itertools/
either_or_both.rs

1use crate::EitherOrBoth::*;
2
3use either::Either;
4
5/// Value that either holds a single A or B, or both.
6#[derive(Clone, PartialEq, Eq, Hash, Debug)]
7pub enum EitherOrBoth<A, B> {
8    /// Both values are present.
9    Both(A, B),
10    /// Only the left value of type `A` is present.
11    Left(A),
12    /// Only the right value of type `B` is present.
13    Right(B),
14}
15
16impl<A, B> EitherOrBoth<A, B> {
17    /// If `Left`, or `Both`, return true, otherwise, return false.
18    pub fn has_left(&self) -> bool {
19        self.as_ref().left().is_some()
20    }
21
22    /// If `Right`, or `Both`, return true, otherwise, return false.
23    pub fn has_right(&self) -> bool {
24        self.as_ref().right().is_some()
25    }
26
27    /// If Left, return true otherwise, return false.
28    /// Exclusive version of [`has_left`](EitherOrBoth::has_left).
29    pub fn is_left(&self) -> bool {
30        match *self {
31            Left(_) => true,
32            _ => false,
33        }
34    }
35
36    /// If Right, return true otherwise, return false.
37    /// Exclusive version of [`has_right`](EitherOrBoth::has_right).
38    pub fn is_right(&self) -> bool {
39        match *self {
40            Right(_) => true,
41            _ => false,
42        }
43    }
44
45    /// If Right, return true otherwise, return false.
46    /// Equivalent to `self.as_ref().both().is_some()`.
47    pub fn is_both(&self) -> bool {
48        self.as_ref().both().is_some()
49    }
50
51    /// If `Left`, or `Both`, return `Some` with the left value, otherwise, return `None`.
52    pub fn left(self) -> Option<A> {
53        match self {
54            Left(left) | Both(left, _) => Some(left),
55            _ => None,
56        }
57    }
58
59    /// If `Right`, or `Both`, return `Some` with the right value, otherwise, return `None`.
60    pub fn right(self) -> Option<B> {
61        match self {
62            Right(right) | Both(_, right) => Some(right),
63            _ => None,
64        }
65    }
66
67    /// If Both, return `Some` tuple containing left and right.
68    pub fn both(self) -> Option<(A, B)> {
69        match self {
70            Both(a, b) => Some((a, b)),
71            _ => None,
72        }
73    }
74
75    /// Converts from `&EitherOrBoth<A, B>` to `EitherOrBoth<&A, &B>`.
76    pub fn as_ref(&self) -> EitherOrBoth<&A, &B> {
77        match *self {
78            Left(ref left) => Left(left),
79            Right(ref right) => Right(right),
80            Both(ref left, ref right) => Both(left, right),
81        }
82    }
83
84    /// Converts from `&mut EitherOrBoth<A, B>` to `EitherOrBoth<&mut A, &mut B>`.
85    pub fn as_mut(&mut self) -> EitherOrBoth<&mut A, &mut B> {
86        match *self {
87            Left(ref mut left) => Left(left),
88            Right(ref mut right) => Right(right),
89            Both(ref mut left, ref mut right) => Both(left, right),
90        }
91    }
92
93    /// Convert `EitherOrBoth<A, B>` to `EitherOrBoth<B, A>`.
94    pub fn flip(self) -> EitherOrBoth<B, A> {
95        match self {
96            Left(a) => Right(a),
97            Right(b) => Left(b),
98            Both(a, b) => Both(b, a),
99        }
100    }
101
102    /// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, b)` variants. If it is
103    /// present rewrapping the result in `self`'s original variant.
104    pub fn map_left<F, M>(self, f: F) -> EitherOrBoth<M, B>
105    where
106        F: FnOnce(A) -> M,
107    {
108        match self {
109            Both(a, b) => Both(f(a), b),
110            Left(a) => Left(f(a)),
111            Right(b) => Right(b),
112        }
113    }
114
115    /// Apply the function `f` on the value `b` in `Right(b)` or `Both(a, b)` variants.
116    /// If it is present rewrapping the result in `self`'s original variant.
117    pub fn map_right<F, M>(self, f: F) -> EitherOrBoth<A, M>
118    where
119        F: FnOnce(B) -> M,
120    {
121        match self {
122            Left(a) => Left(a),
123            Right(b) => Right(f(b)),
124            Both(a, b) => Both(a, f(b)),
125        }
126    }
127
128    /// Apply the functions `f` and `g` on the value `a` and `b` respectively;
129    /// found in `Left(a)`, `Right(b)`, or `Both(a, b)` variants.
130    /// The Result is rewrapped `self`'s original variant.
131    pub fn map_any<F, L, G, R>(self, f: F, g: G) -> EitherOrBoth<L, R>
132    where
133        F: FnOnce(A) -> L,
134        G: FnOnce(B) -> R,
135    {
136        match self {
137            Left(a) => Left(f(a)),
138            Right(b) => Right(g(b)),
139            Both(a, b) => Both(f(a), g(b)),
140        }
141    }
142
143    /// Apply the function `f` on the value `a` in `Left(a)` or `Both(a, _)` variants if it is
144    /// present.
145    pub fn left_and_then<F, L>(self, f: F) -> EitherOrBoth<L, B>
146    where
147        F: FnOnce(A) -> EitherOrBoth<L, B>,
148    {
149        match self {
150            Left(a) | Both(a, _) => f(a),
151            Right(b) => Right(b),
152        }
153    }
154
155    /// Apply the function `f` on the value `b`
156    /// in `Right(b)` or `Both(_, b)` variants if it is present.
157    pub fn right_and_then<F, R>(self, f: F) -> EitherOrBoth<A, R>
158    where
159        F: FnOnce(B) -> EitherOrBoth<A, R>,
160    {
161        match self {
162            Left(a) => Left(a),
163            Right(b) | Both(_, b) => f(b),
164        }
165    }
166
167    /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
168    /// Otherwise, returns the wrapped value for the present element, and the supplied
169    /// value for the other. The first (`l`) argument is used for a missing `Left`
170    /// value. The second (`r`) argument is used for a missing `Right` value.
171    ///
172    /// Arguments passed to `or` are eagerly evaluated; if you are passing
173    /// the result of a function call, it is recommended to use [`or_else`],
174    /// which is lazily evaluated.
175    ///
176    /// [`or_else`]: EitherOrBoth::or_else
177    ///
178    /// # Examples
179    ///
180    /// ```
181    /// # use itertools::EitherOrBoth;
182    /// assert_eq!(EitherOrBoth::Both("tree", 1).or("stone", 5), ("tree", 1));
183    /// assert_eq!(EitherOrBoth::Left("tree").or("stone", 5), ("tree", 5));
184    /// assert_eq!(EitherOrBoth::Right(1).or("stone", 5), ("stone", 1));
185    /// ```
186    pub fn or(self, l: A, r: B) -> (A, B) {
187        match self {
188            Left(inner_l) => (inner_l, r),
189            Right(inner_r) => (l, inner_r),
190            Both(inner_l, inner_r) => (inner_l, inner_r),
191        }
192    }
193
194    /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
195    /// Otherwise, returns the wrapped value for the present element, and the [`default`](Default::default)
196    /// for the other.
197    pub fn or_default(self) -> (A, B)
198    where
199        A: Default,
200        B: Default,
201    {
202        match self {
203            EitherOrBoth::Left(l) => (l, B::default()),
204            EitherOrBoth::Right(r) => (A::default(), r),
205            EitherOrBoth::Both(l, r) => (l, r),
206        }
207    }
208
209    /// Returns a tuple consisting of the `l` and `r` in `Both(l, r)`, if present.
210    /// Otherwise, returns the wrapped value for the present element, and computes the
211    /// missing value with the supplied closure. The first argument (`l`) is used for a
212    /// missing `Left` value. The second argument (`r`) is used for a missing `Right` value.
213    ///
214    /// # Examples
215    ///
216    /// ```
217    /// # use itertools::EitherOrBoth;
218    /// let k = 10;
219    /// assert_eq!(EitherOrBoth::Both("tree", 1).or_else(|| "stone", || 2 * k), ("tree", 1));
220    /// assert_eq!(EitherOrBoth::Left("tree").or_else(|| "stone", || 2 * k), ("tree", 20));
221    /// assert_eq!(EitherOrBoth::Right(1).or_else(|| "stone", || 2 * k), ("stone", 1));
222    /// ```
223    pub fn or_else<L: FnOnce() -> A, R: FnOnce() -> B>(self, l: L, r: R) -> (A, B) {
224        match self {
225            Left(inner_l) => (inner_l, r()),
226            Right(inner_r) => (l(), inner_r),
227            Both(inner_l, inner_r) => (inner_l, inner_r),
228        }
229    }
230}
231
232impl<T> EitherOrBoth<T, T> {
233    /// Return either value of left, right, or the product of `f` applied where `Both` are present.
234    pub fn reduce<F>(self, f: F) -> T
235    where
236        F: FnOnce(T, T) -> T,
237    {
238        match self {
239            Left(a) => a,
240            Right(b) => b,
241            Both(a, b) => f(a, b),
242        }
243    }
244}
245
246impl<A, B> Into<Option<Either<A, B>>> for EitherOrBoth<A, B> {
247    fn into(self) -> Option<Either<A, B>> {
248        match self {
249            EitherOrBoth::Left(l) => Some(Either::Left(l)),
250            EitherOrBoth::Right(r) => Some(Either::Right(r)),
251            _ => None,
252        }
253    }
254}
itertools/either_or_both.rs

itertools/
either_or_both.rs
