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));

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> Allocator for &'_ A where
    A: Allocator + ?Sized, 

pub fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to allocate a block of memory.

pub fn allocate_zeroed(
    &self,
    layout: Layout
) -> Result<NonNull<[u8]>, AllocError>

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

Behaves like allocate, but also ensures that the returned memory is zero-initialized.

pub unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout)

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

Deallocates the memory referenced by ptr.

pub unsafe fn grow(
    &self,
    ptr: NonNull<u8>,
    old_layout: Layout,
    new_layout: Layout
) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to extend the memory block.

pub unsafe fn grow_zeroed(
    &self,
    ptr: NonNull<u8>,
    old_layout: Layout,
    new_layout: Layout
) -> Result<NonNull<[u8]>, AllocError>

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

Behaves like grow, but also ensures that the new contents are set to zero before being returned.

pub unsafe fn shrink(
    &self,
    ptr: NonNull<u8>,
    old_layout: Layout,
    new_layout: Layout
) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to shrink the memory block.

pub fn by_ref(&self) -> &Self

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

Creates a “by reference” adaptor for this instance of Allocator.

impl<'_, T, U> AsMut<U> for &'_ mut T where
    T: AsMut<U> + ?Sized,
    U: ?Sized, 

pub fn as_mut(&mut self) -> &mut U

Performs the conversion.

impl<'_, T, U> AsRef<U> for &'_ mut T where
    T: AsRef<U> + ?Sized,
    U: ?Sized, 

pub fn as_ref(&self) -> &U

Performs the conversion.

impl<'_, T, U> AsRef<U> for &'_ T where
    T: AsRef<U> + ?Sized,
    U: ?Sized, 

pub fn as_ref(&self) -> &U

Performs the conversion.

impl<'_, T> Binary for &'_ T where
    T: Binary + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Binary for &'_ mut T where
    T: Binary + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Borrow<T> for &'_ mut T where
    T: ?Sized, 

pub fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<'_, T> Borrow<T> for &'_ T where
    T: ?Sized, 

pub fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<'_, T> BorrowMut<T> for &'_ mut T where
    T: ?Sized, 

pub fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value.

impl<B: BufRead + ?Sized> BufRead for &mut B

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

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

fn consume(&mut self, amt: usize)

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

fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>

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

fn read_line(&mut self, buf: &mut String) -> Result<usize>

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

fn split(self, byte: u8) -> Split<Self> where
    Self: Sized, 

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

fn lines(self) -> Lines<Self> where
    Self: Sized, 

Returns an iterator over the lines of this reader.

impl<'_, T> Clone for &'_ T where
    T: ?Sized, 

Shared references can be cloned, but mutable references cannot!

pub fn clone(&self) -> &'_ T

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'_, T> !Clone for &'_ mut T where
    T: ?Sized, 

Shared references can be cloned, but mutable references cannot!

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

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, 'b, T, U> CoerceUnsized<&'a U> for &'b T where
    'b: 'a,
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'a, 'b, T, U> CoerceUnsized<&'a U> for &'b mut T where
    'b: 'a,
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'a, T, U> CoerceUnsized<&'a mut U> for &'a mut T where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'a, T, U> CoerceUnsized<*const U> for &'a T where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

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

impl<'a, T, U> CoerceUnsized<*mut U> for &'a mut T where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'_, T> Copy for &'_ T where
    T: ?Sized, 

Shared references can be copied, but mutable references cannot!

impl<'_, T> Debug for &'_ T where
    T: Debug + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Debug for &'_ mut T where
    T: Debug + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Deref for &'_ T where
    T: ?Sized, 

type Target = T

The resulting type after dereferencing.

pub fn deref(&self) -> &T

Dereferences the value.

impl<'_, T> Deref for &'_ mut T where
    T: ?Sized, 

type Target = T

The resulting type after dereferencing.

pub fn deref(&self) -> &T

Dereferences the value.

impl<'_, T> !DerefMut for &'_ T where
    T: ?Sized, 

pub fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<'_, T> DerefMut for &'_ mut T where
    T: ?Sized, 

pub fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<'a, T, U> DispatchFromDyn<&'a U> for &'a T where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'a, T, U> DispatchFromDyn<&'a mut U> for &'a mut T where
    T: Unsize<U> + ?Sized,
    U: ?Sized, 

impl<'_, T> Display for &'_ T where
    T: Display + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Display for &'_ mut T where
    T: Display + ?Sized, 

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

Formats the value using the given formatter.

impl<'a, I> DoubleEndedIterator for &'a mut I where
    I: DoubleEndedIterator + ?Sized, 

pub fn next_back(&mut self) -> Option<<I as Iterator>::Item>

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

pub fn advance_back_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by #77404)

recently added

Advances the iterator from the back by n elements.

pub fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item>

Returns the nth element from the end of the iterator.

pub fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where
    F: FnMut(B, Self::Item) -> R,
    R: Try<Ok = B>, 

This is the reverse version of Iterator::try_fold(): it takes elements starting from the back of the iterator.

pub fn rfold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, Self::Item) -> B, 

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

pub fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where
    P: FnMut(&Self::Item) -> bool, 

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

impl<'_, A> Eq for &'_ mut A where
    A: Eq + ?Sized, 

impl<'_, A> Eq for &'_ A where
    A: Eq + ?Sized, 

impl<'a, T: Error + ?Sized> Error for &'a T

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any.

fn backtrace(&self) -> Option<&Backtrace>

🔬 This is a nightly-only experimental API. (backtrace #53487)

Returns a stack backtrace, if available, of where this error occurred.

impl<'_, I> ExactSizeIterator for &'_ mut I where
    I: ExactSizeIterator + ?Sized, 

pub fn len(&self) -> usize

Returns the exact length of the iterator.

pub fn is_empty(&self) -> bool

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

Returns true if the iterator is empty.

impl<'_, A, F> Fn<A> for &'_ F where
    F: Fn<A> + ?Sized, 

pub extern "rust-call" fn call(&self, args: A) -> <F as FnOnce<A>>::Output

🔬 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, 

pub extern "rust-call" fn call_mut(
    &mut self,
    args: A
) -> <F as FnOnce<A>>::Output

🔬 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, 

pub extern "rust-call" fn call_mut(
    &mut self,
    args: A
) -> <F as FnOnce<A>>::Output

🔬 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, 

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

The returned type after the call operator is used.

pub extern "rust-call" fn call_once(self, args: A) -> <F as FnOnce<A>>::Output

🔬 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, 

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

The returned type after the call operator is used.

pub extern "rust-call" fn call_once(self, args: A) -> <F as FnOnce<A>>::Output

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

Performs the call operation.

impl<'_, I> FusedIterator for &'_ mut I where
    I: FusedIterator + ?Sized, 

impl<'_, F> Future for &'_ mut F where
    F: Future + Unpin + ?Sized, 

type Output = <F as Future>::Output

The type of value produced on completion.

pub fn poll(
    self: Pin<&mut &'_ mut F>,
    cx: &mut Context<'_>
) -> Poll<<&'_ mut F as Future>::Output>

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

impl<'_, G, R> Generator<R> for &'_ mut G where
    G: Generator<R> + Unpin + ?Sized, 

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

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

The type of value this generator yields.

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

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

The type of value this generator returns.

pub fn resume(
    self: Pin<&mut &'_ mut G>,
    arg: R
) -> GeneratorState<<&'_ mut G as Generator<R>>::Yield, <&'_ mut G as Generator<R>>::Return>

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

Resumes the execution of this generator.

impl<'_, T> Hash for &'_ T where
    T: Hash + ?Sized, 

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<'_, T> Hash for &'_ mut T where
    T: Hash + ?Sized, 

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<'_, H> Hasher for &'_ mut H where
    H: Hasher + ?Sized, 

pub fn finish(&self) -> u64

Returns the hash value for the values written so far.

pub fn write(&mut self, bytes: &[u8])

Writes some data into this Hasher.

pub fn write_u8(&mut self, i: u8)

Writes a single u8 into this hasher.

pub fn write_u16(&mut self, i: u16)

Writes a single u16 into this hasher.

pub fn write_u32(&mut self, i: u32)

Writes a single u32 into this hasher.

pub fn write_u64(&mut self, i: u64)

Writes a single u64 into this hasher.

pub fn write_u128(&mut self, i: u128)

Writes a single u128 into this hasher.

pub fn write_usize(&mut self, i: usize)

Writes a single usize into this hasher.

pub fn write_i8(&mut self, i: i8)

Writes a single i8 into this hasher.

pub fn write_i16(&mut self, i: i16)

Writes a single i16 into this hasher.

pub fn write_i32(&mut self, i: i32)

Writes a single i32 into this hasher.

pub fn write_i64(&mut self, i: i64)

Writes a single i64 into this hasher.

pub fn write_i128(&mut self, i: i128)

Writes a single i128 into this hasher.

pub fn write_isize(&mut self, i: isize)

Writes a single isize into this hasher.

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

Advances the iterator and returns the next value.

pub fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

pub fn advance_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by #77404)

recently added

Advances the iterator by n elements.

pub fn nth(&mut self, n: usize) -> Option<<&'_ mut I as Iterator>::Item>

Returns the nth element of the iterator.

pub fn count(self) -> usize

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

pub fn last(self) -> Option<Self::Item>

Consumes the iterator, returning the last element.

pub fn step_by(self, step: usize) -> StepBy<Self>

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

pub fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator<Item = Self::Item>, 

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

pub fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator, 

‘Zips up’ two iterators into a single iterator of pairs.

pub fn intersperse(self, separator: Self::Item) -> Intersperse<Self> where
    Self::Item: Clone, 

🔬 This is a nightly-only experimental API. (iter_intersperse #79524)

recently added

Creates a new iterator which places a copy of separator between adjacent items of the original iterator.

pub fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
    G: FnMut() -> Self::Item, 

🔬 This is a nightly-only experimental API. (iter_intersperse #79524)

recently added

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator.

pub fn map<B, F>(self, f: F) -> Map<Self, F> where
    F: FnMut(Self::Item) -> B, 

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

pub fn for_each<F>(self, f: F) where
    F: FnMut(Self::Item), 

Calls a closure on each element of an iterator.

pub fn filter<P>(self, predicate: P) -> Filter<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

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

pub fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
    F: FnMut(Self::Item) -> Option<B>, 

Creates an iterator that both filters and maps.

pub fn enumerate(self) -> Enumerate<Self>

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

pub fn peekable(self) -> Peekable<Self>

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

pub fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that skips elements based on a predicate.

pub fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that yields elements based on a predicate.

pub fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
    P: FnMut(Self::Item) -> Option<B>, 

🔬 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.

pub fn skip(self, n: usize) -> Skip<Self>

Creates an iterator that skips the first n elements.

pub fn take(self, n: usize) -> Take<Self>

Creates an iterator that yields its first n elements.

pub fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
    F: FnMut(&mut St, Self::Item) -> Option<B>, 

An iterator adaptor similar to fold that holds internal state and produces a new iterator.

pub fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
    F: FnMut(Self::Item) -> U,
    U: IntoIterator, 

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

pub fn flatten(self) -> Flatten<Self> where
    Self::Item: IntoIterator, 

Creates an iterator that flattens nested structure.

pub fn fuse(self) -> Fuse<Self>

Creates an iterator which ends after the first None.

pub fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    F: FnMut(&Self::Item), 

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

pub fn by_ref(&mut self) -> &mut Self

Borrows an iterator, rather than consuming it.

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

Transforms an iterator into a collection.

pub fn partition<B, F>(self, f: F) -> (B, B) where
    F: FnMut(&Self::Item) -> bool,
    B: Default + Extend<Self::Item>, 

Consumes an iterator, creating two collections from it.

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

🔬 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.

pub fn is_partitioned<P>(self, predicate: P) -> bool where
    P: FnMut(Self::Item) -> bool, 

🔬 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.

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    F: FnMut(B, Self::Item) -> R,
    R: Try<Ok = B>, 

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

pub fn try_for_each<F, R>(&mut self, f: F) -> R where
    F: FnMut(Self::Item) -> R,
    R: Try<Ok = ()>, 

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

pub fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, Self::Item) -> B, 

Folds every element into an accumulator by applying an operation, returning the final result.

pub fn reduce<F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(Self::Item, Self::Item) -> Self::Item, 

Reduces the elements to a single one, by repeatedly applying a reducing operation.

pub fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if every element of the iterator matches a predicate.

pub fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if any element of the iterator matches a predicate.

pub fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
    P: FnMut(&Self::Item) -> bool, 

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

pub fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    F: FnMut(Self::Item) -> Option<B>, 

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

pub 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>, 

🔬 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.

pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool, 

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

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

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

pub fn max(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the maximum element of an iterator.

pub fn min(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the minimum element of an iterator.

pub fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item) -> B,
    B: Ord, 

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

pub fn max_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

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

pub fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item) -> B,
    B: Ord, 

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

pub fn min_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

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

pub fn rev(self) -> Rev<Self> where
    Self: DoubleEndedIterator, 

Reverses an iterator’s direction.

pub fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
    Self: Iterator<Item = (A, B)>,
    FromA: Default + Extend<A>,
    FromB: Default + Extend<B>, 

Converts an iterator of pairs into a pair of containers.

pub fn copied<'a, T>(self) -> Copied<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Copy, 

Creates an iterator which copies all of its elements.

pub fn cloned<'a, T>(self) -> Cloned<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Clone, 

Creates an iterator which clones all of its elements.

pub fn cycle(self) -> Cycle<Self> where
    Self: Clone, 

Repeats an iterator endlessly.

pub fn sum<S>(self) -> S where
    S: Sum<Self::Item>, 

Sums the elements of an iterator.

pub fn product<P>(self) -> P where
    P: Product<Self::Item>, 

Iterates over the entire iterator, multiplying all the elements

pub fn cmp<I>(self, other: I) -> Ordering where
    I: IntoIterator<Item = Self::Item>,
    Self::Item: Ord, 

Lexicographically compares the elements of this Iterator with those of another.

pub fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
    I: IntoIterator, 

🔬 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.

pub fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Lexicographically compares the elements of this Iterator with those of another.

pub 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, 

🔬 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.

pub fn eq<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

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

pub fn eq_by<I, F>(self, other: I, eq: F) -> bool where
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
    I: IntoIterator, 

🔬 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.

pub fn ne<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

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

pub fn lt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

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

pub fn le<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

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

pub fn gt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

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

pub fn ge<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

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

pub fn is_sorted(self) -> bool where
    Self::Item: PartialOrd<Self::Item>, 

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

new API

Checks if the elements of this iterator are sorted.

pub fn is_sorted_by<F>(self, compare: F) -> bool where
    F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>, 

🔬 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.

pub fn is_sorted_by_key<F, K>(self, f: F) -> bool where
    F: FnMut(Self::Item) -> K,
    K: PartialOrd<K>, 

🔬 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.

impl<'_, T> LowerExp for &'_ T where
    T: LowerExp + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> LowerExp for &'_ mut T where
    T: LowerExp + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> LowerHex for &'_ T where
    T: LowerHex + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> LowerHex for &'_ mut T where
    T: LowerHex + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Octal for &'_ mut T where
    T: Octal + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Octal for &'_ T where
    T: Octal + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, A> Ord for &'_ A where
    A: Ord + ?Sized, 

pub fn cmp(&self, other: &&'_ A) -> Ordering

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<'_, A> Ord for &'_ mut A where
    A: Ord + ?Sized, 

pub fn cmp(&self, other: &&'_ mut A) -> Ordering

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<'_, '_, A, B> PartialEq<&'_ B> for &'_ A where
    B: ?Sized,
    A: PartialEq<B> + ?Sized, 

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

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

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

This method tests for !=.

impl<'_, '_, A, B> PartialEq<&'_ B> for &'_ mut A where
    B: ?Sized,
    A: PartialEq<B> + ?Sized, 

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

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

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

This method tests for !=.

impl<'_, '_, A, B> PartialEq<&'_ mut B> for &'_ mut A where
    B: ?Sized,
    A: PartialEq<B> + ?Sized, 

pub fn eq(&self, other: &&mut B) -> bool

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

pub fn ne(&self, other: &&mut B) -> bool

This method tests for !=.

impl<'_, '_, A, B> PartialEq<&'_ mut B> for &'_ A where
    B: ?Sized,
    A: PartialEq<B> + ?Sized, 

pub fn eq(&self, other: &&mut B) -> bool

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

pub fn ne(&self, other: &&mut B) -> bool

This method tests for !=.

impl<'_, '_, A, B> PartialOrd<&'_ B> for &'_ A where
    B: ?Sized,
    A: PartialOrd<B> + ?Sized, 

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

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

pub fn lt(&self, other: &&B) -> bool

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

pub fn le(&self, other: &&B) -> bool

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

pub fn gt(&self, other: &&B) -> bool

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

pub fn ge(&self, other: &&B) -> bool

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

impl<'_, '_, A, B> PartialOrd<&'_ mut B> for &'_ mut A where
    B: ?Sized,
    A: PartialOrd<B> + ?Sized, 

pub fn partial_cmp(&self, other: &&mut B) -> Option<Ordering>

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

pub fn lt(&self, other: &&mut B) -> bool

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

pub fn le(&self, other: &&mut B) -> bool

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

pub fn gt(&self, other: &&mut B) -> bool

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

pub fn ge(&self, other: &&mut B) -> bool

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

impl<'_, T> Pointer for &'_ T where
    T: ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> Pointer for &'_ mut T where
    T: ?Sized, 

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

Formats the value using the given formatter.

impl<R: Read + ?Sized> Read for &mut R

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

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

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

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

fn is_read_vectored(&self) -> bool

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

Determines if this Reader has an efficient read_vectored implementation.

unsafe fn initializer(&self) -> Initializer

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

Determines if this Reader can work with buffers of uninitialized memory.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

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

fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

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

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

Read the exact number of bytes required to fill buf.

fn by_ref(&mut self) -> &mut Self where
    Self: Sized, 

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self> where
    Self: Sized, 

Transforms this Read instance to an Iterator over its bytes.

fn chain<R: Read>(self, next: R) -> Chain<Self, R> where
    Self: Sized, 

Creates an adaptor which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self> where
    Self: Sized, 

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

impl<S: Seek + ?Sized> Seek for &mut S

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

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

fn stream_len(&mut self) -> Result<u64>

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

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64>

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

impl<'_, T> Send for &'_ T where
    T: Sync + ?Sized, 

impl<'_, T> Send for &'_ mut T where
    T: Send + ?Sized, 

impl<'_, S> Stream for &'_ mut S where
    S: Stream + Unpin + ?Sized, 

type Item = <S as Stream>::Item

🔬 This is a nightly-only experimental API. (async_stream #79024)

The type of items yielded by the stream.

pub fn poll_next(
    self: Pin<&mut &'_ mut S>,
    cx: &mut Context<'_>
) -> Poll<Option<<&'_ mut S as Stream>::Item>>

🔬 This is a nightly-only experimental API. (async_stream #79024)

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

pub fn size_hint(&self) -> (usize, Option<usize>)

🔬 This is a nightly-only experimental API. (async_stream #79024)

Returns the bounds on the remaining length of the stream.

impl<T: ToSocketAddrs + ?Sized> ToSocketAddrs for &T

type Iter = T::Iter

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

fn to_socket_addrs(&self) -> Result<T::Iter>

Converts this object to an iterator of resolved SocketAddrs.

impl<'_, I> TrustedLen for &'_ mut I where
    I: TrustedLen + ?Sized, 

impl<'a, T> Unpin for &'a mut T where
    T: 'a + ?Sized, 

impl<'a, T> Unpin for &'a T where
    T: 'a + ?Sized, 

impl<T: ?Sized> !UnwindSafe for &mut T

impl<T: RefUnwindSafe + ?Sized> UnwindSafe for &T

impl<'_, T> UpperExp for &'_ mut T where
    T: UpperExp + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> UpperExp for &'_ T where
    T: UpperExp + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> UpperHex for &'_ T where
    T: UpperHex + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, T> UpperHex for &'_ mut T where
    T: UpperHex + ?Sized, 

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

Formats the value using the given formatter.

impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, 

pub fn write_str(&mut self, s: &str) -> Result<(), Error>

Writes a string slice into this writer, returning whether the write succeeded.

pub fn write_char(&mut self, c: char) -> Result<(), Error>

Writes a char into this writer, returning whether the write succeeded.

pub fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Glue for usage of the write! macro with implementors of this trait.

impl<W: Write + ?Sized> Write for &mut W

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

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

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>

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

fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

fn flush(&mut self) -> Result<()>

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

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

Attempts to write an entire buffer into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>

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

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>

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

Attempts to write multiple buffers into this writer.

fn by_ref(&mut self) -> &mut Self where
    Self: Sized, 

Creates a “by reference” adaptor for this instance of Write.