str - Rust
Description: API documentation for the Rust `str` primitive in crate `std`.
Keywords: rust, rustlang, rust-lang, str

# 1.0.0[−]Primitive Type str

String slices.

See also the `std::str` module.

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`.

String slices are always valid UTF-8.

# 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_str` instead.

## Methods

### `impl str`[src]

#### `pub const fn len(&self) -> usize`[src]

Returns the length of `self`.

This length is in bytes, not `char`s 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

#### `pub const fn is_empty(&self) -> bool`[src]

Returns `true` if `self` has a length of zero bytes.

# Examples

Basic usage:

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

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

#### `pub fn is_char_boundary(&self, index: usize) -> bool`1.9.0[src]

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

####
ⓘImportant traits for &'_ [u8]

### Important traits for &'_ [u8]

`impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]`
`pub const fn as_bytes(&self) -> &[u8]`[src]

Converts a string slice to a byte slice. To convert the byte slice back into a string slice, use the `str::from_utf8` function.

# Examples

Basic usage:

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

####
ⓘImportant traits for &'_ [u8]

### Important traits for &'_ [u8]

`impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]`
`pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8]`1.20.0[src]

Converts a mutable string slice to a mutable byte slice. To convert the mutable byte slice back into a mutable string slice, use the `str::from_utf8_mut` function.

# Examples

Basic usage:

    let mut s = String::from("Hello");
    let bytes = unsafe { s.as_bytes_mut() };

    assert_eq!(b"Hello", bytes);Run

Mutability:

    let mut s = String::from("🗻∈🌏");

    unsafe {
        let bytes = s.as_bytes_mut();

        bytes[0] = 0xF0;
        bytes[1] = 0x9F;
        bytes[2] = 0x8D;
        bytes[3] = 0x94;
    }

    assert_eq!("🍔∈🌏", s);Run

#### `pub const fn as_ptr(&self) -> *const u8`[src]

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.

The caller must ensure that the returned pointer is never written to. If you need to mutate the contents of the string slice, use `as_mut_ptr`.

# Examples

Basic usage:

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

#### `pub fn as_mut_ptr(&mut self) -> *mut u8`1.36.0[src]

Converts a mutable 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.

It is your responsibility to make sure that the string slice only gets modified in a way that it remains valid UTF-8.

#### `pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output> where
I: SliceIndex<str>,` 1.20.0[src]

Returns a subslice of `str`.

This is the non-panicking alternative to indexing the `str`. Returns `None` whenever equivalent indexing operation would panic.

# Examples

    let v = String::from("🗻∈🌏");

    assert_eq!(Some("🗻"), v.get(0..4));

    // indices not on UTF-8 sequence boundaries
    assert!(v.get(1..).is_none());
    assert!(v.get(..8).is_none());

    // out of bounds
    assert!(v.get(..42).is_none());Run

#### `pub fn get_mut<I>(
&mut self,
i: I
) -> Option<&mut <I as SliceIndex<str>>::Output> where
I: SliceIndex<str>,` 1.20.0[src]

Returns a mutable subslice of `str`.

This is the non-panicking alternative to indexing the `str`. Returns `None` whenever equivalent indexing operation would panic.

# Examples

    let mut v = String::from("hello");
    // correct length
    assert!(v.get_mut(0..5).is_some());
    // out of bounds
    assert!(v.get_mut(..42).is_none());
    assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));

    assert_eq!("hello", v);
    {
        let s = v.get_mut(0..2);
        let s = s.map(|s| {
            s.make_ascii_uppercase();
            &*s
        });
        assert_eq!(Some("HE"), s);
    }
    assert_eq!("HEllo", v);Run

#### `pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Output where
I: SliceIndex<str>,` 1.20.0[src]

Returns a unchecked subslice of `str`.

This is the unchecked alternative to indexing the `str`.

# Safety

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

- The starting index must come before the ending index;
- Indexes must be within bounds of the original slice;
- Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the `str` type.

# Examples

    let v = "🗻∈🌏";
    unsafe {
        assert_eq!("🗻", v.get_unchecked(0..4));
        assert_eq!("∈", v.get_unchecked(4..7));
        assert_eq!("🌏", v.get_unchecked(7..11));
    }Run

#### `pub unsafe fn get_unchecked_mut<I>(
&mut self,
i: I
) -> &mut <I as SliceIndex<str>>::Output where
I: SliceIndex<str>,` 1.20.0[src]

Returns a mutable, unchecked subslice of `str`.

This is the unchecked alternative to indexing the `str`.

# Safety

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

- The starting index must come before the ending index;
- Indexes must be within bounds of the original slice;
- Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the `str` type.

# Examples

    let mut v = String::from("🗻∈🌏");
    unsafe {
        assert_eq!("🗻", v.get_unchecked_mut(0..4));
        assert_eq!("∈", v.get_unchecked_mut(4..7));
        assert_eq!("🌏", v.get_unchecked_mut(7..11));
    }Run

#### `pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str`[src]

Deprecated since 1.29.0:

use `get_unchecked(begin..end)` instead

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

This is generally not recommended, use with caution! For a safe alternative see `str` and `Index`.

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

#### `pub unsafe fn slice_mut_unchecked(
&mut self,
begin: usize,
end: usize
) -> &mut str`1.5.0[src]

Deprecated since 1.29.0:

use `get_unchecked_mut(begin..end)` instead

Creates a string slice from another string slice, bypassing safety checks. This is generally not recommended, use with caution! For a safe alternative see `str` and `IndexMut`.

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.

#### `pub fn split_at(&self, mid: usize) -> (&str, &str)`1.4.0[src]

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

#### `pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)`1.4.0[src]

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);
        first.make_ascii_uppercase();
        assert_eq!("PER", first);
        assert_eq!(" Martin-Löf", last);
    }
    assert_eq!("PER Martin-Löf", s);Run

####
ⓘImportant traits for Chars<'a>

### Important traits for Chars<'a>

`impl<'a> Iterator for Chars<'a> type Item = char;`
`pub fn chars(&self) -> Chars`[src]

Returns an iterator over the `char`s 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, `char`s 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

####
ⓘImportant traits for CharIndices<'a>

### Important traits for CharIndices<'a>

`impl<'a> Iterator for CharIndices<'a> type Item = (usize, char);`
`pub fn char_indices(&self) -> CharIndices`[src]

Returns an iterator over the `char`s 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 `char`s, 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, `char`s may not match your human intuition about characters:

    let yes = "y̆es";

    let mut char_indices = yes.char_indices();

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

    // note the 3 here - the last character took up two bytes
    assert_eq!(Some((3, 'e')), char_indices.next());
    assert_eq!(Some((4, 's')), char_indices.next());

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

####
ⓘImportant traits for Bytes<'_>

### Important traits for Bytes<'_>

`impl<'_> Iterator for Bytes<'_> type Item = u8;`
`pub fn bytes(&self) -> Bytes`[src]

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

####
ⓘImportant traits for SplitWhitespace<'a>

### Important traits for SplitWhitespace<'a>

`impl<'a> Iterator for SplitWhitespace<'a> type Item = &'a str;`
`pub fn split_whitespace(&self) -> SplitWhitespace`1.1.0[src]

Splits 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`. If you only want to split on ASCII whitespace instead, use `split_ascii_whitespace`.

# 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

####
ⓘImportant traits for SplitAsciiWhitespace<'a>

### Important traits for SplitAsciiWhitespace<'a>

`impl<'a> Iterator for SplitAsciiWhitespace<'a> type Item = &'a str;`
`pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace`1.34.0[src]

Splits a string slice by ASCII whitespace.

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

To split by Unicode `Whitespace` instead, use `split_whitespace`.

# Examples

Basic usage:

    let mut iter = "A few words".split_ascii_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 ASCII whitespace are considered:

    let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_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

####
ⓘImportant traits for Lines<'a>

### Important traits for Lines<'a>

`impl<'a> Iterator for Lines<'a> type Item = &'a str;`
`pub fn lines(&self) -> Lines`[src]

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

####
ⓘImportant traits for LinesAny<'a>

### Important traits for LinesAny<'a>

`impl<'a> Iterator for LinesAny<'a> type Item = &'a str;`
`pub fn lines_any(&self) -> LinesAny`[src]

Deprecated since 1.4.0:

use lines() instead now

An iterator over the lines of a string.

####
ⓘImportant traits for EncodeUtf16<'a>

### Important traits for EncodeUtf16<'a>

`impl<'a> Iterator for EncodeUtf16<'a> type Item = u16;`
`pub fn encode_utf16(&self) -> EncodeUtf16`1.8.0[src]

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

# Examples

Basic usage:

    let text = "Zażółć gęślą jaźń";

    let utf8_len = text.len();
    let utf16_len = text.encode_utf16().count();

    assert!(utf16_len <= utf8_len);Run

#### `pub fn contains<'a, P>(&'a self, pat: P) -> bool where
P: Pattern<'a>,` [src]

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

#### `pub fn starts_with<'a, P>(&'a self, pat: P) -> bool where
P: Pattern<'a>,` [src]

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

#### `pub fn ends_with<'a, P>(&'a self, pat: P) -> bool where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

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

#### `pub fn find<'a, P>(&'a self, pat: P) -> Option<usize> where
P: Pattern<'a>,` [src]

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 using point-free style and 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));
    assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
    assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));Run

Not finding the pattern:

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

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

#### `pub fn rfind<'a, P>(&'a self, pat: P) -> Option<usize> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

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

####
ⓘImportant traits for Split<'a, P>

### Important traits for Split<'a, P>

`impl<'a, P> Iterator for Split<'a, P> where
P: Pattern<'a>, type Item = &'a str;`
`pub fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where
P: Pattern<'a>,` [src]

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

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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, e.g., `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:

ⓘThis example is not tested

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

Use `split_whitespace` for this behavior.

####
ⓘImportant traits for RSplit<'a, P>

### Important traits for RSplit<'a, P>

`impl<'a, P> Iterator for RSplit<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`
`pub fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

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 any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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

####
ⓘImportant traits for SplitTerminator<'a, P>

### Important traits for SplitTerminator<'a, P>

`impl<'a, P> Iterator for SplitTerminator<'a, P> where
P: Pattern<'a>, type Item = &'a str;`
`pub fn split_terminator<'a, P>(&'a self, pat: P) -> SplitTerminator<'a, P> where
P: Pattern<'a>,` [src]

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

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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, e.g., `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

####
ⓘImportant traits for RSplitTerminator<'a, P>

### Important traits for RSplitTerminator<'a, P>

`impl<'a, P> Iterator for RSplitTerminator<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`
`pub fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

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

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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

####
ⓘImportant traits for SplitN<'a, P>

### Important traits for SplitN<'a, P>

`impl<'a, P> Iterator for SplitN<'a, P> where
P: Pattern<'a>, type Item = &'a str;`
`pub fn splitn<'a, P>(&'a self, n: usize, pat: P) -> SplitN<'a, P> where
P: Pattern<'a>,` [src]

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 `n`th substring) will contain the remainder of the string.

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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

####
ⓘImportant traits for RSplitN<'a, P>

### Important traits for RSplitN<'a, P>

`impl<'a, P> Iterator for RSplitN<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`
`pub fn rsplitn<'a, P>(&'a self, n: usize, pat: P) -> RSplitN<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

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 `n`th substring) will contain the remainder of the string.

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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

####
ⓘImportant traits for Matches<'a, P>

### Important traits for Matches<'a, P>

`impl<'a, P> Iterator for Matches<'a, P> where
P: Pattern<'a>, type Item = &'a str;`
`pub fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where
P: Pattern<'a>,` 1.2.0[src]

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

The pattern can be any type that implements the Pattern trait. Notable examples are `&str`, `char`, and closures 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, e.g., `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

####
ⓘImportant traits for RMatches<'a, P>

### Important traits for RMatches<'a, P>

`impl<'a, P> Iterator for RMatches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = &'a str;`
`pub fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` 1.2.0[src]

An iterator over the disjoint 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

####
ⓘImportant traits for MatchIndices<'a, P>

### Important traits for MatchIndices<'a, P>

`impl<'a, P> Iterator for MatchIndices<'a, P> where
P: Pattern<'a>, type Item = (usize, &'a str);`
`pub fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where
P: Pattern<'a>,` 1.5.0[src]

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, e.g., `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

####
ⓘImportant traits for RMatchIndices<'a, P>

### Important traits for RMatchIndices<'a, P>

`impl<'a, P> Iterator for RMatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, type Item = (usize, &'a str);`
`pub fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` 1.5.0[src]

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

#### `#[must_use = "this returns the trimmed string as a slice, without modifying the original"] pub fn trim(&self) -> &str`[src]

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

#### `#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_start(&self) -> &str`1.30.0[src]

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. `start` in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

# Examples

Basic usage:

    let s = " Hello\tworld\t";
    assert_eq!("Hello\tworld\t", s.trim_start());Run

Directionality:

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

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

#### `#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_end(&self) -> &str`1.30.0[src]

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. `end` in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

# Examples

Basic usage:

    let s = " Hello\tworld\t";
    assert_eq!(" Hello\tworld", s.trim_end());Run

Directionality:

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

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

#### `pub fn trim_left(&self) -> &str`[src]

Deprecated since 1.33.0:

superseded by `trim_start`

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

#### `pub fn trim_right(&self) -> &str`[src]

Deprecated since 1.33.0:

superseded by `trim_end`

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

#### `#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,` [src]

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

#### `#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_start_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,` 1.30.0[src]

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. `start` in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

# Examples

Basic usage:

    assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
    assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");

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

#### `#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_end_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` 1.30.0[src]

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. `end` in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

# Examples

Simple patterns:

    assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
    assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");

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

A more complex pattern, using a closure:

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

#### `pub fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,` [src]

Deprecated since 1.33.0:

superseded by `trim_start_matches`

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

#### `pub fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,` [src]

Deprecated since 1.33.0:

superseded by `trim_end_matches`

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_right_matches(|c| c == '1' || c == 'X'), "1foo");Run

#### `pub fn parse<F>(&self) -> Result<F, <F as FromStr>::Err> where
F: FromStr,` [src]

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.

# Examples

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

#### `pub fn is_ascii(&self) -> bool`1.23.0[src]

Checks if all characters in this string are within the ASCII range.

# Examples

    let ascii = "hello!\n";
    let non_ascii = "Grüße, Jürgen ❤";

    assert!(ascii.is_ascii());
    assert!(!non_ascii.is_ascii());Run

#### `pub fn eq_ignore_ascii_case(&self, other: &str) -> bool`1.23.0[src]

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

Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`, but without allocating and copying temporaries.

# Examples

    assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
    assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
    assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));Run

#### `pub fn make_ascii_uppercase(&mut self)`1.23.0[src]

Converts this string to its ASCII upper case equivalent in-place.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use `to_ascii_uppercase`.

# Examples

    let mut s = String::from("Grüße, Jürgen ❤");

    s.make_ascii_uppercase();

    assert_eq!("GRüßE, JüRGEN ❤", s);Run

#### `pub fn make_ascii_lowercase(&mut self)`1.23.0[src]

Converts this string to its ASCII lower case equivalent in-place.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use `to_ascii_lowercase`.

# Examples

    let mut s = String::from("GRÜßE, JÜRGEN ❤");

    s.make_ascii_lowercase();

    assert_eq!("grÜße, jÜrgen ❤", s);Run

####
ⓘImportant traits for EscapeDebug<'a>

### Important traits for EscapeDebug<'a>

`impl<'a> Iterator for EscapeDebug<'a> type Item = char;`
`pub fn escape_debug(&self) -> EscapeDebug`1.34.0[src]

Return an iterator that escapes each char in `self` with `char::escape_debug`.

Note: only extended grapheme codepoints that begin the string will be escaped.

# Examples

As an iterator:

    for c in "❤\n!".escape_debug() {
        print!("{}", c);
    }
    println!();Run

Using `println!` directly:

    println!("{}", "❤\n!".escape_debug());Run

Both are equivalent to:

    println!("❤\\n!");Run

Using `to_string`:

    assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");Run

####
ⓘImportant traits for EscapeDefault<'a>

### Important traits for EscapeDefault<'a>

`impl<'a> Iterator for EscapeDefault<'a> type Item = char;`
`pub fn escape_default(&self) -> EscapeDefault`1.34.0[src]

Return an iterator that escapes each char in `self` with `char::escape_default`.

# Examples

As an iterator:

    for c in "❤\n!".escape_default() {
        print!("{}", c);
    }
    println!();Run

Using `println!` directly:

    println!("{}", "❤\n!".escape_default());Run

Both are equivalent to:

    println!("\\u{{2764}}\\n!");Run

Using `to_string`:

    assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");Run

####
ⓘImportant traits for EscapeUnicode<'a>

### Important traits for EscapeUnicode<'a>

`impl<'a> Iterator for EscapeUnicode<'a> type Item = char;`
`pub fn escape_unicode(&self) -> EscapeUnicode`1.34.0[src]

Return an iterator that escapes each char in `self` with `char::escape_unicode`.

# Examples

As an iterator:

    for c in "❤\n!".escape_unicode() {
        print!("{}", c);
    }
    println!();Run

Using `println!` directly:

    println!("{}", "❤\n!".escape_unicode());Run

Both are equivalent to:

    println!("\\u{{2764}}\\u{{a}}\\u{{21}}");Run

Using `to_string`:

    assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");Run

### `impl str`[src]

Methods for string slices.

####
ⓘImportant traits for Box<I>

### Important traits for Box<I>

`impl<I> Iterator for Box<I> where
I: Iterator, impl<I> Iterator for Box<I> where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<F> Future for Box<F> where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>`
`pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]>`1.20.0[src]

Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating.

# Examples

Basic usage:

    let s = "this is a string";
    let boxed_str = s.to_owned().into_boxed_str();
    let boxed_bytes = boxed_str.into_boxed_bytes();
    assert_eq!(*boxed_bytes, *s.as_bytes());Run

#### `#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replace<'a, P>(&'a self, from: P, to: &str) -> String where
P: Pattern<'a>,` [src]

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

#### `#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replacen<'a, P>(&'a self, pat: P, to: &str, count: usize) -> String where
P: Pattern<'a>,` 1.16.0[src]

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 `count` 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

#### `pub fn to_lowercase(&self) -> String`1.2.0[src]

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`.

Since some characters can expand into multiple characters when changing the case, this function returns a `String` instead of modifying the parameter in-place.

# 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

#### `pub fn to_uppercase(&self) -> String`1.2.0[src]

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`.

Since some characters can expand into multiple characters when changing the case, this function returns a `String` instead of modifying the parameter in-place.

# 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

One character can become multiple:

    let s = "tschüß";

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

#### `pub fn into_string(self: Box<str>) -> String`1.4.0[src]

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

#### `pub fn repeat(&self, n: usize) -> String`1.16.0[src]

Creates a new `String` by repeating a string `n` times.

# Panics

This function will panic if the capacity would overflow.

# Examples

Basic usage:

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

A panic upon overflow:

    fn main() {
        // this will panic at runtime
        "0123456789abcdef".repeat(usize::max_value());
    }Run

#### `pub fn to_ascii_uppercase(&self) -> String`1.23.0[src]

Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To uppercase the value in-place, use `make_ascii_uppercase`.

To uppercase ASCII characters in addition to non-ASCII characters, use `to_uppercase`.

# Examples

    let s = "Grüße, Jürgen ❤";

    assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());Run

#### `pub fn to_ascii_lowercase(&self) -> String`1.23.0[src]

Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To lowercase the value in-place, use `make_ascii_lowercase`.

To lowercase ASCII characters in addition to non-ASCII characters, use `to_lowercase`.

# Examples

    let s = "Grüße, Jürgen ❤";

    assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());Run

## Trait Implementations

### `impl Debug for str`[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

### `impl Hash for str`[src]

#### `fn hash<H>(&self, state: &mut H) where
H: Hasher,` [src]

Feeds this value into the given [`Hasher`]. Read more

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

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl Eq for str`[src]

### `impl PartialEq<str> for str`[src]

#### `fn eq(&self, other: &str) -> bool`[src]

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

#### `fn ne(&self, other: &str) -> bool`[src]

This method tests for `!=`.

### `impl<I> IndexMut<I> for str where
I: SliceIndex<str>,` [src]

#### `fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<str>>::Output`[src]

Performs the mutable indexing (`container[index]`) operation.

### `impl<'_> Default for &'_ str`[src]

#### `fn default() -> &'_ str`[src]

Creates an empty str

### `impl<'_> Default for &'_ mut str` 1.28.0[src]

#### `fn default() -> &'_ mut str`[src]

Creates an empty mutable str

### `impl PartialOrd<str> for str`[src]

Implements comparison operations on strings.

Strings are compared lexicographically by their byte values. This compares Unicode code points based on their positions in the code charts. This is not necessarily the same as "alphabetical" order, which varies by language and locale. Comparing strings according to culturally-accepted standards requires locale-specific data that is outside the scope of the `str` type.

#### `fn partial_cmp(&self, other: &str) -> Option<Ordering>`[src]

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

#### `#[must_use] fn lt(&self, other: &Rhs) -> bool`[src]

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

#### `#[must_use] fn le(&self, other: &Rhs) -> bool`[src]

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

#### `#[must_use] fn gt(&self, other: &Rhs) -> bool`[src]

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

#### `#[must_use] fn ge(&self, other: &Rhs) -> bool`[src]

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

### `impl Ord for str`[src]

Implements ordering of strings.

Strings are ordered lexicographically by their byte values. This orders Unicode code points based on their positions in the code charts. This is not necessarily the same as "alphabetical" order, which varies by language and locale. Sorting strings according to culturally-accepted standards requires locale-specific data that is outside the scope of the `str` type.

#### `fn cmp(&self, other: &str) -> Ordering`[src]

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

#### `fn max(self, other: Self) -> Self`1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `fn clamp(self, min: Self, max: Self) -> Self`[src]

🔬 This is a nightly-only experimental API. (`clamp` #44095)

Restrict a value to a certain interval. Read more

### `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.

#### `type Searcher = StrSearcher<'a, 'b>`

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Associated searcher for this pattern

#### `fn into_searcher(self, haystack: &'a str) -> StrSearcher<'a, 'b>`[src]

🔬 This is a nightly-only experimental API. (`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

#### `fn is_prefix_of(self, haystack: &'a str) -> bool`[src]

🔬 This is a nightly-only experimental API. (`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`[src]

🔬 This is a nightly-only experimental API. (`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`[src]

🔬 This is a nightly-only experimental API. (`pattern` #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches anywhere in the haystack

### `impl Display for str`[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

### `impl AsRef<[u8]> for str`[src]

####
ⓘImportant traits for &'_ [u8]

### Important traits for &'_ [u8]

`impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]`
`fn as_ref(&self) -> &[u8]`[src]

Performs the conversion.

### `impl AsRef<str> for str`[src]

#### `fn as_ref(&self) -> &str`[src]

Performs the conversion.

### `impl<I> Index<I> for str where
I: SliceIndex<str>,` [src]

#### `type Output = <I as SliceIndex<str>>::Output`

The returned type after indexing.

#### `fn index(&self, index: I) -> &<I as SliceIndex<str>>::Output`[src]

Performs the indexing (`container[index]`) operation.

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

#### `fn eq(&self, other: &Cow<'a, str>) -> bool`[src]

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`[src]

This method tests for `!=`.

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

#### `fn eq(&self, other: &String) -> bool`[src]

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

#### `fn ne(&self, other: &String) -> bool`[src]

This method tests for `!=`.

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

#### `fn eq(&self, other: &Cow<'a, str>) -> bool`[src]

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`[src]

This method tests for `!=`.

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

#### `fn eq(&self, other: &String) -> bool`[src]

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

#### `fn ne(&self, other: &String) -> bool`[src]

This method tests for `!=`.

### `impl ToOwned for str`[src]

#### `type Owned = String`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> String`[src]

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

#### `fn clone_into(&self, target: &mut String)`[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl ToString for str` 1.9.0[src]

#### `fn to_string(&self) -> String`[src]

Converts the given value to a `String`. Read more

### `impl AsciiExt for str`[src]

#### `type Owned = String`

Deprecated since 1.26.0:

use inherent methods instead

Container type for copied ASCII characters.

#### `fn is_ascii(&self) -> bool`[src]

Deprecated since 1.26.0:

use inherent methods instead

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

#### `fn to_ascii_uppercase(&self) -> Self::Owned`[src]

Deprecated since 1.26.0:

use inherent methods instead

Makes a copy of the value in its ASCII upper case equivalent. Read more

#### `fn to_ascii_lowercase(&self) -> Self::Owned`[src]

Deprecated since 1.26.0:

use inherent methods instead

Makes a copy of the value in its ASCII lower case equivalent. Read more

#### `fn eq_ignore_ascii_case(&self, o: &Self) -> bool`[src]

Deprecated since 1.26.0:

use inherent methods instead

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

#### `fn make_ascii_uppercase(&mut self)`[src]

Deprecated since 1.26.0:

use inherent methods instead

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

#### `fn make_ascii_lowercase(&mut self)`[src]

Deprecated since 1.26.0:

use inherent methods instead

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

### `impl ToSocketAddrs for str`[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>>`[src]

Converts this object to an iterator of resolved `SocketAddr`s. Read more

### `impl PartialEq<OsString> for str`[src]

#### `fn eq(&self, other: &OsString) -> bool`[src]

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

#### `#[must_use] fn ne(&self, other: &Rhs) -> bool`[src]

This method tests for `!=`.

### `impl<'a> PartialEq<OsString> for &'a str` 1.29.0[src]

#### `fn eq(&self, other: &OsString) -> bool`[src]

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

#### `#[must_use] fn ne(&self, other: &Rhs) -> bool`[src]

This method tests for `!=`.

### `impl PartialEq<OsStr> for str`[src]

#### `fn eq(&self, other: &OsStr) -> bool`[src]

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

#### `#[must_use] fn ne(&self, other: &Rhs) -> bool`[src]

This method tests for `!=`.

### `impl AsRef<OsStr> for str`[src]

#### `fn as_ref(&self) -> &OsStr`[src]

Performs the conversion.

### `impl AsRef<Path> for str`[src]

#### `fn as_ref(&self) -> &Path`[src]

Performs the conversion.

## Auto Trait Implementations

### `impl UnwindSafe for str`

### `impl RefUnwindSafe for str`

### `impl Unpin for str`

### `impl Send for str`

### `impl Sync for str`

## Blanket Implementations

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> T`[src]

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

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `default fn to_string(&self) -> String`[src]

Converts the given value to a `String`. Read more

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