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, 'b, A, B> PartialEq<&'b mut B> for &'a mut 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

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This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b B> for &'a mut 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

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This method tests for !=.

impl<'a, 'b, A, B> PartialEq<&'b mut 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

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This method tests for !=.

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

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This method tests for !=.

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

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, H> Hasher for &'a mut H where
    H: Hasher + ?Sized
1.22.0
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Returns the hash value for the values written so far. Read more

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Writes some data into this Hasher. Read more

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Writes a single u8 into this hasher.

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Writes a single u16 into this hasher.

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Writes a single u32 into this hasher.

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Writes a single u64 into this hasher.

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🔬 This is a nightly-only experimental API. (i128 #35118)

Writes a single u128 into this hasher.

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Writes a single usize into this hasher.

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Writes a single i8 into this hasher.

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Writes a single i16 into this hasher.

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Writes a single i32 into this hasher.

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Writes a single i64 into this hasher.

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🔬 This is a nightly-only experimental API. (i128 #35118)

Writes a single i128 into this hasher.

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Writes a single isize into this hasher.

impl<'a, I> TrustedLen for &'a mut I where
    I: TrustedLen + ?Sized
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impl<'a, A, F> Fn<A> for &'a F where
    F: Fn<A> + ?Sized
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🔬 This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

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

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> 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> Debug for &'a mut T where
    T: Debug + ?Sized
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Formats the value using the given formatter.

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

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

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

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

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

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

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

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

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

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

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

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

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Dereferences the value.

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

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Dereferences the value.

impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized
1.4.0
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Writes a slice of bytes into this writer, returning whether the write succeeded. Read more

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

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

impl<'a, A> Eq for &'a A where
    A: Eq + ?Sized
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impl<'a, A> Eq for &'a mut A where
    A: Eq + ?Sized
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impl<'a, T, U> AsRef<U> for &'a mut T where
    T: AsRef<U> + ?Sized,
    U: ?Sized
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Performs the conversion.

impl<'a, T, U> AsRef<U> for &'a T where
    T: AsRef<U> + ?Sized,
    U: ?Sized
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Performs the conversion.

impl<'a, A, F> FnMut<A> for &'a F where
    F: Fn<A> + ?Sized
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🔬 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
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🔬 This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

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

1.3.0
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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

1.3.0
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Feeds a slice of this type into the given [Hasher]. Read more

impl<'a, T> Borrow<T> for &'a mut T where
    T: ?Sized
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Immutably borrows from an owned value. Read more

impl<'a, T> Borrow<T> for &'a T where
    T: ?Sized
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Immutably borrows from an owned value. 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

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

Resumes the execution of this generator. Read more

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

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

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

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

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, T, U> CoerceUnsized<&'a 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, T, U> CoerceUnsized<*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
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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<*const U> for &'a T where
    T: Unsize<U> + ?Sized,
    U: ?Sized
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impl<'a, I> FusedIterator for &'a mut I where
    I: FusedIterator + ?Sized
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impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized
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The type of the elements being iterated over.

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Advances the iterator and returns the next value. Read more

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

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Returns the nth element of the iterator. Read more

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

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Consumes the iterator, returning the last element. Read more

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🔬 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

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

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

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

1.21.0
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Calls a closure on each element of an iterator. Read more

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

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Creates an iterator that both filters and maps. Read more

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

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

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

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

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

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

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

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

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

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

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Borrows an iterator, rather than consuming it. Read more

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Transforms an iterator into a collection. Read more

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

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

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

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

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

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

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

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Returns the maximum element of an iterator. Read more

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Returns the minimum element of an iterator. Read more

1.6.0
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Returns the element that gives the maximum value from the specified function. Read more

1.15.0
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Returns the element that gives the maximum value with respect to the specified comparison function. Read more

1.6.0
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Returns the element that gives the minimum value from the specified function. Read more

1.15.0
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Returns the element that gives the minimum value with respect to the specified comparison function. Read more

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Reverses an iterator's direction. Read more

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

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

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Repeats an iterator endlessly. Read more

1.11.0
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Sums the elements of an iterator. Read more

1.11.0
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Iterates over the entire iterator, multiplying all the elements Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Determines if the elements of this Iterator are equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are unequal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less or equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than or equal to those of another. Read more

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

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

Performs the call operation.

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.

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

Performs the call operation.

impl<'a, T, U> AsMut<U> for &'a mut T where
    T: AsMut<U> + ?Sized,
    U: ?Sized
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Performs the conversion.

impl<'a, T> DerefMut for &'a mut T where
    T: ?Sized
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Mutably dereferences the value.

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

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

Returns whether the iterator is empty. 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

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🔬 This is a nightly-only experimental API. (iter_rfold #44705)

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

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🔬 This is a nightly-only experimental API. (iter_rfind #39480)

Searches for an element of an iterator from the right 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

1.21.0
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Compares and returns the maximum of two values. Read more

1.21.0
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Compares and returns the minimum of two values. Read more

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

1.21.0
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Compares and returns the maximum of two values. Read more

1.21.0
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Compares and returns the minimum of two values. Read more

impl<'a, T> BorrowMut<T> for &'a mut T where
    T: ?Sized
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Mutably borrows from an owned value. 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

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

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

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

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

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

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

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

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🔬 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

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

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

impl<'a, W: Write + ?Sized> Write for &'a mut W
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Write a buffer into this object, returning how many bytes were written. Read more

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

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

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

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

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

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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

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

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

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

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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

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

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