1.0.0[][src]Enum std::result::Result

#[must_use = "this `Result` may be an `Err` variant, which should be handled"]pub enum Result<T, E> {
    Ok(T),
    Err(E),
}

Result is a type that represents either success (Ok) or failure (Err).

See the std::result module documentation for details.

Variants

Ok(T)

Contains the success value

Err(E)

Contains the error value

Implementations

impl<T, E> Result<T, E>[src]

#[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]pub fn is_ok(&self) -> bool[src]

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);
Run

#[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]pub fn is_err(&self) -> bool[src]

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);
Run

#[must_use]pub fn contains<U>(&self, x: &U) -> bool where
    U: PartialEq<T>, 
[src]

🔬 This is a nightly-only experimental API. (option_result_contains #62358)

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);
Run

#[must_use]pub fn contains_err<F>(&self, f: &F) -> bool where
    F: PartialEq<E>, 
[src]

🔬 This is a nightly-only experimental API. (result_contains_err #62358)

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);
Run

pub fn ok(self) -> Option<T>[src]

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);
Run

pub fn err(self) -> Option<E>[src]

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"));
Run

pub fn as_ref(&self) -> Result<&T, &E>[src]

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"));
Run

pub fn as_mut(&mut self) -> Result<&mut T, &mut E>[src]

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);
Run

pub fn map<U, F>(self, op: F) -> Result<U, E> where
    F: FnOnce(T) -> U, 
[src]

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(..) => {}
    }
}
Run

pub fn map_or<U, F>(self, default: U, f: F) -> U where
    F: FnOnce(T) -> U, 
1.41.0[src]

Applies a function to the contained value (if Ok), or returns the provided default (if Err).

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);
Run

pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U where
    D: FnOnce(E) -> U,
    F: FnOnce(T) -> U, 
1.41.0[src]

Maps a Result<T, E> to U by applying a function to a contained Ok value, or a fallback function to a contained Err 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);
Run

pub fn map_err<F, O>(self, op: O) -> Result<T, F> where
    O: FnOnce(E) -> F, 
[src]

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()));
Run

pub fn iter(&self) -> Iter<T>

Important traits for Iter<'a, T>

impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;
[src]

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);
Run

pub fn iter_mut(&mut self) -> IterMut<T>

Important traits for IterMut<'a, T>

impl<'a, T> Iterator for IterMut<'a, T> type Item = &'a mut T;
[src]

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);
Run

pub fn and<U>(self, res: Result<U, E>) -> Result<U, E>[src]

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"));
Run

pub fn and_then<U, F>(self, op: F) -> Result<U, E> where
    F: FnOnce(T) -> Result<U, E>, 
[src]

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));
Run

pub fn or<F>(self, res: Result<T, F>) -> Result<T, F>[src]

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));
Run

pub fn or_else<F, O>(self, op: O) -> Result<T, F> where
    O: FnOnce(E) -> Result<T, F>, 
[src]

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));
Run

pub fn unwrap_or(self, default: T) -> T[src]

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);
Run

pub fn unwrap_or_else<F>(self, op: F) -> T where
    F: FnOnce(E) -> T, 
[src]

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);
Run

impl<'_, T, E> Result<&'_ T, E> where
    T: Copy
[src]

pub fn copied(self) -> Result<T, E>[src]

🔬 This is a nightly-only experimental API. (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));
Run

impl<'_, T, E> Result<&'_ mut T, E> where
    T: Copy
[src]

pub fn copied(self) -> Result<T, E>[src]

🔬 This is a nightly-only experimental API. (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));
Run

impl<'_, T, E> Result<&'_ T, E> where
    T: Clone
[src]

pub fn cloned(self) -> Result<T, E>[src]

🔬 This is a nightly-only experimental API. (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));
Run

impl<'_, T, E> Result<&'_ mut T, E> where
    T: Clone
[src]

pub fn cloned(self) -> Result<T, E>[src]

🔬 This is a nightly-only experimental API. (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));
Run

impl<T, E> Result<T, E> where
    E: Debug
[src]

pub fn expect(self, msg: &str) -> T1.4.0[src]

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:

This example panics
let x: Result<u32, &str> = Err("emergency failure");
x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
Run

pub fn unwrap(self) -> T[src]

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);
Run
This example panics
let x: Result<u32, &str> = Err("emergency failure");
x.unwrap(); // panics with `emergency failure`
Run

impl<T, E> Result<T, E> where
    T: Debug
[src]

pub fn expect_err(self, msg: &str) -> E1.17.0[src]

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:

This example panics
let x: Result<u32, &str> = Ok(10);
x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
Run

pub fn unwrap_err(self) -> E[src]

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

This example panics
let x: Result<u32, &str> = Ok(2);
x.unwrap_err(); // panics with `2`
Run
let x: Result<u32, &str> = Err("emergency failure");
assert_eq!(x.unwrap_err(), "emergency failure");
Run

impl<T, E> Result<T, E> where
    T: Default
[src]

pub fn unwrap_or_default(self) -> T1.16.0[src]

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);
Run

impl<T, E> Result<T, E> where
    E: Into<!>, 
[src]

pub fn into_ok(self) -> T[src]

🔬 This is a nightly-only experimental API. (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);
Run

impl<T, E> Result<T, E> where
    T: Deref
[src]

pub fn as_deref(&self) -> Result<&<T as Deref>::Target, &E>1.47.0[src]

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);
Run

impl<T, E> Result<T, E> where
    T: DerefMut
[src]

pub fn as_deref_mut(&mut self) -> Result<&mut <T as Deref>::Target, &mut E>1.47.0[src]

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);
Run

impl<T, E> Result<Option<T>, E>[src]

pub fn transpose(self) -> Option<Result<T, E>>1.33.0[src]

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);
Run

impl<T, E> Result<Result<T, E>, E>[src]

pub fn flatten(self) -> Result<T, E>[src]

🔬 This is a nightly-only experimental API. (result_flattening #70142)

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());
Run

Flattening once only removes one level of nesting:

#![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());
Run

Trait Implementations

impl<T, E> Clone for Result<T, E> where
    E: Clone,
    T: Clone
[src]

impl<T, E> Copy for Result<T, E> where
    E: Copy,
    T: Copy
[src]

impl<T, E> Debug for Result<T, E> where
    E: Debug,
    T: Debug
[src]

impl<T, E> Eq for Result<T, E> where
    E: Eq,
    T: Eq
[src]

impl<'_> From<&'_ StreamResult> for Result<MZStatus, MZError>

impl From<StreamResult> for Result<MZStatus, MZError>

impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E> where
    V: FromIterator<A>, 
[src]

fn from_iter<I>(iter: I) -> Result<V, E> where
    I: IntoIterator<Item = Result<A, E>>, 
[src]

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]));
Run

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!"));
Run

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);
Run

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, E> Hash for Result<T, E> where
    E: Hash,
    T: Hash
[src]

impl<'a, T, E> IntoIterator for &'a Result<T, E>1.4.0[src]

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?

impl<'a, T, E> IntoIterator for &'a mut Result<T, E>1.4.0[src]

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?

impl<T, E> IntoIterator for Result<T, E>[src]

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> IntoIter<T>

Important traits for IntoIter<T>

impl<T> Iterator for IntoIter<T> type Item = T;
[src]

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, []);
Run

impl<T, E> Ord for Result<T, E> where
    E: Ord,
    T: Ord
[src]

impl<T, E> PartialEq<Result<T, E>> for Result<T, E> where
    E: PartialEq<E>,
    T: PartialEq<T>, 
[src]

impl<T, E> PartialOrd<Result<T, E>> for Result<T, E> where
    E: PartialOrd<E>,
    T: PartialOrd<T>, 
[src]

impl<T, U, E> Product<Result<U, E>> for Result<T, E> where
    T: Product<U>, 
1.16.0[src]

fn product<I>(iter: I) -> Result<T, E> where
    I: Iterator<Item = Result<U, E>>, 
[src]

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 product of all elements is returned.

impl<T, U, E> Sum<Result<U, E>> for Result<T, E> where
    T: Sum<U>, 
1.16.0[src]

fn sum<I>(iter: I) -> Result<T, E> where
    I: Iterator<Item = Result<U, E>>, 
[src]

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));
Run

impl<E: Debug> Termination for Result<(), E>[src]

impl<E: Debug> Termination for Result<!, E>[src]

Auto Trait Implementations

impl<T, E> RefUnwindSafe for Result<T, E> where
    E: RefUnwindSafe,
    T: RefUnwindSafe

impl<T, E> Send for Result<T, E> where
    E: Send,
    T: Send

impl<T, E> Sync for Result<T, E> where
    E: Sync,
    T: Sync

impl<T, E> Unpin for Result<T, E> where
    E: Unpin,
    T: Unpin

impl<T, E> UnwindSafe for Result<T, E> where
    E: UnwindSafe,
    T: UnwindSafe

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<I> IntoIterator for I where
    I: Iterator
[src]

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?

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

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

The type returned in the event of a conversion error.