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

# 1.0.0[−]Primitive Type reference

References, both shared and mutable.

A reference represents a borrow of some owned value. You can get one by using the `&` or `&mut` operators on a value, or by using a `ref` or `ref mut` pattern.

For those familiar with pointers, a reference is just a pointer that is assumed to be aligned, not null, and pointing to memory containing a valid value of `T` - for example, `&bool` can only point to an allocation containing the integer values `1` (`true`) or `0` (`false`), but creating a `&bool` that points to an allocation containing the value `3` causes undefined behaviour. In fact, `Option<&T>` has the same memory representation as a nullable but aligned pointer, and can be passed across FFI boundaries as such.

In most cases, references can be used much like the original value. Field access, method calling, and indexing work the same (save for mutability rules, of course). In addition, the comparison operators transparently defer to the referent's implementation, allowing references to be compared the same as owned values.

References have a lifetime attached to them, which represents the scope for which the borrow is valid. A lifetime is said to "outlive" another one if its representative scope is as long or longer than the other. The `'static` lifetime is the longest lifetime, which represents the total life of the program. For example, string literals have a `'static` lifetime because the text data is embedded into the binary of the program, rather than in an allocation that needs to be dynamically managed.

`&mut T` references can be freely coerced into `&T` references with the same referent type, and references with longer lifetimes can be freely coerced into references with shorter ones.

Reference equality by address, instead of comparing the values pointed to, is accomplished via implicit reference-pointer coercion and raw pointer equality via `ptr::eq`, while `PartialEq` compares values.

    use std::ptr;

    let five = 5;
    let other_five = 5;
    let five_ref = &five;
    let same_five_ref = &five;
    let other_five_ref = &other_five;

    assert!(five_ref == same_five_ref);
    assert!(five_ref == other_five_ref);

    assert!(ptr::eq(five_ref, same_five_ref));
    assert!(!ptr::eq(five_ref, other_five_ref));

Run

For more information on how to use references, see the book's section on "References and Borrowing".

# Trait implementations

The following traits are implemented for all `&T`, regardless of the type of its referent:

- `Copy`
- `Clone` (Note that this will not defer to `T`'s `Clone` implementation if it exists!)
- `Deref`
- `Borrow`
- `Pointer`

`&mut T` references get all of the above except `Copy` and `Clone` (to prevent creating multiple simultaneous mutable borrows), plus the following, regardless of the type of its referent:

- `DerefMut`
- `BorrowMut`

The following traits are implemented on `&T` references if the underlying `T` also implements that trait:

- All the traits in `std::fmt` except `Pointer` and `fmt::Write`
- `PartialOrd`
- `Ord`
- `PartialEq`
- `Eq`
- `AsRef`
- `Fn` (in addition, `&T` references get `FnMut` and `FnOnce` if `T: Fn`)
- `Hash`
- `ToSocketAddrs`

`&mut T` references get all of the above except `ToSocketAddrs`, plus the following, if `T` implements that trait:

- `AsMut`
- `FnMut` (in addition, `&mut T` references get `FnOnce` if `T: FnMut`)
- `fmt::Write`
- `Iterator`
- `DoubleEndedIterator`
- `ExactSizeIterator`
- `FusedIterator`
- `TrustedLen`
- `Send` (note that `&T` references only get `Send` if `T: Sync`)
- `io::Write`
- `Read`
- `Seek`
- `BufRead`

Note that due to method call deref coercion, simply calling a trait method will act like they work on references as well as they do on owned values! The implementations described here are meant for generic contexts, where the final type `T` is a type parameter or otherwise not locally known.

## Trait Implementations

### `impl<'_, A> AllocRef for &'_ mut A where
A: AllocRef + ?Sized,` [src]

#### `fn alloc(
&mut self,
layout: Layout,
init: AllocInit
) -> Result<MemoryBlock, AllocErr>`[src]

🔬 This is a nightly-only experimental API. (`allocator_api` #32838)

Attempts to allocate a block of memory. Read more

#### `unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout)`[src]

🔬 This is a nightly-only experimental API. (`allocator_api` #32838)

Deallocates the memory referenced by `ptr`. Read more

#### `unsafe fn grow(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
placement: ReallocPlacement,
init: AllocInit
) -> Result<MemoryBlock, AllocErr>`[src]

🔬 This is a nightly-only experimental API. (`allocator_api` #32838)

Attempts to extend the memory block. Read more

#### `unsafe fn shrink(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize,
placement: ReallocPlacement
) -> Result<MemoryBlock, AllocErr>`[src]

🔬 This is a nightly-only experimental API. (`allocator_api` #32838)

Attempts to shrink the memory block. Read more

#### `fn by_ref(&mut self) -> &mut Self`[src]

🔬 This is a nightly-only experimental API. (`allocator_api` #32838)

Creates a "by reference" adaptor for this instance of `AllocRef`. Read more

### `impl<'_, T, U> AsMut<U> for &'_ mut T where
T: AsMut<U> + ?Sized,
U: ?Sized,` [src]

#### `fn as_mut(&mut self) -> &mut U`[src]

Performs the conversion.

### `impl<'_, T, U> AsRef<U> for &'_ mut T where
T: AsRef<U> + ?Sized,
U: ?Sized,` [src]

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

Performs the conversion.

### `impl<'_, T, U> AsRef<U> for &'_ T where
T: AsRef<U> + ?Sized,
U: ?Sized,` [src]

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

Performs the conversion.

### `impl<'_, T> Binary for &'_ T where
T: Binary + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> Binary for &'_ mut T where
T: Binary + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> Borrow<T> for &'_ T where
T: ?Sized,` [src]

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

Immutably borrows from an owned value. Read more

### `impl<'_, T> Borrow<T> for &'_ mut T where
T: ?Sized,` [src]

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

Immutably borrows from an owned value. Read more

### `impl<'_, T> BorrowMut<T> for &'_ mut T where
T: ?Sized,` [src]

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

Mutably borrows from an owned value. Read more

### `impl<'_, B: BufRead + ?Sized> BufRead for &'_ mut B`[src]

#### `fn fill_buf(&mut self) -> Result<&[u8]>`[src]

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more

#### `fn consume(&mut self, amt: usize)`[src]

Tells this buffer that `amt` bytes have been consumed from the buffer, so they should no longer be returned in calls to `read`. Read more

#### `fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>`[src]

Read all bytes into `buf` until the delimiter `byte` or EOF is reached. Read more

#### `fn read_line(&mut self, buf: &mut String) -> Result<usize>`[src]

Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. Read more

#### `fn split(self, byte: u8) -> Split<Self> where
Self: Sized,` [src]

Returns an iterator over the contents of this reader split on the byte `byte`. Read more

#### `fn lines(self) -> Lines<Self> where
Self: Sized,` [src]

Returns an iterator over the lines of this reader. Read more

### `impl<'_, T> !Clone for &'_ mut T where
T: ?Sized,` [src]

Shared references can be cloned, but mutable references cannot!

#### `#[must_use = "cloning is often expensive and is not expected to have side effects"]fn clone(&self) -> Self`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from `source`. Read more

### `impl<'_, T> Clone for &'_ T where
T: ?Sized,` [src]

Shared references can be cloned, but mutable references cannot!

#### `fn clone(&self) -> &'_ T`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from `source`. Read more

### `impl<'a, 'b, T, U> CoerceUnsized<&'a U> for &'b T where
'b: 'a,
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, 'b, T, U> CoerceUnsized<&'a U> for &'b mut T where
'b: 'a,
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, T, U> CoerceUnsized<&'a mut U> for &'a mut T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, T, U> CoerceUnsized<*const U> for &'a T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, T, U> CoerceUnsized<*const U> for &'a mut T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, T, U> CoerceUnsized<*mut U> for &'a mut T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'_, T> Copy for &'_ T where
T: ?Sized,` [src]

Shared references can be copied, but mutable references cannot!

### `impl<'_, T> Debug for &'_ T where
T: Debug + ?Sized,` [src]

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

Formats the value using the given formatter. Read more

### `impl<'_, T> Debug for &'_ mut T where
T: Debug + ?Sized,` [src]

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

Formats the value using the given formatter. Read more

### `impl<'_, T> Deref for &'_ mut T where
T: ?Sized,` [src]

#### `type Target = T`

The resulting type after dereferencing.

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

Dereferences the value.

### `impl<'_, T> Deref for &'_ T where
T: ?Sized,` [src]

#### `type Target = T`

The resulting type after dereferencing.

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

Dereferences the value.

### `impl<'_, T> !DerefMut for &'_ T where
T: ?Sized,` [src]

#### `fn deref_mut(&mut self) -> &mut Self::Target`[src]

Mutably dereferences the value.

### `impl<'_, T> DerefMut for &'_ mut T where
T: ?Sized,` [src]

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

Mutably dereferences the value.

### `impl<'a, T, U> DispatchFromDyn<&'a U> for &'a T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'a, T, U> DispatchFromDyn<&'a mut U> for &'a mut T where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<'_, T> Display for &'_ T where
T: Display + ?Sized,` [src]

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

Formats the value using the given formatter. Read more

### `impl<'_, T> Display for &'_ mut T where
T: Display + ?Sized,` [src]

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

Formats the value using the given formatter. Read more

### `impl<'a, I> DoubleEndedIterator for &'a mut I where
I: DoubleEndedIterator + ?Sized,` [src]

#### `fn next_back(&mut self) -> Option<<I as Iterator>::Item>`[src]

Removes and returns an element from the end of the iterator. Read more

#### `fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item>`[src]

Returns the `n`th element from the end of the iterator. Read more

#### `fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,` 1.27.0[src]

This is the reverse version of [`try_fold()`]: it takes elements starting from the back of the iterator. Read more

#### `fn rfold<B, F>(self, init: B, f: F) -> B where
F: FnMut(B, Self::Item) -> B,` 1.27.0[src]

An iterator method that reduces the iterator's elements to a single, final value, starting from the back. Read more

#### `fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,` 1.27.0[src]

Searches for an element of an iterator from the back that satisfies a predicate. Read more

### `impl<'_, A> Eq for &'_ mut A where
A: Eq + ?Sized,` [src]

### `impl<'_, A> Eq for &'_ A where
A: Eq + ?Sized,` [src]

### `impl<'_, I> ExactSizeIterator for &'_ mut I where
I: ExactSizeIterator + ?Sized,` [src]

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

Returns the exact length of the iterator. Read more

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

🔬 This is a nightly-only experimental API. (`exact_size_is_empty` #35428)

Returns `true` if the iterator is empty. Read more

### `impl<'_, A, F> Fn<A> for &'_ F where
F: Fn<A> + ?Sized,` [src]

#### `extern "rust-call" fn call(&self, args: A) -> <F as FnOnce<A>>::Output`[src]

🔬 This is a nightly-only experimental API. (`fn_traits` #29625)

Performs the call operation.

### `impl<'_, A, F> FnMut<A> for &'_ mut F where
F: FnMut<A> + ?Sized,` [src]

#### `extern "rust-call" fn call_mut(&mut self, args: A) -> <F as FnOnce<A>>::Output`[src]

🔬 This is a nightly-only experimental API. (`fn_traits` #29625)

Performs the call operation.

### `impl<'_, A, F> FnMut<A> for &'_ F where
F: Fn<A> + ?Sized,` [src]

#### `extern "rust-call" fn call_mut(&mut self, args: A) -> <F as FnOnce<A>>::Output`[src]

🔬 This is a nightly-only experimental API. (`fn_traits` #29625)

Performs the call operation.

### `impl<'_, A, F> FnOnce<A> for &'_ mut F where
F: FnMut<A> + ?Sized,` [src]

#### `type Output = <F as FnOnce<A>>::Output`

The returned type after the call operator is used.

#### `extern "rust-call" fn call_once(self, args: A) -> <F as FnOnce<A>>::Output`[src]

🔬 This is a nightly-only experimental API. (`fn_traits` #29625)

Performs the call operation.

### `impl<'_, A, F> FnOnce<A> for &'_ F where
F: Fn<A> + ?Sized,` [src]

#### `type Output = <F as FnOnce<A>>::Output`

The returned type after the call operator is used.

#### `extern "rust-call" fn call_once(self, args: A) -> <F as FnOnce<A>>::Output`[src]

🔬 This is a nightly-only experimental API. (`fn_traits` #29625)

Performs the call operation.

### `impl<'_, I> FusedIterator for &'_ mut I where
I: FusedIterator + ?Sized,` 1.26.0[src]

### `impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,` 1.36.0[src]

#### `type Output = <F as Future>::Output`

The type of value produced on completion.

#### `fn poll(
self: Pin<&mut &'_ mut F>,
cx: &mut Context
) -> Poll<<&'_ mut F as Future>::Output>`[src]

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

### `impl<'_, G, R> Generator<R> for &'_ mut G where
G: Unpin + Generator<R> + ?Sized,` [src]

#### `type Yield = <G as Generator<R>>::Yield`

🔬 This is a nightly-only experimental API. (`generator_trait` #43122)

The type of value this generator yields. Read more

#### `type Return = <G as Generator<R>>::Return`

🔬 This is a nightly-only experimental API. (`generator_trait` #43122)

The type of value this generator returns. Read more

#### `fn resume(
self: Pin<&mut &'_ mut G>,
arg: R
) -> GeneratorState<<&'_ mut G as Generator<R>>::Yield, <&'_ mut G as Generator<R>>::Return>`[src]

🔬 This is a nightly-only experimental API. (`generator_trait` #43122)

Resumes the execution of this generator. Read more

### `impl<'_, T> Hash for &'_ T where
T: Hash + ?Sized,` [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<'_, T> Hash for &'_ mut T where
T: Hash + ?Sized,` [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<'_, H> Hasher for &'_ mut H where
H: Hasher + ?Sized,` 1.22.0[src]

#### `fn finish(&self) -> u64`[src]

Returns the hash value for the values written so far. Read more

#### `fn write(&mut self, bytes: &[u8])`[src]

Writes some data into this `Hasher`. Read more

#### `fn write_u8(&mut self, i: u8)`[src]

Writes a single `u8` into this hasher.

#### `fn write_u16(&mut self, i: u16)`[src]

Writes a single `u16` into this hasher.

#### `fn write_u32(&mut self, i: u32)`[src]

Writes a single `u32` into this hasher.

#### `fn write_u64(&mut self, i: u64)`[src]

Writes a single `u64` into this hasher.

#### `fn write_u128(&mut self, i: u128)`[src]

Writes a single `u128` into this hasher.

#### `fn write_usize(&mut self, i: usize)`[src]

Writes a single `usize` into this hasher.

#### `fn write_i8(&mut self, i: i8)`[src]

Writes a single `i8` into this hasher.

#### `fn write_i16(&mut self, i: i16)`[src]

Writes a single `i16` into this hasher.

#### `fn write_i32(&mut self, i: i32)`[src]

Writes a single `i32` into this hasher.

#### `fn write_i64(&mut self, i: i64)`[src]

Writes a single `i64` into this hasher.

#### `fn write_i128(&mut self, i: i128)`[src]

Writes a single `i128` into this hasher.

#### `fn write_isize(&mut self, i: isize)`[src]

Writes a single `isize` into this hasher.

### `impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,` [src]

#### `type Item = <I as Iterator>::Item`

The type of the elements being iterated over.

#### `fn next(&mut self) -> Option<<I as Iterator>::Item>`[src]

Advances the iterator and returns the next value. Read more

#### `fn size_hint(&self) -> (usize, Option<usize>)`[src]

Returns the bounds on the remaining length of the iterator. Read more

#### `fn nth(&mut self, n: usize) -> Option<<&'_ mut I as Iterator>::Item>`[src]

Returns the `n`th element of the iterator. Read more

#### `fn count(self) -> usize`[src]

Consumes the iterator, counting the number of iterations and returning it. Read more

#### `fn last(self) -> Option<Self::Item>`[src]

Consumes the iterator, returning the last element. Read more

#### `fn step_by(self, step: usize) -> StepBy<Self>`1.28.0[src]

Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more

#### `fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator<Item = Self::Item>,` [src]

Takes two iterators and creates a new iterator over both in sequence. Read more

#### `fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,` [src]

'Zips up' two iterators into a single iterator of pairs. Read more

#### `fn map<B, F>(self, f: F) -> Map<Self, F> where
F: FnMut(Self::Item) -> B,` [src]

Takes a closure and creates an iterator which calls that closure on each element. Read more

#### `fn for_each<F>(self, f: F) where
F: FnMut(Self::Item),` 1.21.0[src]

Calls a closure on each element of an iterator. Read more

#### `fn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,` [src]

Creates an iterator which uses a closure to determine if an element should be yielded. Read more

#### `fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
F: FnMut(Self::Item) -> Option<B>,` [src]

Creates an iterator that both filters and maps. Read more

#### `fn enumerate(self) -> Enumerate<Self>`[src]

Creates an iterator which gives the current iteration count as well as the next value. Read more

#### `fn peekable(self) -> Peekable<Self>`[src]

Creates an iterator which can use `peek` to look at the next element of the iterator without consuming it. Read more

#### `fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,` [src]

Creates an iterator that [`skip`]s elements based on a predicate. Read more

#### `fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,` [src]

Creates an iterator that yields elements based on a predicate. Read more

#### `fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
P: FnMut(Self::Item) -> Option<B>,` [src]

🔬 This is a nightly-only experimental API. (`iter_map_while` #68537)

recently added

Creates an iterator that both yields elements based on a predicate and maps. Read more

#### `fn skip(self, n: usize) -> Skip<Self>`[src]

Creates an iterator that skips the first `n` elements. Read more

#### `fn take(self, n: usize) -> Take<Self>`[src]

Creates an iterator that yields its first `n` elements. Read more

#### `fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
F: FnMut(&mut St, Self::Item) -> Option<B>,` [src]

An iterator adaptor similar to [`fold`] that holds internal state and produces a new iterator. Read more

#### `fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
F: FnMut(Self::Item) -> U,
U: IntoIterator,` [src]

Creates an iterator that works like map, but flattens nested structure. Read more

#### `fn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,` 1.29.0[src]

Creates an iterator that flattens nested structure. Read more

#### `fn fuse(self) -> Fuse<Self>`[src]

Creates an iterator which ends after the first [`None`]. Read more

#### `fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),` [src]

Does something with each element of an iterator, passing the value on. Read more

#### `fn by_ref(&mut self) -> &mut Self`[src]

Borrows an iterator, rather than consuming it. Read more

#### `#[must_use = "if you really need to exhaust the iterator, consider `.for_each(drop)` instead"]fn collect<B>(self) -> B where
B: FromIterator<Self::Item>,` [src]

Transforms an iterator into a collection. Read more

#### `fn partition<B, F>(self, f: F) -> (B, B) where
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,` [src]

Consumes an iterator, creating two collections from it. Read more

#### `fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
P: FnMut(&T) -> bool,
Self: DoubleEndedIterator<Item = &'a mut T>,
T: 'a,` [src]

🔬 This is a nightly-only experimental API. (`iter_partition_in_place` #62543)

new API

Reorders the elements of this iterator in-place according to the given predicate, such that all those that return `true` precede all those that return `false`. Returns the number of `true` elements found. Read more

#### `fn is_partitioned<P>(self, predicate: P) -> bool where
P: FnMut(Self::Item) -> bool,` [src]

🔬 This is a nightly-only experimental API. (`iter_is_partitioned` #62544)

new API

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return `true` precede all those that return `false`. Read more

#### `fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,` 1.27.0[src]

An iterator method that applies a function as long as it returns successfully, producing a single, final value. Read more

#### `fn try_for_each<F, R>(&mut self, f: F) -> R where
F: FnMut(Self::Item) -> R,
R: Try<Ok = ()>,` 1.27.0[src]

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error. Read more

#### `fn fold<B, F>(self, init: B, f: F) -> B where
F: FnMut(B, Self::Item) -> B,` [src]

An iterator method that applies a function, producing a single, final value. Read more

#### `fn fold_first<F>(self, f: F) -> Option<Self::Item> where
F: FnMut(Self::Item, Self::Item) -> Self::Item,` [src]

🔬 This is a nightly-only experimental API. (`iterator_fold_self` #68125)

The same as `fold()`, but uses the first element in the iterator as the initial value, folding every subsequent element into it. If the iterator is empty, return `None`; otherwise, return the result of the fold. Read more

#### `fn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,` [src]

Tests if every element of the iterator matches a predicate. Read more

#### `fn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,` [src]

Tests if any element of the iterator matches a predicate. Read more

#### `fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,` [src]

Searches for an element of an iterator that satisfies a predicate. Read more

#### `fn find_map<B, F>(&mut self, f: F) -> Option<B> where
F: FnMut(Self::Item) -> Option<B>,` 1.30.0[src]

Applies function to the elements of iterator and returns the first non-none result. Read more

#### `fn try_find<F, R>(
&mut self,
f: F
) -> Result<Option<Self::Item>, <R as Try>::Error> where
F: FnMut(&Self::Item) -> R,
R: Try<Ok = bool>,` [src]

🔬 This is a nightly-only experimental API. (`try_find` #63178)

new API

Applies function to the elements of iterator and returns the first true result or the first error. Read more

#### `fn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,` [src]

Searches for an element in an iterator, returning its index. Read more

#### `fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: ExactSizeIterator + DoubleEndedIterator,` [src]

Searches for an element in an iterator from the right, returning its index. Read more

#### `fn max(self) -> Option<Self::Item> where
Self::Item: Ord,` [src]

Returns the maximum element of an iterator. Read more

#### `fn min(self) -> Option<Self::Item> where
Self::Item: Ord,` [src]

Returns the minimum element of an iterator. Read more

#### `fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,` 1.6.0[src]

Returns the element that gives the maximum value from the specified function. Read more

#### `fn max_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,` 1.15.0[src]

Returns the element that gives the maximum value with respect to the specified comparison function. Read more

#### `fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,` 1.6.0[src]

Returns the element that gives the minimum value from the specified function. Read more

#### `fn min_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,` 1.15.0[src]

Returns the element that gives the minimum value with respect to the specified comparison function. Read more

#### `fn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,` [src]

Reverses an iterator's direction. Read more

#### `fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Iterator<Item = (A, B)>,` [src]

Converts an iterator of pairs into a pair of containers. Read more

#### `fn copied<'a, T>(self) -> Copied<Self> where
Self: Iterator<Item = &'a T>,
T: 'a + Copy,` 1.36.0[src]

Creates an iterator which copies all of its elements. Read more

#### `fn cloned<'a, T>(self) -> Cloned<Self> where
Self: Iterator<Item = &'a T>,
T: 'a + Clone,` [src]

Creates an iterator which [`clone`]s all of its elements. Read more

#### `fn cycle(self) -> Cycle<Self> where
Self: Clone,` [src]

Repeats an iterator endlessly. Read more

#### `fn sum<S>(self) -> S where
S: Sum<Self::Item>,` 1.11.0[src]

Sums the elements of an iterator. Read more

#### `fn product<P>(self) -> P where
P: Product<Self::Item>,` 1.11.0[src]

Iterates over the entire iterator, multiplying all the elements Read more

#### `fn cmp<I>(self, other: I) -> Ordering where
I: IntoIterator<Item = Self::Item>,
Self::Item: Ord,` 1.5.0[src]

Lexicographically compares the elements of this `Iterator` with those of another. Read more

#### `fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
I: IntoIterator,` [src]

🔬 This is a nightly-only experimental API. (`iter_order_by` #64295)

Lexicographically compares the elements of this `Iterator` with those of another with respect to the specified comparison function. Read more

#### `fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,` 1.5.0[src]

Lexicographically compares the elements of this `Iterator` with those of another. Read more

#### `fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
I: IntoIterator,` [src]

🔬 This is a nightly-only experimental API. (`iter_order_by` #64295)

Lexicographically compares the elements of this `Iterator` with those of another with respect to the specified comparison function. Read more

#### `fn eq<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are equal to those of another. Read more

#### `fn eq_by<I, F>(self, other: I, eq: F) -> bool where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
I: IntoIterator,` [src]

🔬 This is a nightly-only experimental API. (`iter_order_by` #64295)

Determines if the elements of this `Iterator` are equal to those of another with respect to the specified equality function. Read more

#### `fn ne<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are unequal to those of another. Read more

#### `fn lt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are lexicographically less than those of another. Read more

#### `fn le<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are lexicographically less or equal to those of another. Read more

#### `fn gt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are lexicographically greater than those of another. Read more

#### `fn ge<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,` 1.5.0[src]

Determines if the elements of this `Iterator` are lexicographically greater than or equal to those of another. Read more

#### `fn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,` [src]

🔬 This is a nightly-only experimental API. (`is_sorted` #53485)

new API

Checks if the elements of this iterator are sorted. Read more

#### `fn is_sorted_by<F>(self, compare: F) -> bool where
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,` [src]

🔬 This is a nightly-only experimental API. (`is_sorted` #53485)

new API

Checks if the elements of this iterator are sorted using the given comparator function. Read more

#### `fn is_sorted_by_key<F, K>(self, f: F) -> bool where
F: FnMut(Self::Item) -> K,
K: PartialOrd<K>,` [src]

🔬 This is a nightly-only experimental API. (`is_sorted` #53485)

new API

Checks if the elements of this iterator are sorted using the given key extraction function. Read more

### `impl<'_, T> LowerExp for &'_ mut T where
T: LowerExp + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> LowerExp for &'_ T where
T: LowerExp + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> LowerHex for &'_ T where
T: LowerHex + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> LowerHex for &'_ mut T where
T: LowerHex + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> Octal for &'_ T where
T: Octal + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> Octal for &'_ mut T where
T: Octal + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, A> Ord for &'_ A where
A: Ord + ?Sized,` [src]

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

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

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

Compares and returns the maximum of two values. Read more

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

Compares and returns the minimum of two values. Read more

#### `#[must_use]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> Ord for &'_ mut A where
A: Ord + ?Sized,` [src]

#### `fn cmp(&self, other: &&'_ mut A) -> Ordering`[src]

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

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

Compares and returns the maximum of two values. Read more

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

Compares and returns the minimum of two values. Read more

#### `#[must_use]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> PartialEq<&'_ B> for &'_ A where
A: PartialEq<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

This method tests for `!=`.

### `impl<'_, '_, A, B> PartialEq<&'_ B> for &'_ mut A where
A: PartialEq<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

This method tests for `!=`.

### `impl<'_, '_, A, B> PartialEq<&'_ mut B> for &'_ A where
A: PartialEq<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

This method tests for `!=`.

### `impl<'_, '_, A, B> PartialEq<&'_ mut B> for &'_ mut A where
A: PartialEq<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

This method tests for `!=`.

### `impl<'_, '_, A, B> PartialOrd<&'_ B> for &'_ A where
A: PartialOrd<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

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

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

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

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

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

### `impl<'_, '_, A, B> PartialOrd<&'_ mut B> for &'_ mut A where
A: PartialOrd<B> + ?Sized,
B: ?Sized,` [src]

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

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

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

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

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

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

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

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

### `impl<'_, T> Pointer for &'_ T where
T: ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> Pointer for &'_ mut T where
T: ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, R: Read + ?Sized> Read for &'_ mut R`[src]

#### `fn read(&mut self, buf: &mut [u8]) -> Result<usize>`[src]

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

#### `fn read_vectored(&mut self, bufs: &mut [IoSliceMut]) -> Result<usize>`[src]

Like `read`, except that it reads into a slice of buffers. Read more

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

🔬 This is a nightly-only experimental API. (`can_vector` #69941)

Determines if this `Read`er has an efficient `read_vectored` implementation. Read more

#### `unsafe fn initializer(&self) -> Initializer`[src]

🔬 This is a nightly-only experimental API. (`read_initializer` #42788)

Determines if this `Read`er can work with buffers of uninitialized memory. Read more

#### `fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>`[src]

Read all bytes until EOF in this source, placing them into `buf`. Read more

#### `fn read_to_string(&mut self, buf: &mut String) -> Result<usize>`[src]

Read all bytes until EOF in this source, appending them to `buf`. Read more

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>`[src]

Read the exact number of bytes required to fill `buf`. Read more

#### `fn by_ref(&mut self) -> &mut Self where
Self: Sized,` [src]

Creates a "by reference" adaptor for this instance of `Read`. Read more

#### `fn bytes(self) -> Bytes<Self> where
Self: Sized,` [src]

Transforms this `Read` instance to an [`Iterator`] over its bytes. Read more

#### `fn chain<R: Read>(self, next: R) -> Chain<Self, R> where
Self: Sized,` [src]

Creates an adaptor which will chain this stream with another. Read more

#### `fn take(self, limit: u64) -> Take<Self> where
Self: Sized,` [src]

Creates an adaptor which will read at most `limit` bytes from it. Read more

### `impl<'_, S: Seek + ?Sized> Seek for &'_ mut S`[src]

#### `fn seek(&mut self, pos: SeekFrom) -> Result<u64>`[src]

Seek to an offset, in bytes, in a stream. Read more

#### `fn stream_len(&mut self) -> Result<u64>`[src]

🔬 This is a nightly-only experimental API. (`seek_convenience` #59359)

Returns the length of this stream (in bytes). Read more

#### `fn stream_position(&mut self) -> Result<u64>`[src]

🔬 This is a nightly-only experimental API. (`seek_convenience` #59359)

Returns the current seek position from the start of the stream. Read more

### `impl<'_, T> Send for &'_ mut T where
T: Send + ?Sized,` [src]

### `impl<'_, T> Send for &'_ T where
T: Sync + ?Sized,` [src]

### `impl<'_, T: ToSocketAddrs + ?Sized> ToSocketAddrs for &'_ T`[src]

#### `type Iter = T::Iter`

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

#### `fn to_socket_addrs(&self) -> Result<T::Iter>`[src]

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

### `impl<'_, I> TrustedLen for &'_ mut I where
I: TrustedLen + ?Sized,` [src]

### `impl<'a, T> Unpin for &'a T where
T: 'a + ?Sized,` 1.33.0[src]

### `impl<'a, T> Unpin for &'a mut T where
T: 'a + ?Sized,` 1.33.0[src]

### `impl<'_, T: ?Sized> !UnwindSafe for &'_ mut T` 1.9.0[src]

### `impl<'_, T: RefUnwindSafe + ?Sized> UnwindSafe for &'_ T` 1.9.0[src]

### `impl<'_, T> UpperExp for &'_ T where
T: UpperExp + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> UpperExp for &'_ mut T where
T: UpperExp + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> UpperHex for &'_ mut T where
T: UpperHex + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, T> UpperHex for &'_ T where
T: UpperHex + ?Sized,` [src]

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

Formats the value using the given formatter.

### `impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized,` 1.4.0[src]

#### `fn write_str(&mut self, s: &str) -> Result<(), Error>`[src]

Writes a string slice 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<'_, W: Write + ?Sized> Write for &'_ mut W`[src]

#### `fn write(&mut self, buf: &[u8]) -> Result<usize>`[src]

Write a buffer into this writer, returning how many bytes were written. Read more

#### `fn write_vectored(&mut self, bufs: &[IoSlice]) -> Result<usize>`[src]

Like `write`, except that it writes from a slice of buffers. Read more

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

🔬 This is a nightly-only experimental API. (`can_vector` #69941)

Determines if this `Write`er has an efficient `write_vectored` implementation. Read more

#### `fn flush(&mut self) -> Result<()>`[src]

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

#### `fn write_all(&mut self, buf: &[u8]) -> Result<()>`[src]

Attempts to write an entire buffer into this writer. Read more

#### `fn write_fmt(&mut self, fmt: Arguments) -> Result<()>`[src]

Writes a formatted string into this writer, returning any error encountered. Read more

#### `fn write_all_vectored(&mut self, bufs: &mut [IoSlice]) -> Result<()>`[src]

🔬 This is a nightly-only experimental API. (`write_all_vectored` #70436)

Attempts to write multiple buffers into this writer. Read more

#### `fn by_ref(&mut self) -> &mut Self where
Self: Sized,` [src]

Creates a "by reference" adaptor for this instance of `Write`. Read more