pub type netif_linkoutput_fn = Option<unsafe extern "C" fn(netif: *mut netif, p: *mut pbuf) -> err_t>;
Expand description
Function prototype for netif->linkoutput functions. Only used for ethernet netifs. This function is called by ARP when a packet shall be sent.
@param netif The netif which shall send a packet @param p The packet to send (raw ethernet packet)
Aliased Type§
enum netif_linkoutput_fn {
None,
Some(unsafe extern "C" fn(_: *mut netif, _: *mut pbuf) -> i8),
}
Variants§
None
No value.
Some(unsafe extern "C" fn(_: *mut netif, _: *mut pbuf) -> i8)
Some value of type T
.
Implementations
§impl<T> Option<T>
impl<T> Option<T>
1.0.0 (const: 1.48.0)pub const fn is_some(&self) -> bool
pub const fn is_some(&self) -> bool
Returns true
if the option is a [Some
] value.
§Examples
let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);
let x: Option<u32> = None;
assert_eq!(x.is_some(), false);
1.70.0pub fn is_some_and(self, f: impl FnOnce(T) -> bool) -> bool
pub fn is_some_and(self, f: impl FnOnce(T) -> bool) -> bool
Returns true
if the option is a [Some
] and the value inside of it matches a predicate.
§Examples
let x: Option<u32> = Some(2);
assert_eq!(x.is_some_and(|x| x > 1), true);
let x: Option<u32> = Some(0);
assert_eq!(x.is_some_and(|x| x > 1), false);
let x: Option<u32> = None;
assert_eq!(x.is_some_and(|x| x > 1), false);
1.0.0 (const: 1.48.0)pub const fn is_none(&self) -> bool
pub const fn is_none(&self) -> bool
Returns true
if the option is a [None
] value.
§Examples
let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);
let x: Option<u32> = None;
assert_eq!(x.is_none(), true);
1.82.0pub fn is_none_or(self, f: impl FnOnce(T) -> bool) -> bool
pub fn is_none_or(self, f: impl FnOnce(T) -> bool) -> bool
Returns true
if the option is a [None
] or the value inside of it matches a predicate.
§Examples
let x: Option<u32> = Some(2);
assert_eq!(x.is_none_or(|x| x > 1), true);
let x: Option<u32> = Some(0);
assert_eq!(x.is_none_or(|x| x > 1), false);
let x: Option<u32> = None;
assert_eq!(x.is_none_or(|x| x > 1), true);
1.0.0 (const: 1.48.0)pub const fn as_ref(&self) -> Option<&T>
pub const fn as_ref(&self) -> Option<&T>
Converts from &Option<T>
to Option<&T>
.
§Examples
Calculates the length of an Option<String>
as an Option<[usize]>
without moving the String
. The map
method takes the self
argument by value,
consuming the original, so this technique uses as_ref
to first take an Option
to a
reference to the value inside the original.
let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {text:?}");
1.0.0 (const: 1.83.0)pub const fn as_mut(&mut self) -> Option<&mut T>
pub const fn as_mut(&mut self) -> Option<&mut T>
Converts from &mut Option<T>
to Option<&mut T>
.
§Examples
let mut x = Some(2);
match x.as_mut() {
Some(v) => *v = 42,
None => {},
}
assert_eq!(x, Some(42));
1.33.0 (const: 1.84.0)pub const fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>
pub const fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>
1.33.0 (const: 1.84.0)pub const fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>
pub const fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>
1.75.0 (const: 1.84.0)pub const fn as_slice(&self) -> &[T]
pub const fn as_slice(&self) -> &[T]
Returns a slice of the contained value, if any. If this is None
, an
empty slice is returned. This can be useful to have a single type of
iterator over an Option
or slice.
Note: Should you have an Option<&T>
and wish to get a slice of T
,
you can unpack it via opt.map_or(&[], std::slice::from_ref)
.
§Examples
assert_eq!(
[Some(1234).as_slice(), None.as_slice()],
[&[1234][..], &[][..]],
);
The inverse of this function is (discounting
borrowing) [_]::first
:
for i in [Some(1234_u16), None] {
assert_eq!(i.as_ref(), i.as_slice().first());
}
1.75.0 (const: 1.84.0)pub const fn as_mut_slice(&mut self) -> &mut [T]
pub const fn as_mut_slice(&mut self) -> &mut [T]
Returns a mutable slice of the contained value, if any. If this is
None
, an empty slice is returned. This can be useful to have a
single type of iterator over an Option
or slice.
Note: Should you have an Option<&mut T>
instead of a
&mut Option<T>
, which this method takes, you can obtain a mutable
slice via opt.map_or(&mut [], std::slice::from_mut)
.
§Examples
assert_eq!(
[Some(1234).as_mut_slice(), None.as_mut_slice()],
[&mut [1234][..], &mut [][..]],
);
The result is a mutable slice of zero or one items that points into
our original Option
:
let mut x = Some(1234);
x.as_mut_slice()[0] += 1;
assert_eq!(x, Some(1235));
The inverse of this method (discounting borrowing)
is [_]::first_mut
:
assert_eq!(Some(123).as_mut_slice().first_mut(), Some(&mut 123))
1.0.0 (const: 1.83.0)pub const fn expect(self, msg: &str) -> T
pub const fn expect(self, msg: &str) -> T
Returns the contained [Some
] value, consuming the self
value.
§Panics
Panics if the value is a [None
] with a custom panic message provided by
msg
.
§Examples
let x = Some("value");
assert_eq!(x.expect("fruits are healthy"), "value");
let x: Option<&str> = None;
x.expect("fruits are healthy"); // panics with `fruits are healthy`
§Recommended Message Style
We recommend that expect
messages are used to describe the reason you
expect the Option
should be Some
.
let item = slice.get(0)
.expect("slice should not be empty");
Hint: If you’re having trouble remembering how to phrase expect error messages remember to focus on the word “should” as in “env variable should be set by blah” or “the given binary should be available and executable by the current user”.
For more detail on expect message styles and the reasoning behind our
recommendation please refer to the section on “Common Message
Styles” in the std::error
module docs.
1.0.0 (const: 1.83.0)pub const fn unwrap(self) -> T
pub const fn unwrap(self) -> T
Returns the contained [Some
] value, consuming the self
value.
Because this function may panic, its use is generally discouraged. Panics are meant for unrecoverable errors, and may abort the entire program.
Instead, prefer to use pattern matching and handle the [None
]
case explicitly, or call unwrap_or
, unwrap_or_else
, or
unwrap_or_default
. In functions returning Option
, you can use
the ?
(try) operator.
§Panics
Panics if the self value equals [None
].
§Examples
let x = Some("air");
assert_eq!(x.unwrap(), "air");
let x: Option<&str> = None;
assert_eq!(x.unwrap(), "air"); // fails
1.0.0pub fn unwrap_or(self, default: T) -> T
pub fn unwrap_or(self, default: T) -> T
Returns the contained [Some
] value or a provided default.
Arguments passed to unwrap_or
are eagerly evaluated; if you are passing
the result of a function call, it is recommended to use unwrap_or_else
,
which is lazily evaluated.
§Examples
assert_eq!(Some("car").unwrap_or("bike"), "car");
assert_eq!(None.unwrap_or("bike"), "bike");
1.0.0pub fn unwrap_or_else<F>(self, f: F) -> Twhere
F: FnOnce() -> T,
pub fn unwrap_or_else<F>(self, f: F) -> Twhere
F: FnOnce() -> T,
Returns the contained [Some
] value or computes it from a closure.
§Examples
let k = 10;
assert_eq!(Some(4).unwrap_or_else(|| 2 * k), 4);
assert_eq!(None.unwrap_or_else(|| 2 * k), 20);
1.0.0pub fn unwrap_or_default(self) -> Twhere
T: Default,
pub fn unwrap_or_default(self) -> Twhere
T: Default,
Returns the contained [Some
] value or a default.
Consumes the self
argument then, if [Some
], returns the contained
value, otherwise if [None
], returns the default value for that
type.
§Examples
let x: Option<u32> = None;
let y: Option<u32> = Some(12);
assert_eq!(x.unwrap_or_default(), 0);
assert_eq!(y.unwrap_or_default(), 12);
1.58.0 (const: 1.83.0)pub const unsafe fn unwrap_unchecked(self) -> T
pub const unsafe fn unwrap_unchecked(self) -> T
Returns the contained [Some
] value, consuming the self
value,
without checking that the value is not [None
].
§Safety
Calling this method on [None
] is undefined behavior.
§Examples
let x = Some("air");
assert_eq!(unsafe { x.unwrap_unchecked() }, "air");
let x: Option<&str> = None;
assert_eq!(unsafe { x.unwrap_unchecked() }, "air"); // Undefined behavior!
1.0.0pub fn map<U, F>(self, f: F) -> Option<U>where
F: FnOnce(T) -> U,
pub fn map<U, F>(self, f: F) -> Option<U>where
F: FnOnce(T) -> U,
Maps an Option<T>
to Option<U>
by applying a function to a contained value (if Some
) or returns None
(if None
).
§Examples
Calculates the length of an Option<String>
as an
Option<[usize]>
, consuming the original:
let maybe_some_string = Some(String::from("Hello, World!"));
// `Option::map` takes self *by value*, consuming `maybe_some_string`
let maybe_some_len = maybe_some_string.map(|s| s.len());
assert_eq!(maybe_some_len, Some(13));
let x: Option<&str> = None;
assert_eq!(x.map(|s| s.len()), None);
1.76.0pub fn inspect<F>(self, f: F) -> Option<T>where
F: FnOnce(&T),
pub fn inspect<F>(self, f: F) -> Option<T>where
F: FnOnce(&T),
Calls a function with a reference to the contained value if [Some
].
Returns the original option.
§Examples
let list = vec![1, 2, 3];
// prints "got: 2"
let x = list
.get(1)
.inspect(|x| println!("got: {x}"))
.expect("list should be long enough");
// prints nothing
list.get(5).inspect(|x| println!("got: {x}"));
1.0.0pub fn map_or<U, F>(self, default: U, f: F) -> Uwhere
F: FnOnce(T) -> U,
pub fn map_or<U, F>(self, default: U, f: F) -> Uwhere
F: FnOnce(T) -> U,
Returns the provided default result (if none), or applies a function to the contained value (if any).
Arguments passed to map_or
are eagerly evaluated; if you are passing
the result of a function call, it is recommended to use map_or_else
,
which is lazily evaluated.
§Examples
let x = Some("foo");
assert_eq!(x.map_or(42, |v| v.len()), 3);
let x: Option<&str> = None;
assert_eq!(x.map_or(42, |v| v.len()), 42);
1.0.0pub fn map_or_else<U, D, F>(self, default: D, f: F) -> Uwhere
D: FnOnce() -> U,
F: FnOnce(T) -> U,
pub fn map_or_else<U, D, F>(self, default: D, f: F) -> Uwhere
D: FnOnce() -> U,
F: FnOnce(T) -> U,
Computes a default function result (if none), or applies a different function to the contained value (if any).
§Basic examples
let k = 21;
let x = Some("foo");
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);
let x: Option<&str> = None;
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);
§Handling a Result-based fallback
A somewhat common occurrence when dealing with optional values
in combination with [Result<T, E>
] is the case where one wants to invoke
a fallible fallback if the option is not present. This example
parses a command line argument (if present), or the contents of a file to
an integer. However, unlike accessing the command line argument, reading
the file is fallible, so it must be wrapped with Ok
.
let v: u64 = std::env::args()
.nth(1)
.map_or_else(|| std::fs::read_to_string("/etc/someconfig.conf"), Ok)?
.parse()?;
1.0.0pub fn ok_or<E>(self, err: E) -> Result<T, E>
pub fn ok_or<E>(self, err: E) -> Result<T, E>
Transforms the Option<T>
into a [Result<T, E>
], mapping Some(v)
to
Ok(v)
and [None
] to Err(err)
.
Arguments passed to ok_or
are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use ok_or_else
, which is
lazily evaluated.
§Examples
let x = Some("foo");
assert_eq!(x.ok_or(0), Ok("foo"));
let x: Option<&str> = None;
assert_eq!(x.ok_or(0), Err(0));
1.0.0pub fn ok_or_else<E, F>(self, err: F) -> Result<T, E>where
F: FnOnce() -> E,
pub fn ok_or_else<E, F>(self, err: F) -> Result<T, E>where
F: FnOnce() -> E,
Transforms the Option<T>
into a [Result<T, E>
], mapping Some(v)
to
Ok(v)
and [None
] to Err(err())
.
§Examples
let x = Some("foo");
assert_eq!(x.ok_or_else(|| 0), Ok("foo"));
let x: Option<&str> = None;
assert_eq!(x.ok_or_else(|| 0), Err(0));
1.40.0pub fn as_deref(&self) -> Option<&<T as Deref>::Target>where
T: Deref,
pub fn as_deref(&self) -> Option<&<T as Deref>::Target>where
T: Deref,
Converts from Option<T>
(or &Option<T>
) to Option<&T::Target>
.
Leaves the original Option in-place, creating a new one with a reference
to the original one, additionally coercing the contents via [Deref
].
§Examples
let x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref(), Some("hey"));
let x: Option<String> = None;
assert_eq!(x.as_deref(), None);
1.40.0pub fn as_deref_mut(&mut self) -> Option<&mut <T as Deref>::Target>where
T: DerefMut,
pub fn as_deref_mut(&mut self) -> Option<&mut <T as Deref>::Target>where
T: DerefMut,
Converts from Option<T>
(or &mut Option<T>
) to Option<&mut T::Target>
.
Leaves the original Option
in-place, creating a new one containing a mutable reference to
the inner type’s [Deref::Target
] type.
§Examples
let mut x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref_mut().map(|x| {
x.make_ascii_uppercase();
x
}), Some("HEY".to_owned().as_mut_str()));
1.0.0pub fn iter(&self) -> Iter<'_, T>
pub fn iter(&self) -> Iter<'_, T>
Returns an iterator over the possibly contained value.
§Examples
let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));
let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);
1.0.0pub fn iter_mut(&mut self) -> IterMut<'_, T>
pub fn iter_mut(&mut self) -> IterMut<'_, T>
Returns a mutable iterator over the possibly contained value.
§Examples
let mut x = Some(4);
match x.iter_mut().next() {
Some(v) => *v = 42,
None => {},
}
assert_eq!(x, Some(42));
let mut x: Option<u32> = None;
assert_eq!(x.iter_mut().next(), None);
1.0.0pub fn and<U>(self, optb: Option<U>) -> Option<U>
pub fn and<U>(self, optb: Option<U>) -> Option<U>
Returns [None
] if the option is [None
], otherwise returns optb
.
Arguments passed to and
are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use and_then
, which is
lazily evaluated.
§Examples
let x = Some(2);
let y: Option<&str> = None;
assert_eq!(x.and(y), None);
let x: Option<u32> = None;
let y = Some("foo");
assert_eq!(x.and(y), None);
let x = Some(2);
let y = Some("foo");
assert_eq!(x.and(y), Some("foo"));
let x: Option<u32> = None;
let y: Option<&str> = None;
assert_eq!(x.and(y), None);
1.0.0pub fn and_then<U, F>(self, f: F) -> Option<U>where
F: FnOnce(T) -> Option<U>,
pub fn and_then<U, F>(self, f: F) -> Option<U>where
F: FnOnce(T) -> Option<U>,
Returns [None
] if the option is [None
], otherwise calls f
with the
wrapped value and returns the result.
Some languages call this operation flatmap.
§Examples
fn sq_then_to_string(x: u32) -> Option<String> {
x.checked_mul(x).map(|sq| sq.to_string())
}
assert_eq!(Some(2).and_then(sq_then_to_string), Some(4.to_string()));
assert_eq!(Some(1_000_000).and_then(sq_then_to_string), None); // overflowed!
assert_eq!(None.and_then(sq_then_to_string), None);
Often used to chain fallible operations that may return [None
].
let arr_2d = [["A0", "A1"], ["B0", "B1"]];
let item_0_1 = arr_2d.get(0).and_then(|row| row.get(1));
assert_eq!(item_0_1, Some(&"A1"));
let item_2_0 = arr_2d.get(2).and_then(|row| row.get(0));
assert_eq!(item_2_0, None);
1.27.0pub fn filter<P>(self, predicate: P) -> Option<T>where
P: FnOnce(&T) -> bool,
pub fn filter<P>(self, predicate: P) -> Option<T>where
P: FnOnce(&T) -> bool,
Returns [None
] if the option is [None
], otherwise calls predicate
with the wrapped value and returns:
Some(t)
ifpredicate
returnstrue
(wheret
is the wrapped value), and- [
None
] ifpredicate
returnsfalse
.
This function works similar to [Iterator::filter()
]. You can imagine
the Option<T>
being an iterator over one or zero elements. filter()
lets you decide which elements to keep.
§Examples
fn is_even(n: &i32) -> bool {
n % 2 == 0
}
assert_eq!(None.filter(is_even), None);
assert_eq!(Some(3).filter(is_even), None);
assert_eq!(Some(4).filter(is_even), Some(4));
1.0.0pub fn or(self, optb: Option<T>) -> Option<T>
pub fn or(self, optb: Option<T>) -> Option<T>
Returns the option if it contains a value, otherwise returns optb
.
Arguments passed to or
are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use or_else
, which is
lazily evaluated.
§Examples
let x = Some(2);
let y = None;
assert_eq!(x.or(y), Some(2));
let x = None;
let y = Some(100);
assert_eq!(x.or(y), Some(100));
let x = Some(2);
let y = Some(100);
assert_eq!(x.or(y), Some(2));
let x: Option<u32> = None;
let y = None;
assert_eq!(x.or(y), None);
1.0.0pub fn or_else<F>(self, f: F) -> Option<T>where
F: FnOnce() -> Option<T>,
pub fn or_else<F>(self, f: F) -> Option<T>where
F: FnOnce() -> Option<T>,
Returns the option if it contains a value, otherwise calls f
and
returns the result.
§Examples
fn nobody() -> Option<&'static str> { None }
fn vikings() -> Option<&'static str> { Some("vikings") }
assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));
assert_eq!(None.or_else(vikings), Some("vikings"));
assert_eq!(None.or_else(nobody), None);
1.37.0pub fn xor(self, optb: Option<T>) -> Option<T>
pub fn xor(self, optb: Option<T>) -> Option<T>
Returns [Some
] if exactly one of self
, optb
is [Some
], otherwise returns [None
].
§Examples
let x = Some(2);
let y: Option<u32> = None;
assert_eq!(x.xor(y), Some(2));
let x: Option<u32> = None;
let y = Some(2);
assert_eq!(x.xor(y), Some(2));
let x = Some(2);
let y = Some(2);
assert_eq!(x.xor(y), None);
let x: Option<u32> = None;
let y: Option<u32> = None;
assert_eq!(x.xor(y), None);
1.53.0pub fn insert(&mut self, value: T) -> &mut T
pub fn insert(&mut self, value: T) -> &mut T
Inserts value
into the option, then returns a mutable reference to it.
If the option already contains a value, the old value is dropped.
See also [Option::get_or_insert
], which doesn’t update the value if
the option already contains [Some
].
§Example
let mut opt = None;
let val = opt.insert(1);
assert_eq!(*val, 1);
assert_eq!(opt.unwrap(), 1);
let val = opt.insert(2);
assert_eq!(*val, 2);
*val = 3;
assert_eq!(opt.unwrap(), 3);
1.20.0pub fn get_or_insert(&mut self, value: T) -> &mut T
pub fn get_or_insert(&mut self, value: T) -> &mut T
Inserts value
into the option if it is [None
], then
returns a mutable reference to the contained value.
See also [Option::insert
], which updates the value even if
the option already contains [Some
].
§Examples
let mut x = None;
{
let y: &mut u32 = x.get_or_insert(5);
assert_eq!(y, &5);
*y = 7;
}
assert_eq!(x, Some(7));
1.83.0pub fn get_or_insert_default(&mut self) -> &mut Twhere
T: Default,
pub fn get_or_insert_default(&mut self) -> &mut Twhere
T: Default,
Inserts the default value into the option if it is [None
], then
returns a mutable reference to the contained value.
§Examples
let mut x = None;
{
let y: &mut u32 = x.get_or_insert_default();
assert_eq!(y, &0);
*y = 7;
}
assert_eq!(x, Some(7));
1.20.0pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut Twhere
F: FnOnce() -> T,
pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut Twhere
F: FnOnce() -> T,
Inserts a value computed from f
into the option if it is [None
],
then returns a mutable reference to the contained value.
§Examples
let mut x = None;
{
let y: &mut u32 = x.get_or_insert_with(|| 5);
assert_eq!(y, &5);
*y = 7;
}
assert_eq!(x, Some(7));
1.0.0 (const: 1.83.0)pub const fn take(&mut self) -> Option<T>
pub const fn take(&mut self) -> Option<T>
Takes the value out of the option, leaving a [None
] in its place.
§Examples
let mut x = Some(2);
let y = x.take();
assert_eq!(x, None);
assert_eq!(y, Some(2));
let mut x: Option<u32> = None;
let y = x.take();
assert_eq!(x, None);
assert_eq!(y, None);
1.80.0pub fn take_if<P>(&mut self, predicate: P) -> Option<T>where
P: FnOnce(&mut T) -> bool,
pub fn take_if<P>(&mut self, predicate: P) -> Option<T>where
P: FnOnce(&mut T) -> bool,
Takes the value out of the option, but only if the predicate evaluates to
true
on a mutable reference to the value.
In other words, replaces self
with None
if the predicate returns true
.
This method operates similar to [Option::take
] but conditional.
§Examples
let mut x = Some(42);
let prev = x.take_if(|v| if *v == 42 {
*v += 1;
false
} else {
false
});
assert_eq!(x, Some(43));
assert_eq!(prev, None);
let prev = x.take_if(|v| *v == 43);
assert_eq!(x, None);
assert_eq!(prev, Some(43));
1.31.0 (const: 1.83.0)pub const fn replace(&mut self, value: T) -> Option<T>
pub const fn replace(&mut self, value: T) -> Option<T>
Replaces the actual value in the option by the value given in parameter,
returning the old value if present,
leaving a [Some
] in its place without deinitializing either one.
§Examples
let mut x = Some(2);
let old = x.replace(5);
assert_eq!(x, Some(5));
assert_eq!(old, Some(2));
let mut x = None;
let old = x.replace(3);
assert_eq!(x, Some(3));
assert_eq!(old, None);
1.46.0pub fn zip<U>(self, other: Option<U>) -> Option<(T, U)>
pub fn zip<U>(self, other: Option<U>) -> Option<(T, U)>
Zips self
with another Option
.
If self
is Some(s)
and other
is Some(o)
, this method returns Some((s, o))
.
Otherwise, None
is returned.
§Examples
let x = Some(1);
let y = Some("hi");
let z = None::<u8>;
assert_eq!(x.zip(y), Some((1, "hi")));
assert_eq!(x.zip(z), None);
pub fn zip_with<U, F, R>(self, other: Option<U>, f: F) -> Option<R>where
F: FnOnce(T, U) -> R,
🔬This is a nightly-only experimental API. (option_zip
)
pub fn zip_with<U, F, R>(self, other: Option<U>, f: F) -> Option<R>where
F: FnOnce(T, U) -> R,
option_zip
)Zips self
and another Option
with function f
.
If self
is Some(s)
and other
is Some(o)
, this method returns Some(f(s, o))
.
Otherwise, None
is returned.
§Examples
#![feature(option_zip)]
#[derive(Debug, PartialEq)]
struct Point {
x: f64,
y: f64,
}
impl Point {
fn new(x: f64, y: f64) -> Self {
Self { x, y }
}
}
let x = Some(17.5);
let y = Some(42.7);
assert_eq!(x.zip_with(y, Point::new), Some(Point { x: 17.5, y: 42.7 }));
assert_eq!(x.zip_with(None, Point::new), None);
Trait Implementations
1.0.0§impl<T> Clone for Option<T>where
T: Clone,
impl<T> Clone for Option<T>where
T: Clone,
1.0.0§impl<T> Debug for Option<T>where
T: Debug,
impl<T> Debug for Option<T>where
T: Debug,
1.0.0§impl<T> Default for Option<T>
impl<T> Default for Option<T>
1.12.0§impl<T> From<T> for Option<T>
impl<T> From<T> for Option<T>
1.0.0§impl<A, V> FromIterator<Option<A>> for Option<V>where
V: FromIterator<A>,
impl<A, V> FromIterator<Option<A>> for Option<V>where
V: FromIterator<A>,
§fn from_iter<I>(iter: I) -> Option<V>where
I: IntoIterator<Item = Option<A>>,
fn from_iter<I>(iter: I) -> Option<V>where
I: IntoIterator<Item = Option<A>>,
Takes each element in the [Iterator
]: if it is [None
][Option::None],
no further elements are taken, and the [None
][Option::None] is
returned. Should no [None
][Option::None] occur, a container of type
V
containing the values of each [Option
] is returned.
§Examples
Here is an example which increments every integer in a vector.
We use the checked variant of add
that returns None
when the
calculation would result in an overflow.
let items = vec![0_u16, 1, 2];
let res: Option<Vec<u16>> = items
.iter()
.map(|x| x.checked_add(1))
.collect();
assert_eq!(res, Some(vec![1, 2, 3]));
As you can see, this will return the expected, valid items.
Here is another example that tries to subtract one from another list of integers, this time checking for underflow:
let items = vec![2_u16, 1, 0];
let res: Option<Vec<u16>> = items
.iter()
.map(|x| x.checked_sub(1))
.collect();
assert_eq!(res, None);
Since the last element is zero, it would underflow. Thus, the resulting
value is None
.
Here is a variation on the previous example, showing that no
further elements are taken from iter
after the first None
.
let items = vec![3_u16, 2, 1, 10];
let mut shared = 0;
let res: Option<Vec<u16>> = items
.iter()
.map(|x| { shared += x; x.checked_sub(2) })
.collect();
assert_eq!(res, None);
assert_eq!(shared, 6);
Since the third element caused an underflow, no further elements were taken,
so the final value of shared
is 6 (= 3 + 2 + 1
), not 16.
§impl<T> FromResidual<Option<Infallible>> for Option<T>
impl<T> FromResidual<Option<Infallible>> for Option<T>
§fn from_residual(residual: Option<Infallible>) -> Option<T>
fn from_residual(residual: Option<Infallible>) -> Option<T>
try_trait_v2
)Residual
type. Read more§impl<T> FromResidual<Yeet<()>> for Option<T>
impl<T> FromResidual<Yeet<()>> for Option<T>
§fn from_residual(_: Yeet<()>) -> Option<T>
fn from_residual(_: Yeet<()>) -> Option<T>
try_trait_v2
)Residual
type. Read more1.0.0§impl<T> Hash for Option<T>where
T: Hash,
impl<T> Hash for Option<T>where
T: Hash,
1.0.0§impl<T> IntoIterator for Option<T>
impl<T> IntoIterator for Option<T>
1.0.0§impl<T> Ord for Option<T>where
T: Ord,
impl<T> Ord for Option<T>where
T: Ord,
1.0.0§impl<T> PartialEq for Option<T>where
T: PartialEq,
impl<T> PartialEq for Option<T>where
T: PartialEq,
1.0.0§impl<T> PartialOrd for Option<T>where
T: PartialOrd,
impl<T> PartialOrd for Option<T>where
T: PartialOrd,
1.37.0§impl<T, U> Product<Option<U>> for Option<T>where
T: Product<U>,
impl<T, U> Product<Option<U>> for Option<T>where
T: Product<U>,
§fn product<I>(iter: I) -> Option<T>where
I: Iterator<Item = Option<U>>,
fn product<I>(iter: I) -> Option<T>where
I: Iterator<Item = Option<U>>,
Takes each element in the [Iterator
]: if it is a [None
], no further
elements are taken, and the [None
] is returned. Should no [None
]
occur, the product of all elements is returned.
§Examples
This multiplies each number in a vector of strings,
if a string could not be parsed the operation returns None
:
let nums = vec!["5", "10", "1", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, Some(100));
let nums = vec!["5", "10", "one", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, None);
1.37.0§impl<T, U> Sum<Option<U>> for Option<T>where
T: Sum<U>,
impl<T, U> Sum<Option<U>> for Option<T>where
T: Sum<U>,
§fn sum<I>(iter: I) -> Option<T>where
I: Iterator<Item = Option<U>>,
fn sum<I>(iter: I) -> Option<T>where
I: Iterator<Item = Option<U>>,
Takes each element in the [Iterator
]: if it is a [None
], no further
elements are taken, and the [None
] is returned. Should no [None
]
occur, the sum of all elements is returned.
§Examples
This sums up the position of the character ‘a’ in a vector of strings,
if a word did not have the character ‘a’ the operation returns None
:
let words = vec!["have", "a", "great", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, Some(5));
let words = vec!["have", "a", "good", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, None);
§impl<T> Try for Option<T>
impl<T> Try for Option<T>
§type Output = T
type Output = T
try_trait_v2
)?
when not short-circuiting.§type Residual = Option<Infallible>
type Residual = Option<Infallible>
try_trait_v2
)FromResidual::from_residual
]
as part of ?
when short-circuiting. Read more§fn from_output(output: <Option<T> as Try>::Output) -> Option<T>
fn from_output(output: <Option<T> as Try>::Output) -> Option<T>
try_trait_v2
)Output
type. Read more§fn branch(
self,
) -> ControlFlow<<Option<T> as Try>::Residual, <Option<T> as Try>::Output>
fn branch( self, ) -> ControlFlow<<Option<T> as Try>::Residual, <Option<T> as Try>::Output>
try_trait_v2
)?
to decide whether the operator should produce a value
(because this returned [ControlFlow::Continue
])
or propagate a value back to the caller
(because this returned [ControlFlow::Break
]). Read more