Primitive Type reference1.0.0[]

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.

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

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

&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:

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

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

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, I> Iterator for &'a mut I where
    I: Iterator + ?Sized
[src]

The type of the elements being iterated over.

Advances the iterator and returns the next value. Read more

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

Returns the nth element of the iterator. Read more

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

Consumes the iterator, returning the last element. Read more

Important traits for StepBy<I>

🔬 This is a nightly-only experimental API. (iterator_step_by #27741)

unstable replacement of Range::step_by

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

Important traits for Chain<A, B>

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

Important traits for Zip<A, B>

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

Important traits for Map<I, F>

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

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

Important traits for Filter<I, P>

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

Important traits for FilterMap<I, F>

Creates an iterator that both filters and maps. Read more

Important traits for Enumerate<I>

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

Important traits for Peekable<I>

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

Important traits for SkipWhile<I, P>

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

Important traits for TakeWhile<I, P>

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

Important traits for Skip<I>

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

Important traits for Take<I>

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

Important traits for Scan<I, St, F>

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

Important traits for FlatMap<I, U, F>

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

Important traits for Flatten<I>

🔬 This is a nightly-only experimental API. (iterator_flatten #48213)

Creates an iterator that flattens nested structure. Read more

Important traits for Fuse<I>

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

Important traits for Inspect<I, F>

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

Important traits for &'a mut I

Borrows an iterator, rather than consuming it. Read more

Transforms an iterator into a collection. Read more

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

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

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

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

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

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

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

🔬 This is a nightly-only experimental API. (iterator_find_map #49602)

unstable new API

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

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

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

Returns the maximum element of an iterator. Read more

Returns the minimum element of an iterator. Read more

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

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

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

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

Important traits for Rev<I>

Reverses an iterator's direction. Read more

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

Important traits for Cloned<I>

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

Important traits for Cycle<I>

Repeats an iterator endlessly. Read more

Sums the elements of an iterator. Read more

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

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

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

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

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

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

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

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

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

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

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

Performs the call operation.

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

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

Performs the call operation.

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

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

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

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

impl<'a, T, U> AsRef<U> for &'a T where
    T: AsRef<U> + ?Sized,
    U: ?Sized
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Important traits for &'a mut I

Performs the conversion.

impl<'a, T, U> AsRef<U> for &'a mut T where
    T: AsRef<U> + ?Sized,
    U: ?Sized
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Important traits for &'a mut I

Performs the conversion.

impl<'a, T> UpperExp for &'a T where
    T: UpperExp + ?Sized
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Formats the value using the given formatter.

impl<'a, T> UpperExp for &'a mut T where
    T: UpperExp + ?Sized
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Formats the value using the given formatter.

impl<'a, T> UpperHex for &'a mut T where
    T: UpperHex + ?Sized
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Formats the value using the given formatter.

impl<'a, T> UpperHex for &'a T where
    T: UpperHex + ?Sized
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Formats the value using the given formatter.

impl<'a, T> Clone for &'a T where
    T: ?Sized
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Important traits for &'a mut I

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<'a, T> Octal for &'a mut T where
    T: Octal + ?Sized
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Formats the value using the given formatter.

impl<'a, T> Octal for &'a T where
    T: Octal + ?Sized
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Formats the value using the given formatter.

impl<'a, 'b, A, B> PartialOrd<&'b B> for &'a A where
    A: PartialOrd<B> + ?Sized,
    B: ?Sized
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This method returns an ordering between self and other values if one exists. Read more

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

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

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

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

impl<'a, 'b, A, B> PartialOrd<&'b mut B> for &'a mut A where
    A: PartialOrd<B> + ?Sized,
    B: ?Sized
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This method returns an ordering between self and other values if one exists. Read more

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

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

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

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

impl<'a, T> Generator for &'a mut T where
    T: Generator + ?Sized
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🔬 This is a nightly-only experimental API. (generator_trait #43122)

The type of value this generator yields. Read more

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

The type of value this generator returns. Read more

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

Resumes the execution of this generator. Read more

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

Important traits for &'a mut I

Immutably borrows from an owned value. Read more

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

Important traits for &'a mut I

Immutably borrows from an owned value. Read more

impl<'a, I> DoubleEndedIterator for &'a mut I where
    I: DoubleEndedIterator + ?Sized
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Removes and returns an element from the end of the iterator. Read more

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

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

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

impl<'a, A> Ord for &'a mut A where
    A: Ord + ?Sized
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This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

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

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

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

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

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

Performs the call operation.

impl<'a, H> Hasher for &'a mut H where
    H: Hasher + ?Sized
1.22.0
[src]

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

Writes some data into this Hasher. Read more

Writes a single u8 into this hasher.

Writes a single u16 into this hasher.

Writes a single u32 into this hasher.

Writes a single u64 into this hasher.

Writes a single u128 into this hasher.

Writes a single usize into this hasher.

Writes a single i8 into this hasher.

Writes a single i16 into this hasher.

Writes a single i32 into this hasher.

Writes a single i64 into this hasher.

Writes a single i128 into this hasher.

Writes a single isize into this hasher.

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

impl<'a, T> Hash for &'a mut T where
    T: Hash + ?Sized
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Feeds this value into the given [Hasher]. Read more

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

impl<'a, T> Hash for &'a T where
    T: Hash + ?Sized
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Feeds this value into the given [Hasher]. Read more

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

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

impl<'a, 'b, A, B> PartialEq<&'b B> for &'a A where
    A: PartialEq<B> + ?Sized,
    B: ?Sized
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This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b mut B> for &'a mut A where
    A: PartialEq<B> + ?Sized,
    B: ?Sized
[src]

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

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b B> for &'a mut A where
    A: PartialEq<B> + ?Sized,
    B: ?Sized
[src]

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

This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b mut B> for &'a A where
    A: PartialEq<B> + ?Sized,
    B: ?Sized
[src]

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

This method tests for !=.

impl<'a, I> TrustedLen for &'a mut I where
    I: TrustedLen + ?Sized
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impl<'a, T> LowerExp for &'a mut T where
    T: LowerExp + ?Sized
[src]

Formats the value using the given formatter.

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

Formats the value using the given formatter.

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

Formats the value using the given formatter.

impl<'a, T> LowerHex for &'a mut T where
    T: LowerHex + ?Sized
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Formats the value using the given formatter.

impl<'a, I> ExactSizeIterator for &'a mut I where
    I: ExactSizeIterator + ?Sized
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Returns the exact number of times the iterator will iterate. Read more

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

Returns whether the iterator is empty. Read more

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

Formats the value using the given formatter. Read more

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

Formats the value using the given formatter. Read more

impl<'a, A, F> FnOnce<A> for &'a F where
    F: Fn<A> + ?Sized
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The returned type after the call operator is used.

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

Performs the call operation.

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

The returned type after the call operator is used.

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

Performs the call operation.

impl<'a, T> DerefMut for &'a mut T where
    T: ?Sized
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Important traits for &'a mut I

Mutably dereferences the value.

impl<'a, T> Send for &'a mut T where
    T: Send + ?Sized
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impl<'a, T> Send for &'a T where
    T: Sync + ?Sized
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impl<'a, I> FusedIterator for &'a mut I where
    I: FusedIterator + ?Sized
1.26.0
[src]

impl<'a, T, U> AsMut<U> for &'a mut T where
    T: AsMut<U> + ?Sized,
    U: ?Sized
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Important traits for &'a mut I

Performs the conversion.

impl<'a, T> Deref for &'a T where
    T: ?Sized
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The resulting type after dereferencing.

Important traits for &'a mut I

Dereferences the value.

impl<'a, T> Deref for &'a mut T where
    T: ?Sized
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The resulting type after dereferencing.

Important traits for &'a mut I

Dereferences the value.

impl<'a, T> Pointer for &'a mut T where
    T: ?Sized
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Formats the value using the given formatter.

impl<'a, T> Pointer for &'a T where
    T: ?Sized
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Formats the value using the given formatter.

impl<'a, T> Binary for &'a mut T where
    T: Binary + ?Sized
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Formats the value using the given formatter.

impl<'a, T> Binary for &'a T where
    T: Binary + ?Sized
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Formats the value using the given formatter.

impl<'a, T> BorrowMut<T> for &'a mut T where
    T: ?Sized
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Important traits for &'a mut I

Mutably borrows from an owned value. Read more

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

Formats the value using the given formatter. Read more

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

Formats the value using the given formatter. Read more

impl<'a, R: Read + ?Sized> Read for &'a mut R
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Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

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

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

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

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

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

Important traits for &'a mut I

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

Important traits for Bytes<R>

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

Important traits for Chars<R>

Deprecated since 1.27.0

: Use str::from_utf8 instead: https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples

🔬 This is a nightly-only experimental API. (io #27802)

the semantics of a partial read/write of where errors happen is currently unclear and may change

Transforms this Read instance to an [Iterator] over [char]s. Read more

Important traits for Chain<T, U>

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

Important traits for Take<T>

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

impl<'a, W: Write + ?Sized> Write for &'a mut W
[src]

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

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

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

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

Important traits for &'a mut I

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

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

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

impl<'a, B: BufRead + ?Sized> BufRead for &'a mut B
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Fills the internal buffer of this object, returning the buffer contents. Read more

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

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

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

Important traits for Split<B>

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

Important traits for Lines<B>

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

impl<'a, T: ToSocketAddrs + ?Sized> ToSocketAddrs for &'a T
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Returned iterator over socket addresses which this type may correspond to. Read more

Converts this object to an iterator of resolved SocketAddrs. Read more

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

impl<'a, T: RefUnwindSafe + ?Sized> UnwindSafe for &'a T
1.9.0
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