pub struct String { /* fields omitted */ }
A UTF-8 encoded, growable string.
The String
type is the most common string type that has ownership over the contents of the string. It has a close relationship with its borrowed counterpart, the primitive str
.
You can create a String
from a literal string with String::from
:
let hello = String::from("Hello, world!");
You can append a char
to a String
with the push
method, and append a &str
with the push_str
method:
let mut hello = String::from("Hello, "); hello.push('w'); hello.push_str("orld!");
If you have a vector of UTF-8 bytes, you can create a String
from it with the from_utf8
method:
// some bytes, in a vector let sparkle_heart = vec![240, 159, 146, 150]; // We know these bytes are valid, so we'll use `unwrap()`. let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); assert_eq!("💖", sparkle_heart);
String
s are always valid UTF-8. This has a few implications, the first of which is that if you need a non-UTF-8 string, consider OsString
. It is similar, but without the UTF-8 constraint. The second implication is that you cannot index into a String
:
let s = "hello"; println!("The first letter of s is {}", s[0]); // ERROR!!!
Indexing is intended to be a constant-time operation, but UTF-8 encoding does not allow us to do this. Furthermore, it's not clear what sort of thing the index should return: a byte, a codepoint, or a grapheme cluster. The bytes
and chars
methods return iterators over the first two, respectively.
String
s implement Deref
<Target=str>
, and so inherit all of str
's methods. In addition, this means that you can pass a String
to a function which takes a &str
by using an ampersand (&
):
fn takes_str(s: &str) { } let s = String::from("Hello"); takes_str(&s);
This will create a &str
from the String
and pass it in. This conversion is very inexpensive, and so generally, functions will accept &str
s as arguments unless they need a String
for some specific reason.
In certain cases Rust doesn't have enough information to make this conversion, known as Deref
coercion. In the following example a string slice &'a str
implements the trait TraitExample
, and the function example_func
takes anything that implements the trait. In this case Rust would need to make two implicit conversions, which Rust doesn't have the means to do. For that reason, the following example will not compile.
trait TraitExample {} impl<'a> TraitExample for &'a str {} fn example_func<A: TraitExample>(example_arg: A) {} fn main() { let example_string = String::from("example_string"); example_func(&example_string); }
There are two options that would work instead. The first would be to change the line example_func(&example_string);
to example_func(example_string.as_str());
, using the method as_str()
to explicitly extract the string slice containing the string. The second way changes example_func(&example_string);
to example_func(&*example_string);
. In this case we are dereferencing a String
to a str
, then referencing the str
back to &str
. The second way is more idiomatic, however both work to do the conversion explicitly rather than relying on the implicit conversion.
A String
is made up of three components: a pointer to some bytes, a length, and a capacity. The pointer points to an internal buffer String
uses to store its data. The length is the number of bytes currently stored in the buffer, and the capacity is the size of the buffer in bytes. As such, the length will always be less than or equal to the capacity.
This buffer is always stored on the heap.
You can look at these with the as_ptr
, len
, and capacity
methods:
use std::mem; let story = String::from("Once upon a time..."); let ptr = story.as_ptr(); let len = story.len(); let capacity = story.capacity(); // story has nineteen bytes assert_eq!(19, len); // Now that we have our parts, we throw the story away. mem::forget(story); // We can re-build a String out of ptr, len, and capacity. This is all // unsafe because we are responsible for making sure the components are // valid: let s = unsafe { String::from_raw_parts(ptr as *mut _, len, capacity) } ; assert_eq!(String::from("Once upon a time..."), s);
If a String
has enough capacity, adding elements to it will not re-allocate. For example, consider this program:
let mut s = String::new(); println!("{}", s.capacity()); for _ in 0..5 { s.push_str("hello"); println!("{}", s.capacity()); }
This will output the following:
0 5 10 20 20 40
At first, we have no memory allocated at all, but as we append to the string, it increases its capacity appropriately. If we instead use the with_capacity
method to allocate the correct capacity initially:
let mut s = String::with_capacity(25); println!("{}", s.capacity()); for _ in 0..5 { s.push_str("hello"); println!("{}", s.capacity()); }
We end up with a different output:
25 25 25 25 25 25
Here, there's no need to allocate more memory inside the loop.
impl String
[src]
fn new() -> String
[src]
Creates a new empty String
.
Given that the String
is empty, this will not allocate any initial buffer. While that means that this initial operation is very inexpensive, but may cause excessive allocation later, when you add data. If you have an idea of how much data the String
will hold, consider the with_capacity
method to prevent excessive re-allocation.
Basic usage:
let s = String::new();
fn with_capacity(capacity: usize) -> String
[src]
Creates a new empty String
with a particular capacity.
String
s have an internal buffer to hold their data. The capacity is the length of that buffer, and can be queried with the capacity
method. This method creates an empty String
, but one with an initial buffer that can hold capacity
bytes. This is useful when you may be appending a bunch of data to the String
, reducing the number of reallocations it needs to do.
If the given capacity is 0
, no allocation will occur, and this method is identical to the new
method.
Basic usage:
let mut s = String::with_capacity(10); // The String contains no chars, even though it has capacity for more assert_eq!(s.len(), 0); // These are all done without reallocating... let cap = s.capacity(); for i in 0..10 { s.push('a'); } assert_eq!(s.capacity(), cap); // ...but this may make the vector reallocate s.push('a');
fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error>
[src]
Converts a vector of bytes to a String
.
A string slice (&str
) is made of bytes (u8
), and a vector of bytes (Vec<u8>
) is made of bytes, so this function converts between the two. Not all byte slices are valid String
s, however: String
requires that it is valid UTF-8. from_utf8()
checks to ensure that the bytes are valid UTF-8, and then does the conversion.
If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the validity check, there is an unsafe version of this function, from_utf8_unchecked
, which has the same behavior but skips the check.
This method will take care to not copy the vector, for efficiency's sake.
If you need a &str
instead of a String
, consider str::from_utf8
.
The inverse of this method is as_bytes
.
Returns Err
if the slice is not UTF-8 with a description as to why the provided bytes are not UTF-8. The vector you moved in is also included.
Basic usage:
// some bytes, in a vector let sparkle_heart = vec![240, 159, 146, 150]; // We know these bytes are valid, so we'll use `unwrap()`. let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); assert_eq!("💖", sparkle_heart);
Incorrect bytes:
// some invalid bytes, in a vector let sparkle_heart = vec![0, 159, 146, 150]; assert!(String::from_utf8(sparkle_heart).is_err());
See the docs for FromUtf8Error
for more details on what you can do with this error.
fn from_utf8_lossy(v: &'a [u8]) -> Cow<'a, str>
[src]
Converts a slice of bytes to a string, including invalid characters.
Strings are made of bytes (u8
), and a slice of bytes (&[u8]
) is made of bytes, so this function converts between the two. Not all byte slices are valid strings, however: strings are required to be valid UTF-8. During this conversion, from_utf8_lossy()
will replace any invalid UTF-8 sequences with U+FFFD REPLACEMENT CHARACTER
, which looks like this: �
If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the conversion, there is an unsafe version of this function, from_utf8_unchecked
, which has the same behavior but skips the checks.
This function returns a Cow<'a, str>
. If our byte slice is invalid UTF-8, then we need to insert the replacement characters, which will change the size of the string, and hence, require a String
. But if it's already valid UTF-8, we don't need a new allocation. This return type allows us to handle both cases.
Basic usage:
// some bytes, in a vector let sparkle_heart = vec![240, 159, 146, 150]; let sparkle_heart = String::from_utf8_lossy(&sparkle_heart); assert_eq!("💖", sparkle_heart);
Incorrect bytes:
// some invalid bytes let input = b"Hello \xF0\x90\x80World"; let output = String::from_utf8_lossy(input); assert_eq!("Hello �World", output);
fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error>
[src]
Decode a UTF-16 encoded vector v
into a String
, returning Err
if v
contains any invalid data.
Basic usage:
// 𝄞music let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0x0069, 0x0063]; assert_eq!(String::from("𝄞music"), String::from_utf16(v).unwrap()); // 𝄞mu<invalid>ic let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, 0xD800, 0x0069, 0x0063]; assert!(String::from_utf16(v).is_err());
fn from_utf16_lossy(v: &[u16]) -> String
[src]
Decode a UTF-16 encoded slice v
into a String
, replacing invalid data with the replacement character (U+FFFD).
Unlike from_utf8_lossy
which returns a Cow<'a, str>
, from_utf16_lossy
returns a String
since the UTF-16 to UTF-8 conversion requires a memory allocation.
Basic usage:
// 𝄞mus<invalid>ic<invalid> let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0xDD1E, 0x0069, 0x0063, 0xD834]; assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"), String::from_utf16_lossy(v));
unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String
[src]
Creates a new String
from a length, capacity, and pointer.
This is highly unsafe, due to the number of invariants that aren't checked:
ptr
needs to have been previously allocated by the same allocator the standard library uses.length
needs to be less than or equal to capacity
.capacity
needs to be the correct value.Violating these may cause problems like corrupting the allocator's internal data structures.
The ownership of ptr
is effectively transferred to the String
which may then deallocate, reallocate or change the contents of memory pointed to by the pointer at will. Ensure that nothing else uses the pointer after calling this function.
Basic usage:
use std::mem; unsafe { let s = String::from("hello"); let ptr = s.as_ptr(); let len = s.len(); let capacity = s.capacity(); mem::forget(s); let s = String::from_raw_parts(ptr as *mut _, len, capacity); assert_eq!(String::from("hello"), s); }
unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String
[src]
Converts a vector of bytes to a String
without checking that the string contains valid UTF-8.
See the safe version, from_utf8
, for more details.
This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the String
, as the rest of the standard library assumes that String
s are valid UTF-8.
Basic usage:
// some bytes, in a vector let sparkle_heart = vec![240, 159, 146, 150]; let sparkle_heart = unsafe { String::from_utf8_unchecked(sparkle_heart) }; assert_eq!("💖", sparkle_heart);
fn into_bytes(self) -> Vec<u8>
[src]
Converts a String
into a byte vector.
This consumes the String
, so we do not need to copy its contents.
Basic usage:
let s = String::from("hello"); let bytes = s.into_bytes(); assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
fn as_str(&self) -> &str
Extracts a string slice containing the entire string.
Basic usage:
let s = String::from("foo"); assert_eq!("foo", s.as_str());
fn as_mut_str(&mut self) -> &mut str
Converts a String
into a mutable string slice.
Basic usage:
let mut s = String::from("foobar"); let s_mut_str = s.as_mut_str(); s_mut_str.make_ascii_uppercase(); assert_eq!("FOOBAR", s_mut_str);
fn push_str(&mut self, string: &str)
[src]
Appends a given string slice onto the end of this String
.
Basic usage:
let mut s = String::from("foo"); s.push_str("bar"); assert_eq!("foobar", s);
fn capacity(&self) -> usize
[src]
Returns this String
's capacity, in bytes.
Basic usage:
let s = String::with_capacity(10); assert!(s.capacity() >= 10);
fn reserve(&mut self, additional: usize)
[src]
Ensures that this String
's capacity is at least additional
bytes larger than its length.
The capacity may be increased by more than additional
bytes if it chooses, to prevent frequent reallocations.
If you do not want this "at least" behavior, see the reserve_exact
method.
Panics if the new capacity overflows usize
.
Basic usage:
let mut s = String::new(); s.reserve(10); assert!(s.capacity() >= 10);
This may not actually increase the capacity:
let mut s = String::with_capacity(10); s.push('a'); s.push('b'); // s now has a length of 2 and a capacity of 10 assert_eq!(2, s.len()); assert_eq!(10, s.capacity()); // Since we already have an extra 8 capacity, calling this... s.reserve(8); // ... doesn't actually increase. assert_eq!(10, s.capacity());
fn reserve_exact(&mut self, additional: usize)
[src]
Ensures that this String
's capacity is additional
bytes larger than its length.
Consider using the reserve
method unless you absolutely know better than the allocator.
Panics if the new capacity overflows usize
.
Basic usage:
let mut s = String::new(); s.reserve_exact(10); assert!(s.capacity() >= 10);
This may not actually increase the capacity:
let mut s = String::with_capacity(10); s.push('a'); s.push('b'); // s now has a length of 2 and a capacity of 10 assert_eq!(2, s.len()); assert_eq!(10, s.capacity()); // Since we already have an extra 8 capacity, calling this... s.reserve_exact(8); // ... doesn't actually increase. assert_eq!(10, s.capacity());
fn shrink_to_fit(&mut self)
[src]
Shrinks the capacity of this String
to match its length.
Basic usage:
let mut s = String::from("foo"); s.reserve(100); assert!(s.capacity() >= 100); s.shrink_to_fit(); assert_eq!(3, s.capacity());
fn push(&mut self, ch: char)
[src]
Appends the given char
to the end of this String
.
Basic usage:
let mut s = String::from("abc"); s.push('1'); s.push('2'); s.push('3'); assert_eq!("abc123", s);
fn as_bytes(&self) -> &[u8]
[src]
Returns a byte slice of this String
's contents.
The inverse of this method is from_utf8
.
Basic usage:
let s = String::from("hello"); assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
fn truncate(&mut self, new_len: usize)
[src]
Shortens this String
to the specified length.
If new_len
is greater than the string's current length, this has no effect.
Note that this method has no effect on the allocated capacity of the string
Panics if new_len
does not lie on a char
boundary.
Basic usage:
let mut s = String::from("hello"); s.truncate(2); assert_eq!("he", s);
fn pop(&mut self) -> Option<char>
[src]
Removes the last character from the string buffer and returns it.
Returns None
if this String
is empty.
Basic usage:
let mut s = String::from("foo"); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('o')); assert_eq!(s.pop(), Some('f')); assert_eq!(s.pop(), None);
fn remove(&mut self, idx: usize) -> char
[src]
Removes a char
from this String
at a byte position and returns it.
This is an O(n)
operation, as it requires copying every element in the buffer.
Panics if idx
is larger than or equal to the String
's length, or if it does not lie on a char
boundary.
Basic usage:
let mut s = String::from("foo"); assert_eq!(s.remove(0), 'f'); assert_eq!(s.remove(1), 'o'); assert_eq!(s.remove(0), 'o');
fn retain<F>(&mut self, f: F) where
F: FnMut(char) -> bool,
[src]
Retains only the characters specified by the predicate.
In other words, remove all characters c
such that f(c)
returns false
. This method operates in place and preserves the order of the retained characters.
#![feature(string_retain)] let mut s = String::from("f_o_ob_ar"); s.retain(|c| c != '_'); assert_eq!(s, "foobar");
fn insert(&mut self, idx: usize, ch: char)
[src]
Inserts a character into this String
at a byte position.
This is an O(n)
operation as it requires copying every element in the buffer.
Panics if idx
is larger than the String
's length, or if it does not lie on a char
boundary.
Basic usage:
let mut s = String::with_capacity(3); s.insert(0, 'f'); s.insert(1, 'o'); s.insert(2, 'o'); assert_eq!("foo", s);
fn insert_str(&mut self, idx: usize, string: &str)
Inserts a string slice into this String
at a byte position.
This is an O(n)
operation as it requires copying every element in the buffer.
Panics if idx
is larger than the String
's length, or if it does not lie on a char
boundary.
Basic usage:
let mut s = String::from("bar"); s.insert_str(0, "foo"); assert_eq!("foobar", s);
unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8>
[src]
Returns a mutable reference to the contents of this String
.
This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the String
, as the rest of the standard library assumes that String
s are valid UTF-8.
Basic usage:
let mut s = String::from("hello"); unsafe { let vec = s.as_mut_vec(); assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]); vec.reverse(); } assert_eq!(s, "olleh");
fn len(&self) -> usize
[src]
Returns the length of this String
, in bytes.
Basic usage:
let a = String::from("foo"); assert_eq!(a.len(), 3);
fn is_empty(&self) -> bool
[src]
Returns true
if this String
has a length of zero.
Returns false
otherwise.
Basic usage:
let mut v = String::new(); assert!(v.is_empty()); v.push('a'); assert!(!v.is_empty());
fn split_off(&mut self, at: usize) -> String
Splits the string into two at the given index.
Returns a newly allocated String
. self
contains bytes [0, at)
, and the returned String
contains bytes [at, len)
. at
must be on the boundary of a UTF-8 code point.
Note that the capacity of self
does not change.
Panics if at
is not on a UTF-8
code point boundary, or if it is beyond the last code point of the string.
let mut hello = String::from("Hello, World!"); let world = hello.split_off(7); assert_eq!(hello, "Hello, "); assert_eq!(world, "World!");
fn clear(&mut self)
[src]
Truncates this String
, removing all contents.
While this means the String
will have a length of zero, it does not touch its capacity.
Basic usage:
let mut s = String::from("foo"); s.clear(); assert!(s.is_empty()); assert_eq!(0, s.len()); assert_eq!(3, s.capacity());
fn drain<R>(&mut self, range: R) -> Drain where
R: RangeArgument<usize>,
Creates a draining iterator that removes the specified range in the string and yields the removed chars.
Note: The element range is removed even if the iterator is not consumed until the end.
Panics if the starting point or end point do not lie on a char
boundary, or if they're out of bounds.
Basic usage:
let mut s = String::from("α is alpha, β is beta"); let beta_offset = s.find('β').unwrap_or(s.len()); // Remove the range up until the β from the string let t: String = s.drain(..beta_offset).collect(); assert_eq!(t, "α is alpha, "); assert_eq!(s, "β is beta"); // A full range clears the string s.drain(..); assert_eq!(s, "");
fn splice<R>(&mut self, range: R, replace_with: &str) where
R: RangeArgument<usize>,
[src]
Creates a splicing iterator that removes the specified range in the string, and replaces it with the given string. The given string doesn't need to be the same length as the range.
Note: Unlike Vec::splice
, the replacement happens eagerly, and this method does not return the removed chars.
Panics if the starting point or end point do not lie on a char
boundary, or if they're out of bounds.
Basic usage:
#![feature(splice)] let mut s = String::from("α is alpha, β is beta"); let beta_offset = s.find('β').unwrap_or(s.len()); // Replace the range up until the β from the string s.splice(..beta_offset, "Α is capital alpha; "); assert_eq!(s, "Α is capital alpha; β is beta");
fn into_boxed_str(self) -> Box<str>
Converts this String
into a Box
<
str
>
.
This will drop any excess capacity.
Basic usage:
let s = String::from("hello"); let b = s.into_boxed_str();
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.
Basic usage:
let len = "foo".len(); assert_eq!(3, len); let len = "ƒoo".len(); // fancy f! assert_eq!(4, len);
fn is_empty(&self) -> bool
[src]
Returns true
if self
has a length of zero bytes.
Basic usage:
let s = ""; assert!(s.is_empty()); let s = "not empty"; assert!(!s.is_empty());
fn is_char_boundary(&self, index: usize) -> bool
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()
.
let s = "Löwe 老虎 Léopard"; assert!(s.is_char_boundary(0)); // start of `老` assert!(s.is_char_boundary(6)); assert!(s.is_char_boundary(s.len())); // second byte of `ö` assert!(!s.is_char_boundary(2)); // third byte of `老` assert!(!s.is_char_boundary(8));
fn as_bytes(&self) -> &[u8]
[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.
Basic usage:
let bytes = "bors".as_bytes(); assert_eq!(b"bors", bytes);
unsafe fn as_bytes_mut(&mut self) -> &mut [u8]
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.
Basic usage:
let mut s = String::from("Hello"); let bytes = unsafe { s.as_bytes_mut() }; assert_eq!(b"Hello", bytes);
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);
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.
Basic usage:
let s = "Hello"; let ptr = s.as_ptr();
fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output> where
I: SliceIndex<str>,
Returns a subslice of str
.
This is the non-panicking alternative to indexing the str
. Returns None
whenever equivalent indexing operation would panic.
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());
fn get_mut<I>(&mut self, i: I) -> Option<&mut <I as SliceIndex<str>>::Output> where
I: SliceIndex<str>,
Returns a mutable subslice of str
.
This is the non-panicking alternative to indexing the str
. Returns None
whenever equivalent indexing operation would panic.
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);
unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Output where
I: SliceIndex<str>,
Returns a unchecked subslice of str
.
This is the unchecked alternative to indexing the str
.
Callers of this function are responsible that these preconditions are satisfied:
Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str
type.
let v = "🗻∈🌏"; unsafe { assert_eq!("🗻", v.get_unchecked(0..4)); assert_eq!("∈", v.get_unchecked(4..7)); assert_eq!("🌏", v.get_unchecked(7..11)); }
unsafe fn get_unchecked_mut<I>(
&mut self,
i: I
) -> &mut <I as SliceIndex<str>>::Output where
I: SliceIndex<str>,
Returns a mutable, unchecked subslice of str
.
This is the unchecked alternative to indexing the str
.
Callers of this function are responsible that these preconditions are satisfied:
Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str
type.
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)); }
unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str
[src]
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.
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.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)); }
unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str
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.
Callers of this function are responsible that three preconditions are satisfied:
begin
must come before end
.begin
and end
must be byte positions within the string slice.begin
and end
must lie on UTF-8 sequence boundaries.fn split_at(&self, mid: usize) -> (&str, &str)
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 if mid
is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.
Basic usage:
let s = "Per Martin-Löf"; let (first, last) = s.split_at(3); assert_eq!("Per", first); assert_eq!(" Martin-Löf", last);
fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)
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 if mid
is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.
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);
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.
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());
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());
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.
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());
Remember, char
s 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());
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.
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());
fn split_whitespace(&self) -> SplitWhitespace
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
.
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());
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());
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.
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());
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());
fn lines_any(&self) -> LinesAny
[src]
An iterator over the lines of a string.
fn encode_utf16(&self) -> EncodeUtf16
Returns an iterator of u16
over the string encoded as UTF-16.
Basic usage:
let text = "Zażółć gęślą jaźń"; let utf8_len = text.len(); let utf16_len = text.encode_utf16().count(); assert!(utf16_len <= utf8_len);
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.
Basic usage:
let bananas = "bananas"; assert!(bananas.contains("nana")); assert!(!bananas.contains("apples"));
fn starts_with<'a, P>(&'a self, pat: P) -> bool where
P: Pattern<'a>,
[src]
Returns true
if the given pattern matches a prefix of this string slice.
Returns false
if it does not.
Basic usage:
let bananas = "bananas"; assert!(bananas.starts_with("bana")); assert!(!bananas.starts_with("nana"));
fn ends_with<'a, P>(&'a self, pat: P) -> bool where
P: Pattern<'a>,
<P 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.
Basic usage:
let bananas = "bananas"; assert!(bananas.ends_with("anas")); assert!(!bananas.ends_with("nana"));
fn find<'a, P>(&'a self, pat: P) -> Option<usize> where
P: Pattern<'a>,
[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.
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));
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));
Not finding the pattern:
let s = "Löwe 老虎 Léopard"; let x: &[_] = &['1', '2']; assert_eq!(s.find(x), None);
fn rfind<'a, P>(&'a self, pat: P) -> Option<usize> where
P: Pattern<'a>,
<P 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.
Simple patterns:
let s = "Löwe 老虎 Léopard"; assert_eq!(s.rfind('L'), Some(13)); assert_eq!(s.rfind('é'), Some(14));
More complex patterns with closures:
let s = "Löwe 老虎 Léopard"; assert_eq!(s.rfind(char::is_whitespace), Some(12)); assert_eq!(s.rfind(char::is_lowercase), Some(20));
Not finding the pattern:
let s = "Löwe 老虎 Léopard"; let x: &[_] = &['1', '2']; assert_eq!(s.rfind(x), None);
fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where
P: Pattern<'a>,
[src]
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.
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.
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"]);
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"]);
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"]);
Contiguous separators are separated by the empty string.
let x = "(///)".to_string(); let d: Vec<_> = x.split('/').collect(); assert_eq!(d, &["(", "", "", ")"]);
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", ""]);
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", ""]);
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"]);
It does not give you:
assert_eq!(d, &["a", "b", "c"]);
Use split_whitespace
for this behavior.
fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where
P: Pattern<'a>,
<P 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 a &str
, char
, or a closure that determines the split.
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.
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"]);
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"]);
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 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.
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.
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", ""]);
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 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.
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.
let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect(); assert_eq!(v, ["B", "A"]); let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect(); assert_eq!(v, ["", "B", "", "A"]);
fn splitn<'a, P>(&'a self, 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 a &str
, char
, or a closure that determines the split.
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.
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, [""]);
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"]);
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 a &str
, char
, or a closure that determines the split.
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.
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"]);
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"]);
fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where
P: Pattern<'a>,
An iterator over the disjoint 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.
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.
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"]);
fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,
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.
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.
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"]);
fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where
P: Pattern<'a>,
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.
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.
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`
fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,
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.
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.
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`
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
.
Basic usage:
let s = " Hello\tworld\t"; assert_eq!("Hello\tworld", s.trim());
fn trim_left(&self) -> &str
[src]
Returns a string slice with leading whitespace removed.
'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space
.
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.
Basic usage:
let s = " Hello\tworld\t"; assert_eq!("Hello\tworld\t", s.trim_left());
Directionality:
let s = " English"; assert!(Some('E') == s.trim_left().chars().next()); let s = " עברית"; assert!(Some('ע') == s.trim_left().chars().next());
fn trim_right(&self) -> &str
[src]
Returns a string slice with trailing whitespace removed.
'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space
.
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.
Basic usage:
let s = " Hello\tworld\t"; assert_eq!(" Hello\tworld", s.trim_right());
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());
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.
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");
A more complex pattern, using a closure:
assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,
[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.
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.
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");
fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,
[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.
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.
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");
A more complex pattern, using a closure:
assert_eq!("1fooX".trim_left_matches(|c| c == '1' || c == 'X'), "fooX");
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.
Will return Err
if it's not possible to parse this string slice into the desired type.
Basic usage
let four: u32 = "4".parse().unwrap(); assert_eq!(4, four);
Using the 'turbofish' instead of annotating four
:
let four = "4".parse::<u32>(); assert_eq!(Ok(4), four);
Failing to parse:
let nope = "j".parse::<u32>(); assert!(nope.is_err());
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.
Basic usage:
let s = "this is old"; assert_eq!("this is new", s.replace("old", "new"));
When the pattern doesn't match:
let s = "this is old"; assert_eq!(s, s.replace("cookie monster", "little lamb"));
fn replacen<'a, P>(&'a self, pat: P, to: &str, count: usize) -> String where
P: Pattern<'a>,
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.
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));
When the pattern doesn't match:
let s = "this is old"; assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));
fn to_lowercase(&self) -> String
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.
Basic usage:
let s = "HELLO"; assert_eq!("hello", s.to_lowercase());
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());
Languages without case are not changed:
let new_year = "农历新年"; assert_eq!(new_year, new_year.to_lowercase());
fn to_uppercase(&self) -> String
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.
Basic usage:
let s = "hello"; assert_eq!("HELLO", s.to_uppercase());
Scripts without case are not changed:
let new_year = "农历新年"; assert_eq!(new_year, new_year.to_uppercase());
fn escape_debug(&self) -> String
[src]
Escapes each char in s
with char::escape_debug
.
fn escape_default(&self) -> String
[src]
Escapes each char in s
with char::escape_default
.
fn escape_unicode(&self) -> String
[src]
Escapes each char in s
with char::escape_unicode
.
fn repeat(&self, n: usize) -> String
Create a String
by repeating a string n
times.
Basic usage:
assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
fn is_ascii(&self) -> bool
Checks if all characters in this string are within the ASCII range.
let ascii = "hello!\n"; let non_ascii = "Grüße, Jürgen ❤"; assert!(ascii.is_ascii()); assert!(!non_ascii.is_ascii());
fn to_ascii_uppercase(&self) -> String
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
.
let s = "Grüße, Jürgen ❤"; assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());
fn to_ascii_lowercase(&self) -> String
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
.
let s = "Grüße, Jürgen ❤"; assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());
fn eq_ignore_ascii_case(&self, other: &str) -> bool
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.
assert!("Ferris".eq_ignore_ascii_case("FERRIS")); assert!("Ferrös".eq_ignore_ascii_case("FERRöS")); assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
fn make_ascii_uppercase(&mut self)
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
.
fn make_ascii_lowercase(&mut self)
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
.
fn is_ascii_alphabetic(&self) -> bool
[src]
Checks if all characters of this string are ASCII alphabetic characters:
fn is_ascii_uppercase(&self) -> bool
[src]
Checks if all characters of this string are ASCII uppercase characters: U+0041 'A' ... U+005A 'Z'.
#![feature(ascii_ctype)] // Only ascii uppercase characters assert!("HELLO".is_ascii_uppercase()); // While all characters are ascii, 'y' and 'e' are not uppercase assert!(!"Bye".is_ascii_uppercase()); // While all characters are uppercase, 'Ü' is not ascii assert!(!"TSCHÜSS".is_ascii_uppercase());
fn is_ascii_lowercase(&self) -> bool
[src]
Checks if all characters of this string are ASCII lowercase characters: U+0061 'a' ... U+007A 'z'.
#![feature(ascii_ctype)] // Only ascii uppercase characters assert!("hello".is_ascii_lowercase()); // While all characters are ascii, 'B' is not lowercase assert!(!"Bye".is_ascii_lowercase()); // While all characters are lowercase, 'Ü' is not ascii assert!(!"tschüss".is_ascii_lowercase());
fn is_ascii_alphanumeric(&self) -> bool
[src]
Checks if all characters of this string are ASCII alphanumeric characters:
fn is_ascii_digit(&self) -> bool
[src]
Checks if all characters of this string are ASCII decimal digit: U+0030 '0' ... U+0039 '9'.
fn is_ascii_hexdigit(&self) -> bool
[src]
Checks if all characters of this string are ASCII hexadecimal digits:
fn is_ascii_punctuation(&self) -> bool
[src]
Checks if all characters of this string are ASCII punctuation characters:
! " # $ % & ' ( ) * + , - . /
, or: ; < = > ? @
, or[ \ ] ^ _ `
, or{ | } ~
fn is_ascii_graphic(&self) -> bool
[src]
Checks if all characters of this string are ASCII graphic characters: U+0021 '@' ... U+007E '~'.
fn is_ascii_whitespace(&self) -> bool
[src]
Checks if all characters of this string are ASCII whitespace characters: U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED, U+000C FORM FEED, or U+000D CARRIAGE RETURN.
Rust uses the WhatWG Infra Standard's definition of ASCII whitespace. There are several other definitions in wide use. For instance, the POSIX locale includes U+000B VERTICAL TAB as well as all the above characters, but—from the very same specification—the default rule for "field splitting" in the Bourne shell considers only SPACE, HORIZONTAL TAB, and LINE FEED as whitespace.
If you are writing a program that will process an existing file format, check what that format's definition of whitespace is before using this function.
fn is_ascii_control(&self) -> bool
[src]
Checks if all characters of this string are ASCII control characters:
Note that most ASCII whitespace characters are control characters, but SPACE is not.
impl<'a> From<&'a str> for String
[src]
fn from(s: &'a str) -> String
[src]
Performs the conversion.
impl From<String> for Box<str>
fn from(s: String) -> Box<str>
[src]
Performs the conversion.
impl<'a> From<String> for Cow<'a, str>
[src]
fn from(s: String) -> Cow<'a, str>
[src]
Performs the conversion.
impl From<String> for Rc<str>
fn from(v: String) -> Rc<str>
[src]
Performs the conversion.
impl<'a> From<Cow<'a, str>> for String
fn from(s: Cow<'a, str>) -> String
[src]
Performs the conversion.
impl From<String> for Arc<str>
fn from(v: String) -> Arc<str>
[src]
Performs the conversion.
impl From<Box<str>> for String
fn from(s: Box<str>) -> String
[src]
Performs the conversion.
impl From<String> for Vec<u8>
fn from(string: String) -> Vec<u8>
[src]
Performs the conversion.
impl PartialOrd<String> for String
[src]
fn partial_cmp(&self, __arg_0: &String) -> Option<Ordering>
[src]
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, __arg_0: &String) -> bool
[src]
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, __arg_0: &String) -> bool
[src]
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, __arg_0: &String) -> bool
[src]
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, __arg_0: &String) -> bool
[src]
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl Write for String
[src]
fn write_str(&mut self, s: &str) -> Result<(), Error>
[src]
Writes a slice of bytes into this writer, returning whether the write succeeded. Read more
fn write_char(&mut self, c: char) -> Result<(), Error>
[src]
Writes a [char
] into this writer, returning whether the write succeeded. Read more
fn write_fmt(&mut self, args: Arguments) -> Result<(), Error>
[src]
Glue for usage of the [write!
] macro with implementors of this trait. Read more
impl<'a> Add<&'a str> for String
[src]
Implements the +
operator for concatenating two strings.
This consumes the String
on the left-hand side and re-uses its buffer (growing it if necessary). This is done to avoid allocating a new String
and copying the entire contents on every operation, which would lead to O(n^2)
running time when building an n
-byte string by repeated concatenation.
The string on the right-hand side is only borrowed; its contents are copied into the returned String
.
Concatenating two String
s takes the first by value and borrows the second:
let a = String::from("hello"); let b = String::from(" world"); let c = a + &b; // `a` is moved and can no longer be used here.
If you want to keep using the first String
, you can clone it and append to the clone instead:
let a = String::from("hello"); let b = String::from(" world"); let c = a.clone() + &b; // `a` is still valid here.
Concatenating &str
slices can be done by converting the first to a String
:
let a = "hello"; let b = " world"; let c = a.to_string() + b;
type Output = String
The resulting type after applying the +
operator.
fn add(self, other: &str) -> String
[src]
Performs the +
operation.
impl<'a, 'b> PartialEq<str> for String
[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<'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<'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<String> for Cow<'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<&'a str> for String
[src]
fn eq(&self, other: &&'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: &&'a str) -> bool
[src]
This method tests for !=
.
impl<'a, 'b> PartialEq<Cow<'a, str>> for String
[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 PartialEq<String> for String
[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 Default for String
[src]
fn default() -> String
[src]
Creates an empty String
.
impl FromStr for String
[src]
type Err = ParseError
The associated error which can be returned from parsing.
fn from_str(s: &str) -> Result<String, ParseError>
[src]
Parses a string s
to return a value of this type. Read more
impl Debug for String
[src]
fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
[src]
Formats the value using the given formatter. Read more
impl<'a> AddAssign<&'a str> for String
Implements the +=
operator for appending to a String
.
This has the same behavior as the push_str
method.
fn add_assign(&mut self, other: &str)
[src]
Performs the +=
operation.
impl Borrow<str> for String
[src]
fn borrow(&self) -> &str
[src]
Immutably borrows from an owned value. Read more
impl DerefMut for String
fn deref_mut(&mut self) -> &mut str
[src]
Mutably dereferences the value.
impl FromIterator<char> for String
[src]
fn from_iter<I>(iter: I) -> String where
I: IntoIterator<Item = char>,
[src]
Creates a value from an iterator. Read more
impl<'a> FromIterator<&'a str> for String
[src]
fn from_iter<I>(iter: I) -> String where
I: IntoIterator<Item = &'a str>,
[src]
Creates a value from an iterator. Read more
impl<'a> FromIterator<String> for Cow<'a, str>
fn from_iter<I>(it: I) -> Cow<'a, str> where
I: IntoIterator<Item = String>,
[src]
Creates a value from an iterator. Read more
impl<'a> FromIterator<&'a char> for String
fn from_iter<I>(iter: I) -> String where
I: IntoIterator<Item = &'a char>,
[src]
Creates a value from an iterator. Read more
impl FromIterator<String> for String
fn from_iter<I>(iter: I) -> String where
I: IntoIterator<Item = String>,
[src]
Creates a value from an iterator. Read more
impl<'a> FromIterator<Cow<'a, str>> for String
fn from_iter<I>(iter: I) -> String where
I: IntoIterator<Item = Cow<'a, str>>,
[src]
Creates a value from an iterator. Read more
impl Index<RangeTo<usize>> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, index: RangeTo<usize>) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl Index<RangeInclusive<usize>> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, index: RangeInclusive<usize>) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl Index<Range<usize>> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, index: Range<usize>) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl Index<RangeFrom<usize>> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, index: RangeFrom<usize>) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl Index<RangeFull> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, _index: RangeFull) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl Index<RangeToInclusive<usize>> for String
[src]
type Output = str
The returned type after indexing.
fn index(&self, index: RangeToInclusive<usize>) -> &str
[src]
Performs the indexing (container[index]
) operation.
impl<'a, 'b> Pattern<'a> for &'b String
[src]
A convenience impl that delegates to the impl for &str
type Searcher = <&'b str as Pattern<'a>>::Searcher
Associated searcher for this pattern
fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher
[src]
Constructs the associated searcher from self
and the haystack
to search in. Read more
fn is_contained_in(self, haystack: &'a str) -> bool
[src]
Checks whether the pattern matches anywhere in the haystack
fn is_prefix_of(self, haystack: &'a str) -> bool
[src]
Checks whether the pattern matches at the front of the haystack
fn is_suffix_of(self, haystack: &'a str) -> bool where
Self::Searcher: ReverseSearcher<'a>,
[src]
Checks whether the pattern matches at the back of the haystack
impl Hash for String
[src]
fn hash<H>(&self, hasher: &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,
Feeds a slice of this type into the given [Hasher
]. Read more
impl AsRef<str> for String
[src]
fn as_ref(&self) -> &str
[src]
Performs the conversion.
impl AsRef<[u8]> for String
[src]
fn as_ref(&self) -> &[u8]
[src]
Performs the conversion.
impl<'a> Extend<Cow<'a, str>> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = Cow<'a, str>>,
[src]
Extends a collection with the contents of an iterator. Read more
impl<'a> Extend<&'a char> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a char>,
[src]
Extends a collection with the contents of an iterator. Read more
impl Extend<char> for String
[src]
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = char>,
[src]
Extends a collection with the contents of an iterator. Read more
impl Extend<String> for String
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = String>,
[src]
Extends a collection with the contents of an iterator. Read more
impl<'a> Extend<&'a str> for String
[src]
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a str>,
[src]
Extends a collection with the contents of an iterator. Read more
impl Deref for String
[src]
type Target = str
The resulting type after dereferencing.
fn deref(&self) -> &str
[src]
Dereferences the value.
impl ToString for String
fn to_string(&self) -> String
[src]
Converts the given value to a String
. Read more
impl Clone for String
[src]
fn clone(&self) -> String
[src]
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &String)
[src]
Performs copy-assignment from source
. Read more
impl Eq for String
[src]
impl Display for String
[src]
fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
[src]
Formats the value using the given formatter. Read more
impl Ord for String
[src]
fn cmp(&self, __arg_0: &String) -> Ordering
[src]
This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
impl IndexMut<RangeFrom<usize>> for String
fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl IndexMut<RangeToInclusive<usize>> for String
[src]
fn index_mut(&mut self, index: RangeToInclusive<usize>) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl IndexMut<Range<usize>> for String
fn index_mut(&mut self, index: Range<usize>) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl IndexMut<RangeFull> for String
fn index_mut(&mut self, _index: RangeFull) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl IndexMut<RangeInclusive<usize>> for String
[src]
fn index_mut(&mut self, index: RangeInclusive<usize>) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl IndexMut<RangeTo<usize>> for String
fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str
[src]
Performs the mutable indexing (container[index]
) operation.
impl From<String> for Box<Error + Send + Sync>
[src]
fn from(err: String) -> Box<Error + Send + Sync>
[src]
Performs the conversion.
impl From<String> for Box<Error>
fn from(str_err: String) -> Box<Error>
[src]
Performs the conversion.
impl From<String> for OsString
[src]
fn from(s: String) -> OsString
[src]
Performs the conversion.
impl AsRef<OsStr> for String
[src]
fn as_ref(&self) -> &OsStr
[src]
Performs the conversion.
impl ToSocketAddrs for String
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 From<String> for PathBuf
[src]
fn from(s: String) -> PathBuf
[src]
Performs the conversion.
impl AsRef<Path> for String
[src]
fn as_ref(&self) -> &Path
[src]
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/string/struct.String.html