Enum optional::OptionBool
[−]
[src]
pub enum OptionBool { SomeTrue, SomeFalse, None, }
The OptionBool
type, a space-efficient Option
Variants
SomeTrue
Some(true)
SomeFalse
Some(false)
None
None
Methods
impl OptionBool
[src]
fn some(b: bool) -> Self
Create a SomeTrue for true, SomeFalse for false
fn none() -> Self
Create a None value.
# Examples
assert_eq!(OptionBool::none(), optional::OptionBool::None);
fn is_some(&self) -> bool
Returns true if the option is a Some value.
# Examples
assert!(OptionBool::SomeTrue.is_some()); assert!(OptionBool::SomeFalse.is_some()); assert!(!OptionBool::None.is_some());
fn is_none(&self) -> bool
Returns true if the option is a Some value.
# Examples
assert!(!OptionBool::SomeTrue.is_none()); assert!(!OptionBool::SomeFalse.is_none()); assert!(OptionBool::None.is_none());
fn expect(&self, msg: &str) -> bool
Unwraps the contained bool, panics on None with given message.
# Panics
if self is None
# Examples
For SomeTrue/SomeFalse, the corresponding bool is returned.
assert!(OptionBool::SomeTrue.expect("FAIL")); assert!(!OptionBool::SomeFalse.expect("FAIL"));
On None, it panics with the given message.
OptionBool::None.expect("FAIL"); // panics with FAIL
fn unwrap(&self) -> bool
Unwraps the contained bool, panics on None.
# Panics
if self is None
# Examples
For SomeTrue/SomeFalse, the corresponding bool is returned.
assert!(OptionBool::SomeTrue.unwrap()); assert!(!OptionBool::SomeFalse.unwrap());
On None, it panics with "unwrap called on None"
OptionBool::None.unwrap(); // panics
fn unwrap_or(&self, def: bool) -> bool
Returns the contained bool or a default.
# Examples
assert!(OptionBool::SomeTrue.unwrap_or(false)); assert!(!OptionBool::SomeFalse.unwrap_or(true)); assert!(OptionBool::None.unwrap_or(true)); assert!(!OptionBool::None.unwrap_or(false));
fn unwrap_or_else<F>(self, f: F) -> bool where F: FnOnce() -> bool
Returns the contained bool or a computed default.
# Examples
assert!(OptionBool::SomeTrue.unwrap_or_else(|| false)); assert!(!OptionBool::SomeFalse.unwrap_or_else(|| panic!())); assert!(OptionBool::None.unwrap_or_else(|| true));
fn map<U, F>(self, f: F) -> Option<U> where F: FnOnce(bool) -> U
Maps an OptionBool to an Option by applying the function over the contained bool.
# Examples
Convert the contained bool to a Yes/No message
assert_eq!(Some("Yes"), OptionBool::SomeTrue.map( |b| if b { "Yes" } else { "No" }));
fn map_bool<F>(self, f: F) -> OptionBool where F: FnOnce(bool) -> bool
Maps an OptionBool to another OptionBool by applying the function over the contained bool.
# Examples
Invert the contained bool
assert_eq!(OptionBool::SomeTrue, OptionBool::SomeFalse.map_bool(|b| !b));
fn map_or<U, F>(self, default: U, f: F) -> U where F: FnOnce(bool) -> U
Maps a value to a U by applying the function or return a default U.
# Examples
Map to a string (as per the daily wtf's boolean definition):
assert_eq!("True", OptionBool::SomeTrue.map_or("FileNotFound", |b| if b { "True" } else { "False" }));
fn map_or_else<U, D, F>(self, default: D, f: F) -> U where D: FnOnce() -> U, F: FnOnce(bool) -> U
Maps a value to a U by applying the function or return a computed default.
# Examples
assert_eq!("True", OptionBool::SomeTrue.map_or_else(|| "FileNotFound", |b| if b { "True" } else { "False" }));
fn ok_or<E>(self, err: E) -> Result<bool, E>
Transforms the OptionBool
into a Result<bool, E>
, mapping Some
X to
Ok(
X)
and None
to Err(err)
.
# Examples
assert_eq!(OptionBool::SomeTrue.ok_or("Ouch"), Ok(true)); assert_eq!(OptionBool::None.ok_or("Ouch"), Err("Ouch"));
fn ok_or_else<E, F>(self, err: F) -> Result<bool, E> where F: FnOnce() -> E
Transforms the OptionBool
into a Result<bool, E>
, mapping Some
X to
Ok(
X)
and None
to a calculated Err(err)
.
# Examples
assert_eq!(OptionBool::SomeTrue.ok_or_else(|| panic!()), Ok(true)); assert_eq!(OptionBool::None.ok_or_else(|| "Ouch"), Err("Ouch"));
fn and<U>(self, optb: Option<U>) -> Option<U>
Returns None
if the option is None
, otherwise returns optb
.
# Examples
assert_eq!(Some(1), OptionBool::SomeTrue.and(Some(1))); assert_eq!(None, OptionBool::None.and(Some(1))); let actual : Option<u8> = None; assert_eq!(None, OptionBool::SomeTrue.and(actual));
fn and_bool(self, optb: OptionBool) -> OptionBool
Returns None
if the option is None
, otherwise returns optb
.
# Examples
assert_eq!(OptionBool::SomeTrue, OptionBool::SomeFalse.and_bool(OptionBool::SomeTrue)); assert_eq!(OptionBool::None, OptionBool::None.and_bool(OptionBool::SomeFalse)); assert_eq!(OptionBool::None, OptionBool::SomeTrue.and_bool(OptionBool::None));
fn and_then<U, F>(self, f: F) -> Option<U> where F: FnOnce(bool) -> Option<U>
fn and_then_bool<F>(self, f: F) -> OptionBool where F: FnOnce(bool) -> OptionBool
fn or(self, optb: Option<bool>) -> Option<bool>
Returns this as Option unless this is None
, in which case returns
optb
.
# Examples
assert_eq!(Some(false), OptionBool::SomeFalse.or(Some(true))); assert_eq!(Some(true), OptionBool::None.or(Some(true))); assert_eq!(None, OptionBool::None.or(None));
fn or_bool(self, optb: OptionBool) -> OptionBool
Returns this as Option unless this is None
, in which case returns
optb
.
# Examples
assert_eq!(OptionBool::SomeFalse, OptionBool::SomeFalse.or_bool(OptionBool::SomeTrue)); assert_eq!(OptionBool::SomeTrue, OptionBool::None.or_bool(OptionBool::SomeTrue)); assert_eq!(OptionBool::None, OptionBool::None.or_bool(OptionBool::None));
fn or_else<F>(self, f: F) -> Option<bool> where F: FnOnce() -> Option<bool>
Returns this as Option unless this is None
, in which case use the
supplied function to calculate the result.
# Examples
assert_eq!(Some(false), OptionBool::SomeFalse.or_else(|| Some(true))); assert_eq!(Some(true), OptionBool::None.or_else(|| Some(true))); assert_eq!(None, OptionBool::None.or_else(|| None));
fn or_else_bool<F>(self, f: F) -> OptionBool where F: FnOnce() -> OptionBool
Returns this as Option unless this is None
, in which case use the
supplied function to calculate the result.
# Examples
assert_eq!(OptionBool::SomeFalse, OptionBool::SomeFalse.or_else_bool(|| OptionBool::SomeTrue)); assert_eq!(OptionBool::SomeTrue, OptionBool::None.or_else_bool(|| OptionBool::SomeTrue)); assert_eq!(OptionBool::None, OptionBool::None.or_else_bool(|| OptionBool::None));
fn iter(&self) -> Iter<bool>
return an iterator over all contained (that is zero or one) values.
# Examples
assert_eq!(None, OptionBool::None.iter().next()); assert_eq!(Some(&true), OptionBool::SomeTrue.iter().next());
fn as_slice(self) -> &'static [bool]
return a possibly empty slice with the contained value, if any.
# Examples
assert_eq!(&[true], OptionBool::SomeTrue.as_slice()); assert!(OptionBool::None.as_slice().is_empty());
fn take(&mut self) -> Option<bool>
Takes the value out of the OptionBool
and returns ist as
Option<bool>
, changing self to None
.
# Examples
let mut x = OptionBool::some(true); assert_eq!(Some(true), x.take()); assert_eq!(OptionBool::None, x);
fn take_bool(&mut self) -> OptionBool
Takes the value out of the OptionBool
, changing self to None
.
# Examples
let mut x = OptionBool::some(true); assert_eq!(OptionBool::some(true), x.take_bool()); assert_eq!(OptionBool::None, x);
Methods from Deref<Target=Option<bool>>
fn is_some(&self) -> bool
1.0.0
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);
fn is_none(&self) -> bool
1.0.0
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);
fn as_ref(&self) -> Option<&T>
1.0.0
Converts from Option<T>
to Option<&T>
Examples
Convert an Option<String>
into an Option<usize>
, preserving the original.
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 num_as_str: Option<String> = Some("10".to_string()); // First, cast `Option<String>` to `Option<&String>` with `as_ref`, // then consume *that* with `map`, leaving `num_as_str` on the stack. let num_as_int: Option<usize> = num_as_str.as_ref().map(|n| n.len()); println!("still can print num_as_str: {:?}", num_as_str);
fn as_mut(&mut self) -> Option<&mut T>
1.0.0
Converts from 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));
fn expect(self, msg: &str) -> T
1.0.0
Unwraps an option, yielding the content of a Some
.
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("the world is ending"), "value");
let x: Option<&str> = None; x.expect("the world is ending"); // panics with `the world is ending`
fn unwrap(self) -> T
1.0.0
Moves the value v
out of the Option<T>
if it is Some(v)
.
Panics
Panics if the self value equals None
.
Safety note
In general, because this function may panic, its use is discouraged.
Instead, prefer to use pattern matching and handle the None
case explicitly.
Examples
let x = Some("air"); assert_eq!(x.unwrap(), "air");
let x: Option<&str> = None; assert_eq!(x.unwrap(), "air"); // fails
fn unwrap_or(self, def: T) -> T
1.0.0
Returns the contained value or a default.
Examples
assert_eq!(Some("car").unwrap_or("bike"), "car"); assert_eq!(None.unwrap_or("bike"), "bike");
fn unwrap_or_else<F>(self, f: F) -> T where F: FnOnce() -> T
1.0.0
Returns the contained 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);
fn map<U, F>(self, f: F) -> Option<U> where F: FnOnce(T) -> U
1.0.0
Maps an Option<T>
to Option<U>
by applying a function to a contained value
Examples
Convert an Option<String>
into 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));
fn map_or<U, F>(self, default: U, f: F) -> U where F: FnOnce(T) -> U
1.0.0
Applies a function to the contained value (if any),
or returns a default
(if not).
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);
fn map_or_else<U, D, F>(self, default: D, f: F) -> U where D: FnOnce() -> U, F: FnOnce(T) -> U
1.0.0
Applies a function to the contained value (if any),
or computes a default
(if not).
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);
fn ok_or<E>(self, err: E) -> Result<T, E>
1.0.0
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(0), Ok("foo")); let x: Option<&str> = None; assert_eq!(x.ok_or(0), Err(0));
fn ok_or_else<E, F>(self, err: F) -> Result<T, E> where F: FnOnce() -> E
1.0.0
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));
fn iter(&self) -> Iter<T>
1.0.0
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);
fn iter_mut(&mut self) -> IterMut<T>
1.0.0
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);
fn and<U>(self, optb: Option<U>) -> Option<U>
1.0.0
Returns None
if the option is None
, otherwise returns optb
.
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);
fn and_then<U, F>(self, f: F) -> Option<U> where F: FnOnce(T) -> Option<U>
1.0.0
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(x: u32) -> Option<u32> { Some(x * x) } fn nope(_: u32) -> Option<u32> { None } assert_eq!(Some(2).and_then(sq).and_then(sq), Some(16)); assert_eq!(Some(2).and_then(sq).and_then(nope), None); assert_eq!(Some(2).and_then(nope).and_then(sq), None); assert_eq!(None.and_then(sq).and_then(sq), None);
fn or(self, optb: Option<T>) -> Option<T>
1.0.0
Returns the option if it contains a value, otherwise returns optb
.
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);
fn or_else<F>(self, f: F) -> Option<T> where F: FnOnce() -> Option<T>
1.0.0
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);
fn take(&mut self) -> Option<T>
1.0.0
Takes the value out of the option, leaving a None
in its place.
Examples
let mut x = Some(2); x.take(); assert_eq!(x, None); let mut x: Option<u32> = None; x.take(); assert_eq!(x, None);
fn cloned(self) -> Option<T>
1.0.0
Maps an Option<&T>
to an Option<T>
by cloning the contents of the
option.
fn unwrap_or_default(self) -> T
1.0.0
Returns the contained 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
Convert 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
None
on error.
let good_year_from_input = "1909"; let bad_year_from_input = "190blarg"; let good_year = good_year_from_input.parse().ok().unwrap_or_default(); let bad_year = bad_year_from_input.parse().ok().unwrap_or_default(); assert_eq!(1909, good_year); assert_eq!(0, bad_year);
Trait Implementations
impl Hash for OptionBool
[src]
fn hash<__H: Hasher>(&self, __arg_0: &mut __H)
Feeds this value into the state given, updating the hasher as necessary.
fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher
1.3.0
Feeds a slice of this type into the state provided.
impl Ord for OptionBool
[src]
fn cmp(&self, __arg_0: &OptionBool) -> Ordering
This method returns an Ordering
between self
and other
. Read more
impl Eq for OptionBool
[src]
impl Clone for OptionBool
[src]
fn clone(&self) -> OptionBool
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0
Performs copy-assignment from source
. Read more
impl Copy for OptionBool
[src]
impl Deref for OptionBool
[src]
We can deref-coerce to Option
type Target = Option<bool>
The resulting type after dereferencing
fn deref(&self) -> &'static Option<bool>
The method called to dereference a value
impl PartialEq for OptionBool
[src]
fn eq(&self, other: &OptionBool) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
1.0.0
This method tests for !=
.
impl<'a> PartialEq<OptionBool> for &'a OptionBool
[src]
fn eq(&self, other: &OptionBool) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
1.0.0
This method tests for !=
.
impl PartialOrd for OptionBool
[src]
Some(true) > Some(false) > None
fn partial_cmp(&self, other: &OptionBool) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
1.0.0
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &Rhs) -> bool
1.0.0
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
1.0.0
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &Rhs) -> bool
1.0.0
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl Debug for OptionBool
[src]
impl Default for OptionBool
[src]
fn default() -> OptionBool
Returns the "default value" for a type. Read more