# Struct alloc::boxed::Box
1.0.0[−][src]

    pub struct Box<T: ?Sized, A: Allocator = Global>(_, _);

Expand description

A pointer type for heap allocation.

See the module-level documentation for more.

## Implementations

[src]

### impl<T> Box<T>

[src]

#### pub fn new(x: T) -> Self

Allocates memory on the heap and then places `x` into it.

This doesn’t actually allocate if `T` is zero-sized.

##### Examples

    let five = Box::new(5);

Run
[src]

#### pub fn new_uninit() -> Box<MaybeUninit<T>>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new box with uninitialized contents.

##### Examples

    #![feature(new_uninit)]

    let mut five = Box::<u32>::new_uninit();

    let five = unsafe {
        // Deferred initialization:
        five.as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5)

Run
[src]

#### pub fn new_zeroed() -> Box<MaybeUninit<T>>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new `Box` with uninitialized contents, with the memory being filled with `0` bytes.

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(new_uninit)]

    let zero = Box::<u32>::new_zeroed();
    let zero = unsafe { zero.assume_init() };

    assert_eq!(*zero, 0)

Run
1.33.0[src]

#### pub fn pin(x: T) -> Pin<Box<T>>

Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then `x` will be pinned in memory and unable to be moved.

[src]

#### pub fn try_new(x: T) -> Result<Self, AllocError>

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

Allocates memory on the heap then places `x` into it, returning an error if the allocation fails

This doesn’t actually allocate if `T` is zero-sized.

##### Examples

    #![feature(allocator_api)]

    let five = Box::try_new(5)?;

Run
[src]

#### pub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>

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

Constructs a new box with uninitialized contents on the heap, returning an error if the allocation fails

##### Examples

    #![feature(allocator_api, new_uninit)]

    let mut five = Box::<u32>::try_new_uninit()?;

    let five = unsafe {
        // Deferred initialization:
        five.as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5);

Run
[src]

#### pub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>

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

Constructs a new `Box` with uninitialized contents, with the memory being filled with `0` bytes on the heap

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(allocator_api, new_uninit)]

    let zero = Box::<u32>::try_new_zeroed()?;
    let zero = unsafe { zero.assume_init() };

    assert_eq!(*zero, 0);

Run
[src]

### impl<T, A: Allocator> Box<T, A>

[src]

#### pub fn new_in(x: T, alloc: A) -> Self where
A: ~constAllocator,

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

Allocates memory in the given allocator then places `x` into it.

This doesn’t actually allocate if `T` is zero-sized.

##### Examples

    #![feature(allocator_api)]

    use std::alloc::System;

    let five = Box::new_in(5, System);

Run
[src]

#### pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> where
T: ,
A: ~constAllocator,

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

Allocates memory in the given allocator then places `x` into it, returning an error if the allocation fails

This doesn’t actually allocate if `T` is zero-sized.

##### Examples

    #![feature(allocator_api)]

    use std::alloc::System;

    let five = Box::try_new_in(5, System)?;

Run
[src]

#### pub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`
where
A: ~constAllocator,

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

Constructs a new box with uninitialized contents in the provided allocator.

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let mut five = Box::<u32, _>::new_uninit_in(System);

    let five = unsafe {
        // Deferred initialization:
        five.as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5)

Run
[src]

#### pub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: ~constAllocator,

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

Constructs a new box with uninitialized contents in the provided allocator, returning an error if the allocation fails

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let mut five = Box::<u32, _>::try_new_uninit_in(System)?;

    let five = unsafe {
        // Deferred initialization:
        five.as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5);

Run
[src]

#### pub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`
where
A: ~constAllocator,

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

Constructs a new `Box` with uninitialized contents, with the memory being filled with `0` bytes in the provided allocator.

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let zero = Box::<u32, _>::new_zeroed_in(System);
    let zero = unsafe { zero.assume_init() };

    assert_eq!(*zero, 0)

Run
[src]

#### pub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: ~constAllocator,

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

Constructs a new `Box` with uninitialized contents, with the memory being filled with `0` bytes in the provided allocator, returning an error if the allocation fails,

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
    let zero = unsafe { zero.assume_init() };

    assert_eq!(*zero, 0);

Run
[src]

#### pub fn pin_in(x: T, alloc: A) -> Pin<Self> where
A: 'static + ~constAllocator,

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

Constructs a new `Pin<Box<T, A>>`. If `T` does not implement `Unpin`, then `x` will be pinned in memory and unable to be moved.

[src]

#### pub fn into_boxed_slice(boxed: Self) -> Box<[T], A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`box_into_boxed_slice` #71582)

Converts a `Box<T>` into a `Box<[T]>`

This conversion does not allocate on the heap and happens in place.

[src]

#### pub fn into_inner(boxed: Self) -> T where
Self: ,

🔬 This is a nightly-only experimental API. (`box_into_inner` #80437)

Consumes the `Box`, returning the wrapped value.

##### Examples

    #![feature(box_into_inner)]

    let c = Box::new(5);

    assert_eq!(Box::into_inner(c), 5);

Run
[src]

### impl<T> Box<[T]>

[src]

#### pub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new boxed slice with uninitialized contents.

##### Examples

    #![feature(new_uninit)]

    let mut values = Box::<[u32]>::new_uninit_slice(3);

    let values = unsafe {
        // Deferred initialization:
        values[0].as_mut_ptr().write(1);
        values[1].as_mut_ptr().write(2);
        values[2].as_mut_ptr().write(3);

        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3])

Run
[src]

#### pub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new boxed slice with uninitialized contents, with the memory being filled with `0` bytes.

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(new_uninit)]

    let values = Box::<[u32]>::new_zeroed_slice(3);
    let values = unsafe { values.assume_init() };

    assert_eq!(*values, [0, 0, 0])

Run
[src]

#### pub fn try_new_uninit_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>

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

Constructs a new boxed slice with uninitialized contents. Returns an error if the allocation fails

##### Examples

    #![feature(allocator_api, new_uninit)]

    let mut values = Box::<[u32]>::try_new_uninit_slice(3)?;
    let values = unsafe {
        // Deferred initialization:
        values[0].as_mut_ptr().write(1);
        values[1].as_mut_ptr().write(2);
        values[2].as_mut_ptr().write(3);
        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3]);

Run
[src]

#### pub fn try_new_zeroed_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>

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

Constructs a new boxed slice with uninitialized contents, with the memory being filled with `0` bytes. Returns an error if the allocation fails

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(allocator_api, new_uninit)]

    let values = Box::<[u32]>::try_new_zeroed_slice(3)?;
    let values = unsafe { values.assume_init() };

    assert_eq!(*values, [0, 0, 0]);

Run
[src]

### impl<T, A: Allocator> Box<[T], A>

[src]

#### pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

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

Constructs a new boxed slice with uninitialized contents in the provided allocator.

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);

    let values = unsafe {
        // Deferred initialization:
        values[0].as_mut_ptr().write(1);
        values[1].as_mut_ptr().write(2);
        values[2].as_mut_ptr().write(3);

        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3])

Run
[src]

#### pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

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

Constructs a new boxed slice with uninitialized contents in the provided allocator, with the memory being filled with `0` bytes.

See `MaybeUninit::zeroed` for examples of correct and incorrect usage of this method.

##### Examples

    #![feature(allocator_api, new_uninit)]

    use std::alloc::System;

    let values = Box::<[u32], _>::new_zeroed_slice_in(3, System);
    let values = unsafe { values.assume_init() };

    assert_eq!(*values, [0, 0, 0])

Run
[src]

### impl<T, A: Allocator> Box<MaybeUninit<T>, A>

[src]

#### pub unsafe fn assume_init(self) -> Box<T, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Converts to `Box<T, A>`.

##### Safety

As with `MaybeUninit::assume_init`, it is up to the caller to guarantee that the value really is in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

##### Examples

    #![feature(new_uninit)]

    let mut five = Box::<u32>::new_uninit();

    let five: Box<u32> = unsafe {
        // Deferred initialization:
        five.as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5)

Run
[src]

#### pub fn write(boxed: Self, value: T) -> Box<T, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Writes the value and converts to `Box<T, A>`.

This method converts the box similarly to `Box::assume_init` but writes `value` into it before conversion thus guaranteeing safety. In some scenarios use of this method may improve performance because the compiler may be able to optimize copying from stack.

##### Examples

    #![feature(new_uninit)]

    let big_box = Box::<[usize; 1024]>::new_uninit();

    let mut array = [0; 1024];
    for (i, place) in array.iter_mut().enumerate() {
        *place = i;
    }

    // The optimizer may be able to elide this copy, so previous code writes
    // to heap directly.
    let big_box = Box::write(big_box, array);

    for (i, x) in big_box.iter().enumerate() {
        assert_eq!(*x, i);
    }

Run
[src]

### impl<T, A: Allocator> Box<[MaybeUninit<T>], A>

[src]

#### pub unsafe fn assume_init(self) -> Box<[T], A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Converts to `Box<[T], A>`.

##### Safety

As with `MaybeUninit::assume_init`, it is up to the caller to guarantee that the values really are in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

##### Examples

    #![feature(new_uninit)]

    let mut values = Box::<[u32]>::new_uninit_slice(3);

    let values = unsafe {
        // Deferred initialization:
        values[0].as_mut_ptr().write(1);
        values[1].as_mut_ptr().write(2);
        values[2].as_mut_ptr().write(3);

        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3])

Run
[src]

### impl<T: ?Sized> Box<T>

1.4.0[src]

#### pub unsafe fn from_raw(raw: *mut T) -> Self

Constructs a box from a raw pointer.

After calling this function, the raw pointer is owned by the resulting `Box`. Specifically, the `Box` destructor will call the destructor of `T` and free the allocated memory. For this to be safe, the memory must have been allocated in accordance with the memory layout used by `Box` .

##### Safety

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

The safety conditions are described in the memory layout section.

##### Examples

Recreate a `Box` which was previously converted to a raw pointer using `Box::into_raw`:

    let x = Box::new(5);
    let ptr = Box::into_raw(x);
    let x = unsafe { Box::from_raw(ptr) };

Run

Manually create a `Box` from scratch by using the global allocator:

    use std::alloc::{alloc, Layout};

    unsafe {
        let ptr = alloc(Layout::new::<i32>()) as *mut i32;
        // In general .write is required to avoid attempting to destruct
        // the (uninitialized) previous contents of `ptr`, though for this
        // simple example `*ptr = 5` would have worked as well.
        ptr.write(5);
        let x = Box::from_raw(ptr);
    }

Run
[src]

### impl<T: ?Sized, A: Allocator> Box<T, A>

[src]

#### pub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self

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

Constructs a box from a raw pointer in the given allocator.

After calling this function, the raw pointer is owned by the resulting `Box`. Specifically, the `Box` destructor will call the destructor of `T` and free the allocated memory. For this to be safe, the memory must have been allocated in accordance with the memory layout used by `Box` .

##### Safety

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

##### Examples

Recreate a `Box` which was previously converted to a raw pointer using `Box::into_raw_with_allocator`:

    #![feature(allocator_api)]

    use std::alloc::System;

    let x = Box::new_in(5, System);
    let (ptr, alloc) = Box::into_raw_with_allocator(x);
    let x = unsafe { Box::from_raw_in(ptr, alloc) };

Run

Manually create a `Box` from scratch by using the system allocator:

    #![feature(allocator_api, slice_ptr_get)]

    use std::alloc::{Allocator, Layout, System};

    unsafe {
        let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
        // In general .write is required to avoid attempting to destruct
        // the (uninitialized) previous contents of `ptr`, though for this
        // simple example `*ptr = 5` would have worked as well.
        ptr.write(5);
        let x = Box::from_raw_in(ptr, System);
    }

Run
1.4.0[src]

#### pub fn into_raw(b: Self) -> *mut T

Consumes the `Box`, returning a wrapped raw pointer.

The pointer will be properly aligned and non-null.

After calling this function, the caller is responsible for the memory previously managed by the `Box`. In particular, the caller should properly destroy `T` and release the memory, taking into account the memory layout used by `Box`. The easiest way to do this is to convert the raw pointer back into a `Box` with the `Box::from_raw` function, allowing the `Box` destructor to perform the cleanup.

Note: this is an associated function, which means that you have to call it as `Box::into_raw(b)` instead of `b.into_raw()`. This is so that there is no conflict with a method on the inner type.

##### Examples

Converting the raw pointer back into a `Box` with `Box::from_raw` for automatic cleanup:

    let x = Box::new(String::from("Hello"));
    let ptr = Box::into_raw(x);
    let x = unsafe { Box::from_raw(ptr) };

Run

Manual cleanup by explicitly running the destructor and deallocating the memory:

    use std::alloc::{dealloc, Layout};
    use std::ptr;

    let x = Box::new(String::from("Hello"));
    let p = Box::into_raw(x);
    unsafe {
        ptr::drop_in_place(p);
        dealloc(p as *mut u8, Layout::new::<String>());
    }

Run
[src]

#### pub fn into_raw_with_allocator(b: Self) -> (*mut T, A)

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

Consumes the `Box`, returning a wrapped raw pointer and the allocator.

The pointer will be properly aligned and non-null.

After calling this function, the caller is responsible for the memory previously managed by the `Box`. In particular, the caller should properly destroy `T` and release the memory, taking into account the memory layout used by `Box`. The easiest way to do this is to convert the raw pointer back into a `Box` with the `Box::from_raw_in` function, allowing the `Box` destructor to perform the cleanup.

Note: this is an associated function, which means that you have to call it as `Box::into_raw_with_allocator(b)` instead of `b.into_raw_with_allocator()`. This is so that there is no conflict with a method on the inner type.

##### Examples

Converting the raw pointer back into a `Box` with `Box::from_raw_in` for automatic cleanup:

    #![feature(allocator_api)]

    use std::alloc::System;

    let x = Box::new_in(String::from("Hello"), System);
    let (ptr, alloc) = Box::into_raw_with_allocator(x);
    let x = unsafe { Box::from_raw_in(ptr, alloc) };

Run

Manual cleanup by explicitly running the destructor and deallocating the memory:

    #![feature(allocator_api)]

    use std::alloc::{Allocator, Layout, System};
    use std::ptr::{self, NonNull};

    let x = Box::new_in(String::from("Hello"), System);
    let (ptr, alloc) = Box::into_raw_with_allocator(x);
    unsafe {
        ptr::drop_in_place(ptr);
        let non_null = NonNull::new_unchecked(ptr);
        alloc.deallocate(non_null.cast(), Layout::new::<String>());
    }

Run
[src]

#### pub fn allocator(b: &Self) -> &A

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

Returns a reference to the underlying allocator.

Note: this is an associated function, which means that you have to call it as `Box::allocator(&b)` instead of `b.allocator()`. This is so that there is no conflict with a method on the inner type.

1.26.0 (const: unstable)[src]

#### pub fn leak<'a>(b: Self) -> &'a mut T where
A: 'a,

Consumes and leaks the `Box`, returning a mutable reference, `&'a mut T`. Note that the type `T` must outlive the chosen lifetime `'a`. If the type has only static references, or none at all, then this may be chosen to be `'static`.

This function is mainly useful for data that lives for the remainder of the program’s life. Dropping the returned reference will cause a memory leak. If this is not acceptable, the reference should first be wrapped with the `Box::from_raw` function producing a `Box`. This `Box` can then be dropped which will properly destroy `T` and release the allocated memory.

Note: this is an associated function, which means that you have to call it as `Box::leak(b)` instead of `b.leak()`. This is so that there is no conflict with a method on the inner type.

##### Examples

Simple usage:

    let x = Box::new(41);
    let static_ref: &'static mut usize = Box::leak(x);
    *static_ref += 1;
    assert_eq!(*static_ref, 42);

Run

Unsized data:

    let x = vec![1, 2, 3].into_boxed_slice();
    let static_ref = Box::leak(x);
    static_ref[0] = 4;
    assert_eq!(*static_ref, [4, 2, 3]);

Run
[src]

#### pub fn into_pin(boxed: Self) -> Pin<Self> where
A: 'static,

🔬 This is a nightly-only experimental API. (`box_into_pin` #62370)

Converts a `Box<T>` into a `Pin<Box<T>>`

This conversion does not allocate on the heap and happens in place.

This is also available via `From`.

[src]

### impl<A: Allocator> Box<dyn Any, A>

[src]

#### pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>

Attempt to downcast the box to a concrete type.

##### Examples

    use std::any::Any;

    fn print_if_string(value: Box<dyn Any>) {
        if let Ok(string) = value.downcast::<String>() {
            println!("String ({}): {}", string.len(), string);
        }
    }

    let my_string = "Hello World".to_string();
    print_if_string(Box::new(my_string));
    print_if_string(Box::new(0i8));

Run
[src]

#### pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`downcast_unchecked` #90850)

Downcasts the box to a concrete type.

For a safe alternative see `downcast`.

##### Examples

    #![feature(downcast_unchecked)]

    use std::any::Any;

    let x: Box<dyn Any> = Box::new(1_usize);

    unsafe {
        assert_eq!(*x.downcast_unchecked::<usize>(), 1);
    }

Run

##### Safety

The contained value must be of type `T`. Calling this method with the incorrect type is undefined behavior.

[src]

### impl<A: Allocator> Box<dyn Any + Send, A>

[src]

#### pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>

Attempt to downcast the box to a concrete type.

##### Examples

    use std::any::Any;

    fn print_if_string(value: Box<dyn Any + Send>) {
        if let Ok(string) = value.downcast::<String>() {
            println!("String ({}): {}", string.len(), string);
        }
    }

    let my_string = "Hello World".to_string();
    print_if_string(Box::new(my_string));
    print_if_string(Box::new(0i8));

Run
[src]

#### pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`downcast_unchecked` #90850)

Downcasts the box to a concrete type.

For a safe alternative see `downcast`.

##### Examples

    #![feature(downcast_unchecked)]

    use std::any::Any;

    let x: Box<dyn Any + Send> = Box::new(1_usize);

    unsafe {
        assert_eq!(*x.downcast_unchecked::<usize>(), 1);
    }

Run

##### Safety

The contained value must be of type `T`. Calling this method with the incorrect type is undefined behavior.

[src]

### impl<A: Allocator> Box<dyn Any + Send + Sync, A>

1.51.0[src]

#### pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>

Attempt to downcast the box to a concrete type.

##### Examples

    use std::any::Any;

    fn print_if_string(value: Box<dyn Any + Send + Sync>) {
        if let Ok(string) = value.downcast::<String>() {
            println!("String ({}): {}", string.len(), string);
        }
    }

    let my_string = "Hello World".to_string();
    print_if_string(Box::new(my_string));
    print_if_string(Box::new(0i8));

Run
[src]

#### pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

🔬 This is a nightly-only experimental API. (`downcast_unchecked` #90850)

Downcasts the box to a concrete type.

For a safe alternative see `downcast`.

##### Examples

    #![feature(downcast_unchecked)]

    use std::any::Any;

    let x: Box<dyn Any + Send + Sync> = Box::new(1_usize);

    unsafe {
        assert_eq!(*x.downcast_unchecked::<usize>(), 1);
    }

Run

##### Safety

The contained value must be of type `T`. Calling this method with the incorrect type is undefined behavior.

## Trait Implementations

1.5.0[src]

### impl<T: ?Sized, A: Allocator> AsMut<T> for Box<T, A>

[src]

#### fn as_mut(&mut self) -> &mut T

Performs the conversion.

1.5.0[src]

### impl<T: ?Sized, A: Allocator> AsRef<T> for Box<T, A>

[src]

#### fn as_ref(&self) -> &T

Performs the conversion.

1.1.0[src]

### impl<T: ?Sized, A: Allocator> Borrow<T> for Box<T, A>

[src]

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

1.1.0[src]

### impl<T: ?Sized, A: Allocator> BorrowMut<T> for Box<T, A>

[src]

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

Mutably borrows from an owned value. Read more

[src]

### impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A>

[src]

#### fn clone(&self) -> Self

Returns a new box with a `clone()` of this box’s contents.

##### Examples

    let x = Box::new(5);
    let y = x.clone();

    // The value is the same
    assert_eq!(x, y);

    // But they are unique objects
    assert_ne!(&*x as *const i32, &*y as *const i32);

Run
[src]

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

Copies `source`’s contents into `self` without creating a new allocation.

##### Examples

    let x = Box::new(5);
    let mut y = Box::new(10);
    let yp: *const i32 = &*y;

    y.clone_from(&x);

    // The value is the same
    assert_eq!(x, y);

    // And no allocation occurred
    assert_eq!(yp, &*y);

Run
1.3.0[src]

### impl Clone for Box<str>

[src]

#### fn clone(&self) -> Self

Returns a copy of the value. Read more

[src]

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

Performs copy-assignment from `source`. Read more

1.3.0[src]

### impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A>

[src]

#### fn clone(&self) -> Self

Returns a copy of the value. Read more

[src]

#### fn clone_from(&mut self, other: &Self)

Performs copy-assignment from `source`. Read more

[src]

### impl<T: Debug + ?Sized, A: Allocator> Debug for Box<T, A>

[src]

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

Formats the value using the given formatter. Read more

[src]

### impl<T: Default> Default for Box<T>

[src]

#### fn default() -> Self

Creates a `Box<T>`, with the `Default` value for T.

[src]

### impl<T> Default for Box<[T]>

[src]

#### fn default() -> Self

Returns the “default value” for a type. Read more

1.17.0[src]

### impl Default for Box<str>

[src]

#### fn default() -> Self

Returns the “default value” for a type. Read more

1.0.0 (const: unstable)[src]

### impl<T: ?Sized, A: Allocator> Deref for Box<T, A>

#### type Target = T

The resulting type after dereferencing.

[src]

#### fn deref(&self) -> &T

Dereferences the value.

1.0.0 (const: unstable)[src]

### impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A>

[src]

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

Mutably dereferences the value.

[src]

### impl<T: Display + ?Sized, A: Allocator> Display for Box<T, A>

[src]

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

Formats the value using the given formatter. Read more

[src]

### impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A>

[src]

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

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

[src]

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

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

[src]

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

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

Advances the iterator from the back by `n` elements. Read more

1.27.0[src]

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

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

1.27.0[src]

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

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

1.27.0[src]

#### 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. Read more

1.0.0 (const: unstable)[src]

### impl<T: ?Sized, A: Allocator> Drop for Box<T, A>

[src]

#### fn drop(&mut self)

Executes the destructor for this type. Read more

[src]

### impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A>

[src]

#### fn len(&self) -> usize

Returns the exact length of the iterator. Read more

[src]

#### fn is_empty(&self) -> bool

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

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

1.45.0[src]

### impl Extend<Box<str, Global>> for String

[src]

#### fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I)

Extends a collection with the contents of an iterator. Read more

[src]

#### fn extend_one(&mut self, item: A)

🔬 This is a nightly-only experimental API. (`extend_one` #72631)

Extends a collection with exactly one element.

[src]

#### fn extend_reserve(&mut self, additional: usize)

🔬 This is a nightly-only experimental API. (`extend_one` #72631)

Reserves capacity in a collection for the given number of additional elements. Read more

1.35.0[src]

### impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A>

[src]

#### extern "rust-call" fn call(&self, args: Args) -> Self::Output

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

Performs the call operation.

1.35.0[src]

### impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A>

[src]

#### extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output

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

Performs the call operation.

1.35.0[src]

### impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A>

#### type Output = <F as FnOnce<Args>>::Output

The returned type after the call operator is used.

[src]

#### extern "rust-call" fn call_once(self, args: Args) -> Self::Output

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

Performs the call operation.

1.17.0[src]

### impl<T: Copy> From<&'_ [T]> for Box<[T]>

[src]

#### fn from(slice: &[T]) -> Box<[T]>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts a `&[T]` into a `Box<[T]>`

This conversion allocates on the heap and performs a copy of `slice`.

##### Examples

    // create a &[u8] which will be used to create a Box<[u8]>
    let slice: &[u8] = &[104, 101, 108, 108, 111];
    let boxed_slice: Box<[u8]> = Box::from(slice);

    println!("{:?}", boxed_slice);

Run
1.17.0[src]

### impl From<&'_ str> for Box<str>

[src]

#### fn from(s: &str) -> Box<str>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts a `&str` into a `Box<str>`

This conversion allocates on the heap and performs a copy of `s`.

##### Examples

    let boxed: Box<str> = Box::from("hello");
    println!("{}", boxed);

Run
1.45.0[src]

### impl<T, const N: usize> From<[T; N]> for Box<[T]>

[src]

#### fn from(array: [T; N]) -> Box<[T]>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts a `[T; N]` into a `Box<[T]>`

This conversion moves the array to newly heap-allocated memory.

##### Examples

    let boxed: Box<[u8]> = Box::from([4, 2]);
    println!("{:?}", boxed);

Run
1.18.0[src]

### impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A>

[src]

#### fn from(s: Box<[T], A>) -> Self

Convert a boxed slice into a vector by transferring ownership of the existing heap allocation.

##### Examples

    let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice();
    assert_eq!(Vec::from(b), vec![1, 2, 3]);

Run
1.33.0 (const: unstable)[src]

### impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>> where
A: 'static,

[src]

#### fn from(boxed: Box<T, A>) -> Self

Converts a `Box<T>` into a `Pin<Box<T>>`

This conversion does not allocate on the heap and happens in place.

1.21.0[src]

### impl<T: ?Sized> From<Box<T, Global>> for Rc<T>

[src]

#### fn from(v: Box<T>) -> Rc<T>

Move a boxed object to a new, reference counted, allocation.

##### Example

    let original: Box<i32> = Box::new(1);
    let shared: Rc<i32> = Rc::from(original);
    assert_eq!(1, *shared);

Run
1.21.0[src]

### impl<T: ?Sized> From<Box<T, Global>> for Arc<T>

[src]

#### fn from(v: Box<T>) -> Arc<T>

Move a boxed object to a new, reference-counted allocation.

##### Example

    let unique: Box<str> = Box::from("eggplant");
    let shared: Arc<str> = Arc::from(unique);
    assert_eq!("eggplant", &shared[..]);

Run
1.19.0[src]

### impl<A: Allocator> From<Box<str, A>> for Box<[u8], A>

[src]

#### fn from(s: Box<str, A>) -> Self

Converts a `Box<str>` into a `Box<[u8]>`

This conversion does not allocate on the heap and happens in place.

##### Examples

    // create a Box<str> which will be used to create a Box<[u8]>
    let boxed: Box<str> = Box::from("hello");
    let boxed_str: Box<[u8]> = Box::from(boxed);

    // create a &[u8] which will be used to create a Box<[u8]>
    let slice: &[u8] = &[104, 101, 108, 108, 111];
    let boxed_slice = Box::from(slice);

    assert_eq!(boxed_slice, boxed_str);

Run
1.18.0[src]

### impl From<Box<str, Global>> for String

[src]

#### fn from(s: Box<str>) -> String

Converts the given boxed `str` slice to a `String`. It is notable that the `str` slice is owned.

##### Examples

Basic usage:

    let s1: String = String::from("hello world");
    let s2: Box<str> = s1.into_boxed_str();
    let s3: String = String::from(s2);

    assert_eq!("hello world", s3)

Run
1.45.0[src]

### impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]>

[src]

#### fn from(cow: Cow<'_, [T]>) -> Box<[T]>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts a `Cow<'_, [T]>` into a `Box<[T]>`

When `cow` is the `Cow::Borrowed` variant, this conversion allocates on the heap and copies the underlying slice. Otherwise, it will try to reuse the owned `Vec`’s allocation.

1.45.0[src]

### impl From<Cow<'_, str>> for Box<str>

[src]

#### fn from(cow: Cow<'_, str>) -> Box<str>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts a `Cow<'_, str>` into a `Box<str>`

When `cow` is the `Cow::Borrowed` variant, this conversion allocates on the heap and copies the underlying `str`. Otherwise, it will try to reuse the owned `String`’s allocation.

##### Examples

    use std::borrow::Cow;

    let unboxed = Cow::Borrowed("hello");
    let boxed: Box<str> = Box::from(unboxed);
    println!("{}", boxed);

Run

    let unboxed = Cow::Owned("hello".to_string());
    let boxed: Box<str> = Box::from(unboxed);
    println!("{}", boxed);

Run
1.20.0[src]

### impl From<String> for Box<str>

[src]

#### fn from(s: String) -> Box<str>ⓘ
Notable traits for Box<F, A>
`impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;`

Converts the given `String` to a boxed `str` slice that is owned.

##### Examples

Basic usage:

    let s1: String = String::from("hello world");
    let s2: Box<str> = Box::from(s1);
    let s3: String = String::from(s2);

    assert_eq!("hello world", s3)

Run
1.6.0[src]

### impl<T> From<T> for Box<T>

[src]

#### fn from(t: T) -> Self

Converts a `T` into a `Box<T>`

The conversion allocates on the heap and moves `t` from the stack into it.

##### Examples

    let x = 5;
    let boxed = Box::new(5);

    assert_eq!(Box::from(x), boxed);

Run
1.20.0[src]

### impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A>

[src]

#### fn from(v: Vec<T, A>) -> Self

Convert a vector into a boxed slice.

If `v` has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity.

##### Examples

    assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());

Run
1.45.0[src]

### impl FromIterator<Box<str, Global>> for String

[src]

#### fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String

Creates a value from an iterator. Read more

1.32.0[src]

### impl<I> FromIterator<I> for Box<[I]>

[src]

#### fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self

Creates a value from an iterator. Read more

1.36.0[src]

### impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static,

#### type Output = F::Output

The type of value produced on completion.

[src]

#### fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

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

[src]

### impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A> where
A: 'static,

#### type Yield = G::Yield

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

The type of value this generator yields. Read more

#### type Return = G::Return

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

The type of value this generator returns. Read more

[src]

#### fn resume(
self: Pin<&mut Self>,
arg: R
) -> GeneratorState<Self::Yield, Self::Return>

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

Resumes the execution of this generator. Read more

[src]

### impl<T: ?Sized + Hash, A: Allocator> Hash for Box<T, A>

[src]

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

Feeds this value into the given `Hasher`. Read more

1.3.0[src]

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

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

1.22.0[src]

### impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A>

[src]

#### fn finish(&self) -> u64

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

[src]

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

Writes some data into this `Hasher`. Read more

[src]

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

Writes a single `u8` into this hasher.

[src]

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

Writes a single `u16` into this hasher.

[src]

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

Writes a single `u32` into this hasher.

[src]

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

Writes a single `u64` into this hasher.

[src]

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

Writes a single `u128` into this hasher.

[src]

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

Writes a single `usize` into this hasher.

[src]

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

Writes a single `i8` into this hasher.

[src]

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

Writes a single `i16` into this hasher.

[src]

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

Writes a single `i32` into this hasher.

[src]

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

Writes a single `i64` into this hasher.

[src]

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

Writes a single `i128` into this hasher.

[src]

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

Writes a single `isize` into this hasher.

[src]

### impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A>

#### type Item = I::Item

The type of the elements being iterated over.

[src]

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

Advances the iterator and returns the next value. Read more

[src]

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

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

[src]

#### fn nth(&mut self, n: usize) -> Option<I::Item>

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

[src]

#### fn last(self) -> Option<I::Item>

Consumes the iterator, returning the last element. Read more

[src]

#### fn count(self) -> usize

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

[src]

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

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

Advances the iterator by `n` elements. Read more

1.28.0[src]

#### 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. Read more

[src]

#### 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. Read more

[src]

#### 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. Read more

[src]

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

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

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

[src]

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

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

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

[src]

#### 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. Read more

1.21.0[src]

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

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

[src]

#### 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. Read more

[src]

#### 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. Read more

[src]

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

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

[src]

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

Creates an iterator which can use the `peek` and `peek_mut` methods to look at the next element of the iterator without consuming it. See their documentation for more information. Read more

[src]

#### 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. Read more

[src]

#### 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. Read more

1.57.0[src]

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

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

[src]

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

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

[src]

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

Creates an iterator that yields the first `n` elements, or fewer if the underlying iterator ends sooner. Read more

[src]

#### 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 adapter similar to `fold` that holds internal state and produces a new iterator. Read more

[src]

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

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

1.29.0[src]

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

Creates an iterator that flattens nested structure. Read more

[src]

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

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

[src]

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

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

[src]

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

Borrows an iterator, rather than consuming it. Read more

[src]

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

Transforms an iterator into a collection. Read more

[src]

#### 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. Read more

[src]

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

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

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

[src]

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

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

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

1.27.0[src]

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

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

1.27.0[src]

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

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

[src]

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

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

1.51.0[src]

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

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

[src]

#### fn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType where
F: FnMut(Self::Item, Self::Item) -> R,
R: Try<Output = Self::Item>,
<R as Try>::Residual: Residual<Option<Self::Item>>,

🔬 This is a nightly-only experimental API. (`iterator_try_reduce` #87053)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately. Read more

[src]

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

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

[src]

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

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

[src]

#### 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. Read more

1.30.0[src]

#### 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. Read more

[src]

#### fn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType where
F: FnMut(&Self::Item) -> R,
R: Try<Output = bool>,
<R as Try>::Residual: Residual<Option<Self::Item>>,

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

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

[src]

#### 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. Read more

[src]

#### 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. Read more

[src]

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

Returns the maximum element of an iterator. Read more

[src]

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

Returns the minimum element of an iterator. Read more

1.6.0[src]

#### 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. Read more

1.15.0[src]

#### 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. Read more

1.6.0[src]

#### 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. Read more

1.15.0[src]

#### 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. Read more

[src]

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

Reverses an iterator’s direction. Read more

[src]

#### 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. Read more

1.36.0[src]

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

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

[src]

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

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

[src]

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

Repeats an iterator endlessly. Read more

1.11.0[src]

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

Sums the elements of an iterator. Read more

1.11.0[src]

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

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

1.5.0[src]

#### 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. Read more

[src]

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

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

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

1.5.0[src]

#### 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. Read more

[src]

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

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

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

1.5.0[src]

#### 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. Read more

[src]

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

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

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

1.5.0[src]

#### 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. Read more

1.5.0[src]

#### 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. Read more

1.5.0[src]

#### 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. Read more

1.5.0[src]

#### 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. Read more

1.5.0[src]

#### 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. Read more

[src]

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

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

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

[src]

#### 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)

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

[src]

#### 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)

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

[src]

### impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A>

[src]

#### fn cmp(&self, other: &Self) -> Ordering

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

1.21.0[src]

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

Compares and returns the maximum of two values. Read more

1.21.0[src]

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

Compares and returns the minimum of two values. Read more

1.50.0[src]

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

Restrict a value to a certain interval. Read more

[src]

### impl<T: ?Sized + PartialEq, A: Allocator> PartialEq<Box<T, A>> for Box<T, A>

[src]

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

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

[src]

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

This method tests for `!=`.

[src]

### impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd<Box<T, A>> for Box<T, A>

[src]

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

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

[src]

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

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

[src]

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

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

[src]

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

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

[src]

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

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

[src]

### impl<T: ?Sized, A: Allocator> Pointer for Box<T, A>

[src]

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

Formats the value using the given formatter.

[src]

### impl<S: ?Sized + Stream + Unpin> Stream for Box<S>

#### type Item = S::Item

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

The type of items yielded by the stream.

[src]

#### fn poll_next(
self: Pin<&mut Self>,
cx: &mut Context<'_>
) -> Poll<Option<Self::Item>>

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

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

[src]

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

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

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

1.43.0[src]

### impl<T, const N: usize> TryFrom<Box<[T], Global>> for Box<[T; N]>

[src]

#### fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error>

Attempts to convert a `Box<[T]>` into a `Box<[T; N]>`.

The conversion occurs in-place and does not require a new memory allocation.

##### Errors

Returns the old `Box<[T]>` in the `Err` variant if `boxed_slice.len()` does not equal `N`.

#### type Error = Box<[T]>

The type returned in the event of a conversion error.

[src]

### impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A>

[src]

### impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U, Global>> for Box<T, Global>

[src]

### impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A>

1.26.0[src]

### impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A>

1.33.0 (const: unstable)[src]

### impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where
A: 'static,

## Auto Trait Implementations

### impl<T: ?Sized, A> RefUnwindSafe for Box<T, A> where
A: RefUnwindSafe,
T: RefUnwindSafe,

### impl<T: ?Sized, A> Send for Box<T, A> where
A: Send,
T: Send,

### impl<T: ?Sized, A> Sync for Box<T, A> where
A: Sync,
T: Sync,

### impl<T: ?Sized, A> UnwindSafe for Box<T, A> where
A: UnwindSafe,
T: UnwindSafe,

## Blanket Implementations

[src]

### impl<T> Any for T where
T: 'static + ?Sized,

[src]

#### pub fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

[src]

### impl<T> Borrow<T> for T where
T: ?Sized,

[src]

#### pub fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

[src]

### impl<T> BorrowMut<T> for T where
T: ?Sized,

[src]

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

Mutably borrows from an owned value. Read more

[src]

### impl<T> From<!> for T

[src]

#### pub fn from(t: !) -> T

Performs the conversion.

[src]

### impl<T> From<T> for T

[src]

#### pub fn from(t: T) -> T

Performs the conversion.

[src]

### impl<T, U> Into<U> for T where
U: From<T>,

[src]

#### pub fn into(self) -> U

Performs the conversion.

[src]

### impl<F> IntoFuture for F where
F: Future,

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

🔬 This is a nightly-only experimental API. (`into_future` #67644)

The output that the future will produce on completion.

#### type Future = F

🔬 This is a nightly-only experimental API. (`into_future` #67644)

Which kind of future are we turning this into?

[src]

#### pub fn into_future(self) -> <F as IntoFuture>::Future

🔬 This is a nightly-only experimental API. (`into_future` #67644)

Creates a future from a value.

[src]

### impl<I> IntoIterator for I where
I: Iterator,

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

The type of the elements being iterated over.

#### type IntoIter = I

Which kind of iterator are we turning this into?

[src]

#### pub fn into_iter(self) -> I

Creates an iterator from a value. Read more

[src]

### impl<'a, F> Pattern<'a> for F where
F: FnMut(char) -> bool,

#### type Searcher = CharPredicateSearcher<'a, F>

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Associated searcher for this pattern

[src]

#### pub fn into_searcher(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Constructs the associated searcher from `self` and the `haystack` to search in. Read more

[src]

#### pub fn is_contained_in(self, haystack: &'a str) -> bool

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Checks whether the pattern matches anywhere in the haystack

[src]

#### pub fn is_prefix_of(self, haystack: &'a str) -> bool

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Checks whether the pattern matches at the front of the haystack

[src]

#### pub fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str>

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Removes the pattern from the front of haystack, if it matches.

[src]

#### pub fn is_suffix_of(self, haystack: &'a str) -> bool where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Checks whether the pattern matches at the back of the haystack

[src]

#### pub fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,

🔬 This is a nightly-only experimental API. (`pattern` #27721)

Removes the pattern from the back of haystack, if it matches.

[src]

### impl<T> ToOwned for T where
T: Clone,

#### type Owned = T

The resulting type after obtaining ownership.

[src]

#### pub fn to_owned(&Self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

[src]

#### pub fn clone_into(&Self, &mut T)

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

Uses borrowed data to replace owned data, usually by cloning. Read more

[src]

### impl<T> ToString for T where
T: Display + ?Sized,

[src]

#### pub default fn to_string(&Self) -> String

Converts the given value to a `String`. Read more

[src]

### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

[src]

#### pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

[src]

### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

[src]

#### pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.