Enum std::result::Result
pub enum Result<T, E> { Ok(T), Err(E), }
Result
is a type that represents either success (Ok
) or failure (Err
).
See the module documentation for details.
Variants
Ok(T)
Contains the success value
Tuple Fields of Ok
0: T
Err(E)
Contains the error value
Tuple Fields of Err
0: E
Implementations
impl<T, E> Result<T, E>
pub const fn is_ok(&self) -> bool
Returns true
if the result is Ok
.
Examples
Basic usage:
let x: Result<i32, &str> = Ok(-3); assert_eq!(x.is_ok(), true); let x: Result<i32, &str> = Err("Some error message"); assert_eq!(x.is_ok(), false);
pub const fn is_err(&self) -> bool
Returns true
if the result is Err
.
Examples
Basic usage:
let x: Result<i32, &str> = Ok(-3); assert_eq!(x.is_err(), false); let x: Result<i32, &str> = Err("Some error message"); assert_eq!(x.is_err(), true);
Returns true
if the result is an Ok
value containing the given value.
Examples
#![feature(option_result_contains)] let x: Result<u32, &str> = Ok(2); assert_eq!(x.contains(&2), true); let x: Result<u32, &str> = Ok(3); assert_eq!(x.contains(&2), false); let x: Result<u32, &str> = Err("Some error message"); assert_eq!(x.contains(&2), false);
Returns true
if the result is an Err
value containing the given value.
Examples
#![feature(result_contains_err)] let x: Result<u32, &str> = Ok(2); assert_eq!(x.contains_err(&"Some error message"), false); let x: Result<u32, &str> = Err("Some error message"); assert_eq!(x.contains_err(&"Some error message"), true); let x: Result<u32, &str> = Err("Some other error message"); assert_eq!(x.contains_err(&"Some error message"), false);
pub fn ok(self) -> Option<T>
Converts from Result<T, E>
to Option<T>
.
Converts self
into an Option<T>
, consuming self
, and discarding the error, if any.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.ok(), Some(2)); let x: Result<u32, &str> = Err("Nothing here"); assert_eq!(x.ok(), None);
pub fn err(self) -> Option<E>
Converts from Result<T, E>
to Option<E>
.
Converts self
into an Option<E>
, consuming self
, and discarding the success value, if any.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.err(), None); let x: Result<u32, &str> = Err("Nothing here"); assert_eq!(x.err(), Some("Nothing here"));
pub const fn as_ref(&self) -> Result<&T, &E>
Converts from &Result<T, E>
to Result<&T, &E>
.
Produces a new Result
, containing a reference into the original, leaving the original in place.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.as_ref(), Ok(&2)); let x: Result<u32, &str> = Err("Error"); assert_eq!(x.as_ref(), Err(&"Error"));
pub fn as_mut(&mut self) -> Result<&mut T, &mut E>
Converts from &mut Result<T, E>
to Result<&mut T, &mut E>
.
Examples
Basic usage:
fn mutate(r: &mut Result<i32, i32>) { match r.as_mut() { Ok(v) => *v = 42, Err(e) => *e = 0, } } let mut x: Result<i32, i32> = Ok(2); mutate(&mut x); assert_eq!(x.unwrap(), 42); let mut x: Result<i32, i32> = Err(13); mutate(&mut x); assert_eq!(x.unwrap_err(), 0);
Maps a Result<T, E>
to Result<U, E>
by applying a function to a contained Ok
value, leaving an Err
value untouched.
This function can be used to compose the results of two functions.
Examples
Print the numbers on each line of a string multiplied by two.
let line = "1\n2\n3\n4\n"; for num in line.lines() { match num.parse::<i32>().map(|i| i * 2) { Ok(n) => println!("{}", n), Err(..) => {} } }
Returns the provided default (if Err
), or applies a function to the contained value (if Ok
),
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: Result<_, &str> = Ok("foo"); assert_eq!(x.map_or(42, |v| v.len()), 3); let x: Result<&str, _> = Err("bar"); assert_eq!(x.map_or(42, |v| v.len()), 42);
Maps a Result<T, E>
to U
by applying a fallback function to a contained Err
value, or a default function to a contained Ok
value.
This function can be used to unpack a successful result while handling an error.
Examples
Basic usage:
let k = 21; let x : Result<_, &str> = Ok("foo"); assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 3); let x : Result<&str, _> = Err("bar"); assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 42);
Maps a Result<T, E>
to Result<T, F>
by applying a function to a contained Err
value, leaving an Ok
value untouched.
This function can be used to pass through a successful result while handling an error.
Examples
Basic usage:
fn stringify(x: u32) -> String { format!("error code: {}", x) } let x: Result<u32, u32> = Ok(2); assert_eq!(x.map_err(stringify), Ok(2)); let x: Result<u32, u32> = Err(13); assert_eq!(x.map_err(stringify), Err("error code: 13".to_string()));
pub fn iter(&self) -> Iter<'_, T>
impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;
Returns an iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(7); assert_eq!(x.iter().next(), Some(&7)); let x: Result<u32, &str> = Err("nothing!"); assert_eq!(x.iter().next(), None);
pub fn iter_mut(&mut self) -> IterMut<'_, T>
impl<'a, T> Iterator for IterMut<'a, T> type Item = &'a mut T;
Returns a mutable iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let mut x: Result<u32, &str> = Ok(7); match x.iter_mut().next() { Some(v) => *v = 40, None => {}, } assert_eq!(x, Ok(40)); let mut x: Result<u32, &str> = Err("nothing!"); assert_eq!(x.iter_mut().next(), None);
pub fn and<U>(self, res: Result<U, E>) -> Result<U, E>
Returns res
if the result is Ok
, otherwise returns the Err
value of self
.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); let y: Result<&str, &str> = Err("late error"); assert_eq!(x.and(y), Err("late error")); let x: Result<u32, &str> = Err("early error"); let y: Result<&str, &str> = Ok("foo"); assert_eq!(x.and(y), Err("early error")); let x: Result<u32, &str> = Err("not a 2"); let y: Result<&str, &str> = Err("late error"); assert_eq!(x.and(y), Err("not a 2")); let x: Result<u32, &str> = Ok(2); let y: Result<&str, &str> = Ok("different result type"); assert_eq!(x.and(y), Ok("different result type"));
Calls op
if the result is Ok
, otherwise returns the Err
value of self
.
This function can be used for control flow based on Result
values.
Examples
Basic usage:
fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) } fn err(x: u32) -> Result<u32, u32> { Err(x) } assert_eq!(Ok(2).and_then(sq).and_then(sq), Ok(16)); assert_eq!(Ok(2).and_then(sq).and_then(err), Err(4)); assert_eq!(Ok(2).and_then(err).and_then(sq), Err(2)); assert_eq!(Err(3).and_then(sq).and_then(sq), Err(3));
pub fn or<F>(self, res: Result<T, F>) -> Result<T, F>
Returns res
if the result is Err
, otherwise returns the Ok
value of self
.
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
Basic usage:
let x: Result<u32, &str> = Ok(2); let y: Result<u32, &str> = Err("late error"); assert_eq!(x.or(y), Ok(2)); let x: Result<u32, &str> = Err("early error"); let y: Result<u32, &str> = Ok(2); assert_eq!(x.or(y), Ok(2)); let x: Result<u32, &str> = Err("not a 2"); let y: Result<u32, &str> = Err("late error"); assert_eq!(x.or(y), Err("late error")); let x: Result<u32, &str> = Ok(2); let y: Result<u32, &str> = Ok(100); assert_eq!(x.or(y), Ok(2));
Calls op
if the result is Err
, otherwise returns the Ok
value of self
.
This function can be used for control flow based on result values.
Examples
Basic usage:
fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) } fn err(x: u32) -> Result<u32, u32> { Err(x) } assert_eq!(Ok(2).or_else(sq).or_else(sq), Ok(2)); assert_eq!(Ok(2).or_else(err).or_else(sq), Ok(2)); assert_eq!(Err(3).or_else(sq).or_else(err), Ok(9)); assert_eq!(Err(3).or_else(err).or_else(err), Err(3));
pub fn unwrap_or(self, default: T) -> T
Returns the contained Ok
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
Basic usage:
let default = 2; let x: Result<u32, &str> = Ok(9); assert_eq!(x.unwrap_or(default), 9); let x: Result<u32, &str> = Err("error"); assert_eq!(x.unwrap_or(default), default);
Returns the contained Ok
value or computes it from a closure.
Examples
Basic usage:
fn count(x: &str) -> usize { x.len() } assert_eq!(Ok(2).unwrap_or_else(count), 2); assert_eq!(Err("foo").unwrap_or_else(count), 3);
pub unsafe fn unwrap_unchecked(self) -> T
option_result_unwrap_unchecked
#81383)newly added
Returns the contained Ok
value, consuming the self
value, without checking that the value is not an Err
.
Safety
Calling this method on an Err
is undefined behavior.
Examples
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Ok(2); assert_eq!(unsafe { x.unwrap_unchecked() }, 2);
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Err("emergency failure"); unsafe { x.unwrap_unchecked(); } // Undefined behavior!
pub unsafe fn unwrap_err_unchecked(self) -> E
option_result_unwrap_unchecked
#81383)newly added
Returns the contained Err
value, consuming the self
value, without checking that the value is not an Ok
.
Safety
Calling this method on an Ok
is undefined behavior.
Examples
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Ok(2); unsafe { x.unwrap_err_unchecked() }; // Undefined behavior!
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Err("emergency failure"); assert_eq!(unsafe { x.unwrap_err_unchecked() }, "emergency failure");
pub fn copied(self) -> Result<T, E>
result_copied
#63168)newly added
Maps a Result<&T, E>
to a Result<T, E>
by copying the contents of the Ok
part.
Examples
#![feature(result_copied)] let val = 12; let x: Result<&i32, i32> = Ok(&val); assert_eq!(x, Ok(&12)); let copied = x.copied(); assert_eq!(copied, Ok(12));
pub fn copied(self) -> Result<T, E>
result_copied
#63168)newly added
Maps a Result<&mut T, E>
to a Result<T, E>
by copying the contents of the Ok
part.
Examples
#![feature(result_copied)] let mut val = 12; let x: Result<&mut i32, i32> = Ok(&mut val); assert_eq!(x, Ok(&mut 12)); let copied = x.copied(); assert_eq!(copied, Ok(12));
pub fn cloned(self) -> Result<T, E>
result_cloned
#63168)newly added
Maps a Result<&T, E>
to a Result<T, E>
by cloning the contents of the Ok
part.
Examples
#![feature(result_cloned)] let val = 12; let x: Result<&i32, i32> = Ok(&val); assert_eq!(x, Ok(&12)); let cloned = x.cloned(); assert_eq!(cloned, Ok(12));
pub fn cloned(self) -> Result<T, E>
result_cloned
#63168)newly added
Maps a Result<&mut T, E>
to a Result<T, E>
by cloning the contents of the Ok
part.
Examples
#![feature(result_cloned)] let mut val = 12; let x: Result<&mut i32, i32> = Ok(&mut val); assert_eq!(x, Ok(&mut 12)); let cloned = x.cloned(); assert_eq!(cloned, Ok(12));
pub fn expect(self, msg: &str) -> T
Returns the contained Ok
value, consuming the self
value.
Panics
Panics if the value is an Err
, with a panic message including the passed message, and the content of the Err
.
Examples
Basic usage:
let x: Result<u32, &str> = Err("emergency failure"); x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
pub fn unwrap(self) -> T
Returns the contained Ok
value, consuming the self
value.
Because this function may panic, its use is generally discouraged. Instead, prefer to use pattern matching and handle the Err
case explicitly, or call unwrap_or
, unwrap_or_else
, or unwrap_or_default
.
Panics
Panics if the value is an Err
, with a panic message provided by the Err
’s value.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.unwrap(), 2);
let x: Result<u32, &str> = Err("emergency failure"); x.unwrap(); // panics with `emergency failure`
pub fn expect_err(self, msg: &str) -> E
Returns the contained Err
value, consuming the self
value.
Panics
Panics if the value is an Ok
, with a panic message including the passed message, and the content of the Ok
.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(10); x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
pub fn unwrap_err(self) -> E
Returns the contained Err
value, consuming the self
value.
Panics
Panics if the value is an Ok
, with a custom panic message provided by the Ok
’s value.
Examples
let x: Result<u32, &str> = Ok(2); x.unwrap_err(); // panics with `2`
let x: Result<u32, &str> = Err("emergency failure"); assert_eq!(x.unwrap_err(), "emergency failure");
pub fn unwrap_or_default(self) -> T
Returns the contained Ok
value or a default
Consumes the self
argument then, if Ok
, returns the contained value, otherwise if Err
, returns the default value for that type.
Examples
Converts a string to an integer, turning poorly-formed strings into 0 (the default value for integers). parse
converts a string to any other type that implements FromStr
, returning an Err
on error.
let good_year_from_input = "1909"; let bad_year_from_input = "190blarg"; let good_year = good_year_from_input.parse().unwrap_or_default(); let bad_year = bad_year_from_input.parse().unwrap_or_default(); assert_eq!(1909, good_year); assert_eq!(0, bad_year);
pub fn into_ok(self) -> T
unwrap_infallible
#61695)newly added
Returns the contained Ok
value, but never panics.
Unlike unwrap
, this method is known to never panic on the result types it is implemented for. Therefore, it can be used instead of unwrap
as a maintainability safeguard that will fail to compile if the error type of the Result
is later changed to an error that can actually occur.
Examples
Basic usage:
fn only_good_news() -> Result<String, !> { Ok("this is fine".into()) } let s: String = only_good_news().into_ok(); println!("{}", s);
pub fn into_err(self) -> E
unwrap_infallible
#61695)newly added
Returns the contained Err
value, but never panics.
Unlike unwrap_err
, this method is known to never panic on the result types it is implemented for. Therefore, it can be used instead of unwrap_err
as a maintainability safeguard that will fail to compile if the ok type of the Result
is later changed to a type that can actually occur.
Examples
Basic usage:
fn only_bad_news() -> Result<!, String> { Err("Oops, it failed".into()) } let error: String = only_bad_news().into_err(); println!("{}", error);
pub fn as_deref(&self) -> Result<&<T as Deref>::Target, &E>
Converts from Result<T, E>
(or &Result<T, E>
) to Result<&<T as Deref>::Target, &E>
.
Coerces the Ok
variant of the original Result
via Deref
and returns the new Result
.
Examples
let x: Result<String, u32> = Ok("hello".to_string()); let y: Result<&str, &u32> = Ok("hello"); assert_eq!(x.as_deref(), y); let x: Result<String, u32> = Err(42); let y: Result<&str, &u32> = Err(&42); assert_eq!(x.as_deref(), y);
pub fn as_deref_mut(&mut self) -> Result<&mut <T as Deref>::Target, &mut E>
Converts from Result<T, E>
(or &mut Result<T, E>
) to Result<&mut <T as DerefMut>::Target, &mut E>
.
Coerces the Ok
variant of the original Result
via DerefMut
and returns the new Result
.
Examples
let mut s = "HELLO".to_string(); let mut x: Result<String, u32> = Ok("hello".to_string()); let y: Result<&mut str, &mut u32> = Ok(&mut s); assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y); let mut i = 42; let mut x: Result<String, u32> = Err(42); let y: Result<&mut str, &mut u32> = Err(&mut i); assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
impl<T, E> Result<Option<T>, E>
Transposes a Result
of an Option
into an Option
of a Result
.
Ok(None)
will be mapped to None
. Ok(Some(_))
and Err(_)
will be mapped to Some(Ok(_))
and Some(Err(_))
.
Examples
#[derive(Debug, Eq, PartialEq)] struct SomeErr; let x: Result<Option<i32>, SomeErr> = Ok(Some(5)); let y: Option<Result<i32, SomeErr>> = Some(Ok(5)); assert_eq!(x.transpose(), y);
impl<T, E> Result<Result<T, E>, E>
pub fn flatten(self) -> Result<T, E>
Converts from Result<Result<T, E>, E>
to Result<T, E>
Examples
Basic usage:
#![feature(result_flattening)] let x: Result<Result<&'static str, u32>, u32> = Ok(Ok("hello")); assert_eq!(Ok("hello"), x.flatten()); let x: Result<Result<&'static str, u32>, u32> = Ok(Err(6)); assert_eq!(Err(6), x.flatten()); let x: Result<Result<&'static str, u32>, u32> = Err(6); assert_eq!(Err(6), x.flatten());
Flattening only removes one level of nesting at a time:
#![feature(result_flattening)] let x: Result<Result<Result<&'static str, u32>, u32>, u32> = Ok(Ok(Ok("hello"))); assert_eq!(Ok(Ok("hello")), x.flatten()); assert_eq!(Ok("hello"), x.flatten().flatten());
impl<T> Result<T, T>
pub const fn into_ok_or_err(self) -> T
result_into_ok_or_err
#82223)newly added
Returns the Ok
value if self
is Ok
, and the Err
value if self
is Err
.
In other words, this function returns the value (the T
) of a Result<T, T>
, regardless of whether or not that result is Ok
or Err
.
This can be useful in conjunction with APIs such as Atomic*::compare_exchange
, or slice::binary_search
, but only in cases where you don’t care if the result was Ok
or not.
Examples
#![feature(result_into_ok_or_err)] let ok: Result<u32, u32> = Ok(3); let err: Result<u32, u32> = Err(4); assert_eq!(ok.into_ok_or_err(), 3); assert_eq!(err.into_ok_or_err(), 4);
Trait Implementations
pub fn clone(&self) -> Result<T, E>
Returns a copy of the value. Read more
pub fn clone_from(&mut self, source: &Result<T, E>)
Performs copy-assignment from source
. Read more
pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl<'_> From<&'_ StreamResult> for Result<MZStatus, MZError>
pub fn from(res: &StreamResult) -> Result<MZStatus, MZError>
Performs the conversion.
impl From<StreamResult> for Result<MZStatus, MZError>
pub fn from(res: StreamResult) -> Result<MZStatus, MZError>
Performs the conversion.
impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E> where
V: FromIterator<A>,
pub fn from_iter<I>(iter: I) -> Result<V, E> where
I: IntoIterator<Item = Result<A, E>>,
Takes each element in the Iterator
: if it is an Err
, no further elements are taken, and the Err
is returned. Should no Err
occur, a container with the values of each Result
is returned.
Here is an example which increments every integer in a vector, checking for overflow:
let v = vec![1, 2]; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| x.checked_add(1).ok_or("Overflow!") ).collect(); assert_eq!(res, Ok(vec![2, 3]));
Here is another example that tries to subtract one from another list of integers, this time checking for underflow:
let v = vec![1, 2, 0]; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| x.checked_sub(1).ok_or("Underflow!") ).collect(); assert_eq!(res, Err("Underflow!"));
Here is a variation on the previous example, showing that no further elements are taken from iter
after the first Err
.
let v = vec![3, 2, 1, 10]; let mut shared = 0; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| { shared += x; x.checked_sub(2).ok_or("Underflow!") }).collect(); assert_eq!(res, Err("Underflow!")); 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.
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
Constructs the type from a compatible Residual
type. Read more
pub fn from_residual(residual: Result<Infallible, E>) -> Result<T, F>
Constructs the type from a compatible Residual
type. Read more
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
Constructs the type from a compatible Residual
type. Read more
impl<'a, T, E> IntoIterator for &'a mut Result<T, E>
type Item = &'a mut T
The type of the elements being iterated over.
type IntoIter = IterMut<'a, T>
Which kind of iterator are we turning this into?
pub fn into_iter(self) -> IterMut<'a, T>
impl<'a, T> Iterator for IterMut<'a, T> type Item = &'a mut T;
Creates an iterator from a value. Read more
impl<'a, T, E> IntoIterator for &'a Result<T, E>
type Item = &'a T
The type of the elements being iterated over.
type IntoIter = Iter<'a, T>
Which kind of iterator are we turning this into?
pub fn into_iter(self) -> Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;
Creates an iterator from a value. Read more
impl<T, E> IntoIterator for Result<T, E>
pub fn into_iter(self) -> IntoIter<T>
impl<T> Iterator for IntoIter<T> type Item = T;
Returns a consuming iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(5); let v: Vec<u32> = x.into_iter().collect(); assert_eq!(v, [5]); let x: Result<u32, &str> = Err("nothing!"); let v: Vec<u32> = x.into_iter().collect(); assert_eq!(v, []);
type Item = T
The type of the elements being iterated over.
type IntoIter = IntoIter<T>
Which kind of iterator are we turning this into?
pub fn cmp(&self, other: &Result<T, E>) -> Ordering
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
fn clamp(self, min: Self, max: Self) -> Self
Restrict a value to a certain interval. Read more
pub fn eq(&self, other: &Result<T, E>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
pub fn ne(&self, other: &Result<T, E>) -> bool
This method tests for !=
.
impl<T, E> PartialOrd<Result<T, E>> for Result<T, E> where
T: PartialOrd<T>,
E: PartialOrd<E>,
pub fn partial_cmp(&self, other: &Result<T, E>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, other: &Rhs) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &Rhs) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
Takes each element in the Iterator
: if it is an Err
, no further elements are taken, and the Err
is returned. Should no Err
occur, the sum of all elements is returned.
Examples
This sums up every integer in a vector, rejecting the sum if a negative element is encountered:
let v = vec![1, 2]; let res: Result<i32, &'static str> = v.iter().map(|&x: &i32| if x < 0 { Err("Negative element found") } else { Ok(x) } ).sum(); assert_eq!(res, Ok(3));
impl<E: Debug> Termination for Result<(), E>
fn report(self) -> i32
Is called to get the representation of the value as status code. This status code is returned to the operating system. Read more
impl<E: Debug> Termination for Result<!, E>
fn report(self) -> i32
Is called to get the representation of the value as status code. This status code is returned to the operating system. Read more
impl<T, E> Try for Result<T, E>
type Output = T
The type of the value produced by ?
when not short-circuiting.
type Residual = Result<Infallible, E>
The type of the value passed to FromResidual::from_residual
as part of ?
when short-circuiting. Read more
pub fn from_output(output: <Result<T, E> as Try>::Output) -> Result<T, E>
Constructs the type from its Output
type. Read more
pub fn branch(
self
) -> ControlFlow<<Result<T, E> as Try>::Residual, <Result<T, E> as Try>::Output>
Used in ?
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
impl<T, E> StructuralEq for Result<T, E>
impl<T, E> StructuralPartialEq for Result<T, E>
Auto Trait Implementations
impl<T, E> RefUnwindSafe for Result<T, E> where
E: RefUnwindSafe,
T: RefUnwindSafe,
impl<T, E> UnwindSafe for Result<T, E> where
E: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
toowned_clone_into
#41263)recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/result/enum.Result.html