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> {
/// 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 {
match *self {
Left(_) => true,
_ => false,
}
}
/// If `Right`, return true. Otherwise, return false.
/// Exclusive version of [`has_right`](EitherOrBoth::has_right).
pub fn is_right(&self) -> bool {
match *self {
Right(_) => true,
_ => false,
}
}
/// 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,
}
}
/// 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 {
EitherOrBoth::Left(l) => (l, B::default()),
EitherOrBoth::Right(r) => (A::default(), r),
EitherOrBoth::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.
///
/// # 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);
/// ```
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> Into<Option<Either<A, B>>> for EitherOrBoth<A, B> {
fn into(self) -> Option<Either<A, B>> {
match self {
EitherOrBoth::Left(l) => Some(Either::Left(l)),
EitherOrBoth::Right(r) => Some(Either::Right(r)),
_ => None,
}
}
}
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