1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Unicode string slices.
13 //! The `&str` type is one of the two main string types, the other being `String`.
14 //! Unlike its `String` counterpart, its contents are borrowed.
18 //! A basic string declaration of `&str` type:
21 //! let hello_world = "Hello, World!";
24 //! Here we have declared a string literal, also known as a string slice.
25 //! String literals have a static lifetime, which means the string `hello_world`
26 //! is guaranteed to be valid for the duration of the entire program.
27 //! We can explicitly specify `hello_world`'s lifetime as well:
30 //! let hello_world: &'static str = "Hello, world!";
33 //! *[See also the `str` primitive type](../../std/primitive.str.html).*
35 #![stable(feature = "rust1", since = "1.0.0")]
37 // Many of the usings in this module are only used in the test configuration.
38 // It's cleaner to just turn off the unused_imports warning than to fix them.
39 #![allow(unused_imports)]
42 use core::str as core_str;
43 use core::str::pattern::Pattern;
44 use core::str::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher};
46 use core::iter::FusedIterator;
47 use std_unicode::str::{UnicodeStr, Utf16Encoder};
49 use vec_deque::VecDeque;
50 use borrow::{Borrow, ToOwned};
54 use slice::{SliceConcatExt, SliceIndex};
57 #[stable(feature = "rust1", since = "1.0.0")]
58 pub use core::str::{FromStr, Utf8Error};
60 #[stable(feature = "rust1", since = "1.0.0")]
61 pub use core::str::{Lines, LinesAny};
62 #[stable(feature = "rust1", since = "1.0.0")]
63 pub use core::str::{Split, RSplit};
64 #[stable(feature = "rust1", since = "1.0.0")]
65 pub use core::str::{SplitN, RSplitN};
66 #[stable(feature = "rust1", since = "1.0.0")]
67 pub use core::str::{SplitTerminator, RSplitTerminator};
68 #[stable(feature = "rust1", since = "1.0.0")]
69 pub use core::str::{Matches, RMatches};
70 #[stable(feature = "rust1", since = "1.0.0")]
71 pub use core::str::{MatchIndices, RMatchIndices};
72 #[stable(feature = "rust1", since = "1.0.0")]
73 pub use core::str::{from_utf8, from_utf8_mut, Chars, CharIndices, Bytes};
74 #[stable(feature = "rust1", since = "1.0.0")]
75 pub use core::str::{from_utf8_unchecked, from_utf8_unchecked_mut, ParseBoolError};
76 #[unstable(feature = "str_box_extras", issue = "41119")]
77 pub use alloc::str::from_boxed_utf8_unchecked;
78 #[stable(feature = "rust1", since = "1.0.0")]
79 pub use std_unicode::str::SplitWhitespace;
80 #[stable(feature = "rust1", since = "1.0.0")]
81 pub use core::str::pattern;
84 #[unstable(feature = "slice_concat_ext",
85 reason = "trait should not have to exist",
87 impl<S: Borrow<str>> SliceConcatExt<str> for [S] {
90 fn concat(&self) -> String {
95 // `len` calculation may overflow but push_str will check boundaries
96 let len = self.iter().map(|s| s.borrow().len()).sum();
97 let mut result = String::with_capacity(len);
100 result.push_str(s.borrow())
106 fn join(&self, sep: &str) -> String {
108 return String::new();
113 return self.concat();
116 // this is wrong without the guarantee that `self` is non-empty
117 // `len` calculation may overflow but push_str but will check boundaries
118 let len = sep.len() * (self.len() - 1) +
119 self.iter().map(|s| s.borrow().len()).sum::<usize>();
120 let mut result = String::with_capacity(len);
121 let mut first = true;
127 result.push_str(sep);
129 result.push_str(s.borrow());
134 fn connect(&self, sep: &str) -> String {
139 /// An iterator of [`u16`] over the string encoded as UTF-16.
141 /// [`u16`]: ../../std/primitive.u16.html
143 /// This struct is created by the [`encode_utf16`] method on [`str`].
144 /// See its documentation for more.
146 /// [`encode_utf16`]: ../../std/primitive.str.html#method.encode_utf16
147 /// [`str`]: ../../std/primitive.str.html
149 #[stable(feature = "encode_utf16", since = "1.8.0")]
150 pub struct EncodeUtf16<'a> {
151 encoder: Utf16Encoder<Chars<'a>>,
154 #[stable(feature = "collection_debug", since = "1.17.0")]
155 impl<'a> fmt::Debug for EncodeUtf16<'a> {
156 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
157 f.pad("EncodeUtf16 { .. }")
161 #[stable(feature = "encode_utf16", since = "1.8.0")]
162 impl<'a> Iterator for EncodeUtf16<'a> {
166 fn next(&mut self) -> Option<u16> {
171 fn size_hint(&self) -> (usize, Option<usize>) {
172 self.encoder.size_hint()
176 #[unstable(feature = "fused", issue = "35602")]
177 impl<'a> FusedIterator for EncodeUtf16<'a> {}
179 // Return the initial codepoint accumulator for the first byte.
180 // The first byte is special, only want bottom 5 bits for width 2, 4 bits
181 // for width 3, and 3 bits for width 4
182 macro_rules! utf8_first_byte {
183 ($byte:expr, $width:expr) => (($byte & (0x7F >> $width)) as u32)
186 // return the value of $ch updated with continuation byte $byte
187 macro_rules! utf8_acc_cont_byte {
188 ($ch:expr, $byte:expr) => (($ch << 6) | ($byte & 63) as u32)
191 #[stable(feature = "rust1", since = "1.0.0")]
192 impl Borrow<str> for String {
194 fn borrow(&self) -> &str {
199 #[stable(feature = "rust1", since = "1.0.0")]
200 impl ToOwned for str {
202 fn to_owned(&self) -> String {
203 unsafe { String::from_utf8_unchecked(self.as_bytes().to_owned()) }
206 fn clone_into(&self, target: &mut String) {
207 let mut b = mem::replace(target, String::new()).into_bytes();
208 self.as_bytes().clone_into(&mut b);
209 *target = unsafe { String::from_utf8_unchecked(b) }
213 /// Methods for string slices.
217 /// Returns the length of `self`.
219 /// This length is in bytes, not [`char`]s or graphemes. In other words,
220 /// it may not be what a human considers the length of the string.
222 /// [`char`]: primitive.char.html
229 /// let len = "foo".len();
230 /// assert_eq!(3, len);
232 /// let len = "ƒoo".len(); // fancy f!
233 /// assert_eq!(4, len);
235 #[stable(feature = "rust1", since = "1.0.0")]
237 pub fn len(&self) -> usize {
238 core_str::StrExt::len(self)
241 /// Returns `true` if `self` has a length of zero bytes.
249 /// assert!(s.is_empty());
251 /// let s = "not empty";
252 /// assert!(!s.is_empty());
255 #[stable(feature = "rust1", since = "1.0.0")]
256 pub fn is_empty(&self) -> bool {
257 core_str::StrExt::is_empty(self)
260 /// Checks that `index`-th byte lies at the start and/or end of a
261 /// UTF-8 code point sequence.
263 /// The start and end of the string (when `index == self.len()`) are
267 /// Returns `false` if `index` is greater than `self.len()`.
272 /// let s = "Löwe 老虎 Léopard";
273 /// assert!(s.is_char_boundary(0));
275 /// assert!(s.is_char_boundary(6));
276 /// assert!(s.is_char_boundary(s.len()));
278 /// // second byte of `ö`
279 /// assert!(!s.is_char_boundary(2));
281 /// // third byte of `老`
282 /// assert!(!s.is_char_boundary(8));
284 #[stable(feature = "is_char_boundary", since = "1.9.0")]
286 pub fn is_char_boundary(&self, index: usize) -> bool {
287 core_str::StrExt::is_char_boundary(self, index)
290 /// Converts a string slice to a byte slice.
297 /// let bytes = "bors".as_bytes();
298 /// assert_eq!(b"bors", bytes);
300 #[stable(feature = "rust1", since = "1.0.0")]
302 pub fn as_bytes(&self) -> &[u8] {
303 core_str::StrExt::as_bytes(self)
306 /// Converts a mutable string slice to a mutable byte slice.
307 #[unstable(feature = "str_mut_extras", issue = "41119")]
309 pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8] {
310 core_str::StrExt::as_bytes_mut(self)
313 /// Converts a string slice to a raw pointer.
315 /// As string slices are a slice of bytes, the raw pointer points to a
316 /// [`u8`]. This pointer will be pointing to the first byte of the string
319 /// [`u8`]: primitive.u8.html
327 /// let ptr = s.as_ptr();
329 #[stable(feature = "rust1", since = "1.0.0")]
331 pub fn as_ptr(&self) -> *const u8 {
332 core_str::StrExt::as_ptr(self)
335 /// Returns a subslice of `str`.
337 /// This is the non-panicking alternative to indexing the `str`. Returns
338 /// [`None`] whenever equivalent indexing operation would panic.
340 /// [`None`]: option/enum.Option.html#variant.None
345 /// # #![feature(str_checked_slicing)]
347 /// assert_eq!(Some("🗻"), v.get(0..4));
348 /// assert!(v.get(1..).is_none());
349 /// assert!(v.get(..8).is_none());
350 /// assert!(v.get(..42).is_none());
352 #[unstable(feature = "str_checked_slicing", issue = "39932")]
354 pub fn get<I: SliceIndex<str>>(&self, i: I) -> Option<&I::Output> {
355 core_str::StrExt::get(self, i)
358 /// Returns a mutable subslice of `str`.
360 /// This is the non-panicking alternative to indexing the `str`. Returns
361 /// [`None`] whenever equivalent indexing operation would panic.
363 /// [`None`]: option/enum.Option.html#variant.None
368 /// # #![feature(str_checked_slicing)]
369 /// let mut v = String::from("🗻∈🌏");
370 /// assert_eq!(Some("🗻"), v.get_mut(0..4).map(|v| &*v));
371 /// assert!(v.get_mut(1..).is_none());
372 /// assert!(v.get_mut(..8).is_none());
373 /// assert!(v.get_mut(..42).is_none());
375 #[unstable(feature = "str_checked_slicing", issue = "39932")]
377 pub fn get_mut<I: SliceIndex<str>>(&mut self, i: I) -> Option<&mut I::Output> {
378 core_str::StrExt::get_mut(self, i)
381 /// Returns a unchecked subslice of `str`.
383 /// This is the unchecked alternative to indexing the `str`.
387 /// Callers of this function are responsible that these preconditions are
390 /// * The starting index must come before the ending index;
391 /// * Indexes must be within bounds of the original slice;
392 /// * Indexes must lie on UTF-8 sequence boundaries.
394 /// Failing that, the returned string slice may reference invalid memory or
395 /// violate the invariants communicated by the `str` type.
400 /// # #![feature(str_checked_slicing)]
403 /// assert_eq!("🗻", v.get_unchecked(0..4));
404 /// assert_eq!("∈", v.get_unchecked(4..7));
405 /// assert_eq!("🌏", v.get_unchecked(7..11));
408 #[unstable(feature = "str_checked_slicing", issue = "39932")]
410 pub unsafe fn get_unchecked<I: SliceIndex<str>>(&self, i: I) -> &I::Output {
411 core_str::StrExt::get_unchecked(self, i)
414 /// Returns a mutable, unchecked subslice of `str`.
416 /// This is the unchecked alternative to indexing the `str`.
420 /// Callers of this function are responsible that these preconditions are
423 /// * The starting index must come before the ending index;
424 /// * Indexes must be within bounds of the original slice;
425 /// * Indexes must lie on UTF-8 sequence boundaries.
427 /// Failing that, the returned string slice may reference invalid memory or
428 /// violate the invariants communicated by the `str` type.
433 /// # #![feature(str_checked_slicing)]
434 /// let mut v = String::from("🗻∈🌏");
436 /// assert_eq!("🗻", v.get_unchecked_mut(0..4));
437 /// assert_eq!("∈", v.get_unchecked_mut(4..7));
438 /// assert_eq!("🌏", v.get_unchecked_mut(7..11));
441 #[unstable(feature = "str_checked_slicing", issue = "39932")]
443 pub unsafe fn get_unchecked_mut<I: SliceIndex<str>>(&mut self, i: I) -> &mut I::Output {
444 core_str::StrExt::get_unchecked_mut(self, i)
447 /// Creates a string slice from another string slice, bypassing safety
450 /// This new slice goes from `begin` to `end`, including `begin` but
453 /// To get a mutable string slice instead, see the
454 /// [`slice_mut_unchecked`] method.
456 /// [`slice_mut_unchecked`]: #method.slice_mut_unchecked
460 /// Callers of this function are responsible that three preconditions are
463 /// * `begin` must come before `end`.
464 /// * `begin` and `end` must be byte positions within the string slice.
465 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
472 /// let s = "Löwe 老虎 Léopard";
475 /// assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
478 /// let s = "Hello, world!";
481 /// assert_eq!("world", s.slice_unchecked(7, 12));
484 #[stable(feature = "rust1", since = "1.0.0")]
486 pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
487 core_str::StrExt::slice_unchecked(self, begin, end)
490 /// Creates a string slice from another string slice, bypassing safety
493 /// This new slice goes from `begin` to `end`, including `begin` but
496 /// To get an immutable string slice instead, see the
497 /// [`slice_unchecked`] method.
499 /// [`slice_unchecked`]: #method.slice_unchecked
503 /// Callers of this function are responsible that three preconditions are
506 /// * `begin` must come before `end`.
507 /// * `begin` and `end` must be byte positions within the string slice.
508 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
509 #[stable(feature = "str_slice_mut", since = "1.5.0")]
511 pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str {
512 core_str::StrExt::slice_mut_unchecked(self, begin, end)
515 /// Divide one string slice into two at an index.
517 /// The argument, `mid`, should be a byte offset from the start of the
518 /// string. It must also be on the boundary of a UTF-8 code point.
520 /// The two slices returned go from the start of the string slice to `mid`,
521 /// and from `mid` to the end of the string slice.
523 /// To get mutable string slices instead, see the [`split_at_mut`]
526 /// [`split_at_mut`]: #method.split_at_mut
530 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is
531 /// beyond the last code point of the string slice.
538 /// let s = "Per Martin-Löf";
540 /// let (first, last) = s.split_at(3);
542 /// assert_eq!("Per", first);
543 /// assert_eq!(" Martin-Löf", last);
546 #[stable(feature = "str_split_at", since = "1.4.0")]
547 pub fn split_at(&self, mid: usize) -> (&str, &str) {
548 core_str::StrExt::split_at(self, mid)
551 /// Divide one mutable string slice into two at an index.
553 /// The argument, `mid`, should be a byte offset from the start of the
554 /// string. It must also be on the boundary of a UTF-8 code point.
556 /// The two slices returned go from the start of the string slice to `mid`,
557 /// and from `mid` to the end of the string slice.
559 /// To get immutable string slices instead, see the [`split_at`] method.
561 /// [`split_at`]: #method.split_at
565 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is
566 /// beyond the last code point of the string slice.
573 /// let mut s = "Per Martin-Löf".to_string();
575 /// let (first, last) = s.split_at_mut(3);
577 /// assert_eq!("Per", first);
578 /// assert_eq!(" Martin-Löf", last);
581 #[stable(feature = "str_split_at", since = "1.4.0")]
582 pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
583 core_str::StrExt::split_at_mut(self, mid)
586 /// Returns an iterator over the [`char`]s of a string slice.
588 /// As a string slice consists of valid UTF-8, we can iterate through a
589 /// string slice by [`char`]. This method returns such an iterator.
591 /// It's important to remember that [`char`] represents a Unicode Scalar
592 /// Value, and may not match your idea of what a 'character' is. Iteration
593 /// over grapheme clusters may be what you actually want.
595 /// [`char`]: primitive.char.html
602 /// let word = "goodbye";
604 /// let count = word.chars().count();
605 /// assert_eq!(7, count);
607 /// let mut chars = word.chars();
609 /// assert_eq!(Some('g'), chars.next());
610 /// assert_eq!(Some('o'), chars.next());
611 /// assert_eq!(Some('o'), chars.next());
612 /// assert_eq!(Some('d'), chars.next());
613 /// assert_eq!(Some('b'), chars.next());
614 /// assert_eq!(Some('y'), chars.next());
615 /// assert_eq!(Some('e'), chars.next());
617 /// assert_eq!(None, chars.next());
620 /// Remember, [`char`]s may not match your human intuition about characters:
625 /// let mut chars = y.chars();
627 /// assert_eq!(Some('y'), chars.next()); // not 'y̆'
628 /// assert_eq!(Some('\u{0306}'), chars.next());
630 /// assert_eq!(None, chars.next());
632 #[stable(feature = "rust1", since = "1.0.0")]
634 pub fn chars(&self) -> Chars {
635 core_str::StrExt::chars(self)
637 /// Returns an iterator over the [`char`]s of a string slice, and their
640 /// As a string slice consists of valid UTF-8, we can iterate through a
641 /// string slice by [`char`]. This method returns an iterator of both
642 /// these [`char`]s, as well as their byte positions.
644 /// The iterator yields tuples. The position is first, the [`char`] is
647 /// [`char`]: primitive.char.html
654 /// let word = "goodbye";
656 /// let count = word.char_indices().count();
657 /// assert_eq!(7, count);
659 /// let mut char_indices = word.char_indices();
661 /// assert_eq!(Some((0, 'g')), char_indices.next());
662 /// assert_eq!(Some((1, 'o')), char_indices.next());
663 /// assert_eq!(Some((2, 'o')), char_indices.next());
664 /// assert_eq!(Some((3, 'd')), char_indices.next());
665 /// assert_eq!(Some((4, 'b')), char_indices.next());
666 /// assert_eq!(Some((5, 'y')), char_indices.next());
667 /// assert_eq!(Some((6, 'e')), char_indices.next());
669 /// assert_eq!(None, char_indices.next());
672 /// Remember, [`char`]s may not match your human intuition about characters:
677 /// let mut char_indices = y.char_indices();
679 /// assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
680 /// assert_eq!(Some((1, '\u{0306}')), char_indices.next());
682 /// assert_eq!(None, char_indices.next());
684 #[stable(feature = "rust1", since = "1.0.0")]
686 pub fn char_indices(&self) -> CharIndices {
687 core_str::StrExt::char_indices(self)
690 /// An iterator over the bytes of a string slice.
692 /// As a string slice consists of a sequence of bytes, we can iterate
693 /// through a string slice by byte. This method returns such an iterator.
700 /// let mut bytes = "bors".bytes();
702 /// assert_eq!(Some(b'b'), bytes.next());
703 /// assert_eq!(Some(b'o'), bytes.next());
704 /// assert_eq!(Some(b'r'), bytes.next());
705 /// assert_eq!(Some(b's'), bytes.next());
707 /// assert_eq!(None, bytes.next());
709 #[stable(feature = "rust1", since = "1.0.0")]
711 pub fn bytes(&self) -> Bytes {
712 core_str::StrExt::bytes(self)
715 /// Split a string slice by whitespace.
717 /// The iterator returned will return string slices that are sub-slices of
718 /// the original string slice, separated by any amount of whitespace.
720 /// 'Whitespace' is defined according to the terms of the Unicode Derived
721 /// Core Property `White_Space`.
728 /// let mut iter = "A few words".split_whitespace();
730 /// assert_eq!(Some("A"), iter.next());
731 /// assert_eq!(Some("few"), iter.next());
732 /// assert_eq!(Some("words"), iter.next());
734 /// assert_eq!(None, iter.next());
737 /// All kinds of whitespace are considered:
740 /// let mut iter = " Mary had\ta\u{2009}little \n\t lamb".split_whitespace();
741 /// assert_eq!(Some("Mary"), iter.next());
742 /// assert_eq!(Some("had"), iter.next());
743 /// assert_eq!(Some("a"), iter.next());
744 /// assert_eq!(Some("little"), iter.next());
745 /// assert_eq!(Some("lamb"), iter.next());
747 /// assert_eq!(None, iter.next());
749 #[stable(feature = "split_whitespace", since = "1.1.0")]
751 pub fn split_whitespace(&self) -> SplitWhitespace {
752 UnicodeStr::split_whitespace(self)
755 /// An iterator over the lines of a string, as string slices.
757 /// Lines are ended with either a newline (`\n`) or a carriage return with
758 /// a line feed (`\r\n`).
760 /// The final line ending is optional.
767 /// let text = "foo\r\nbar\n\nbaz\n";
768 /// let mut lines = text.lines();
770 /// assert_eq!(Some("foo"), lines.next());
771 /// assert_eq!(Some("bar"), lines.next());
772 /// assert_eq!(Some(""), lines.next());
773 /// assert_eq!(Some("baz"), lines.next());
775 /// assert_eq!(None, lines.next());
778 /// The final line ending isn't required:
781 /// let text = "foo\nbar\n\r\nbaz";
782 /// let mut lines = text.lines();
784 /// assert_eq!(Some("foo"), lines.next());
785 /// assert_eq!(Some("bar"), lines.next());
786 /// assert_eq!(Some(""), lines.next());
787 /// assert_eq!(Some("baz"), lines.next());
789 /// assert_eq!(None, lines.next());
791 #[stable(feature = "rust1", since = "1.0.0")]
793 pub fn lines(&self) -> Lines {
794 core_str::StrExt::lines(self)
797 /// An iterator over the lines of a string.
798 #[stable(feature = "rust1", since = "1.0.0")]
799 #[rustc_deprecated(since = "1.4.0", reason = "use lines() instead now")]
802 pub fn lines_any(&self) -> LinesAny {
803 core_str::StrExt::lines_any(self)
806 /// Returns an iterator of `u16` over the string encoded as UTF-16.
807 #[stable(feature = "encode_utf16", since = "1.8.0")]
808 pub fn encode_utf16(&self) -> EncodeUtf16 {
809 EncodeUtf16 { encoder: Utf16Encoder::new(self[..].chars()) }
812 /// Returns `true` if the given pattern matches a sub-slice of
813 /// this string slice.
815 /// Returns `false` if it does not.
822 /// let bananas = "bananas";
824 /// assert!(bananas.contains("nana"));
825 /// assert!(!bananas.contains("apples"));
827 #[stable(feature = "rust1", since = "1.0.0")]
828 pub fn contains<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool {
829 core_str::StrExt::contains(self, pat)
832 /// Returns `true` if the given pattern matches a prefix of this
835 /// Returns `false` if it does not.
842 /// let bananas = "bananas";
844 /// assert!(bananas.starts_with("bana"));
845 /// assert!(!bananas.starts_with("nana"));
847 #[stable(feature = "rust1", since = "1.0.0")]
848 pub fn starts_with<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool {
849 core_str::StrExt::starts_with(self, pat)
852 /// Returns `true` if the given pattern matches a suffix of this
855 /// Returns `false` if it does not.
862 /// let bananas = "bananas";
864 /// assert!(bananas.ends_with("anas"));
865 /// assert!(!bananas.ends_with("nana"));
867 #[stable(feature = "rust1", since = "1.0.0")]
868 pub fn ends_with<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool
869 where P::Searcher: ReverseSearcher<'a>
871 core_str::StrExt::ends_with(self, pat)
874 /// Returns the byte index of the first character of this string slice that
875 /// matches the pattern.
877 /// Returns [`None`] if the pattern doesn't match.
879 /// The pattern can be a `&str`, [`char`], or a closure that determines if
880 /// a character matches.
882 /// [`char`]: primitive.char.html
883 /// [`None`]: option/enum.Option.html#variant.None
890 /// let s = "Löwe 老虎 Léopard";
892 /// assert_eq!(s.find('L'), Some(0));
893 /// assert_eq!(s.find('é'), Some(14));
894 /// assert_eq!(s.find("Léopard"), Some(13));
897 /// More complex patterns with closures:
900 /// let s = "Löwe 老虎 Léopard";
902 /// assert_eq!(s.find(char::is_whitespace), Some(5));
903 /// assert_eq!(s.find(char::is_lowercase), Some(1));
906 /// Not finding the pattern:
909 /// let s = "Löwe 老虎 Léopard";
910 /// let x: &[_] = &['1', '2'];
912 /// assert_eq!(s.find(x), None);
914 #[stable(feature = "rust1", since = "1.0.0")]
915 pub fn find<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize> {
916 core_str::StrExt::find(self, pat)
919 /// Returns the byte index of the last character of this string slice that
920 /// matches the pattern.
922 /// Returns [`None`] if the pattern doesn't match.
924 /// The pattern can be a `&str`, [`char`], or a closure that determines if
925 /// a character matches.
927 /// [`char`]: primitive.char.html
928 /// [`None`]: option/enum.Option.html#variant.None
935 /// let s = "Löwe 老虎 Léopard";
937 /// assert_eq!(s.rfind('L'), Some(13));
938 /// assert_eq!(s.rfind('é'), Some(14));
941 /// More complex patterns with closures:
944 /// let s = "Löwe 老虎 Léopard";
946 /// assert_eq!(s.rfind(char::is_whitespace), Some(12));
947 /// assert_eq!(s.rfind(char::is_lowercase), Some(20));
950 /// Not finding the pattern:
953 /// let s = "Löwe 老虎 Léopard";
954 /// let x: &[_] = &['1', '2'];
956 /// assert_eq!(s.rfind(x), None);
958 #[stable(feature = "rust1", since = "1.0.0")]
959 pub fn rfind<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize>
960 where P::Searcher: ReverseSearcher<'a>
962 core_str::StrExt::rfind(self, pat)
965 /// An iterator over substrings of this string slice, separated by
966 /// characters matched by a pattern.
968 /// The pattern can be a `&str`, [`char`], or a closure that determines the
971 /// # Iterator behavior
973 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
974 /// allows a reverse search and forward/reverse search yields the same
975 /// elements. This is true for, eg, [`char`] but not for `&str`.
977 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
979 /// If the pattern allows a reverse search but its results might differ
980 /// from a forward search, the [`rsplit`] method can be used.
982 /// [`char`]: primitive.char.html
983 /// [`rsplit`]: #method.rsplit
990 /// let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
991 /// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);
993 /// let v: Vec<&str> = "".split('X').collect();
994 /// assert_eq!(v, [""]);
996 /// let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
997 /// assert_eq!(v, ["lion", "", "tiger", "leopard"]);
999 /// let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
1000 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1002 /// let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
1003 /// assert_eq!(v, ["abc", "def", "ghi"]);
1005 /// let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
1006 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1009 /// A more complex pattern, using a closure:
1012 /// let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
1013 /// assert_eq!(v, ["abc", "def", "ghi"]);
1016 /// If a string contains multiple contiguous separators, you will end up
1017 /// with empty strings in the output:
1020 /// let x = "||||a||b|c".to_string();
1021 /// let d: Vec<_> = x.split('|').collect();
1023 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1026 /// Contiguous separators are separated by the empty string.
1029 /// let x = "(///)".to_string();
1030 /// let d: Vec<_> = x.split('/').collect();;
1032 /// assert_eq!(d, &["(", "", "", ")"]);
1035 /// Separators at the start or end of a string are neighbored
1036 /// by empty strings.
1039 /// let d: Vec<_> = "010".split("0").collect();
1040 /// assert_eq!(d, &["", "1", ""]);
1043 /// When the empty string is used as a separator, it separates
1044 /// every character in the string, along with the beginning
1045 /// and end of the string.
1048 /// let f: Vec<_> = "rust".split("").collect();
1049 /// assert_eq!(f, &["", "r", "u", "s", "t", ""]);
1052 /// Contiguous separators can lead to possibly surprising behavior
1053 /// when whitespace is used as the separator. This code is correct:
1056 /// let x = " a b c".to_string();
1057 /// let d: Vec<_> = x.split(' ').collect();
1059 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1062 /// It does _not_ give you:
1065 /// assert_eq!(d, &["a", "b", "c"]);
1068 /// Use [`split_whitespace`] for this behavior.
1070 /// [`split_whitespace`]: #method.split_whitespace
1071 #[stable(feature = "rust1", since = "1.0.0")]
1072 pub fn split<'a, P: Pattern<'a>>(&'a self, pat: P) -> Split<'a, P> {
1073 core_str::StrExt::split(self, pat)
1076 /// An iterator over substrings of the given string slice, separated by
1077 /// characters matched by a pattern and yielded in reverse order.
1079 /// The pattern can be a `&str`, [`char`], or a closure that determines the
1082 /// [`char`]: primitive.char.html
1084 /// # Iterator behavior
1086 /// The returned iterator requires that the pattern supports a reverse
1087 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1088 /// search yields the same elements.
1090 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1092 /// For iterating from the front, the [`split`] method can be used.
1094 /// [`split`]: #method.split
1098 /// Simple patterns:
1101 /// let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
1102 /// assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);
1104 /// let v: Vec<&str> = "".rsplit('X').collect();
1105 /// assert_eq!(v, [""]);
1107 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
1108 /// assert_eq!(v, ["leopard", "tiger", "", "lion"]);
1110 /// let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
1111 /// assert_eq!(v, ["leopard", "tiger", "lion"]);
1114 /// A more complex pattern, using a closure:
1117 /// let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
1118 /// assert_eq!(v, ["ghi", "def", "abc"]);
1120 #[stable(feature = "rust1", since = "1.0.0")]
1121 pub fn rsplit<'a, P: Pattern<'a>>(&'a self, pat: P) -> RSplit<'a, P>
1122 where P::Searcher: ReverseSearcher<'a>
1124 core_str::StrExt::rsplit(self, pat)
1127 /// An iterator over substrings of the given string slice, separated by
1128 /// characters matched by a pattern.
1130 /// The pattern can be a `&str`, [`char`], or a closure that determines the
1133 /// Equivalent to [`split`], except that the trailing substring
1134 /// is skipped if empty.
1136 /// [`split`]: #method.split
1138 /// This method can be used for string data that is _terminated_,
1139 /// rather than _separated_ by a pattern.
1141 /// # Iterator behavior
1143 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1144 /// allows a reverse search and forward/reverse search yields the same
1145 /// elements. This is true for, eg, [`char`] but not for `&str`.
1147 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1148 /// [`char`]: primitive.char.html
1150 /// If the pattern allows a reverse search but its results might differ
1151 /// from a forward search, the [`rsplit_terminator`] method can be used.
1153 /// [`rsplit_terminator`]: #method.rsplit_terminator
1160 /// let v: Vec<&str> = "A.B.".split_terminator('.').collect();
1161 /// assert_eq!(v, ["A", "B"]);
1163 /// let v: Vec<&str> = "A..B..".split_terminator(".").collect();
1164 /// assert_eq!(v, ["A", "", "B", ""]);
1166 #[stable(feature = "rust1", since = "1.0.0")]
1167 pub fn split_terminator<'a, P: Pattern<'a>>(&'a self, pat: P) -> SplitTerminator<'a, P> {
1168 core_str::StrExt::split_terminator(self, pat)
1171 /// An iterator over substrings of `self`, separated by characters
1172 /// matched by a pattern and yielded in reverse order.
1174 /// The pattern can be a simple `&str`, [`char`], or a closure that
1175 /// determines the split.
1176 /// Additional libraries might provide more complex patterns like
1177 /// regular expressions.
1179 /// [`char`]: primitive.char.html
1181 /// Equivalent to [`split`], except that the trailing substring is
1182 /// skipped if empty.
1184 /// [`split`]: #method.split
1186 /// This method can be used for string data that is _terminated_,
1187 /// rather than _separated_ by a pattern.
1189 /// # Iterator behavior
1191 /// The returned iterator requires that the pattern supports a
1192 /// reverse search, and it will be double ended if a forward/reverse
1193 /// search yields the same elements.
1195 /// For iterating from the front, the [`split_terminator`] method can be
1198 /// [`split_terminator`]: #method.split_terminator
1203 /// let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
1204 /// assert_eq!(v, ["B", "A"]);
1206 /// let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
1207 /// assert_eq!(v, ["", "B", "", "A"]);
1209 #[stable(feature = "rust1", since = "1.0.0")]
1210 pub fn rsplit_terminator<'a, P: Pattern<'a>>(&'a self, pat: P) -> RSplitTerminator<'a, P>
1211 where P::Searcher: ReverseSearcher<'a>
1213 core_str::StrExt::rsplit_terminator(self, pat)
1216 /// An iterator over substrings of the given string slice, separated by a
1217 /// pattern, restricted to returning at most `n` items.
1219 /// If `n` substrings are returned, the last substring (the `n`th substring)
1220 /// will contain the remainder of the string.
1222 /// The pattern can be a `&str`, [`char`], or a closure that determines the
1225 /// [`char`]: primitive.char.html
1227 /// # Iterator behavior
1229 /// The returned iterator will not be double ended, because it is
1230 /// not efficient to support.
1232 /// If the pattern allows a reverse search, the [`rsplitn`] method can be
1235 /// [`rsplitn`]: #method.rsplitn
1239 /// Simple patterns:
1242 /// let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
1243 /// assert_eq!(v, ["Mary", "had", "a little lambda"]);
1245 /// let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
1246 /// assert_eq!(v, ["lion", "", "tigerXleopard"]);
1248 /// let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
1249 /// assert_eq!(v, ["abcXdef"]);
1251 /// let v: Vec<&str> = "".splitn(1, 'X').collect();
1252 /// assert_eq!(v, [""]);
1255 /// A more complex pattern, using a closure:
1258 /// let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
1259 /// assert_eq!(v, ["abc", "defXghi"]);
1261 #[stable(feature = "rust1", since = "1.0.0")]
1262 pub fn splitn<'a, P: Pattern<'a>>(&'a self, n: usize, pat: P) -> SplitN<'a, P> {
1263 core_str::StrExt::splitn(self, n, pat)
1266 /// An iterator over substrings of this string slice, separated by a
1267 /// pattern, starting from the end of the string, restricted to returning
1268 /// at most `n` items.
1270 /// If `n` substrings are returned, the last substring (the `n`th substring)
1271 /// will contain the remainder of the string.
1273 /// The pattern can be a `&str`, [`char`], or a closure that
1274 /// determines the split.
1276 /// [`char`]: primitive.char.html
1278 /// # Iterator behavior
1280 /// The returned iterator will not be double ended, because it is not
1281 /// efficient to support.
1283 /// For splitting from the front, the [`splitn`] method can be used.
1285 /// [`splitn`]: #method.splitn
1289 /// Simple patterns:
1292 /// let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
1293 /// assert_eq!(v, ["lamb", "little", "Mary had a"]);
1295 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
1296 /// assert_eq!(v, ["leopard", "tiger", "lionX"]);
1298 /// let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
1299 /// assert_eq!(v, ["leopard", "lion::tiger"]);
1302 /// A more complex pattern, using a closure:
1305 /// let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
1306 /// assert_eq!(v, ["ghi", "abc1def"]);
1308 #[stable(feature = "rust1", since = "1.0.0")]
1309 pub fn rsplitn<'a, P: Pattern<'a>>(&'a self, n: usize, pat: P) -> RSplitN<'a, P>
1310 where P::Searcher: ReverseSearcher<'a>
1312 core_str::StrExt::rsplitn(self, n, pat)
1315 /// An iterator over the matches of a pattern within the given string
1318 /// The pattern can be a `&str`, [`char`], or a closure that
1319 /// determines if a character matches.
1321 /// [`char`]: primitive.char.html
1323 /// # Iterator behavior
1325 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1326 /// allows a reverse search and forward/reverse search yields the same
1327 /// elements. This is true for, eg, [`char`] but not for `&str`.
1329 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1330 /// [`char`]: primitive.char.html
1332 /// If the pattern allows a reverse search but its results might differ
1333 /// from a forward search, the [`rmatches`] method can be used.
1335 /// [`rmatches`]: #method.rmatches
1342 /// let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
1343 /// assert_eq!(v, ["abc", "abc", "abc"]);
1345 /// let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
1346 /// assert_eq!(v, ["1", "2", "3"]);
1348 #[stable(feature = "str_matches", since = "1.2.0")]
1349 pub fn matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> Matches<'a, P> {
1350 core_str::StrExt::matches(self, pat)
1353 /// An iterator over the matches of a pattern within this string slice,
1354 /// yielded in reverse order.
1356 /// The pattern can be a `&str`, [`char`], or a closure that determines if
1357 /// a character matches.
1359 /// [`char`]: primitive.char.html
1361 /// # Iterator behavior
1363 /// The returned iterator requires that the pattern supports a reverse
1364 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1365 /// search yields the same elements.
1367 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1369 /// For iterating from the front, the [`matches`] method can be used.
1371 /// [`matches`]: #method.matches
1378 /// let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
1379 /// assert_eq!(v, ["abc", "abc", "abc"]);
1381 /// let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
1382 /// assert_eq!(v, ["3", "2", "1"]);
1384 #[stable(feature = "str_matches", since = "1.2.0")]
1385 pub fn rmatches<'a, P: Pattern<'a>>(&'a self, pat: P) -> RMatches<'a, P>
1386 where P::Searcher: ReverseSearcher<'a>
1388 core_str::StrExt::rmatches(self, pat)
1391 /// An iterator over the disjoint matches of a pattern within this string
1392 /// slice as well as the index that the match starts at.
1394 /// For matches of `pat` within `self` that overlap, only the indices
1395 /// corresponding to the first match are returned.
1397 /// The pattern can be a `&str`, [`char`], or a closure that determines
1398 /// if a character matches.
1400 /// [`char`]: primitive.char.html
1402 /// # Iterator behavior
1404 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1405 /// allows a reverse search and forward/reverse search yields the same
1406 /// elements. This is true for, eg, [`char`] but not for `&str`.
1408 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1410 /// If the pattern allows a reverse search but its results might differ
1411 /// from a forward search, the [`rmatch_indices`] method can be used.
1413 /// [`rmatch_indices`]: #method.rmatch_indices
1420 /// let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
1421 /// assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);
1423 /// let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
1424 /// assert_eq!(v, [(1, "abc"), (4, "abc")]);
1426 /// let v: Vec<_> = "ababa".match_indices("aba").collect();
1427 /// assert_eq!(v, [(0, "aba")]); // only the first `aba`
1429 #[stable(feature = "str_match_indices", since = "1.5.0")]
1430 pub fn match_indices<'a, P: Pattern<'a>>(&'a self, pat: P) -> MatchIndices<'a, P> {
1431 core_str::StrExt::match_indices(self, pat)
1434 /// An iterator over the disjoint matches of a pattern within `self`,
1435 /// yielded in reverse order along with the index of the match.
1437 /// For matches of `pat` within `self` that overlap, only the indices
1438 /// corresponding to the last match are returned.
1440 /// The pattern can be a `&str`, [`char`], or a closure that determines if a
1441 /// character matches.
1443 /// [`char`]: primitive.char.html
1445 /// # Iterator behavior
1447 /// The returned iterator requires that the pattern supports a reverse
1448 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1449 /// search yields the same elements.
1451 /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
1453 /// For iterating from the front, the [`match_indices`] method can be used.
1455 /// [`match_indices`]: #method.match_indices
1462 /// let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
1463 /// assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);
1465 /// let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
1466 /// assert_eq!(v, [(4, "abc"), (1, "abc")]);
1468 /// let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
1469 /// assert_eq!(v, [(2, "aba")]); // only the last `aba`
1471 #[stable(feature = "str_match_indices", since = "1.5.0")]
1472 pub fn rmatch_indices<'a, P: Pattern<'a>>(&'a self, pat: P) -> RMatchIndices<'a, P>
1473 where P::Searcher: ReverseSearcher<'a>
1475 core_str::StrExt::rmatch_indices(self, pat)
1478 /// Returns a string slice with leading and trailing whitespace removed.
1480 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1481 /// Core Property `White_Space`.
1488 /// let s = " Hello\tworld\t";
1490 /// assert_eq!("Hello\tworld", s.trim());
1492 #[stable(feature = "rust1", since = "1.0.0")]
1493 pub fn trim(&self) -> &str {
1494 UnicodeStr::trim(self)
1497 /// Returns a string slice with leading whitespace removed.
1499 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1500 /// Core Property `White_Space`.
1502 /// # Text directionality
1504 /// A string is a sequence of bytes. 'Left' in this context means the first
1505 /// position of that byte string; for a language like Arabic or Hebrew
1506 /// which are 'right to left' rather than 'left to right', this will be
1507 /// the _right_ side, not the left.
1514 /// let s = " Hello\tworld\t";
1516 /// assert_eq!("Hello\tworld\t", s.trim_left());
1522 /// let s = " English";
1523 /// assert!(Some('E') == s.trim_left().chars().next());
1525 /// let s = " עברית";
1526 /// assert!(Some('ע') == s.trim_left().chars().next());
1528 #[stable(feature = "rust1", since = "1.0.0")]
1529 pub fn trim_left(&self) -> &str {
1530 UnicodeStr::trim_left(self)
1533 /// Returns a string slice with trailing whitespace removed.
1535 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1536 /// Core Property `White_Space`.
1538 /// # Text directionality
1540 /// A string is a sequence of bytes. 'Right' in this context means the last
1541 /// position of that byte string; for a language like Arabic or Hebrew
1542 /// which are 'right to left' rather than 'left to right', this will be
1543 /// the _left_ side, not the right.
1550 /// let s = " Hello\tworld\t";
1552 /// assert_eq!(" Hello\tworld", s.trim_right());
1558 /// let s = "English ";
1559 /// assert!(Some('h') == s.trim_right().chars().rev().next());
1561 /// let s = "עברית ";
1562 /// assert!(Some('ת') == s.trim_right().chars().rev().next());
1564 #[stable(feature = "rust1", since = "1.0.0")]
1565 pub fn trim_right(&self) -> &str {
1566 UnicodeStr::trim_right(self)
1569 /// Returns a string slice with all prefixes and suffixes that match a
1570 /// pattern repeatedly removed.
1572 /// The pattern can be a [`char`] or a closure that determines if a
1573 /// character matches.
1575 /// [`char`]: primitive.char.html
1579 /// Simple patterns:
1582 /// assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
1583 /// assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");
1585 /// let x: &[_] = &['1', '2'];
1586 /// assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");
1589 /// A more complex pattern, using a closure:
1592 /// assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
1594 #[stable(feature = "rust1", since = "1.0.0")]
1595 pub fn trim_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str
1596 where P::Searcher: DoubleEndedSearcher<'a>
1598 core_str::StrExt::trim_matches(self, pat)
1601 /// Returns a string slice with all prefixes that match a pattern
1602 /// repeatedly removed.
1604 /// The pattern can be a `&str`, [`char`], or a closure that determines if
1605 /// a character matches.
1607 /// [`char`]: primitive.char.html
1609 /// # Text directionality
1611 /// A string is a sequence of bytes. 'Left' in this context means the first
1612 /// position of that byte string; for a language like Arabic or Hebrew
1613 /// which are 'right to left' rather than 'left to right', this will be
1614 /// the _right_ side, not the left.
1621 /// assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
1622 /// assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");
1624 /// let x: &[_] = &['1', '2'];
1625 /// assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");
1627 #[stable(feature = "rust1", since = "1.0.0")]
1628 pub fn trim_left_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str {
1629 core_str::StrExt::trim_left_matches(self, pat)
1632 /// Returns a string slice with all suffixes that match a pattern
1633 /// repeatedly removed.
1635 /// The pattern can be a `&str`, [`char`], or a closure that
1636 /// determines if a character matches.
1638 /// [`char`]: primitive.char.html
1640 /// # Text directionality
1642 /// A string is a sequence of bytes. 'Right' in this context means the last
1643 /// position of that byte string; for a language like Arabic or Hebrew
1644 /// which are 'right to left' rather than 'left to right', this will be
1645 /// the _left_ side, not the right.
1649 /// Simple patterns:
1652 /// assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
1653 /// assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");
1655 /// let x: &[_] = &['1', '2'];
1656 /// assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");
1659 /// A more complex pattern, using a closure:
1662 /// assert_eq!("1fooX".trim_left_matches(|c| c == '1' || c == 'X'), "fooX");
1664 #[stable(feature = "rust1", since = "1.0.0")]
1665 pub fn trim_right_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str
1666 where P::Searcher: ReverseSearcher<'a>
1668 core_str::StrExt::trim_right_matches(self, pat)
1671 /// Parses this string slice into another type.
1673 /// Because `parse` is so general, it can cause problems with type
1674 /// inference. As such, `parse` is one of the few times you'll see
1675 /// the syntax affectionately known as the 'turbofish': `::<>`. This
1676 /// helps the inference algorithm understand specifically which type
1677 /// you're trying to parse into.
1679 /// `parse` can parse any type that implements the [`FromStr`] trait.
1681 /// [`FromStr`]: str/trait.FromStr.html
1685 /// Will return [`Err`] if it's not possible to parse this string slice into
1686 /// the desired type.
1688 /// [`Err`]: str/trait.FromStr.html#associatedtype.Err
1695 /// let four: u32 = "4".parse().unwrap();
1697 /// assert_eq!(4, four);
1700 /// Using the 'turbofish' instead of annotating `four`:
1703 /// let four = "4".parse::<u32>();
1705 /// assert_eq!(Ok(4), four);
1708 /// Failing to parse:
1711 /// let nope = "j".parse::<u32>();
1713 /// assert!(nope.is_err());
1716 #[stable(feature = "rust1", since = "1.0.0")]
1717 pub fn parse<F: FromStr>(&self) -> Result<F, F::Err> {
1718 core_str::StrExt::parse(self)
1721 /// Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating.
1722 #[unstable(feature = "str_box_extras", issue = "41119")]
1723 pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> {
1727 /// Replaces all matches of a pattern with another string.
1729 /// `replace` creates a new [`String`], and copies the data from this string slice into it.
1730 /// While doing so, it attempts to find matches of a pattern. If it finds any, it
1731 /// replaces them with the replacement string slice.
1733 /// [`String`]: string/struct.String.html
1740 /// let s = "this is old";
1742 /// assert_eq!("this is new", s.replace("old", "new"));
1745 /// When the pattern doesn't match:
1748 /// let s = "this is old";
1749 /// assert_eq!(s, s.replace("cookie monster", "little lamb"));
1751 #[stable(feature = "rust1", since = "1.0.0")]
1752 pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String {
1753 let mut result = String::new();
1754 let mut last_end = 0;
1755 for (start, part) in self.match_indices(from) {
1756 result.push_str(unsafe { self.slice_unchecked(last_end, start) });
1757 result.push_str(to);
1758 last_end = start + part.len();
1760 result.push_str(unsafe { self.slice_unchecked(last_end, self.len()) });
1764 /// Replaces first N matches of a pattern with another string.
1766 /// `replacen` creates a new [`String`], and copies the data from this string slice into it.
1767 /// While doing so, it attempts to find matches of a pattern. If it finds any, it
1768 /// replaces them with the replacement string slice at most `count` times.
1770 /// [`String`]: string/struct.String.html
1777 /// let s = "foo foo 123 foo";
1778 /// assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
1779 /// assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
1780 /// assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));
1783 /// When the pattern doesn't match:
1786 /// let s = "this is old";
1787 /// assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));
1789 #[stable(feature = "str_replacen", since = "1.16.0")]
1790 pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String {
1791 // Hope to reduce the times of re-allocation
1792 let mut result = String::with_capacity(32);
1793 let mut last_end = 0;
1794 for (start, part) in self.match_indices(pat).take(count) {
1795 result.push_str(unsafe { self.slice_unchecked(last_end, start) });
1796 result.push_str(to);
1797 last_end = start + part.len();
1799 result.push_str(unsafe { self.slice_unchecked(last_end, self.len()) });
1803 /// Returns the lowercase equivalent of this string slice, as a new [`String`].
1805 /// 'Lowercase' is defined according to the terms of the Unicode Derived Core Property
1808 /// Since some characters can expand into multiple characters when changing
1809 /// the case, this function returns a [`String`] instead of modifying the
1810 /// parameter in-place.
1812 /// [`String`]: string/struct.String.html
1819 /// let s = "HELLO";
1821 /// assert_eq!("hello", s.to_lowercase());
1824 /// A tricky example, with sigma:
1827 /// let sigma = "Σ";
1829 /// assert_eq!("σ", sigma.to_lowercase());
1831 /// // but at the end of a word, it's ς, not σ:
1832 /// let odysseus = "ὈΔΥΣΣΕΎΣ";
1834 /// assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());
1837 /// Languages without case are not changed:
1840 /// let new_year = "农历新年";
1842 /// assert_eq!(new_year, new_year.to_lowercase());
1844 #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
1845 pub fn to_lowercase(&self) -> String {
1846 let mut s = String::with_capacity(self.len());
1847 for (i, c) in self[..].char_indices() {
1849 // Σ maps to σ, except at the end of a word where it maps to ς.
1850 // This is the only conditional (contextual) but language-independent mapping
1851 // in `SpecialCasing.txt`,
1852 // so hard-code it rather than have a generic "condition" mechanism.
1853 // See https://github.com/rust-lang/rust/issues/26035
1854 map_uppercase_sigma(self, i, &mut s)
1856 s.extend(c.to_lowercase());
1861 fn map_uppercase_sigma(from: &str, i: usize, to: &mut String) {
1862 // See http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
1863 // for the definition of `Final_Sigma`.
1864 debug_assert!('Σ'.len_utf8() == 2);
1865 let is_word_final = case_ignoreable_then_cased(from[..i].chars().rev()) &&
1866 !case_ignoreable_then_cased(from[i + 2..].chars());
1867 to.push_str(if is_word_final { "ς" } else { "σ" });
1870 fn case_ignoreable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool {
1871 use std_unicode::derived_property::{Cased, Case_Ignorable};
1872 match iter.skip_while(|&c| Case_Ignorable(c)).next() {
1873 Some(c) => Cased(c),
1879 /// Returns the uppercase equivalent of this string slice, as a new [`String`].
1881 /// 'Uppercase' is defined according to the terms of the Unicode Derived Core Property
1884 /// Since some characters can expand into multiple characters when changing
1885 /// the case, this function returns a [`String`] instead of modifying the
1886 /// parameter in-place.
1888 /// [`String`]: string/struct.String.html
1895 /// let s = "hello";
1897 /// assert_eq!("HELLO", s.to_uppercase());
1900 /// Scripts without case are not changed:
1903 /// let new_year = "农历新年";
1905 /// assert_eq!(new_year, new_year.to_uppercase());
1907 #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
1908 pub fn to_uppercase(&self) -> String {
1909 let mut s = String::with_capacity(self.len());
1910 s.extend(self.chars().flat_map(|c| c.to_uppercase()));
1914 /// Escapes each char in `s` with [`char::escape_debug`].
1916 /// [`char::escape_debug`]: primitive.char.html#method.escape_debug
1917 #[unstable(feature = "str_escape",
1918 reason = "return type may change to be an iterator",
1920 pub fn escape_debug(&self) -> String {
1921 self.chars().flat_map(|c| c.escape_debug()).collect()
1924 /// Escapes each char in `s` with [`char::escape_default`].
1926 /// [`char::escape_default`]: primitive.char.html#method.escape_default
1927 #[unstable(feature = "str_escape",
1928 reason = "return type may change to be an iterator",
1930 pub fn escape_default(&self) -> String {
1931 self.chars().flat_map(|c| c.escape_default()).collect()
1934 /// Escapes each char in `s` with [`char::escape_unicode`].
1936 /// [`char::escape_unicode`]: primitive.char.html#method.escape_unicode
1937 #[unstable(feature = "str_escape",
1938 reason = "return type may change to be an iterator",
1940 pub fn escape_unicode(&self) -> String {
1941 self.chars().flat_map(|c| c.escape_unicode()).collect()
1944 /// Converts a [`Box<str>`] into a [`String`] without copying or allocating.
1946 /// [`String`]: string/struct.String.html
1947 /// [`Box<str>`]: boxed/struct.Box.html
1954 /// let string = String::from("birthday gift");
1955 /// let boxed_str = string.clone().into_boxed_str();
1957 /// assert_eq!(boxed_str.into_string(), string);
1959 #[stable(feature = "box_str", since = "1.4.0")]
1960 pub fn into_string(self: Box<str>) -> String {
1962 let slice = mem::transmute::<Box<str>, Box<[u8]>>(self);
1963 String::from_utf8_unchecked(slice.into_vec())
1967 /// Create a [`String`] by repeating a string `n` times.
1969 /// [`String`]: string/struct.String.html
1976 /// assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
1978 #[stable(feature = "repeat_str", since = "1.16.0")]
1979 pub fn repeat(&self, n: usize) -> String {
1980 let mut s = String::with_capacity(self.len() * n);
1981 s.extend((0..n).map(|_| self));