Enum optional::OptionBool
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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
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pub fn some(b: bool) -> Self
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Create a SomeTrue for true, SomeFalse for false
pub fn none() -> Self
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pub fn is_some(&self) -> bool
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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());
pub fn is_none(&self) -> bool
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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());
pub fn expect(&self, msg: &str) -> bool
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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
pub fn unwrap(&self) -> bool
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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
pub fn unwrap_or(&self, def: bool) -> bool
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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));
pub fn unwrap_or_else<F>(self, f: F) -> bool where
F: FnOnce() -> bool,
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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));
pub fn map<U, F>(self, f: F) -> Option<U> where
F: FnOnce(bool) -> U,
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F: FnOnce(bool) -> U,
Maps an OptionBool
to an Option<U>
by applying the function
over the contained bool.
Note that there is also map_bool(..)
which works
similarly, but returns another OptionBool
.
Examples
Convert the contained bool to a Yes/No message
assert_eq!(Some("Yes"), OptionBool::SomeTrue.map( |b| if b { "Yes" } else { "No" }));
pub fn map_bool<F>(self, f: F) -> OptionBool where
F: FnOnce(bool) -> bool,
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F: FnOnce(bool) -> bool,
Maps an OptionBool
to another OptionBool
by applying the
function over the contained bool.
Note that there is also map(..)
which works
similarly, but returns an Option<bool>
.
Examples
Invert the contained bool
assert_eq!(OptionBool::SomeTrue, OptionBool::SomeFalse.map_bool(|b| !b));
pub fn map_or<U, F>(self, default: U, f: F) -> U where
F: FnOnce(bool) -> U,
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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" }));
pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U where
D: FnOnce() -> U,
F: FnOnce(bool) -> U,
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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" }));
pub fn ok_or<E>(self, err: E) -> Result<bool, E>
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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"));
pub fn ok_or_else<E, F>(self, err: F) -> Result<bool, E> where
F: FnOnce() -> E,
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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(|| something_expensive()), Ok(true)); assert_eq!(OptionBool::None.ok_or_else(|| "Ouch"), Err("Ouch"));
pub fn and<U>(self, optb: Option<U>) -> Option<U>
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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));
pub fn and_bool(self, optb: OptionBool) -> OptionBool
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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));
pub fn and_then<U, F>(self, f: F) -> Option<U> where
F: FnOnce(bool) -> Option<U>,
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F: FnOnce(bool) -> Option<U>,
returns None
if the OptionBool
is None
, otherwise calls f
with
the boolean value and returns the result as an Option<U>
Note that there is also and_then_bool(..)
which works similarly, but returns another OptionBool
.
Examples
assert_eq!(None, OptionBool::SomeFalse.and_then( |x| if x { Some(true) } else { None }));
pub fn and_then_bool<F>(self, f: F) -> OptionBool where
F: FnOnce(bool) -> OptionBool,
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F: FnOnce(bool) -> OptionBool,
returns None
if the OptionBool
is None
, otherwise calls f
with
the boolean value and returns the result as an OptionBool
Note that there is also and_then(..)
which works
similarly, but returns an Option<bool>
.
Examples
assert_eq!(OptionBool::None, OptionBool::SomeFalse.and_then_bool( |x| if x { OptionBool::SomeTrue } else { OptionBool::None }));
pub fn or(self, optb: Option<bool>) -> Option<bool>
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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));
pub fn or_bool(self, optb: OptionBool) -> OptionBool
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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));
pub fn or_else<F>(self, f: F) -> Option<bool> where
F: FnOnce() -> Option<bool>,
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F: FnOnce() -> Option<bool>,
Returns this as Option unless this is None
, in which case use the
supplied function to calculate the result.
Note that there is also or_else_bool(..)
which works similarly, but returns another OptionBool
.
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));
pub fn or_else_bool<F>(self, f: F) -> OptionBool where
F: FnOnce() -> OptionBool,
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F: FnOnce() -> OptionBool,
Returns this as Option unless this is None
, in which case use the
supplied function to calculate the result.
Note that there is also or_else(..)
which works
similarly, but returns an Option<bool>
.
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));
ⓘImportant traits for Iter<'a, T>pub fn iter(&self) -> Iter<bool>
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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());
pub fn as_slice(self) -> &'static [bool]
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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());
pub fn take(&mut self) -> Option<bool>
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Takes the value out of the OptionBool
and returns ist as
Option<bool>
, changing self to None
.
Note that there is also take_bool(..)
which
works similarly, but returns an OptionBool
.
Examples
let mut x = OptionBool::some(true); assert_eq!(Some(true), x.take()); assert_eq!(OptionBool::None, x);
pub fn take_bool(&mut self) -> OptionBool
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Methods from Deref<Target = Option<bool>>
pub fn is_some(&self) -> bool
1.0.0[src]
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);
pub fn is_none(&self) -> bool
1.0.0[src]
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);
pub fn as_ref(&self) -> Option<&T>
1.0.0[src]
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 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);
ⓘImportant traits for Iter<'a, A>pub fn iter(&self) -> Iter<T>
1.0.0[src]
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);
Trait Implementations
impl Copy for OptionBool
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impl Clone for OptionBool
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fn clone(&self) -> OptionBool
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Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl PartialEq for OptionBool
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fn eq(&self, __arg_0: &OptionBool) -> bool
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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[src]
This method tests for !=
.
impl Eq for OptionBool
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impl Ord for OptionBool
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fn cmp(&self, __arg_0: &OptionBool) -> Ordering
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This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
1.21.0[src]
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
1.21.0[src]
Compares and returns the minimum of two values. Read more
impl Hash for OptionBool
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fn hash<__H: Hasher>(&self, __arg_0: &mut __H)
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Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl Deref for OptionBool
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We can deref-coerce to Option<bool>
type Target = Option<bool>
The resulting type after dereferencing.
fn deref(&self) -> &'static Option<bool>
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Dereferences the value.
impl<'a> PartialEq<OptionBool> for &'a OptionBool
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fn eq(&self, other: &OptionBool) -> bool
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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[src]
This method tests for !=
.
impl Index<RangeFull> for OptionBool
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Index for RangeFull
(to slice)
type Output = [bool]
The returned type after indexing.
fn index<'a>(&'a self, _: RangeFull) -> &'static [bool]
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Performs the indexing (container[index]
) operation.
impl PartialOrd for OptionBool
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Some(true) > Some(false) > None
fn partial_cmp(&self, other: &OptionBool) -> Option<Ordering>
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This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
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[src]
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[src]
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[src]
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl Debug for OptionBool
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
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Formats the value using the given formatter. Read more
impl IntoIterator for OptionBool
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IntoIterator
works as expected
Examples
let mut pass : bool = false; for b in OptionBool::SomeTrue { pass = b; } assert!(pass); for b in OptionBool::None { assert!(false); }
type Item = bool
The type of the elements being iterated over.
type IntoIter = IterBool
Which kind of iterator are we turning this into?
ⓘImportant traits for IterBoolfn into_iter(self) -> IterBool
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Creates an iterator from a value. Read more
impl Default for OptionBool
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OptionBool
defaults to None
.
fn default() -> OptionBool
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Returns the "default value" for a type. Read more
impl From<OptionBool> for Option<bool>
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fn from(o: OptionBool) -> Option<bool>
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Performs the conversion.
impl<'a> From<&'a OptionBool> for Option<bool>
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fn from(o: &'a OptionBool) -> Option<bool>
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Performs the conversion.