, F> where F: FnMut(&mut Self) -> Option<B>, Self: Sized, { Batching::new(self, f) } /// Group iterator elements. Consecutive elements that map to the same key (“runs”), /// are returned as the iterator elements of **GroupBy**. /// /// Iterator element type is **(K, Vec\<Self::Item\>)** fn group_by<K, F: FnMut(&Self::Item) -> K>(self, key: F) -> GroupBy<K, Self, F> where Self: Sized, { GroupBy::new(self, key) } /// Split into an iterator pair that both yield all elements from /// the original iterator. /// /// **Note:** If the iterator is clonable, prefer using that instead /// of using this method. It is likely to be more efficient. /// /// Iterator element type is **Self::Item**. /// /// ## Example /// ``` /// use itertools::Itertools; /// let xs = vec![0, 1, 2, 3]; /// /// let (mut t1, mut t2) = xs.into_iter().tee(); /// assert_eq!(t1.next(), Some(0)); /// assert_eq!(t1.next(), Some(1)); /// assert_eq!(t2.next(), Some(0)); /// assert_eq!(t1.next(), Some(2)); /// assert_eq!(t1.next(), Some(3)); /// assert_eq!(t1.next(), None); /// assert_eq!(t2.next(), Some(1)); /// ``` fn tee(self) -> (Tee<Self>, Tee<Self>) where Self: Sized, Self::Item: Clone { tee::new(self) } /// Return a sliced iterator. /// /// **Note:** slicing an iterator is not constant time, and much less efficient than /// slicing for example a vector. /// /// Iterator element type is **Self::Item**. /// /// ## Example /// ``` /// use std::iter::repeat; /// use itertools::Itertools; /// /// let it = repeat('a').slice(..3); /// assert_eq!(it.count(), 3); /// ``` fn slice<R>(self, range: R) -> ISlice<Self> where R: misc::GenericRange, Self: Sized, { ISlice::new(self, range) } /// Return an iterator inside a **Rc\<RefCell\<_\>\>** wrapper. /// /// The returned **RcIter** can be cloned, and each clone will refer back to the /// same original iterator. /// /// **RcIter** allows doing interesting things like using **.zip()** on an iterator with /// itself, at the cost of runtime borrow checking. /// (If it is not obvious: this has a performance penalty.) /// /// Iterator element type is **Self::Item**. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let mut rit = (0..9).into_rc(); /// let mut z = rit.clone().zip(rit.clone()); /// assert_eq!(z.next(), Some((0, 1))); /// assert_eq!(z.next(), Some((2, 3))); /// assert_eq!(z.next(), Some((4, 5))); /// assert_eq!(rit.next(), Some(6)); /// assert_eq!(z.next(), Some((7, 8))); /// assert_eq!(z.next(), None); /// ``` /// /// **Panics** in iterator methods if a borrow error is encountered, /// but it can only happen if the RcIter is reentered in for example **.next()**, /// i.e. if it somehow participates in an “iterator knot” where it is an adaptor of itself. fn into_rc(self) -> RcIter<Self> where Self: Sized, { RcIter::new(self) } /// Return an iterator adaptor that steps **n** elements in the base iterator /// for each iteration. /// /// The iterator steps by yielding the next element from the base iterator, /// then skipping forward **n - 1** elements. /// /// Iterator element type is **Self::Item**. /// /// **Panics** if the step is 0. /// /// ## Example /// ``` /// use itertools::Itertools; /// /// let it = (0..8).step(3); /// assert!(itertools::equal(it, vec![0, 3, 6])); /// ``` fn step(self, n: usize) -> Step<Self> where Self: Sized, { Step::new(self, n) } /// Return an iterator adaptor that merges the two base iterators in ascending order. /// If both base iterators are sorted (ascending), the result is sorted. /// /// Iterator element type is **Self::Item**. /// /// ## Example /// ``` /// use itertools::Itertools; /// /// let a = (0..11).step(3); /// let b = (0..11).step(5); /// let it = a.merge(b); /// assert!(itertools::equal(it, vec![0, 0, 3, 5, 6, 9, 10])); /// ``` fn merge<J>(self, other: J) -> MergeAscend<Self, J::IntoIter> where Self: Sized, Self::Item: PartialOrd, J: IntoIterator<Item=Self::Item>, { fn wrapper<A: PartialOrd>(a: &A, b: &A) -> Ordering { a.partial_cmp(b).unwrap_or(Ordering::Less) }; self.merge_by(other, wrapper) } /// Return an iterator adaptor that merges the two base iterators in order. /// This is much like *.merge()* but allows for a custom ordering. /// /// This can be especially useful for sequences of tuples. /// /// Iterator element type is **Self::Item**. /// /// ## Example /// ``` /// use itertools::Itertools; /// /// let a = (0..).zip("bc".chars()); /// let b = (0..).zip("ad".chars()); /// let it = a.merge_by(b, |x, y| x.1.cmp(&y.1)); /// assert!(itertools::equal(it, vec![(0, 'a'), (0, 'b'), (1, 'c'), (1, 'd')])); /// ``` fn merge_by<J, F>(self, other: J, cmp: F) -> Merge<Self, J::IntoIter, F> where Self: Sized, J: IntoIterator<Item=Self::Item>, F: FnMut(&Self::Item, &Self::Item) -> Ordering { Merge::new(self, other.into_iter(), cmp) } /// Return an iterator adaptor that iterates over the cartesian product of /// the element sets of two iterators **self** and **J**. /// /// Iterator element type is **(Self::Item, J::Item)**. /// /// ``` /// use itertools::Itertools; /// /// let it = (0..2).cartesian_product("αβ".chars()); /// assert!(itertools::equal(it, vec![(0, 'α'), (0, 'β'), (1, 'α'), (1, 'β')])); /// ``` fn cartesian_product<J>(self, other: J) -> Product<Self, J::IntoIter> where Self: Sized, Self::Item: Clone, J: IntoIterator, J::IntoIter: Clone, { Product::new(self, other.into_iter()) } /// Return an iterator adaptor that enumerates the iterator elements, /// starting from **start** and incrementing by one. /// /// Iterator element type is **(K, Self::Item)**. /// /// ``` /// use itertools::Itertools; /// /// assert_eq!( /// "αβγ".chars().enumerate_from(-10i8).collect_vec(), /// [(-10, 'α'), (-9, 'β'), (-8, 'γ')] /// ); /// ``` #[cfg(feature = "unstable")] fn enumerate_from<K>(self, start: K) -> EnumerateFrom<Self, K> where Self: Sized, { EnumerateFrom::new(self, start) } /// Return an iterator adapter that allows peeking multiple values. /// /// After a call to *.next()* the peeking cursor is reset. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let nums = vec![1u8,2,3,4,5]; /// let mut peekable = nums.into_iter().multipeek(); /// assert_eq!(peekable.peek(), Some(&1)); /// assert_eq!(peekable.peek(), Some(&2)); /// assert_eq!(peekable.peek(), Some(&3)); /// assert_eq!(peekable.next(), Some(1)); /// assert_eq!(peekable.peek(), Some(&2)); /// ``` fn multipeek(self) -> MultiPeek<Self> where Self: Sized { MultiPeek::new(self) } /// Return an iterator adaptor that uses the passed-in closure to /// optionally merge together consecutive elements. For each pair the closure /// is passed the latest two elements, `x`, `y` and may return either `Ok(z)` /// to merge the two values or `Err((x, y))` to indicate they can't be merged. /// /// *.dedup()* and *.mend_slices()* are specializations of the coalesce /// adaptor. /// /// Iterator element type is **Self::Item**. /// /// This iterator is *fused*. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// // sum same-sign runs together /// let data = vec![-1., -2., -3., 3., 1., 0., -1.]; /// assert!(itertools::equal(data.into_iter().coalesce(|x, y| /// if (x >= 0.) == (y >= 0.) { /// Ok(x + y) /// } else { /// Err((x, y)) /// }), /// vec![-6., 4., -1.])); /// ``` fn coalesce<F>(self, f: F) -> Coalesce<Self, F> where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Result<Self::Item, (Self::Item, Self::Item)> { Coalesce::new(self, f) } /// Remove duplicates from sections of consecutive identical elements. /// If the iterator is sorted, all elements will be unique. /// /// Iterator element type is **Self::Item**. /// /// This iterator is *fused*. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let data = vec![1., 1., 2., 3., 3., 2., 2.]; /// assert!(itertools::equal(data.into_iter().dedup(), /// vec![1., 2., 3., 2.])); /// ``` fn dedup(self) -> CoalesceFn<Self> where Self: Sized, Self::Item: PartialEq, { fn eq<T: PartialEq>(x: T, y: T) -> Result<T, (T, T)> { if x == y { Ok(x) } else { Err((x, y)) } } Coalesce::new(self, eq) } /// Return an iterator adaptor that joins together adjacent slices if possible. /// /// Only implemented for iterators with slice or string slice elements. /// Only slices that are contiguous together can be joined. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let text = String::from("let there be text"); /// let excerpts = vec![&text[0..4], &text[4..9], &text[10..12], &text[12..]]; /// /// assert!(itertools::equal(excerpts.into_iter().mend_slices(), /// vec!["let there", "be text"])); /// ``` fn mend_slices(self) -> CoalesceFn<Self> where Self: Sized, Self::Item: misc::MendSlice { fn mend<T: misc::MendSlice>(x: T, y: T) -> Result<T, (T, T)> { match misc::MendSlice::mend(x, y) { Some(z) => Ok(z), None => Err((x, y)), } } Coalesce::new(self, mend) } /// Return an iterator adaptor that borrows from a **Clone**-able iterator /// to only pick off elements while the predicate **f** returns **true**. /// /// It uses the **Clone** trait to restore the original iterator so that the last /// and rejected element is still available when **TakeWhileRef** is done. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let mut alphanumerics = "abcdef012345".chars(); /// /// let alphas = alphanumerics.take_while_ref(|c| c.is_alphabetic()) /// .collect::<String>(); /// assert_eq!(alphas, "abcdef"); /// assert_eq!(alphanumerics.next(), Some('0')); /// /// ``` fn take_while_ref<'a, F>(&'a mut self, f: F) -> TakeWhileRef<'a, Self, F> where Self: Clone, F: FnMut(&Self::Item) -> bool, { TakeWhileRef::new(self, f) } /// Like regular *.map()*, specialized to using a simple function pointer instead, /// so that the resulting **Map** iterator value can be cloned. /// /// Iterator element type is **B**. fn map_fn<B>(self, f: fn(Self::Item) -> B) -> MapFn<Self, B> where Self: Sized { self.map(f) } /// **Deprecated:** Use *.map_fn()* instead. fn fn_map<B>(self, map: fn(Self::Item) -> B) -> FnMap<B, Self> where Self: Sized { FnMap::new(self, map) } // non-adaptor methods /// Find the position and value of the first element satisfying a predicate. fn find_position<P>(&mut self, mut pred: P) -> Option<(usize, Self::Item)> where P: FnMut(&Self::Item) -> bool, { let mut index = 0usize; for elt in self { if pred(&elt) { return Some((index, elt)) } index += 1; } None } /// Consume the first **n** elements of the iterator eagerly. /// /// Return actual number of elements consumed, /// until done or reaching the end. fn dropn(&mut self, mut n: usize) -> usize { let start = n; while n > 0 { match self.next() { Some(..) => n -= 1, None => break } } start - n } /// Consume the first **n** elements from the iterator eagerly, /// and return the same iterator again. /// /// It works similarly to **.skip(n)** except it is eager and /// preserves the iterator type. fn dropping(mut self, n: usize) -> Self where Self: Sized, { self.dropn(n); self } /// Consume the last **n** elements from the iterator eagerly, /// and return the same iterator again. /// /// This is only possible on double ended iterators. **n** may be /// larger than the number of elements. /// /// Note: This method is eager, dropping the back elements immediately and /// preserves the iterator type. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// let init = vec![0, 3, 6, 9].into_iter().dropping_back(1); /// assert!(itertools::equal(init, vec![0, 3, 6])); /// ``` fn dropping_back(mut self, n: usize) -> Self where Self: Sized, Self: DoubleEndedIterator, { self.by_ref().rev().dropn(n); self } /// Run the closure **f** eagerly on each element of the iterator. /// /// Consumes the iterator until its end. /// /// ## Example /// /// ``` /// use std::sync::mpsc::channel; /// use itertools::Itertools; /// /// let (tx, rx) = channel(); /// /// // use .foreach() to apply a function to each value -- sending it /// (0..5).map(|x| x * 2 + 1).foreach(|x| { tx.send(x).unwrap(); } ); /// /// drop(tx); /// /// assert!(itertools::equal(rx.iter(), vec![1, 3, 5, 7, 9])); /// ``` fn foreach<F>(&mut self, mut f: F) where F: FnMut(Self::Item), { for elt in self { f(elt) } } /// **.collect_vec()** is simply a type specialization of **.collect()**, /// for convenience. fn collect_vec(self) -> Vec<Self::Item> where Self: Sized, { self.collect() } /// Assign to each reference in **self** from the **from** iterator, /// stopping at the shortest of the two iterators. /// /// The **from** iterator is queried for its next element before the **self** /// iterator, and if either is exhausted the method is done. /// /// Return the number of elements written. /// /// ## Example /// ``` /// use itertools::Itertools; /// /// let mut xs = [0; 4]; /// xs.iter_mut().set_from(1..); /// assert_eq!(xs, [1, 2, 3, 4]); /// ``` #[inline] fn set_from<'a, A: 'a, J>(&mut self, from: J) -> usize where Self: Iterator<Item=&'a mut A>, J: IntoIterator<Item=A>, { let mut count = 0; for elt in from { match self.next() { None => break, Some(ptr) => *ptr = elt } count += 1; } count } /// Combine all iterator elements into one String, seperated by **sep**. /// /// Use the **Display** implementation of each element. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// assert_eq!(["a", "b", "c"].iter().join(", "), "a, b, c"); /// assert_eq!([1, 2, 3].iter().join(", "), "1, 2, 3"); /// ``` fn join(&mut self, sep: &str) -> String where Self::Item: std::fmt::Display, { match self.next() { None => String::new(), Some(first_elt) => { // estimate lower bound of capacity needed let (lower, _) = self.size_hint(); let mut result = String::with_capacity(sep.len() * lower); write!(&mut result, "{}", first_elt).unwrap(); for elt in self { result.push_str(sep); write!(&mut result, "{}", elt).unwrap(); } result } } } /// Fold **Result** values from an iterator. /// /// Only **Ok** values are folded. If no error is encountered, the folded /// value is returned inside **Ok**. Otherwise, the operation terminates /// and returns the first **Err** value it encounters. No iterator elements are /// consumed after the first error. /// /// The first accumulator value is the **start** parameter. /// Each iteration passes the accumulator value and the next value inside **Ok** /// to the fold function **f** and its return value becomes the new accumulator value. /// /// For example the sequence *Ok(1), Ok(2), Ok(3)* will result in a /// computation like this: /// /// ```ignore /// let mut accum = start; /// accum = f(accum, 1); /// accum = f(accum, 2); /// accum = f(accum, 3); /// ``` /// /// With a **start** value of 0 and an addition as folding function, /// this effetively results in *((0 + 1) + 2) + 3* /// /// ## Example /// /// ``` /// use std::ops::Add; /// use itertools::Itertools; /// /// let values = [1, 2, -2, -1, 2, 1]; /// assert_eq!( /// values.iter() /// .map(Ok::<_, ()>) /// .fold_results(0, Add::add), /// Ok(3) /// ); /// assert!( /// values.iter() /// .map(|&x| if x >= 0 { Ok(x) } else { Err("Negative number") }) /// .fold_results(0, Add::add) /// .is_err() /// ); /// ``` fn fold_results<A, E, B, F>(&mut self, mut start: B, mut f: F) -> Result<B, E> where Self: Iterator<Item=Result<A, E>>, F: FnMut(B, A) -> B, { for elt in self { match elt { Ok(v) => start = f(start, v), Err(u) => return Err(u), } } Ok(start) } /// Accumulator of the elements in the iterator. /// /// Like *.fold()*, without a base case. If the iterator is /// empty, return **None**. With just one element, return it. /// Otherwise elements are accumulated in sequence using the closure **f**. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// assert_eq!((0..10).fold1(|x, y| x + y).unwrap_or(0), 45); /// assert_eq!((0..0).fold1(|x, y| x * y), None); /// ``` fn fold1<F>(&mut self, mut f: F) -> Option<Self::Item> where F: FnMut(Self::Item, Self::Item) -> Self::Item, { match self.next() { None => None, Some(mut x) => { for y in self { x = f(x, y); } Some(x) } } } /// Tell if the iterator is empty or not according to its size hint. /// Return **None** if the size hint does not tell, or return a **Some** /// value with the emptiness if it's possible to tell. /// /// ## Example /// /// ``` /// use itertools::Itertools; /// /// assert_eq!((1..1).is_empty_hint(), Some(true)); /// assert_eq!([1, 2, 3].iter().is_empty_hint(), Some(false)); /// assert_eq!((0..10).filter(|&x| x > 0).is_empty_hint(), None); /// ``` fn is_empty_hint(&self) -> Option<bool> { let (low, opt_hi) = self.size_hint(); // check for erronous hint if let Some(hi) = opt_hi { if hi < low { return None } } if opt_hi == Some(0) { Some(true) } else if low > 0 { Some(false) } else { None } } } /// Return **true** if both iterators produce equal sequences /// (elements pairwise equal and sequences of the same length), /// **false** otherwise. /// /// ## Example /// /// ``` /// assert!(itertools::equal(vec![1, 2, 3], 1..4)); /// assert!(!itertools::equal(&[0, 0], &[0, 0, 0])); /// ``` pub fn equal<I, J>(a: I, b: J) -> bool where I: IntoIterator, J: IntoIterator, I::Item: PartialEq<J::Item>, { let mut ia = a.into_iter(); let mut ib = b.into_iter(); loop { match (ia.next(), ib.next()) { (Some(ref x), Some(ref y)) if x == y => { } (None, None) => return true, _ => return false, } } } /// Partition a sequence using predicate **pred** so that elements /// that map to **true** are placed before elements which map to **false**. /// /// The order within the partitions is arbitrary. /// /// Return the index of the split point. /// /// ## Example /// /// ``` /// use itertools::partition; /// /// let mut data = [7, 1, 1, 9, 1, 1, 3]; /// let split_index = partition(&mut data, |elt| *elt >= 3); /// /// assert_eq!(data, [7, 3, 9, 1, 1, 1, 1]); /// assert_eq!(split_index, 3); /// ``` pub fn partition<'a, T: 'a, I, F>(it: I, mut pred: F) -> usize where I: IntoIterator<Item=&'a mut T>, I::IntoIter: DoubleEndedIterator, F: FnMut(&T) -> bool, { let mut split_index = 0; let mut it = it.into_iter(); 'main: while let Some(front) = it.next() { if !pred(&*front) { loop { if let Some(back) = it.next_back() { if pred(&*back) { std::mem::swap(front, back); break; } } else { break 'main; } } } split_index += 1; } split_index } impl<T: ?Sized> Itertools for T where T: Iterator { }