1//! The trait [`IntoEither`] provides methods for converting a type `Self`, whose
2//! size is constant and known at compile-time, into an [`Either`] variant.
3
4use super::{Either, Left, Right};
5
6/// Provides methods for converting a type `Self` into either a [`Left`] or [`Right`]
7/// variant of [`Either<Self, Self>`](Either).
8///
9/// The [`into_either`](IntoEither::into_either) method takes a [`bool`] to determine
10/// whether to convert to [`Left`] or [`Right`].
11///
12/// The [`into_either_with`](IntoEither::into_either_with) method takes a
13/// [predicate function](FnOnce) to determine whether to convert to [`Left`] or [`Right`].
14pub trait IntoEither: Sized {
15 /// Converts `self` into a [`Left`] variant of [`Either<Self, Self>`](Either)
16 /// if `into_left` is `true`.
17 /// Converts `self` into a [`Right`] variant of [`Either<Self, Self>`](Either)
18 /// otherwise.
19 ///
20 /// # Examples
21 ///
22 /// ```
23 /// use either::{IntoEither, Left, Right};
24 ///
25 /// let x = 0;
26 /// assert_eq!(x.into_either(true), Left(x));
27 /// assert_eq!(x.into_either(false), Right(x));
28 /// ```
29 fn into_either(self, into_left: bool) -> Either<Self, Self> {
30 if into_left {
31 Left(self)
32 } else {
33 Right(self)
34 }
35 }
36
37 /// Converts `self` into a [`Left`] variant of [`Either<Self, Self>`](Either)
38 /// if `into_left(&self)` returns `true`.
39 /// Converts `self` into a [`Right`] variant of [`Either<Self, Self>`](Either)
40 /// otherwise.
41 ///
42 /// # Examples
43 ///
44 /// ```
45 /// use either::{IntoEither, Left, Right};
46 ///
47 /// fn is_even(x: &u8) -> bool {
48 /// x % 2 == 0
49 /// }
50 ///
51 /// let x = 0;
52 /// assert_eq!(x.into_either_with(is_even), Left(x));
53 /// assert_eq!(x.into_either_with(|x| !is_even(x)), Right(x));
54 /// ```
55 fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
56 where
57 F: FnOnce(&Self) -> bool,
58 {
59 let into_left = into_left(&self);
60 self.into_either(into_left)
61 }
62}
63
64impl<T> IntoEither for T {}
65