vendor/itertools/src/either_or_both.rs - toolchain/rustc - Git at Google

 use core::ops::{Deref, DerefMut};

 use crate::EitherOrBoth::*;

 use either::Either;

 /// Value that either holds a single A or B, or both.
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub enum EitherOrBoth<A, B = A> {
     /// Both values are present.
     Both(A, B),
     /// Only the left value of type `A` is present.
     Left(A),
     /// Only the right value of type `B` is present.
     Right(B),
 }

 impl<A, B> EitherOrBoth<A, B> {
     /// If `Left`, or `Both`, return true. Otherwise, return false.
     pub fn has_left(&self) -> bool {
         self.as_ref().left().is_some()
     }

     /// If `Right`, or `Both`, return true, otherwise, return false.
     pub fn has_right(&self) -> bool {
         self.as_ref().right().is_some()
     }

     /// If `Left`, return true. Otherwise, return false.
     /// Exclusive version of [`has_left`](EitherOrBoth::has_left).
     pub fn is_left(&self) -> bool {
         matches!(self, Left(_))
     }

     /// If `Right`, return true. Otherwise, return false.
     /// Exclusive version of [`has_right`](EitherOrBoth::has_right).
     pub fn is_right(&self) -> bool {
         matches!(self, Right(_))
     }

     /// If `Both`, return true. Otherwise, return false.
     pub fn is_both(&self) -> bool {
         self.as_ref().both().is_some()
     }

     /// If `Left`, or `Both`, return `Some` with the left value. Otherwise, return `None`.
     pub fn left(self) -> Option<A> {
         match self {
             Left(left) | Both(left, _) => Some(left),
             _ => None,
         }
     }

     /// If `Right`, or `Both`, return `Some` with the right value. Otherwise, return `None`.
     pub fn right(self) -> Option<B> {
         match self {
             Right(right) | Both(_, right) => Some(right),
             _ => None,
         }
     }

     /// Return tuple of options corresponding to the left and right value respectively
     ///
     /// If `Left` return `(Some(..), None)`, if `Right` return `(None,Some(..))`, else return
     /// `(Some(..),Some(..))`
     pub fn left_and_right(self) -> (Option<A>, Option<B>) {
         self.map_any(Some, Some).or_default()
     }

     /// If `Left`, return `Some` with the left value. If `Right` or `Both`, return `None`.
     ///
     /// # Examples
     ///
     /// ```
     /// // On the `Left` variant.
     /// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Right, Both}};
     /// let x: EitherOrBoth<_, ()> = Left("bonjour");
     /// assert_eq!(x.just_left(), Some("bonjour"));
     ///
     /// // On the `Right` variant.
     /// let x: EitherOrBoth<(), _> = Right("hola");
     /// assert_eq!(x.just_left(), None);
     ///
     /// // On the `Both` variant.
     /// let x = Both("bonjour", "hola");
     /// assert_eq!(x.just_left(), None);
     /// ```
     pub fn just_left(self) -> Option<A> {
         match self {
             Left(left) => Some(left),
             _ => None,
         }
     }

     /// If `Right`, return `Some` with the right value. If `Left` or `Both`, return `None`.
     ///
     /// # Examples
     ///
     /// ```
     /// // On the `Left` variant.
     /// # use itertools::{EitherOrBoth::{Left, Right, Both}, EitherOrBoth};
     /// let x: EitherOrBoth<_, ()> = Left("auf wiedersehen");
     /// assert_eq!(x.just_left(), Some("auf wiedersehen"));
     ///
     /// // On the `Right` variant.
     /// let x: EitherOrBoth<(), _> = Right("adios");
     /// assert_eq!(x.just_left(), None);
     ///
     /// // On the `Both` variant.
     /// let x = Both("auf wiedersehen", "adios");
     /// assert_eq!(x.just_left(), None);
     /// ```
     pub fn just_right(self) -> Option<B> {
         match self {
             Right(right) => Some(right),
             _ => None,
         }
     }

     /// If `Both`, return `Some` containing the left and right values. Otherwise, return `None`.
     pub fn both(self) -> Option<(A, B)> {
         match self {
             Both(a, b) => Some((a, b)),
             _ => None,
         }
     }

     /// If `Left` or `Both`, return the left value. Otherwise, convert the right value and return it.
     pub fn into_left(self) -> A
     where
         B: Into<A>,
     {
         match self {
             Left(a) | Both(a, _) => a,
             Right(b) => b.into(),
         }
     }

     /// If `Right` or `Both`, return the right value. Otherwise, convert the left value and return it.
     pub fn into_right(self) -> B
     where
         A: Into<B>,
     {
         match self {
             Right(b) | Both(_, b) => b,
             Left(a) => a.into(),
         }
     }

     /// Converts from `&EitherOrBoth<A, B>` to `EitherOrBoth<&A, &B>`.
     pub fn as_ref(&self) -> EitherOrBoth<&A, &B> {
         match *self {
             Left(ref left) => Left(left),
             Right(ref right) => Right(right),
             Both(ref left, ref right) => Both(left, right),
         }
     }

     /// Converts from `&mut EitherOrBoth<A, B>` to `EitherOrBoth<&mut A, &mut B>`.
     pub fn as_mut(&mut self) -> EitherOrBoth<&mut A, &mut B> {
         match *self {
             Left(ref mut left) => Left(left),
             Right(ref mut right) => Right(right),
             Both(ref mut left, ref mut right) => Both(left, right),
         }
     }

     /// Converts from `&EitherOrBoth<A, B>` to `EitherOrBoth<&_, &_>` using the [`Deref`] trait.
     pub fn as_deref(&self) -> EitherOrBoth<&A::Target, &B::Target>
     where
         A: Deref,
         B: Deref,
     {
         match *self {
             Left(ref left) => Left(left),
             Right(ref right) => Right(right),
             Both(ref left, ref right) => Both(left, right),
         }
     }

     /// Converts from `&mut EitherOrBoth<A, B>` to `EitherOrBoth<&mut _, &mut _>` using the [`DerefMut`] trait.
     pub fn as_deref_mut(&mut self) -> EitherOrBoth<&mut A::Target, &mut B::Target>
     where
         A: DerefMut,
         B: DerefMut,
     {
         match *self {
             Left(ref mut left) => Left(left),
             Right(ref mut right) => Right(right),
             Both(ref mut left, ref mut right) => Both(left, right),
         }
     }

     /// Convert `EitherOrBoth<A, B>` to `EitherOrBoth<B, A>`.
     pub fn flip(self) -> EitherOrBoth<B, A> {
         match self {
             Left(a) => Right(a),
             Right(b) => Left(b),
             Both(a, b) => Both(b, a),
         }
     }

     /// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, b)` variants. If it is
     /// present rewrapping the result in `self`'s original variant.
     pub fn map_left<F, M>(self, f: F) -> EitherOrBoth<M, B>
     where
         F: FnOnce(A) -> M,
     {
         match self {
             Both(a, b) => Both(f(a), b),
             Left(a) => Left(f(a)),
             Right(b) => Right(b),
         }
     }

     /// Apply the function `f` on the value `b` in `Right(b)` or `Both(a, b)` variants.
     /// If it is present rewrapping the result in `self`'s original variant.
     pub fn map_right<F, M>(self, f: F) -> EitherOrBoth<A, M>
     where
         F: FnOnce(B) -> M,
     {
         match self {
             Left(a) => Left(a),
             Right(b) => Right(f(b)),
             Both(a, b) => Both(a, f(b)),
         }
     }

     /// Apply the functions `f` and `g` on the value `a` and `b` respectively;
     /// found in `Left(a)`, `Right(b)`, or `Both(a, b)` variants.
     /// The Result is rewrapped `self`'s original variant.
     pub fn map_any<F, L, G, R>(self, f: F, g: G) -> EitherOrBoth<L, R>
     where
         F: FnOnce(A) -> L,
         G: FnOnce(B) -> R,
     {
         match self {
             Left(a) => Left(f(a)),
             Right(b) => Right(g(b)),
             Both(a, b) => Both(f(a), g(b)),
         }
     }

     /// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, _)` variants if it is
     /// present.
     pub fn left_and_then<F, L>(self, f: F) -> EitherOrBoth<L, B>
     where
         F: FnOnce(A) -> EitherOrBoth<L, B>,
     {
         match self {
             Left(a) | Both(a, _) => f(a),
             Right(b) => Right(b),
         }
     }

     /// Apply the function `f` on the value `b`
     /// in `Right(b)` or `Both(_, b)` variants if it is present.
     pub fn right_and_then<F, R>(self, f: F) -> EitherOrBoth<A, R>
     where
         F: FnOnce(B) -> EitherOrBoth<A, R>,
     {
         match self {
             Left(a) => Left(a),
             Right(b) | Both(_, b) => f(b),
         }
     }

     /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
     /// Otherwise, returns the wrapped value for the present element, and the supplied
     /// value for the other. The first (`l`) argument is used for a missing `Left`
     /// value. The second (`r`) argument is used for a missing `Right` value.
     ///
     /// 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.
     ///
     /// [`or_else`]: EitherOrBoth::or_else
     ///
     /// # Examples
     ///
     /// ```
     /// # use itertools::EitherOrBoth;
     /// assert_eq!(EitherOrBoth::Both("tree", 1).or("stone", 5), ("tree", 1));
     /// assert_eq!(EitherOrBoth::Left("tree").or("stone", 5), ("tree", 5));
     /// assert_eq!(EitherOrBoth::Right(1).or("stone", 5), ("stone", 1));
     /// ```
     pub fn or(self, l: A, r: B) -> (A, B) {
         match self {
             Left(inner_l) => (inner_l, r),
             Right(inner_r) => (l, inner_r),
             Both(inner_l, inner_r) => (inner_l, inner_r),
         }
     }

     /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
     /// Otherwise, returns the wrapped value for the present element, and the [`default`](Default::default)
     /// for the other.
     pub fn or_default(self) -> (A, B)
     where
         A: Default,
         B: Default,
     {
         match self {
             Left(l) => (l, B::default()),
             Right(r) => (A::default(), r),
             Both(l, r) => (l, r),
         }
     }

     /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
     /// Otherwise, returns the wrapped value for the present element, and computes the
     /// missing value with the supplied closure. The first argument (`l`) is used for a
     /// missing `Left` value. The second argument (`r`) is used for a missing `Right` value.
     ///
     /// # Examples
     ///
     /// ```
     /// # use itertools::EitherOrBoth;
     /// let k = 10;
     /// assert_eq!(EitherOrBoth::Both("tree", 1).or_else(|| "stone", || 2 * k), ("tree", 1));
     /// assert_eq!(EitherOrBoth::Left("tree").or_else(|| "stone", || 2 * k), ("tree", 20));
     /// assert_eq!(EitherOrBoth::Right(1).or_else(|| "stone", || 2 * k), ("stone", 1));
     /// ```
     pub fn or_else<L: FnOnce() -> A, R: FnOnce() -> B>(self, l: L, r: R) -> (A, B) {
         match self {
             Left(inner_l) => (inner_l, r()),
             Right(inner_r) => (l(), inner_r),
             Both(inner_l, inner_r) => (inner_l, inner_r),
         }
     }

     /// Returns a mutable reference to the left value. If the left value is not present,
     /// it is replaced with `val`.
     pub fn left_or_insert(&mut self, val: A) -> &mut A {
         self.left_or_insert_with(|| val)
     }

     /// Returns a mutable reference to the right value. If the right value is not present,
     /// it is replaced with `val`.
     pub fn right_or_insert(&mut self, val: B) -> &mut B {
         self.right_or_insert_with(|| val)
     }

     /// If the left value is not present, replace it the value computed by the closure `f`.
     /// Returns a mutable reference to the now-present left value.
     pub fn left_or_insert_with<F>(&mut self, f: F) -> &mut A
     where
         F: FnOnce() -> A,
     {
         match self {
             Left(left) | Both(left, _) => left,
             Right(_) => self.insert_left(f()),
         }
     }

     /// If the right value is not present, replace it the value computed by the closure `f`.
     /// Returns a mutable reference to the now-present right value.
     pub fn right_or_insert_with<F>(&mut self, f: F) -> &mut B
     where
         F: FnOnce() -> B,
     {
         match self {
             Right(right) | Both(_, right) => right,
             Left(_) => self.insert_right(f()),
         }
     }

     /// Sets the `left` value of this instance, and returns a mutable reference to it.
     /// Does not affect the `right` value.
     ///
     /// # Examples
     /// ```
     /// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Right, Both}};
     ///
     /// // Overwriting a pre-existing value.
     /// let mut either: EitherOrBoth<_, ()> = Left(0_u32);
     /// assert_eq!(*either.insert_left(69), 69);
     ///
     /// // Inserting a second value.
     /// let mut either = Right("no");
     /// assert_eq!(*either.insert_left("yes"), "yes");
     /// assert_eq!(either, Both("yes", "no"));
     /// ```
     pub fn insert_left(&mut self, val: A) -> &mut A {
         match self {
             Left(left) | Both(left, _) => {
                 *left = val;
                 left
             }
             Right(right) => {
                 // This is like a map in place operation. We move out of the reference,
                 // change the value, and then move back into the reference.
                 unsafe {
                     // SAFETY: We know this pointer is valid for reading since we got it from a reference.
                     let right = std::ptr::read(right as *mut _);
                     // SAFETY: Again, we know the pointer is valid since we got it from a reference.
                     std::ptr::write(self as *mut _, Both(val, right));
                 }

                 if let Both(left, _) = self {
                     left
                 } else {
                     // SAFETY: The above pattern will always match, since we just
                     // set `self` equal to `Both`.
                     unsafe { std::hint::unreachable_unchecked() }
                 }
             }
         }
     }

     /// Sets the `right` value of this instance, and returns a mutable reference to it.
     /// Does not affect the `left` value.
     ///
     /// # Examples
     /// ```
     /// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Both}};
     /// // Overwriting a pre-existing value.
     /// let mut either: EitherOrBoth<_, ()> = Left(0_u32);
     /// assert_eq!(*either.insert_left(69), 69);
     ///
     /// // Inserting a second value.
     /// let mut either = Left("what's");
     /// assert_eq!(*either.insert_right(9 + 10), 21 - 2);
     /// assert_eq!(either, Both("what's", 9+10));
     /// ```
     pub fn insert_right(&mut self, val: B) -> &mut B {
         match self {
             Right(right) | Both(_, right) => {
                 *right = val;
                 right
             }
             Left(left) => {
                 // This is like a map in place operation. We move out of the reference,
                 // change the value, and then move back into the reference.
                 unsafe {
                     // SAFETY: We know this pointer is valid for reading since we got it from a reference.
                     let left = std::ptr::read(left as *mut _);
                     // SAFETY: Again, we know the pointer is valid since we got it from a reference.
                     std::ptr::write(self as *mut _, Both(left, val));
                 }
                 if let Both(_, right) = self {
                     right
                 } else {
                     // SAFETY: The above pattern will always match, since we just
                     // set `self` equal to `Both`.
                     unsafe { std::hint::unreachable_unchecked() }
                 }
             }
         }
     }

     /// Set `self` to `Both(..)`, containing the specified left and right values,
     /// and returns a mutable reference to those values.
     pub fn insert_both(&mut self, left: A, right: B) -> (&mut A, &mut B) {
         *self = Both(left, right);
         if let Both(left, right) = self {
             (left, right)
         } else {
             // SAFETY: The above pattern will always match, since we just
             // set `self` equal to `Both`.
             unsafe { std::hint::unreachable_unchecked() }
         }
     }
 }

 impl<T> EitherOrBoth<T, T> {
     /// Return either value of left, right, or apply a function `f` to both values if both are present.
     /// The input function has to return the same type as both Right and Left carry.
     ///
     /// This function can be used to preferrably extract the left resp. right value,
     /// but fall back to the other (i.e. right resp. left) if the preferred one is not present.
     ///
     /// # Examples
     /// ```
     /// # use itertools::EitherOrBoth;
     /// assert_eq!(EitherOrBoth::Both(3, 7).reduce(u32::max), 7);
     /// assert_eq!(EitherOrBoth::Left(3).reduce(u32::max), 3);
     /// assert_eq!(EitherOrBoth::Right(7).reduce(u32::max), 7);
     ///
     /// // Extract the left value if present, fall back to the right otherwise.
     /// assert_eq!(EitherOrBoth::Left("left").reduce(|l, _r| l), "left");
     /// assert_eq!(EitherOrBoth::Right("right").reduce(|l, _r| l), "right");
     /// assert_eq!(EitherOrBoth::Both("left", "right").reduce(|l, _r| l), "left");
     /// ```
     pub fn reduce<F>(self, f: F) -> T
     where
         F: FnOnce(T, T) -> T,
     {
         match self {
             Left(a) => a,
             Right(b) => b,
             Both(a, b) => f(a, b),
         }
     }
 }

 impl<A, B> From<EitherOrBoth<A, B>> for Option<Either<A, B>> {
     fn from(value: EitherOrBoth<A, B>) -> Self {
         match value {
             Left(l) => Some(Either::Left(l)),
             Right(r) => Some(Either::Right(r)),
             Both(..) => None,
         }
     }
 }

 impl<A, B> From<Either<A, B>> for EitherOrBoth<A, B> {
     fn from(either: Either<A, B>) -> Self {
         match either {
             Either::Left(l) => Left(l),
             Either::Right(l) => Right(l),
         }
     }
 }
	use core::ops::{Deref, DerefMut};

	use crate::EitherOrBoth::*;

	use either::Either;

	/// Value that either holds a single A or B, or both.
	#[derive(Clone, PartialEq, Eq, Hash, Debug)]
	pub enum EitherOrBoth<A, B = A> {
	/// Both values are present.
	Both(A, B),
	/// Only the left value of type `A` is present.
	Left(A),
	/// Only the right value of type `B` is present.
	Right(B),
	}

	impl<A, B> EitherOrBoth<A, B> {
	/// If `Left`, or `Both`, return true. Otherwise, return false.
	pub fn has_left(&self) -> bool {
	self.as_ref().left().is_some()
	}

	/// If `Right`, or `Both`, return true, otherwise, return false.
	pub fn has_right(&self) -> bool {
	self.as_ref().right().is_some()
	}

	/// If `Left`, return true. Otherwise, return false.
	/// Exclusive version of [`has_left`](EitherOrBoth::has_left).
	pub fn is_left(&self) -> bool {
	matches!(self, Left(_))
	}

	/// If `Right`, return true. Otherwise, return false.
	/// Exclusive version of [`has_right`](EitherOrBoth::has_right).
	pub fn is_right(&self) -> bool {
	matches!(self, Right(_))
	}

	/// If `Both`, return true. Otherwise, return false.
	pub fn is_both(&self) -> bool {
	self.as_ref().both().is_some()
	}

	/// If `Left`, or `Both`, return `Some` with the left value. Otherwise, return `None`.
	pub fn left(self) -> Option<A> {
	match self {
	Left(left) \| Both(left, _) => Some(left),
	_ => None,
	}
	}

	/// If `Right`, or `Both`, return `Some` with the right value. Otherwise, return `None`.
	pub fn right(self) -> Option<B> {
	match self {
	Right(right) \| Both(_, right) => Some(right),
	_ => None,
	}
	}

	/// Return tuple of options corresponding to the left and right value respectively
	///
	/// If `Left` return `(Some(..), None)`, if `Right` return `(None,Some(..))`, else return
	/// `(Some(..),Some(..))`
	pub fn left_and_right(self) -> (Option<A>, Option<B>) {
	self.map_any(Some, Some).or_default()
	}

	/// If `Left`, return `Some` with the left value. If `Right` or `Both`, return `None`.
	///
	/// # Examples
	///
	/// ```
	/// // On the `Left` variant.
	/// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Right, Both}};
	/// let x: EitherOrBoth<_, ()> = Left("bonjour");
	/// assert_eq!(x.just_left(), Some("bonjour"));
	///
	/// // On the `Right` variant.
	/// let x: EitherOrBoth<(), _> = Right("hola");
	/// assert_eq!(x.just_left(), None);
	///
	/// // On the `Both` variant.
	/// let x = Both("bonjour", "hola");
	/// assert_eq!(x.just_left(), None);
	/// ```
	pub fn just_left(self) -> Option<A> {
	match self {
	Left(left) => Some(left),
	_ => None,
	}
	}

	/// If `Right`, return `Some` with the right value. If `Left` or `Both`, return `None`.
	///
	/// # Examples
	///
	/// ```
	/// // On the `Left` variant.
	/// # use itertools::{EitherOrBoth::{Left, Right, Both}, EitherOrBoth};
	/// let x: EitherOrBoth<_, ()> = Left("auf wiedersehen");
	/// assert_eq!(x.just_left(), Some("auf wiedersehen"));
	///
	/// // On the `Right` variant.
	/// let x: EitherOrBoth<(), _> = Right("adios");
	/// assert_eq!(x.just_left(), None);
	///
	/// // On the `Both` variant.
	/// let x = Both("auf wiedersehen", "adios");
	/// assert_eq!(x.just_left(), None);
	/// ```
	pub fn just_right(self) -> Option<B> {
	match self {
	Right(right) => Some(right),
	_ => None,
	}
	}

	/// If `Both`, return `Some` containing the left and right values. Otherwise, return `None`.
	pub fn both(self) -> Option<(A, B)> {
	match self {
	Both(a, b) => Some((a, b)),
	_ => None,
	}
	}

	/// If `Left` or `Both`, return the left value. Otherwise, convert the right value and return it.
	pub fn into_left(self) -> A
	where
	B: Into<A>,
	{
	match self {
	Left(a) \| Both(a, _) => a,
	Right(b) => b.into(),
	}
	}

	/// If `Right` or `Both`, return the right value. Otherwise, convert the left value and return it.
	pub fn into_right(self) -> B
	where
	A: Into<B>,
	{
	match self {
	Right(b) \| Both(_, b) => b,
	Left(a) => a.into(),
	}
	}

	/// Converts from `&EitherOrBoth<A, B>` to `EitherOrBoth<&A, &B>`.
	pub fn as_ref(&self) -> EitherOrBoth<&A, &B> {
	match *self {
	Left(ref left) => Left(left),
	Right(ref right) => Right(right),
	Both(ref left, ref right) => Both(left, right),
	}
	}

	/// Converts from `&mut EitherOrBoth<A, B>` to `EitherOrBoth<&mut A, &mut B>`.
	pub fn as_mut(&mut self) -> EitherOrBoth<&mut A, &mut B> {
	match *self {
	Left(ref mut left) => Left(left),
	Right(ref mut right) => Right(right),
	Both(ref mut left, ref mut right) => Both(left, right),
	}
	}

	/// Converts from `&EitherOrBoth<A, B>` to `EitherOrBoth<&_, &_>` using the [`Deref`] trait.
	pub fn as_deref(&self) -> EitherOrBoth<&A::Target, &B::Target>
	where
	A: Deref,
	B: Deref,
	{
	match *self {
	Left(ref left) => Left(left),
	Right(ref right) => Right(right),
	Both(ref left, ref right) => Both(left, right),
	}
	}

	/// Converts from `&mut EitherOrBoth<A, B>` to `EitherOrBoth<&mut _, &mut _>` using the [`DerefMut`] trait.
	pub fn as_deref_mut(&mut self) -> EitherOrBoth<&mut A::Target, &mut B::Target>
	where
	A: DerefMut,
	B: DerefMut,
	{
	match *self {
	Left(ref mut left) => Left(left),
	Right(ref mut right) => Right(right),
	Both(ref mut left, ref mut right) => Both(left, right),
	}
	}

	/// Convert `EitherOrBoth<A, B>` to `EitherOrBoth<B, A>`.
	pub fn flip(self) -> EitherOrBoth<B, A> {
	match self {
	Left(a) => Right(a),
	Right(b) => Left(b),
	Both(a, b) => Both(b, a),
	}
	}

	/// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, b)` variants. If it is
	/// present rewrapping the result in `self`'s original variant.
	pub fn map_left<F, M>(self, f: F) -> EitherOrBoth<M, B>
	where
	F: FnOnce(A) -> M,
	{
	match self {
	Both(a, b) => Both(f(a), b),
	Left(a) => Left(f(a)),
	Right(b) => Right(b),
	}
	}

	/// Apply the function `f` on the value `b` in `Right(b)` or `Both(a, b)` variants.
	/// If it is present rewrapping the result in `self`'s original variant.
	pub fn map_right<F, M>(self, f: F) -> EitherOrBoth<A, M>
	where
	F: FnOnce(B) -> M,
	{
	match self {
	Left(a) => Left(a),
	Right(b) => Right(f(b)),
	Both(a, b) => Both(a, f(b)),
	}
	}

	/// Apply the functions `f` and `g` on the value `a` and `b` respectively;
	/// found in `Left(a)`, `Right(b)`, or `Both(a, b)` variants.
	/// The Result is rewrapped `self`'s original variant.
	pub fn map_any<F, L, G, R>(self, f: F, g: G) -> EitherOrBoth<L, R>
	where
	F: FnOnce(A) -> L,
	G: FnOnce(B) -> R,
	{
	match self {
	Left(a) => Left(f(a)),
	Right(b) => Right(g(b)),
	Both(a, b) => Both(f(a), g(b)),
	}
	}

	/// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, _)` variants if it is
	/// present.
	pub fn left_and_then<F, L>(self, f: F) -> EitherOrBoth<L, B>
	where
	F: FnOnce(A) -> EitherOrBoth<L, B>,
	{
	match self {
	Left(a) \| Both(a, _) => f(a),
	Right(b) => Right(b),
	}
	}

	/// Apply the function `f` on the value `b`
	/// in `Right(b)` or `Both(_, b)` variants if it is present.
	pub fn right_and_then<F, R>(self, f: F) -> EitherOrBoth<A, R>
	where
	F: FnOnce(B) -> EitherOrBoth<A, R>,
	{
	match self {
	Left(a) => Left(a),
	Right(b) \| Both(_, b) => f(b),
	}
	}

	/// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
	/// Otherwise, returns the wrapped value for the present element, and the supplied
	/// value for the other. The first (`l`) argument is used for a missing `Left`
	/// value. The second (`r`) argument is used for a missing `Right` value.
	///
	/// 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.
	///
	/// [`or_else`]: EitherOrBoth::or_else
	///
	/// # Examples
	///
	/// ```
	/// # use itertools::EitherOrBoth;
	/// assert_eq!(EitherOrBoth::Both("tree", 1).or("stone", 5), ("tree", 1));
	/// assert_eq!(EitherOrBoth::Left("tree").or("stone", 5), ("tree", 5));
	/// assert_eq!(EitherOrBoth::Right(1).or("stone", 5), ("stone", 1));
	/// ```
	pub fn or(self, l: A, r: B) -> (A, B) {
	match self {
	Left(inner_l) => (inner_l, r),
	Right(inner_r) => (l, inner_r),
	Both(inner_l, inner_r) => (inner_l, inner_r),
	}
	}

	/// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
	/// Otherwise, returns the wrapped value for the present element, and the [`default`](Default::default)
	/// for the other.
	pub fn or_default(self) -> (A, B)
	where
	A: Default,
	B: Default,
	{
	match self {
	Left(l) => (l, B::default()),
	Right(r) => (A::default(), r),
	Both(l, r) => (l, r),
	}
	}

	/// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
	/// Otherwise, returns the wrapped value for the present element, and computes the
	/// missing value with the supplied closure. The first argument (`l`) is used for a
	/// missing `Left` value. The second argument (`r`) is used for a missing `Right` value.
	///
	/// # Examples
	///
	/// ```
	/// # use itertools::EitherOrBoth;
	/// let k = 10;
	/// assert_eq!(EitherOrBoth::Both("tree", 1).or_else(\|\| "stone", \|\| 2 * k), ("tree", 1));
	/// assert_eq!(EitherOrBoth::Left("tree").or_else(\|\| "stone", \|\| 2 * k), ("tree", 20));
	/// assert_eq!(EitherOrBoth::Right(1).or_else(\|\| "stone", \|\| 2 * k), ("stone", 1));
	/// ```
	pub fn or_else<L: FnOnce() -> A, R: FnOnce() -> B>(self, l: L, r: R) -> (A, B) {
	match self {
	Left(inner_l) => (inner_l, r()),
	Right(inner_r) => (l(), inner_r),
	Both(inner_l, inner_r) => (inner_l, inner_r),
	}
	}

	/// Returns a mutable reference to the left value. If the left value is not present,
	/// it is replaced with `val`.
	pub fn left_or_insert(&mut self, val: A) -> &mut A {
	self.left_or_insert_with(\|\| val)
	}

	/// Returns a mutable reference to the right value. If the right value is not present,
	/// it is replaced with `val`.
	pub fn right_or_insert(&mut self, val: B) -> &mut B {
	self.right_or_insert_with(\|\| val)
	}

	/// If the left value is not present, replace it the value computed by the closure `f`.
	/// Returns a mutable reference to the now-present left value.
	pub fn left_or_insert_with<F>(&mut self, f: F) -> &mut A
	where
	F: FnOnce() -> A,
	{
	match self {
	Left(left) \| Both(left, _) => left,
	Right(_) => self.insert_left(f()),
	}
	}

	/// If the right value is not present, replace it the value computed by the closure `f`.
	/// Returns a mutable reference to the now-present right value.
	pub fn right_or_insert_with<F>(&mut self, f: F) -> &mut B
	where
	F: FnOnce() -> B,
	{
	match self {
	Right(right) \| Both(_, right) => right,
	Left(_) => self.insert_right(f()),
	}
	}

	/// Sets the `left` value of this instance, and returns a mutable reference to it.
	/// Does not affect the `right` value.
	///
	/// # Examples
	/// ```
	/// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Right, Both}};
	///
	/// // Overwriting a pre-existing value.
	/// let mut either: EitherOrBoth<_, ()> = Left(0_u32);
	/// assert_eq!(*either.insert_left(69), 69);
	///
	/// // Inserting a second value.
	/// let mut either = Right("no");
	/// assert_eq!(*either.insert_left("yes"), "yes");
	/// assert_eq!(either, Both("yes", "no"));
	/// ```
	pub fn insert_left(&mut self, val: A) -> &mut A {
	match self {
	Left(left) \| Both(left, _) => {
	*left = val;
	left
	}
	Right(right) => {
	// This is like a map in place operation. We move out of the reference,
	// change the value, and then move back into the reference.
	unsafe {
	// SAFETY: We know this pointer is valid for reading since we got it from a reference.
	let right = std::ptr::read(right as *mut _);
	// SAFETY: Again, we know the pointer is valid since we got it from a reference.
	std::ptr::write(self as *mut _, Both(val, right));
	}

	if let Both(left, _) = self {
	left
	} else {
	// SAFETY: The above pattern will always match, since we just
	// set `self` equal to `Both`.
	unsafe { std::hint::unreachable_unchecked() }
	}
	}
	}
	}

	/// Sets the `right` value of this instance, and returns a mutable reference to it.
	/// Does not affect the `left` value.
	///
	/// # Examples
	/// ```
	/// # use itertools::{EitherOrBoth, EitherOrBoth::{Left, Both}};
	/// // Overwriting a pre-existing value.
	/// let mut either: EitherOrBoth<_, ()> = Left(0_u32);
	/// assert_eq!(*either.insert_left(69), 69);
	///
	/// // Inserting a second value.
	/// let mut either = Left("what's");
	/// assert_eq!(*either.insert_right(9 + 10), 21 - 2);
	/// assert_eq!(either, Both("what's", 9+10));
	/// ```
	pub fn insert_right(&mut self, val: B) -> &mut B {
	match self {
	Right(right) \| Both(_, right) => {
	*right = val;
	right
	}
	Left(left) => {
	// This is like a map in place operation. We move out of the reference,
	// change the value, and then move back into the reference.
	unsafe {
	// SAFETY: We know this pointer is valid for reading since we got it from a reference.
	let left = std::ptr::read(left as *mut _);
	// SAFETY: Again, we know the pointer is valid since we got it from a reference.
	std::ptr::write(self as *mut _, Both(left, val));
	}
	if let Both(_, right) = self {
	right
	} else {
	// SAFETY: The above pattern will always match, since we just
	// set `self` equal to `Both`.
	unsafe { std::hint::unreachable_unchecked() }
	}
	}
	}
	}

	/// Set `self` to `Both(..)`, containing the specified left and right values,
	/// and returns a mutable reference to those values.
	pub fn insert_both(&mut self, left: A, right: B) -> (&mut A, &mut B) {
	*self = Both(left, right);
	if let Both(left, right) = self {
	(left, right)
	} else {
	// SAFETY: The above pattern will always match, since we just
	// set `self` equal to `Both`.
	unsafe { std::hint::unreachable_unchecked() }
	}
	}
	}

	impl<T> EitherOrBoth<T, T> {
	/// Return either value of left, right, or apply a function `f` to both values if both are present.
	/// The input function has to return the same type as both Right and Left carry.
	///
	/// This function can be used to preferrably extract the left resp. right value,
	/// but fall back to the other (i.e. right resp. left) if the preferred one is not present.
	///
	/// # Examples
	/// ```
	/// # use itertools::EitherOrBoth;
	/// assert_eq!(EitherOrBoth::Both(3, 7).reduce(u32::max), 7);
	/// assert_eq!(EitherOrBoth::Left(3).reduce(u32::max), 3);
	/// assert_eq!(EitherOrBoth::Right(7).reduce(u32::max), 7);
	///
	/// // Extract the left value if present, fall back to the right otherwise.
	/// assert_eq!(EitherOrBoth::Left("left").reduce(\|l, _r\| l), "left");
	/// assert_eq!(EitherOrBoth::Right("right").reduce(\|l, _r\| l), "right");
	/// assert_eq!(EitherOrBoth::Both("left", "right").reduce(\|l, _r\| l), "left");
	/// ```
	pub fn reduce<F>(self, f: F) -> T
	where
	F: FnOnce(T, T) -> T,
	{
	match self {
	Left(a) => a,
	Right(b) => b,
	Both(a, b) => f(a, b),
	}
	}
	}

	impl<A, B> From<EitherOrBoth<A, B>> for Option<Either<A, B>> {
	fn from(value: EitherOrBoth<A, B>) -> Self {
	match value {
	Left(l) => Some(Either::Left(l)),
	Right(r) => Some(Either::Right(r)),
	Both(..) => None,
	}
	}
	}

	impl<A, B> From<Either<A, B>> for EitherOrBoth<A, B> {
	fn from(either: Either<A, B>) -> Self {
	match either {
	Either::Left(l) => Left(l),
	Either::Right(l) => Right(l),
	}
	}
	}