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 not be null. In fact, Option<&T> has the same memory representation as a nullable 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<'_, T, U> AsMut<U> for &'_ mut T where
    T: AsMut<U> + ?Sized,
    U: ?Sized, 

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

Performs the conversion.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

Mutably borrows from an owned value.

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

fn finish(&self) -> u64

Returns the hash value for the values written so far.

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

Writes some data into this Hasher.

fn write_u8(&mut self, i: u8)

Writes a single u8 into this hasher.

fn write_u16(&mut self, i: u16)

Writes a single u16 into this hasher.

fn write_u32(&mut self, i: u32)

Writes a single u32 into this hasher.

fn write_u64(&mut self, i: u64)

Writes a single u64 into this hasher.

fn write_u128(&mut self, i: u128)

Writes a single u128 into this hasher.

fn write_usize(&mut self, i: usize)

Writes a single usize into this hasher.

fn write_i8(&mut self, i: i8)

Writes a single i8 into this hasher.

fn write_i16(&mut self, i: i16)

Writes a single i16 into this hasher.

fn write_i32(&mut self, i: i32)

Writes a single i32 into this hasher.

fn write_i64(&mut self, i: i64)

Writes a single i64 into this hasher.

fn write_i128(&mut self, i: i128)

Writes a single i128 into this hasher.

fn write_isize(&mut self, i: isize)

Writes a single isize into this hasher.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

Mutably dereferences the value.

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

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, 

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

Formats the value using the given formatter.

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

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, 

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

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>

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

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

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

Feeds this value into the given [Hasher].

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, 

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

Feeds this value into the given [Hasher].

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

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

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

type Target = T

The resulting type after dereferencing.

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn deref(&self) -> &T

Dereferences the value.

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

type Target = T

The resulting type after dereferencing.

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn deref(&self) -> &T

Dereferences the value.

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

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

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

type Yield = <G as Generator>::Yield

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

The type of value this generator yields.

type Return = <G as Generator>::Return

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

The type of value this generator returns.

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

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

Resumes the execution of this generator.

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

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

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

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

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

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.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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 &'_ F where
    F: Fn<A> + ?Sized, 

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

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

Performs the call operation.

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

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

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

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

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

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

Returns a copy of the value.

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

Performs copy-assignment from source.

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

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

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

Formats the value using the given formatter.

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

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, 

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

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

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

🔬 This is a nightly-only experimental API. (iter_nth_back #56995)

Returns the nth element from the end of the iterator.

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 [try_fold()]: it takes elements starting from the back of the iterator.

fn rfold<B, F>(self, accum: 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.

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn as_ref(&self) -> &U

Performs the conversion.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn as_ref(&self) -> &U

Performs the conversion.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn borrow(&self) -> &T

Immutably borrows from an owned value.

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn borrow(&self) -> &T

Immutably borrows from an owned value.

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

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

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

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

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

Restrict a value to a certain interval.

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

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

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

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

Restrict a value to a certain interval.

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

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

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

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

This method tests for !=.

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

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

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

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

This method tests for !=.

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

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

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

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

This method tests for !=.

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

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

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

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

This method tests for !=.

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

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

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

Advances the iterator and returns the next value.

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

Returns the bounds on the remaining length of the iterator.

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

Returns the nth element of the iterator.

fn count(self) -> usize

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

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

Consumes the iterator, returning the last element.

Important traits for StepBy<I>

impl<I> Iterator for StepBy<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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.

Important traits for Chain<A, B>

impl<A, B> Iterator for Chain<A, B> where
    A: Iterator,
    B: Iterator<Item = <A as Iterator>::Item>,  type Item = <A as Iterator>::Item;

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.

Important traits for Zip<A, B>

impl<A, B> Iterator for Zip<A, B> where
    A: Iterator,
    B: Iterator,  type Item = (<A as Iterator>::Item, <B as Iterator>::Item);

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.

Important traits for Map<I, F>

impl<B, I, F> Iterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: Iterator,  type Item = B;

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.

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

Calls a closure on each element of an iterator.

Important traits for Filter<I, P>

impl<I, P> Iterator for Filter<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

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.

Important traits for FilterMap<I, F>

impl<B, I, F> Iterator for FilterMap<I, F> where
    F: FnMut(<I as Iterator>::Item) -> Option<B>,
    I: Iterator,  type Item = B;

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.

Important traits for Enumerate<I>

impl<I> Iterator for Enumerate<I> where
    I: Iterator,  type Item = (usize, <I as Iterator>::Item);

fn enumerate(self) -> Enumerate<Self>

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

Important traits for Peekable<I>

impl<I> Iterator for Peekable<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

fn peekable(self) -> Peekable<Self>

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

Important traits for SkipWhile<I, P>

impl<I, P> Iterator for SkipWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

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

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

Important traits for TakeWhile<I, P>

impl<I, P> Iterator for TakeWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool,  type Item = <I as Iterator>::Item;

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.

Important traits for Skip<I>

impl<I> Iterator for Skip<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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

Creates an iterator that skips the first n elements.

Important traits for Take<I>

impl<I> Iterator for Take<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

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

Creates an iterator that yields its first n elements.

Important traits for Scan<I, St, F>

impl<B, I, St, F> Iterator for Scan<I, St, F> where
    F: FnMut(&mut St, <I as Iterator>::Item) -> Option<B>,
    I: Iterator,  type Item = B;

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.

Important traits for FlatMap<I, U, F>

impl<I, U, F> Iterator for FlatMap<I, U, F> where
    F: FnMut(<I as Iterator>::Item) -> U,
    I: Iterator,
    U: IntoIterator,  type Item = <U as IntoIterator>::Item;

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.

Important traits for Flatten<I>

impl<I, U> Iterator for Flatten<I> where
    I: Iterator,
    U: Iterator,
    <I as Iterator>::Item: IntoIterator,
    <<I as Iterator>::Item as IntoIterator>::IntoIter == U,
    <<I as Iterator>::Item as IntoIterator>::Item == <U as Iterator>::Item,  type Item = <U as Iterator>::Item;

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

Creates an iterator that flattens nested structure.

Important traits for Fuse<I>

impl<I> Iterator for Fuse<I> where
    I: FusedIterator, impl<I> Iterator for Fuse<I> where
    I: Iterator,  type Item = <I as Iterator>::Item;

fn fuse(self) -> Fuse<Self>

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

Important traits for Inspect<I, F>

impl<I, F> Iterator for Inspect<I, F> where
    F: FnMut(&<I as Iterator>::Item),
    I: Iterator,  type Item = <I as Iterator>::Item;

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

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

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

fn 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"]

fn collect<B>(self) -> B where
    B: FromIterator<Self::Item>, 

Transforms an iterator into a collection.

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

Consumes an iterator, creating two collections from it.

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.

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.

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

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

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

Tests if every element of the iterator matches a predicate.

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

Tests if any element of the iterator matches a predicate.

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.

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.

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.

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

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

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

Returns the maximum element of an iterator.

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

Returns the minimum element of an iterator.

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

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

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.

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

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

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.

Important traits for Rev<I>

impl<I> Iterator for Rev<I> where
    I: DoubleEndedIterator,  type Item = <I as Iterator>::Item;

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

Reverses an iterator's direction.

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

Converts an iterator of pairs into a pair of containers.

Important traits for Copied<I>

impl<'a, I, T> Iterator for Copied<I> where
    I: Iterator<Item = &'a T>,
    T: 'a + Copy,  type Item = T;

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.

Important traits for Cloned<I>

impl<'a, I, T> Iterator for Cloned<I> where
    I: Iterator<Item = &'a T>,
    T: 'a + Clone,  type Item = T;

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

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

Important traits for Cycle<I>

impl<I> Iterator for Cycle<I> where
    I: Clone + Iterator,  type Item = <I as Iterator>::Item;

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

Repeats an iterator endlessly.

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

Sums the elements of an iterator.

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

Iterates over the entire iterator, multiplying all the elements

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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

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

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

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

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

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

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

fn len(&self) -> usize

Returns the exact number of times the iterator will iterate.

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

impl<'a, T, U> CoerceUnsized<&'a mut 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<'a, T, U> CoerceUnsized<*const U> for &'a mut T where
    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, 'b, T, U> CoerceUnsized<&'a U> for &'b T where
    'b: 'a,
    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, F> FnMut<A> for &'_ F where
    F: Fn<A> + ?Sized, 

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, 

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

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

Formats the value using the given formatter.

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

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

Formats the value using the given formatter.

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

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.

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.

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

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

Important traits for Bytes<R>

impl<R: Read> Iterator for Bytes<R> type Item = Result<u8>;

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

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

Important traits for Chain<T, U>

impl<T: Read, U: Read> Read for Chain<T, U>

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

Creates an adaptor which will chain this stream with another.

Important traits for Take<T>

impl<T: Read> Read for Take<T>

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

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

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 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.

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W

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

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

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_convenience #59359)

Returns the length of this stream (in bytes).

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

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

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

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.

Important traits for Split<B>

impl<B: BufRead> Iterator for Split<B> type Item = Result<Vec<u8>>;

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

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

Important traits for Lines<B>

impl<B: BufRead> Iterator for Lines<B> type Item = Result<String>;

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

Returns an iterator over the lines of this reader.

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<T: ?Sized, '_> !UnwindSafe for &'_ mut T

impl<T: RefUnwindSafe + ?Sized, '_> UnwindSafe for &'_ T