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:

let hello = "Hello, world!";

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

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:

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));Run

Note: This example shows the internals of &str. unsafe should not be used to get a string slice under normal circumstances. Use .as_slice() instead.

Methods

impl str
[src]

Methods for string slices.

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:

let len = "foo".len();
assert_eq!(3, len);

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

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

Examples

Basic usage:

let s = "";
assert!(s.is_empty());

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

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

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));Run

Converts a string slice to a byte slice.

Examples

Basic usage:

let bytes = "bors".as_bytes();
assert_eq!(b"bors", bytes);Run

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:

let s = "Hello";
let ptr = s.as_ptr();Run

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:

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));
}Run

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.

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:

let s = "Per Martin-Löf";

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

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

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:

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);Run

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:

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());Run

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

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());Run

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:

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());Run

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

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());Run

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:

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());Run

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:

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());Run

All kinds of whitespace are considered:

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());Run

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:

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());Run

The final line ending isn't required:

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());Run

Deprecated since 1.4.0

: use lines() instead now

An iterator over the lines of a string.

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

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

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

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

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

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

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

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

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

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

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:

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));Run

More complex patterns with closures:

let s = "Löwe 老虎 Léopard";

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

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

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

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:

let s = "Löwe 老虎 Léopard";

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

More complex patterns with closures:

let s = "Löwe 老虎 Léopard";

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

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

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

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:

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"]);Run

A more complex pattern, using a closure:

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

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

let x = "||||a||b|c".to_string();
let d: Vec<_> = x.split('|').collect();

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

Contiguous separators are separated by the empty string.

let x = "(///)".to_string();
let d: Vec<_> = x.split('/').collect();;

assert_eq!(d, &["(", "", "", ")"]);Run

Separators at the start or end of a string are neighbored by empty strings.

let d: Vec<_> = "010".split("0").collect();
assert_eq!(d, &["", "1", ""]);Run

When the empty string is used as a separator, it separates every character in the string, along with the beginning and end of the string.

let f: Vec<_> = "rust".split("").collect();
assert_eq!(f, &["", "r", "u", "s", "t", ""]);Run

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

let x = "    a  b c".to_string();
let d: Vec<_> = x.split(' ').collect();

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

It does not give you:

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

Use split_whitespace() for this behavior.

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:

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"]);Run

A more complex pattern, using a closure:

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

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:

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", ""]);Run

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

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"]);Run

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

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

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:

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, [""]);Run

A more complex pattern, using a closure:

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

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

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

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:

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"]);Run

A more complex pattern, using a closure:

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

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:

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"]);Run

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:

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"]);Run

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:

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`Run

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:

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`Run

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:

let s = " Hello\tworld\t";

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

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:

let s = " Hello\tworld\t";

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

Directionality:

let s = "  English";
assert!(Some('E') == s.trim_left().chars().next());

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

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:

let s = " Hello\tworld\t";

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

Directionality:

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

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

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

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

Examples

Simple patterns:

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");Run

A more complex pattern, using a closure:

assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");Run

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:

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");Run

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:

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");Run

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_left_matches(|c| c == '1' || c == 'X'), "fooX");Run

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

let four: u32 = "4".parse().unwrap();

assert_eq!(4, four);Run

Using the 'turbofish' instead of annotating four:

let four = "4".parse::<u32>();

assert_eq!(Ok(4), four);Run

Failing to parse:

let nope = "j".parse::<u32>();

assert!(nope.is_err());Run

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:

let s = "this is old";

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

When the pattern doesn't match:

let s = "this is old";
assert_eq!(s, s.replace("cookie monster", "little lamb"));Run

Unstable (str_replacen #36436)

: only need to replace first N matches

Replaces first N matches of a pattern with another string.

replacen 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 at most N times.

Examples

Basic usage:

let s = "foo foo 123 foo";
assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));Run

When the pattern doesn't match:

let s = "this is old";
assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));Run

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:

let s = "HELLO";

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

A tricky example, with sigma:

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());Run

Languages without case are not changed:

let new_year = "农历新年";

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

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:

let s = "hello";

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

Scripts without case are not changed:

let new_year = "农历新年";

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

Unstable (str_escape #27791)

: return type may change to be an iterator

Escapes each char in s with char::escape_debug.

Unstable (str_escape #27791)

: return type may change to be an iterator

Escapes each char in s with char::escape_default.

Unstable (str_escape #27791)

: return type may change to be an iterator

Escapes each char in s with char::escape_unicode.

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

Examples

Basic usage:

let string = String::from("birthday gift");
let boxed_str = string.clone().into_boxed_str();

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

Unstable (repeat_str #37079)

Create a String by repeating a string n times.

Examples

Basic usage:

#![feature(repeat_str)]

assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));Run

Trait Implementations

impl ToString for str
1.9.0
[src]

Converts the given value to a String. Read more

impl ToOwned for str
1.0.0
[src]

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

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

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

This method tests for !=.

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

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

This method tests for !=.

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

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

This method tests for !=.

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

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

This method tests for !=.

impl AsRef<str> for str
1.0.0
[src]

Performs the conversion.

impl AsRef<[u8]> for str
1.0.0
[src]

Performs the conversion.

impl<'a, 'b> Pattern<'a> for &'b str
[src]

Non-allocating substring search.

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

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Associated searcher for this pattern

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

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

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the front of the haystack

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the back of the haystack

Unstable (pattern #27721)

: API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches anywhere in the haystack

impl Debug for str
1.0.0
[src]

Formats the value using the given formatter.

impl Ord for str
1.0.0
[src]

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

impl PartialOrd<str> for str
1.0.0
[src]

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

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

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

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

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

impl IndexMut<Range<usize>> for str
1.2.0
[src]

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.

The method for the mutable indexing (container[index]) operation

impl IndexMut<RangeTo<usize>> for str
1.2.0
[src]

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].

The method for the mutable indexing (container[index]) operation

impl IndexMut<RangeFrom<usize>> for str
1.2.0
[src]

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].

The method for the mutable indexing (container[index]) operation

impl IndexMut<RangeFull> for str
1.2.0
[src]

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].

The method for the mutable indexing (container[index]) operation

impl IndexMut<RangeInclusive<usize>> for str
[src]

The method for the mutable indexing (container[index]) operation

impl IndexMut<RangeToInclusive<usize>> for str
[src]

The method for the mutable indexing (container[index]) operation

impl Index<Range<usize>> for str
1.0.0
[src]

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

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];Run

The returned type after indexing

The method for the indexing (container[index]) operation

impl Index<RangeTo<usize>> for str
1.0.0
[src]

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].

The returned type after indexing

The method for the indexing (container[index]) operation

impl Index<RangeFrom<usize>> for str
1.0.0
[src]

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].

The returned type after indexing

The method for the indexing (container[index]) operation

impl Index<RangeFull> for str
1.0.0
[src]

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

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

Equivalent to &self[0 .. len].

The returned type after indexing

The method for the indexing (container[index]) operation

impl Index<RangeInclusive<usize>> for str
[src]

The returned type after indexing

The method for the indexing (container[index]) operation

impl Index<RangeToInclusive<usize>> for str
[src]

The returned type after indexing

The method for the indexing (container[index]) operation

impl PartialEq<str> for str
1.0.0
[src]

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

This method tests for !=.

impl<'a> Default for &'a str
1.0.0
[src]

Creates an empty str

impl Hash for str
1.0.0
[src]

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

Feeds a slice of this type into the state provided.

impl Eq for str
1.0.0
[src]

impl Display for str
1.0.0
[src]

Formats the value using the given formatter.

impl UnicodeStr for str
[src]

Unstable (unicode #27783)

Unstable (unicode #27783)

Unstable (unicode #27783)

Unstable (unicode #27783)

Unstable (unicode #27783)

Unstable (unicode #27783)

impl AsciiExt for str
1.0.0
[src]

Container type for copied ASCII characters.

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

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

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

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

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

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

impl PartialEq<OsString> for str
1.0.0
[src]

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

This method tests for !=.

impl PartialEq<OsStr> for str
1.0.0
[src]

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

This method tests for !=.

impl AsRef<OsStr> for str
1.0.0
[src]

Performs the conversion.

impl ToSocketAddrs for str
1.0.0
[src]

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

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

impl AsRef<Path> for str
1.0.0
[src]

Performs the conversion.