diff options
| -rw-r--r-- | src/libcore/cmp.rs | 38 |
1 files changed, 22 insertions, 16 deletions
diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs index 86f28a957cd..d43a5c1032c 100644 --- a/src/libcore/cmp.rs +++ b/src/libcore/cmp.rs @@ -91,6 +91,8 @@ use self::Ordering::*; /// For example, let's tweak our previous code a bit: /// /// ``` +/// // The derive implements <BookFormat> == <BookFormat> comparisons +/// #[derive(PartialEq)] /// enum BookFormat { /// Paperback, /// Hardback, @@ -102,31 +104,34 @@ use self::Ordering::*; /// format: BookFormat, /// } /// +/// // Implement <Book> == <BookFormat> comparisons /// impl PartialEq<BookFormat> for Book { /// fn eq(&self, other: &BookFormat) -> bool { -/// match (&self.format, other) { -/// (BookFormat::Paperback, BookFormat::Paperback) => true, -/// (BookFormat::Hardback, BookFormat::Hardback) => true, -/// (BookFormat::Ebook, BookFormat::Ebook) => true, -/// (_, _) => false, -/// } +/// self.format == *other +/// } +/// } +/// +/// // Implement <BookFormat> == <Book> comparisons +/// impl PartialEq<Book> for BookFormat { +/// fn eq(&self, other: &Book) -> bool { +/// *self == other.format /// } /// } /// /// let b1 = Book { isbn: 3, format: BookFormat::Paperback }; /// /// assert!(b1 == BookFormat::Paperback); -/// assert!(b1 != BookFormat::Ebook); +/// assert!(BookFormat::Ebook != b1); /// ``` /// /// By changing `impl PartialEq for Book` to `impl PartialEq<BookFormat> for Book`, -/// we've changed what type we can use on the right side of the `==` operator. -/// This lets us use it in the `assert!` statements at the bottom. +/// we allow `BookFormat`s to be compared with `Book`s. /// /// You can also combine these implementations to let the `==` operator work with /// two different types: /// /// ``` +/// #[derive(PartialEq)] /// enum BookFormat { /// Paperback, /// Hardback, @@ -140,12 +145,13 @@ use self::Ordering::*; /// /// impl PartialEq<BookFormat> for Book { /// fn eq(&self, other: &BookFormat) -> bool { -/// match (&self.format, other) { -/// (&BookFormat::Paperback, &BookFormat::Paperback) => true, -/// (&BookFormat::Hardback, &BookFormat::Hardback) => true, -/// (&BookFormat::Ebook, &BookFormat::Ebook) => true, -/// (_, _) => false, -/// } +/// self.format == *other +/// } +/// } +/// +/// impl PartialEq<Book> for BookFormat { +/// fn eq(&self, other: &Book) -> bool { +/// *self == other.format /// } /// } /// @@ -159,7 +165,7 @@ use self::Ordering::*; /// let b2 = Book { isbn: 3, format: BookFormat::Ebook }; /// /// assert!(b1 == BookFormat::Paperback); -/// assert!(b1 != BookFormat::Ebook); +/// assert!(BookFormat::Ebook != b1); /// assert!(b1 == b2); /// ``` /// |