Enum optional::OptionBool

pub enum OptionBool {
    SomeTrue,
    SomeFalse,
    None,
}

The OptionBool type, a space-efficient Option replacement

Variants

SomeTrue

Some(true)

SomeFalse

Some(false)

None

None

Methods

impl OptionBool

pub fn some(b: bool) -> Self

Create a SomeTrue for true, SomeFalse for false

pub fn none() -> Self

Create a None value.

Examples

assert_eq!(OptionBool::none(), optional::OptionBool::None);

pub 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());

pub 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());

pub 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

pub 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

pub 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));

pub 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));

pub fn map<U, F>(self, f: F) -> Option<U> where
    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, 

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, 

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, 

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>

Transforms the OptionBool into a Result<bool, E>, mapping SomeX 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, 

Transforms the OptionBool into a Result<bool, E>, mapping SomeX 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>

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

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>, 

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, 

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>

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

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>, 

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, 

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>

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

pub 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());

Important traits for &'a mut [u8]

impl<'a> Write for &'a mut [u8]impl<'a> Read for &'a [u8]

pub 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());

pub fn take(&mut self) -> Option<bool>

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

Takes the value out of the OptionBool, changing self to None.

Note that there is also take(..) which works similarly, but returns an Option<bool>.

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>>

pub 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);

pub 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);

pub fn as_ref(&self) -> Option<&T>

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>

impl<'a, A> Iterator for Iter<'a, A> type Item = &'a A;

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);

Trait Implementations

impl Copy for OptionBool

impl Clone for OptionBool

fn clone(&self) -> OptionBool

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl PartialEq for OptionBool

fn eq(&self, __arg_0: &OptionBool) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl Eq for OptionBool

impl Ord for OptionBool

fn cmp(&self, __arg_0: &OptionBool) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

impl Hash for OptionBool

fn hash<__H: Hasher>(&self, __arg_0: &mut __H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Deref for OptionBool

We can deref-coerce to Option<bool>

type Target = Option<bool>

The resulting type after dereferencing.

fn deref(&self) -> &'static Option<bool>

Dereferences the value.

impl<'a> PartialEq<OptionBool> for &'a OptionBool

fn eq(&self, other: &OptionBool) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl Index<RangeFull> for OptionBool

Index for RangeFull (to slice)

type Output = [bool]

The returned type after indexing.

Important traits for &'a mut [u8]

impl<'a> Write for &'a mut [u8]impl<'a> Read for &'a [u8]

fn index<'a>(&'a self, _: RangeFull) -> &'static [bool]

Performs the indexing (container[index]) operation.

impl PartialOrd for OptionBool

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.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Debug for OptionBool

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl IntoIterator for OptionBool

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 IterBool

impl Iterator for IterBool type Item = bool;

fn into_iter(self) -> IterBool

Creates an iterator from a value.

impl Default for OptionBool

OptionBool defaults to None.

fn default() -> OptionBool

Returns the "default value" for a type.

impl From<OptionBool> for Option<bool>

fn from(o: OptionBool) -> Option<bool>

Performs the conversion.

impl<'a> From<&'a OptionBool> for Option<bool>

fn from(o: &'a OptionBool) -> Option<bool>

Performs the conversion.

impl From<Option<bool>> for OptionBool

fn from(o: Option<bool>) -> Self

Performs the conversion.

impl<'a> From<&'a Option<bool>> for OptionBool

fn from(o: &'a Option<bool>) -> Self

Performs the conversion.