Primitive Type str []

String slices.

The str type, also called a 'string slice', is the most primitive string type. It is usually seen in its borrowed form, &str. It is also the type of string literals, &'static str.

Strings slices are always valid UTF-8.

This documentation describes a number of methods and trait implementations on the str type. For technical reasons, there is additional, separate documentation in the std::str module as well.

Examples

String literals are string slices:

fn main() { let hello = "Hello, world!"; // with an explicit type annotation let hello: &'static str = "Hello, world!"; }
let hello = "Hello, world!";

// with an explicit type annotation
let hello: &'static str = "Hello, world!";

They are 'static because they're stored directly in the final binary, and so will be valid for the 'static duration.

Representation

A &str is made up of two components: a pointer to some bytes, and a length. You can look at these with the .as_ptr() and len() methods:

fn main() { use std::slice; use std::str; let story = "Once upon a time..."; let ptr = story.as_ptr(); let len = story.len(); // story has nineteen bytes assert_eq!(19, len); // We can re-build a str out of ptr and len. This is all unsafe because // we are responsible for making sure the two components are valid: let s = unsafe { // First, we build a &[u8]... let slice = slice::from_raw_parts(ptr, len); // ... and then convert that slice into a string slice str::from_utf8(slice) }; assert_eq!(s, Ok(story)); }
use std::slice;
use std::str;

let story = "Once upon a time...";

let ptr = story.as_ptr();
let len = story.len();

// story has nineteen bytes
assert_eq!(19, len);

// We can re-build a str out of ptr and len. This is all unsafe because
// we are responsible for making sure the two components are valid:
let s = unsafe {
    // First, we build a &[u8]...
    let slice = slice::from_raw_parts(ptr, len);

    // ... and then convert that slice into a string slice
    str::from_utf8(slice)
};

assert_eq!(s, Ok(story));

Methods

impl str

Methods for string slices.

fn len(&self) -> usize
1.0.0

Returns the length of self.

This length is in bytes, not chars or graphemes. In other words, it may not be what a human considers the length of the string.

Examples

Basic usage:

fn main() { let len = "foo".len(); assert_eq!(3, len); let len = "ƒoo".len(); // fancy f! assert_eq!(4, len); }
let len = "foo".len();
assert_eq!(3, len);

let len = "ƒoo".len(); // fancy f!
assert_eq!(4, len);

fn is_empty(&self) -> bool
1.0.0

Returns true if this slice has a length of zero bytes.

Examples

Basic usage:

fn main() { let s = ""; assert!(s.is_empty()); let s = "not empty"; assert!(!s.is_empty()); }
let s = "";
assert!(s.is_empty());

let s = "not empty";
assert!(!s.is_empty());

fn is_char_boundary(&self, index: usize) -> bool
1.9.0

Checks that index-th byte lies at the start and/or end of a UTF-8 code point sequence.

The start and end of the string (when index == self.len()) are considered to be boundaries.

Returns false if index is greater than self.len().

Examples

fn main() { let s = "Löwe 老虎 Léopard"; assert!(s.is_char_boundary(0)); // start of `老` assert!(s.is_char_boundary(6)); assert!(s.is_char_boundary(s.len())); // second byte of `ö` assert!(!s.is_char_boundary(2)); // third byte of `老` assert!(!s.is_char_boundary(8)); }
let s = "Löwe 老虎 Léopard";
assert!(s.is_char_boundary(0));
// start of `老`
assert!(s.is_char_boundary(6));
assert!(s.is_char_boundary(s.len()));

// second byte of `ö`
assert!(!s.is_char_boundary(2));

// third byte of `老`
assert!(!s.is_char_boundary(8));

fn as_bytes(&self) -> &[u8]
1.0.0

Converts a string slice to a byte slice.

Examples

Basic usage:

fn main() { let bytes = "bors".as_bytes(); assert_eq!(b"bors", bytes); }
let bytes = "bors".as_bytes();
assert_eq!(b"bors", bytes);

fn as_ptr(&self) -> *const u8
1.0.0

Converts a string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

Examples

Basic usage:

fn main() { let s = "Hello"; let ptr = s.as_ptr(); }
let s = "Hello";
let ptr = s.as_ptr();

unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str
1.0.0

Creates a string slice from another string slice, bypassing safety checks.

This new slice goes from begin to end, including begin but excluding end.

To get a mutable string slice instead, see the slice_mut_unchecked() method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must come before end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.

Examples

Basic usage:

fn main() { let s = "Löwe 老虎 Léopard"; unsafe { assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21)); } let s = "Hello, world!"; unsafe { assert_eq!("world", s.slice_unchecked(7, 12)); } }
let s = "Löwe 老虎 Léopard";

unsafe {
    assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
}

let s = "Hello, world!";

unsafe {
    assert_eq!("world", s.slice_unchecked(7, 12));
}

unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str
1.5.0

Creates a string slice from another string slice, bypassing safety checks.

This new slice goes from begin to end, including begin but excluding end.

To get an immutable string slice instead, see the slice_unchecked() method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must come before end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.

fn char_range_at(&self, start: usize) -> CharRange

Deprecated since 1.9.0

: use slicing plus chars() plus len_utf8

Unstable (str_char #27754)

: use slicing plus chars() plus len_utf8

Given a byte position, returns the next char and its index.

Panics

If i is greater than or equal to the length of the string. If i is not the index of the beginning of a valid UTF-8 sequence.

Examples

This example manually iterates through the code points of a string; this should normally be done by .chars() or .char_indices().

#![feature(str_char)] fn main() { #![allow(deprecated)] use std::str::CharRange; let s = "中华Việt Nam"; let mut i = 0; while i < s.len() { let CharRange {ch, next} = s.char_range_at(i); println!("{}: {}", i, ch); i = next; } }
#![feature(str_char)]
#![allow(deprecated)]

use std::str::CharRange;

let s = "中华Việt Nam";
let mut i = 0;
while i < s.len() {
    let CharRange {ch, next} = s.char_range_at(i);
    println!("{}: {}", i, ch);
    i = next;
}

This outputs:

0: 中
3: 华
6: V
7: i
8: e
9:
11:
13: t
14:
15: N
16: a
17: m

fn char_range_at_reverse(&self, start: usize) -> CharRange

Deprecated since 1.9.0

: use slicing plus chars().rev() plus len_utf8

Unstable (str_char #27754)

: use slicing plus chars().rev() plus len_utf8

Given a byte position, returns the previous char and its position.

Note that Unicode has many features, such as combining marks, ligatures, and direction marks, that need to be taken into account to correctly reverse a string.

Returns 0 for next index if called on start index 0.

Panics

If i is greater than the length of the string. If i is not an index following a valid UTF-8 sequence.

Examples

This example manually iterates through the code points of a string; this should normally be done by .chars().rev() or .char_indices().

#![feature(str_char)] fn main() { #![allow(deprecated)] use std::str::CharRange; let s = "中华Việt Nam"; let mut i = s.len(); while i > 0 { let CharRange {ch, next} = s.char_range_at_reverse(i); println!("{}: {}", i, ch); i = next; } }
#![feature(str_char)]
#![allow(deprecated)]

use std::str::CharRange;

let s = "中华Việt Nam";
let mut i = s.len();
while i > 0 {
    let CharRange {ch, next} = s.char_range_at_reverse(i);
    println!("{}: {}", i, ch);
    i = next;
}

This outputs:

18: m
17: a
16: N
15:
14: t
13:
11:
9: e
8: i
7: V
6: 华
3: 中

fn char_at(&self, i: usize) -> char

Deprecated since 1.9.0

: use slicing plus chars()

Unstable (str_char #27754)

: use slicing plus chars()

Given a byte position, returns the char at that position.

Panics

If i is greater than or equal to the length of the string. If i is not the index of the beginning of a valid UTF-8 sequence.

Examples

#![feature(str_char)] fn main() { #![allow(deprecated)] let s = "abπc"; assert_eq!(s.char_at(1), 'b'); assert_eq!(s.char_at(2), 'π'); assert_eq!(s.char_at(4), 'c'); }
#![feature(str_char)]
#![allow(deprecated)]

let s = "abπc";
assert_eq!(s.char_at(1), 'b');
assert_eq!(s.char_at(2), 'π');
assert_eq!(s.char_at(4), 'c');

fn char_at_reverse(&self, i: usize) -> char

Deprecated since 1.9.0

: use slicing plus chars().rev()

Unstable (str_char #27754)

: use slicing plus chars().rev()

Given a byte position, returns the char at that position, counting from the end.

Panics

If i is greater than the length of the string. If i is not an index following a valid UTF-8 sequence.

Examples

#![feature(str_char)] fn main() { #![allow(deprecated)] let s = "abπc"; assert_eq!(s.char_at_reverse(1), 'a'); assert_eq!(s.char_at_reverse(2), 'b'); assert_eq!(s.char_at_reverse(3), 'π'); }
#![feature(str_char)]
#![allow(deprecated)]

let s = "abπc";
assert_eq!(s.char_at_reverse(1), 'a');
assert_eq!(s.char_at_reverse(2), 'b');
assert_eq!(s.char_at_reverse(3), 'π');

fn slice_shift_char(&self) -> Option<(char, &str)>

Deprecated since 1.9.0

: use chars() plus Chars::as_str

Unstable (str_char #27754)

: use chars() plus Chars::as_str

Retrieves the first char from a &str and returns it.

Note that a single Unicode character (grapheme cluster) can be composed of multiple chars.

This does not allocate a new string; instead, it returns a slice that points one code point beyond the code point that was shifted.

None is returned if the slice is empty.

Examples

#![feature(str_char)] fn main() { #![allow(deprecated)] let s = "Łódź"; // \u{141}o\u{301}dz\u{301} let (c, s1) = s.slice_shift_char().unwrap(); assert_eq!(c, 'Ł'); assert_eq!(s1, "ódź"); let (c, s2) = s1.slice_shift_char().unwrap(); assert_eq!(c, 'o'); assert_eq!(s2, "\u{301}dz\u{301}"); }
#![feature(str_char)]
#![allow(deprecated)]

let s = "Łódź"; // \u{141}o\u{301}dz\u{301}
let (c, s1) = s.slice_shift_char().unwrap();

assert_eq!(c, 'Ł');
assert_eq!(s1, "ódź");

let (c, s2) = s1.slice_shift_char().unwrap();

assert_eq!(c, 'o');
assert_eq!(s2, "\u{301}dz\u{301}");

fn split_at(&self, mid: usize) -> (&str, &str)
1.4.0

Divide one string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get mutable string slices instead, see the split_at_mut() method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

Examples

Basic usage:

fn main() { let s = "Per Martin-Löf"; let (first, last) = s.split_at(3); assert_eq!("Per", first); assert_eq!(" Martin-Löf", last); }
let s = "Per Martin-Löf";

let (first, last) = s.split_at(3);

assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);

fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)
1.4.0

Divide one mutable string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get immutable string slices instead, see the split_at() method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

Examples

Basic usage:

fn main() { let mut s = "Per Martin-Löf".to_string(); let (first, last) = s.split_at_mut(3); assert_eq!("Per", first); assert_eq!(" Martin-Löf", last); }
let mut s = "Per Martin-Löf".to_string();

let (first, last) = s.split_at_mut(3);

assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);

fn chars(&self) -> Chars
1.0.0

Returns an iterator over the chars of a string slice.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns such an iterator.

It's important to remember that char represents a Unicode Scalar Value, and may not match your idea of what a 'character' is. Iteration over grapheme clusters may be what you actually want.

Examples

Basic usage:

fn main() { let word = "goodbye"; let count = word.chars().count(); assert_eq!(7, count); let mut chars = word.chars(); assert_eq!(Some('g'), chars.next()); assert_eq!(Some('o'), chars.next()); assert_eq!(Some('o'), chars.next()); assert_eq!(Some('d'), chars.next()); assert_eq!(Some('b'), chars.next()); assert_eq!(Some('y'), chars.next()); assert_eq!(Some('e'), chars.next()); assert_eq!(None, chars.next()); }
let word = "goodbye";

let count = word.chars().count();
assert_eq!(7, count);

let mut chars = word.chars();

assert_eq!(Some('g'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('d'), chars.next());
assert_eq!(Some('b'), chars.next());
assert_eq!(Some('y'), chars.next());
assert_eq!(Some('e'), chars.next());

assert_eq!(None, chars.next());

Remember, chars may not match your human intuition about characters:

fn main() { let y = "y̆"; let mut chars = y.chars(); assert_eq!(Some('y'), chars.next()); // not 'y̆' assert_eq!(Some('\u{0306}'), chars.next()); assert_eq!(None, chars.next()); }
let y = "y̆";

let mut chars = y.chars();

assert_eq!(Some('y'), chars.next()); // not 'y̆'
assert_eq!(Some('\u{0306}'), chars.next());

assert_eq!(None, chars.next());

fn char_indices(&self) -> CharIndices
1.0.0

Returns an iterator over the chars of a string slice, and their positions.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns an iterator of both these chars, as well as their byte positions.

The iterator yields tuples. The position is first, the char is second.

Examples

Basic usage:

fn main() { let word = "goodbye"; let count = word.char_indices().count(); assert_eq!(7, count); let mut char_indices = word.char_indices(); assert_eq!(Some((0, 'g')), char_indices.next()); assert_eq!(Some((1, 'o')), char_indices.next()); assert_eq!(Some((2, 'o')), char_indices.next()); assert_eq!(Some((3, 'd')), char_indices.next()); assert_eq!(Some((4, 'b')), char_indices.next()); assert_eq!(Some((5, 'y')), char_indices.next()); assert_eq!(Some((6, 'e')), char_indices.next()); assert_eq!(None, char_indices.next()); }
let word = "goodbye";

let count = word.char_indices().count();
assert_eq!(7, count);

let mut char_indices = word.char_indices();

assert_eq!(Some((0, 'g')), char_indices.next());
assert_eq!(Some((1, 'o')), char_indices.next());
assert_eq!(Some((2, 'o')), char_indices.next());
assert_eq!(Some((3, 'd')), char_indices.next());
assert_eq!(Some((4, 'b')), char_indices.next());
assert_eq!(Some((5, 'y')), char_indices.next());
assert_eq!(Some((6, 'e')), char_indices.next());

assert_eq!(None, char_indices.next());

Remember, chars may not match your human intuition about characters:

fn main() { let y = "y̆"; let mut char_indices = y.char_indices(); assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆') assert_eq!(Some((1, '\u{0306}')), char_indices.next()); assert_eq!(None, char_indices.next()); }
let y = "y̆";

let mut char_indices = y.char_indices();

assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
assert_eq!(Some((1, '\u{0306}')), char_indices.next());

assert_eq!(None, char_indices.next());

fn bytes(&self) -> Bytes
1.0.0

An iterator over the bytes of a string slice.

As a string slice consists of a sequence of bytes, we can iterate through a string slice by byte. This method returns such an iterator.

Examples

Basic usage:

fn main() { let mut bytes = "bors".bytes(); assert_eq!(Some(b'b'), bytes.next()); assert_eq!(Some(b'o'), bytes.next()); assert_eq!(Some(b'r'), bytes.next()); assert_eq!(Some(b's'), bytes.next()); assert_eq!(None, bytes.next()); }
let mut bytes = "bors".bytes();

assert_eq!(Some(b'b'), bytes.next());
assert_eq!(Some(b'o'), bytes.next());
assert_eq!(Some(b'r'), bytes.next());
assert_eq!(Some(b's'), bytes.next());

assert_eq!(None, bytes.next());

fn split_whitespace(&self) -> SplitWhitespace
1.1.0

Split a string slice by whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of whitespace.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Examples

Basic usage:

fn main() { let mut iter = "A few words".split_whitespace(); assert_eq!(Some("A"), iter.next()); assert_eq!(Some("few"), iter.next()); assert_eq!(Some("words"), iter.next()); assert_eq!(None, iter.next()); }
let mut iter = "A few words".split_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());

All kinds of whitespace are considered:

fn main() { let mut iter = " Mary had\ta\u{2009}little \n\t lamb".split_whitespace(); assert_eq!(Some("Mary"), iter.next()); assert_eq!(Some("had"), iter.next()); assert_eq!(Some("a"), iter.next()); assert_eq!(Some("little"), iter.next()); assert_eq!(Some("lamb"), iter.next()); assert_eq!(None, iter.next()); }
let mut iter = " Mary   had\ta\u{2009}little  \n\t lamb".split_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());

fn lines(&self) -> Lines
1.0.0

An iterator over the lines of a string, as string slices.

Lines are ended with either a newline (\n) or a carriage return with a line feed (\r\n).

The final line ending is optional.

Examples

Basic usage:

fn main() { let text = "foo\r\nbar\n\nbaz\n"; let mut lines = text.lines(); assert_eq!(Some("foo"), lines.next()); assert_eq!(Some("bar"), lines.next()); assert_eq!(Some(""), lines.next()); assert_eq!(Some("baz"), lines.next()); assert_eq!(None, lines.next()); }
let text = "foo\r\nbar\n\nbaz\n";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());

The final line ending isn't required:

fn main() { let text = "foo\nbar\n\r\nbaz"; let mut lines = text.lines(); assert_eq!(Some("foo"), lines.next()); assert_eq!(Some("bar"), lines.next()); assert_eq!(Some(""), lines.next()); assert_eq!(Some("baz"), lines.next()); assert_eq!(None, lines.next()); }
let text = "foo\nbar\n\r\nbaz";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());

fn lines_any(&self) -> LinesAny
1.0.0

Deprecated since 1.4.0

: use lines() instead now

An iterator over the lines of a string.

fn utf16_units(&self) -> EncodeUtf16

Deprecated since 1.8.0

: renamed to encode_utf16

Unstable (str_utf16 #27714)

: renamed to encode_utf16

Returns an iterator of u16 over the string encoded as UTF-16.

fn encode_utf16(&self) -> EncodeUtf16
1.8.0

Returns an iterator of u16 over the string encoded as UTF-16.

fn contains<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>
1.0.0

Returns true if the given pattern matches a sub-slice of this string slice.

Returns false if it does not.

Examples

Basic usage:

fn main() { let bananas = "bananas"; assert!(bananas.contains("nana")); assert!(!bananas.contains("apples")); }
let bananas = "bananas";

assert!(bananas.contains("nana"));
assert!(!bananas.contains("apples"));

fn starts_with<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>
1.0.0

Returns true if the given pattern matches a prefix of this string slice.

Returns false if it does not.

Examples

Basic usage:

fn main() { let bananas = "bananas"; assert!(bananas.starts_with("bana")); assert!(!bananas.starts_with("nana")); }
let bananas = "bananas";

assert!(bananas.starts_with("bana"));
assert!(!bananas.starts_with("nana"));

fn ends_with<'a, P>(&'a self, pat: P) -> bool where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

Returns true if the given pattern matches a suffix of this string slice.

Returns false if it does not.

Examples

Basic usage:

fn main() { let bananas = "bananas"; assert!(bananas.ends_with("anas")); assert!(!bananas.ends_with("nana")); }
let bananas = "bananas";

assert!(bananas.ends_with("anas"));
assert!(!bananas.ends_with("nana"));

fn find<'a, P>(&'a self, pat: P) -> Option<usize> where P: Pattern<'a>
1.0.0

Returns the byte index of the first character of this string slice that matches the pattern.

Returns None if the pattern doesn't match.

The pattern can be a &str, char, or a closure that determines if a character matches.

Examples

Simple patterns:

fn main() { let s = "Löwe 老虎 Léopard"; assert_eq!(s.find('L'), Some(0)); assert_eq!(s.find('é'), Some(14)); assert_eq!(s.find("Léopard"), Some(13)); }
let s = "Löwe 老虎 Léopard";

assert_eq!(s.find('L'), Some(0));
assert_eq!(s.find('é'), Some(14));
assert_eq!(s.find("Léopard"), Some(13));

More complex patterns with closures:

fn main() { let s = "Löwe 老虎 Léopard"; assert_eq!(s.find(char::is_whitespace), Some(5)); assert_eq!(s.find(char::is_lowercase), Some(1)); }
let s = "Löwe 老虎 Léopard";

assert_eq!(s.find(char::is_whitespace), Some(5));
assert_eq!(s.find(char::is_lowercase), Some(1));

Not finding the pattern:

fn main() { let s = "Löwe 老虎 Léopard"; let x: &[_] = &['1', '2']; assert_eq!(s.find(x), None); }
let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.find(x), None);

fn rfind<'a, P>(&'a self, pat: P) -> Option<usize> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

Returns the byte index of the last character of this string slice that matches the pattern.

Returns None if the pattern doesn't match.

The pattern can be a &str, char, or a closure that determines if a character matches.

Examples

Simple patterns:

fn main() { let s = "Löwe 老虎 Léopard"; assert_eq!(s.rfind('L'), Some(13)); assert_eq!(s.rfind('é'), Some(14)); }
let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind('L'), Some(13));
assert_eq!(s.rfind('é'), Some(14));

More complex patterns with closures:

fn main() { let s = "Löwe 老虎 Léopard"; assert_eq!(s.rfind(char::is_whitespace), Some(12)); assert_eq!(s.rfind(char::is_lowercase), Some(20)); }
let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind(char::is_whitespace), Some(12));
assert_eq!(s.rfind(char::is_lowercase), Some(20));

Not finding the pattern:

fn main() { let s = "Löwe 老虎 Léopard"; let x: &[_] = &['1', '2']; assert_eq!(s.rfind(x), None); }
let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.rfind(x), None);

fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where P: Pattern<'a>
1.0.0

An iterator over substrings of this string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, or a closure that determines the split.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, char but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit() method can be used.

Examples

Simple patterns:

fn main() { let v: Vec<&str> = "Mary had a little lamb".split(' ').collect(); assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]); let v: Vec<&str> = "".split('X').collect(); assert_eq!(v, [""]); let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect(); assert_eq!(v, ["lion", "", "tiger", "leopard"]); let v: Vec<&str> = "lion::tiger::leopard".split("::").collect(); assert_eq!(v, ["lion", "tiger", "leopard"]); let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect(); assert_eq!(v, ["abc", "def", "ghi"]); let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect(); assert_eq!(v, ["lion", "tiger", "leopard"]); }
let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

let v: Vec<&str> = "".split('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
assert_eq!(v, ["lion", "", "tiger", "leopard"]);

let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
assert_eq!(v, ["abc", "def", "ghi"]);

let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

A more complex pattern, using a closure:

fn main() { let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect(); assert_eq!(v, ["abc", "def", "ghi"]); }
let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "def", "ghi"]);

If a string contains multiple contiguous separators, you will end up with empty strings in the output:

fn main() { let x = "||||a||b|c".to_string(); let d: Vec<_> = x.split('|').collect(); assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]); }
let x = "||||a||b|c".to_string();
let d: Vec<_> = x.split('|').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);

This can lead to possibly surprising behavior when whitespace is used as the separator. This code is correct:

fn main() { let x = " a b c".to_string(); let d: Vec<_> = x.split(' ').collect(); assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]); }
let x = "    a  b c".to_string();
let d: Vec<_> = x.split(' ').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);

It does not give you:

fn main() { assert_eq!(d, &["a", "b", "c"]); }
assert_eq!(d, &["a", "b", "c"]);

Use split_whitespace() for this behavior.

fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

An iterator over substrings of the given string slice, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a &str, char, or a closure that determines the split.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the split() method can be used.

Examples

Simple patterns:

fn main() { let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect(); assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]); let v: Vec<&str> = "".rsplit('X').collect(); assert_eq!(v, [""]); let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect(); assert_eq!(v, ["leopard", "tiger", "", "lion"]); let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect(); assert_eq!(v, ["leopard", "tiger", "lion"]); }
let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);

let v: Vec<&str> = "".rsplit('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
assert_eq!(v, ["leopard", "tiger", "", "lion"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
assert_eq!(v, ["leopard", "tiger", "lion"]);

A more complex pattern, using a closure:

fn main() { let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect(); assert_eq!(v, ["ghi", "def", "abc"]); }
let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "def", "abc"]);

fn split_terminator<'a, P>(&'a self, pat: P) -> SplitTerminator<'a, P> where P: Pattern<'a>
1.0.0

An iterator over substrings of the given string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, or a closure that determines the split.

Equivalent to split(), except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, char but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit_terminator() method can be used.

Examples

Basic usage:

fn main() { let v: Vec<&str> = "A.B.".split_terminator('.').collect(); assert_eq!(v, ["A", "B"]); let v: Vec<&str> = "A..B..".split_terminator(".").collect(); assert_eq!(v, ["A", "", "B", ""]); }
let v: Vec<&str> = "A.B.".split_terminator('.').collect();
assert_eq!(v, ["A", "B"]);

let v: Vec<&str> = "A..B..".split_terminator(".").collect();
assert_eq!(v, ["A", "", "B", ""]);

fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

An iterator over substrings of self, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a simple &str, char, or a closure that determines the split. Additional libraries might provide more complex patterns like regular expressions.

Equivalent to split(), except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be double ended if a forward/reverse search yields the same elements.

For iterating from the front, the split_terminator() method can be used.

Examples

fn main() { let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect(); assert_eq!(v, ["B", "A"]); let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect(); assert_eq!(v, ["", "B", "", "A"]); }
let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
assert_eq!(v, ["B", "A"]);

let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
assert_eq!(v, ["", "B", "", "A"]);

fn splitn<'a, P>(&'a self, count: usize, pat: P) -> SplitN<'a, P> where P: Pattern<'a>
1.0.0

An iterator over substrings of the given string slice, separated by a pattern, restricted to returning at most count items.

The last element returned, if any, will contain the remainder of the string slice.

The pattern can be a &str, char, or a closure that determines the split.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

If the pattern allows a reverse search, the rsplitn() method can be used.

Examples

Simple patterns:

fn main() { let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect(); assert_eq!(v, ["Mary", "had", "a little lambda"]); let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect(); assert_eq!(v, ["lion", "", "tigerXleopard"]); let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect(); assert_eq!(v, ["abcXdef"]); let v: Vec<&str> = "".splitn(1, 'X').collect(); assert_eq!(v, [""]); }
let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
assert_eq!(v, ["Mary", "had", "a little lambda"]);

let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
assert_eq!(v, ["lion", "", "tigerXleopard"]);

let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
assert_eq!(v, ["abcXdef"]);

let v: Vec<&str> = "".splitn(1, 'X').collect();
assert_eq!(v, [""]);

A more complex pattern, using a closure:

fn main() { let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect(); assert_eq!(v, ["abc", "defXghi"]); }
let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "defXghi"]);

fn rsplitn<'a, P>(&'a self, count: usize, pat: P) -> RSplitN<'a, P> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

An iterator over substrings of this string slice, separated by a pattern, starting from the end of the string, restricted to returning at most count items.

The last element returned, if any, will contain the remainder of the string slice.

The pattern can be a &str, char, or a closure that determines the split.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

For splitting from the front, the splitn() method can be used.

Examples

Simple patterns:

fn main() { let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect(); assert_eq!(v, ["lamb", "little", "Mary had a"]); let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect(); assert_eq!(v, ["leopard", "tiger", "lionX"]); let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect(); assert_eq!(v, ["leopard", "lion::tiger"]); }
let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
assert_eq!(v, ["lamb", "little", "Mary had a"]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
assert_eq!(v, ["leopard", "tiger", "lionX"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
assert_eq!(v, ["leopard", "lion::tiger"]);

A more complex pattern, using a closure:

fn main() { let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect(); assert_eq!(v, ["ghi", "abc1def"]); }
let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "abc1def"]);

fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where P: Pattern<'a>
1.2.0

An iterator over the matches of a pattern within the given string slice.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, char but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatches() method can be used.

Examples

Basic usage:

fn main() { let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect(); assert_eq!(v, ["abc", "abc", "abc"]); let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect(); assert_eq!(v, ["1", "2", "3"]); }
let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
assert_eq!(v, ["1", "2", "3"]);

fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.2.0

An iterator over the matches of a pattern within this string slice, yielded in reverse order.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the matches() method can be used.

Examples

Basic usage:

fn main() { let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect(); assert_eq!(v, ["abc", "abc", "abc"]); let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect(); assert_eq!(v, ["3", "2", "1"]); }
let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
assert_eq!(v, ["3", "2", "1"]);

fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where P: Pattern<'a>
1.5.0

An iterator over the disjoint matches of a pattern within this string slice as well as the index that the match starts at.

For matches of pat within self that overlap, only the indices corresponding to the first match are returned.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, eg, char but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatch_indices() method can be used.

Examples

Basic usage:

fn main() { let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect(); assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]); let v: Vec<_> = "1abcabc2".match_indices("abc").collect(); assert_eq!(v, [(1, "abc"), (4, "abc")]); let v: Vec<_> = "ababa".match_indices("aba").collect(); assert_eq!(v, [(0, "aba")]); // only the first `aba` }
let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
assert_eq!(v, [(1, "abc"), (4, "abc")]);

let v: Vec<_> = "ababa".match_indices("aba").collect();
assert_eq!(v, [(0, "aba")]); // only the first `aba`

fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.5.0

An iterator over the disjoint matches of a pattern within self, yielded in reverse order along with the index of the match.

For matches of pat within self that overlap, only the indices corresponding to the last match are returned.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the match_indices() method can be used.

Examples

Basic usage:

fn main() { let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect(); assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]); let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect(); assert_eq!(v, [(4, "abc"), (1, "abc")]); let v: Vec<_> = "ababa".rmatch_indices("aba").collect(); assert_eq!(v, [(2, "aba")]); // only the last `aba` }
let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
assert_eq!(v, [(4, "abc"), (1, "abc")]);

let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
assert_eq!(v, [(2, "aba")]); // only the last `aba`

fn trim(&self) -> &str
1.0.0

Returns a string slice with leading and trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Examples

Basic usage:

fn main() { let s = " Hello\tworld\t"; assert_eq!("Hello\tworld", s.trim()); }
let s = " Hello\tworld\t";

assert_eq!("Hello\tworld", s.trim());

fn trim_left(&self) -> &str
1.0.0

Returns a string slice with leading whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

Examples

Basic usage:

fn main() { let s = " Hello\tworld\t"; assert_eq!("Hello\tworld\t", s.trim_left()); }
let s = " Hello\tworld\t";

assert_eq!("Hello\tworld\t", s.trim_left());

Directionality:

fn main() { let s = " English"; assert!(Some('E') == s.trim_left().chars().next()); let s = " עברית"; assert!(Some('ע') == s.trim_left().chars().next()); }
let s = "  English";
assert!(Some('E') == s.trim_left().chars().next());

let s = "  עברית";
assert!(Some('ע') == s.trim_left().chars().next());

fn trim_right(&self) -> &str
1.0.0

Returns a string slice with trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

Examples

Basic usage:

fn main() { let s = " Hello\tworld\t"; assert_eq!(" Hello\tworld", s.trim_right()); }
let s = " Hello\tworld\t";

assert_eq!(" Hello\tworld", s.trim_right());

Directionality:

fn main() { let s = "English "; assert!(Some('h') == s.trim_right().chars().rev().next()); let s = "עברית "; assert!(Some('ת') == s.trim_right().chars().rev().next()); }
let s = "English  ";
assert!(Some('h') == s.trim_right().chars().rev().next());

let s = "עברית  ";
assert!(Some('ת') == s.trim_right().chars().rev().next());

fn trim_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>, P::Searcher: DoubleEndedSearcher<'a>
1.0.0

Returns a string slice with all prefixes and suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Examples

Simple patterns:

fn main() { assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar"); assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar"); let x: &[_] = &['1', '2']; assert_eq!("12foo1bar12".trim_matches(x), "foo1bar"); }
assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");

A more complex pattern, using a closure:

fn main() { assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar"); }
assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");

fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>
1.0.0

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

Examples

Basic usage:

fn main() { assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11"); assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123"); let x: &[_] = &['1', '2']; assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12"); }
assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");

fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str where P: Pattern<'a>, P::Searcher: ReverseSearcher<'a>
1.0.0

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

Examples

Simple patterns:

fn main() { assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar"); assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar"); let x: &[_] = &['1', '2']; assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar"); }
assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");

A more complex pattern, using a closure:

fn main() { assert_eq!("1fooX".trim_left_matches(|c| c == '1' || c == 'X'), "fooX"); }
assert_eq!("1fooX".trim_left_matches(|c| c == '1' || c == 'X'), "fooX");

fn parse<F>(&self) -> Result<F, F::Err> where F: FromStr
1.0.0

Parses this string slice into another type.

Because parse() is so general, it can cause problems with type inference. As such, parse() is one of the few times you'll see the syntax affectionately known as the 'turbofish': ::<>. This helps the inference algorithm understand specifically which type you're trying to parse into.

parse() can parse any type that implements the FromStr trait.

Errors

Will return Err if it's not possible to parse this string slice into the desired type.

Example

Basic usage

fn main() { let four: u32 = "4".parse().unwrap(); assert_eq!(4, four); }
let four: u32 = "4".parse().unwrap();

assert_eq!(4, four);

Using the 'turbofish' instead of annotating four:

fn main() { let four = "4".parse::<u32>(); assert_eq!(Ok(4), four); }
let four = "4".parse::<u32>();

assert_eq!(Ok(4), four);

Failing to parse:

fn main() { let nope = "j".parse::<u32>(); assert!(nope.is_err()); }
let nope = "j".parse::<u32>();

assert!(nope.is_err());

fn replace<'a, P>(&'a self, from: P, to: &str) -> String where P: Pattern<'a>
1.0.0

Replaces all matches of a pattern with another string.

replace creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice.

Examples

Basic usage:

fn main() { let s = "this is old"; assert_eq!("this is new", s.replace("old", "new")); }
let s = "this is old";

assert_eq!("this is new", s.replace("old", "new"));

When the pattern doesn't match:

fn main() { let s = "this is old"; assert_eq!(s, s.replace("cookie monster", "little lamb")); }
let s = "this is old";
assert_eq!(s, s.replace("cookie monster", "little lamb"));

fn to_lowercase(&self) -> String
1.2.0

Returns the lowercase equivalent of this string slice, as a new String.

'Lowercase' is defined according to the terms of the Unicode Derived Core Property Lowercase.

Examples

Basic usage:

fn main() { let s = "HELLO"; assert_eq!("hello", s.to_lowercase()); }
let s = "HELLO";

assert_eq!("hello", s.to_lowercase());

A tricky example, with sigma:

fn main() { let sigma = "Σ"; assert_eq!("σ", sigma.to_lowercase()); // but at the end of a word, it's ς, not σ: let odysseus = "ὈΔΥΣΣΕΎΣ"; assert_eq!("ὀδυσσεύς", odysseus.to_lowercase()); }
let sigma = "Σ";

assert_eq!("σ", sigma.to_lowercase());

// but at the end of a word, it's ς, not σ:
let odysseus = "ὈΔΥΣΣΕΎΣ";

assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());

Languages without case are not changed:

fn main() { let new_year = "农历新年"; assert_eq!(new_year, new_year.to_lowercase()); }
let new_year = "农历新年";

assert_eq!(new_year, new_year.to_lowercase());

fn to_uppercase(&self) -> String
1.2.0

Returns the uppercase equivalent of this string slice, as a new String.

'Uppercase' is defined according to the terms of the Unicode Derived Core Property Uppercase.

Examples

Basic usage:

fn main() { let s = "hello"; assert_eq!("HELLO", s.to_uppercase()); }
let s = "hello";

assert_eq!("HELLO", s.to_uppercase());

Scripts without case are not changed:

fn main() { let new_year = "农历新年"; assert_eq!(new_year, new_year.to_uppercase()); }
let new_year = "农历新年";

assert_eq!(new_year, new_year.to_uppercase());

fn escape_default(&self) -> String

Unstable (str_escape #27791)

: return type may change to be an iterator

Escapes each char in s with char::escape_default.

fn escape_unicode(&self) -> String

Unstable (str_escape #27791)

: return type may change to be an iterator

Escapes each char in s with char::escape_unicode.

fn into_string(self: Box<str>) -> String
1.4.0

Converts a Box<str> into a String without copying or allocating.

Examples

Basic usage:

fn main() { let string = String::from("birthday gift"); let boxed_str = string.clone().into_boxed_str(); assert_eq!(boxed_str.into_string(), string); }
let string = String::from("birthday gift");
let boxed_str = string.clone().into_boxed_str();

assert_eq!(boxed_str.into_string(), string);

Trait Implementations

impl AsRef<str> for str
1.0.0

fn as_ref(&self) -> &str

Performs the conversion.

impl Repr<Slice<u8>> for str

fn repr(&self) -> T

This function "unwraps" a rust value (without consuming it) into its raw struct representation. This can be used to read/write different values for the struct. This is a safe method because by default it does not enable write-access to the fields of the return value in safe code. Read more

impl<'a, 'b> Pattern<'a> for &'b str

Non-allocating substring search.

Will handle the pattern "" as returning empty matches at each character boundary.

type Searcher = StrSearcher<'a, 'b>

Associated searcher for this pattern

fn into_searcher(self, haystack: &'a str) -> StrSearcher<'a, 'b>

Constructs the associated searcher from self and the haystack to search in. Read more

fn is_prefix_of(self, haystack: &'a str) -> bool

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the front of the haystack

fn is_suffix_of(self, haystack: &'a str) -> bool

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the back of the haystack

fn is_contained_in(self, haystack: &'a str) -> bool

Checks whether the pattern matches anywhere in the haystack

impl Ord for str
1.0.0

fn cmp(&self, other: &str) -> Ordering

This method returns an Ordering between self and other. Read more

impl PartialEq<str> for str
1.0.0

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &str) -> bool

This method tests for !=.

impl Eq for str
1.0.0

impl PartialOrd<str> for str
1.0.0

fn partial_cmp(&self, other: &str) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more

fn lt(&self, other: &Rhs) -> bool
1.0.0

This method tests less than (for self and other) and is used by the < operator. Read more

fn le(&self, other: &Rhs) -> bool
1.0.0

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

fn gt(&self, other: &Rhs) -> bool
1.0.0

This method tests greater than (for self and other) and is used by the > operator. Read more

fn ge(&self, other: &Rhs) -> bool
1.0.0

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl Index<Range<usize>> for str
1.0.0

Implements substring slicing with syntax &self[begin .. end].

Returns a slice of the given string from the byte range [begin..end).

This operation is O(1).

Panics

Panics if begin or end does not point to the starting byte offset of a character (as defined by is_char_boundary). Requires that begin <= end and end <= len where len is the length of the string.

Examples

fn main() { let s = "Löwe 老虎 Léopard"; assert_eq!(&s[0 .. 1], "L"); assert_eq!(&s[1 .. 9], "öwe 老"); // these will panic: // byte 2 lies within `ö`: // &s[2 ..3]; // byte 8 lies within `老` // &s[1 .. 8]; // byte 100 is outside the string // &s[3 .. 100]; }
let s = "Löwe 老虎 Léopard";
assert_eq!(&s[0 .. 1], "L");

assert_eq!(&s[1 .. 9], "öwe 老");

// these will panic:
// byte 2 lies within `ö`:
// &s[2 ..3];

// byte 8 lies within `老`
// &s[1 .. 8];

// byte 100 is outside the string
// &s[3 .. 100];

type Output = str

The returned type after indexing

fn index(&self, index: Range<usize>) -> &str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<Range<usize>> for str
1.2.0

Implements mutable substring slicing with syntax &mut self[begin .. end].

Returns a mutable slice of the given string from the byte range [begin..end).

This operation is O(1).

Panics

Panics if begin or end does not point to the starting byte offset of a character (as defined by is_char_boundary). Requires that begin <= end and end <= len where len is the length of the string.

fn index_mut(&mut self, index: Range<usize>) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl Index<RangeTo<usize>> for str
1.0.0

Implements substring slicing with syntax &self[.. end].

Returns a slice of the string from the beginning to byte offset end.

Equivalent to &self[0 .. end].

type Output = str

The returned type after indexing

fn index(&self, index: RangeTo<usize>) -> &str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<RangeTo<usize>> for str
1.2.0

Implements mutable substring slicing with syntax &mut self[.. end].

Returns a mutable slice of the string from the beginning to byte offset end.

Equivalent to &mut self[0 .. end].

fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl Index<RangeFrom<usize>> for str
1.0.0

Implements substring slicing with syntax &self[begin ..].

Returns a slice of the string from byte offset begin to the end of the string.

Equivalent to &self[begin .. len].

type Output = str

The returned type after indexing

fn index(&self, index: RangeFrom<usize>) -> &str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<RangeFrom<usize>> for str
1.2.0

Implements mutable substring slicing with syntax &mut self[begin ..].

Returns a mutable slice of the string from byte offset begin to the end of the string.

Equivalent to &mut self[begin .. len].

fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl Index<RangeFull> for str
1.0.0

Implements substring slicing with syntax &self[..].

Returns a slice of the whole string. This operation can never panic.

Equivalent to &self[0 .. len].

type Output = str

The returned type after indexing

fn index(&self, _index: RangeFull) -> &str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<RangeFull> for str
1.2.0

Implements mutable substring slicing with syntax &mut self[..].

Returns a mutable slice of the whole string. This operation can never panic.

Equivalent to &mut self[0 .. len].

fn index_mut(&mut self, _index: RangeFull) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl Index<RangeInclusive<usize>> for str

type Output = str

The returned type after indexing

fn index(&self, index: RangeInclusive<usize>) -> &str

The method for the indexing (Foo[Bar]) operation

impl Index<RangeToInclusive<usize>> for str

type Output = str

The returned type after indexing

fn index(&self, index: RangeToInclusive<usize>) -> &str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<RangeInclusive<usize>> for str

fn index_mut(&mut self, index: RangeInclusive<usize>) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl IndexMut<RangeToInclusive<usize>> for str

fn index_mut(&mut self, index: RangeToInclusive<usize>) -> &mut str

The method for the indexing (Foo[Bar]) operation

impl AsRef<[u8]> for str
1.0.0

fn as_ref(&self) -> &[u8]

Performs the conversion.

impl<'a> Default for &'a str
1.0.0

fn default() -> &'a str

Returns the "default value" for a type. Read more

impl Hash for str
1.0.0

fn hash<H>(&self, state: &mut H) where H: Hasher

Feeds this value into the state given, updating the hasher as necessary.

fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher
1.3.0

Feeds a slice of this type into the state provided.

impl Debug for str
1.0.0

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl Display for str
1.0.0

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl ToOwned for str
1.0.0

type Owned = String

fn to_owned(&self) -> String

Creates owned data from borrowed data, usually by cloning. Read more

impl<'a, 'b> PartialEq<String> for str
1.0.0

fn eq(&self, other: &String) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &String) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<String> for &'a str
1.0.0

fn eq(&self, other: &String) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &String) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, str>> for str
1.0.0

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=.

impl<'a, 'b> PartialEq<Cow<'a, str>> for &'b str
1.0.0

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=.

impl ToString for str
1.9.0

fn to_string(&self) -> String

Converts the given value to a String. Read more

impl UnicodeStr for str

fn split_whitespace(&self) -> SplitWhitespace

fn is_whitespace(&self) -> bool

fn is_alphanumeric(&self) -> bool

fn trim(&self) -> &str

fn trim_left(&self) -> &str

fn trim_right(&self) -> &str

impl AsciiExt for str
1.0.0
[src]

type Owned = String

Container type for copied ASCII characters.

fn is_ascii(&self) -> bool

Checks if the value is within the ASCII range. Read more

fn to_ascii_uppercase(&self) -> String

Makes a copy of the string in ASCII upper case. Read more

fn to_ascii_lowercase(&self) -> String

Makes a copy of the string in ASCII lower case. Read more

fn eq_ignore_ascii_case(&self, other: &str) -> bool

Checks that two strings are an ASCII case-insensitive match. Read more

fn make_ascii_uppercase(&mut self)

Converts this type to its ASCII upper case equivalent in-place. Read more

fn make_ascii_lowercase(&mut self)

Converts this type to its ASCII lower case equivalent in-place. Read more

impl PartialEq<OsString> for str
1.0.0
[src]

fn eq(&self, other: &OsString) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &Rhs) -> bool
1.0.0

This method tests for !=.

impl PartialEq<OsStr> for str
1.0.0
[src]

fn eq(&self, other: &OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==. Read more

fn ne(&self, other: &Rhs) -> bool
1.0.0

This method tests for !=.

impl AsRef<OsStr> for str
1.0.0
[src]

fn as_ref(&self) -> &OsStr

Performs the conversion.

impl ToSocketAddrs for str
1.0.0
[src]

type Iter = IntoIter<SocketAddr>

Returned iterator over socket addresses which this type may correspond to. Read more

fn to_socket_addrs(&self) -> Result<IntoIter<SocketAddr>>

Converts this object to an iterator of resolved SocketAddrs. Read more

impl AsRef<Path> for str
1.0.0
[src]

fn as_ref(&self) -> &Path

Performs the conversion.