diff options
Diffstat (limited to 'src/test/ui/traits/typeclasses-eq-example.rs')
-rw-r--r-- | src/test/ui/traits/typeclasses-eq-example.rs | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/src/test/ui/traits/typeclasses-eq-example.rs b/src/test/ui/traits/typeclasses-eq-example.rs new file mode 100644 index 000000000..4400301e6 --- /dev/null +++ b/src/test/ui/traits/typeclasses-eq-example.rs @@ -0,0 +1,64 @@ +// run-pass + +#![allow(non_camel_case_types)] +#![allow(non_snake_case)] +#![allow(dead_code)] + +// Example from lkuper's intern talk, August 2012. +use Color::{cyan, magenta, yellow, black}; +use ColorTree::{leaf, branch}; + +trait Equal { + fn isEq(&self, a: &Self) -> bool; +} + +#[derive(Clone, Copy)] +enum Color { cyan, magenta, yellow, black } + +impl Equal for Color { + fn isEq(&self, a: &Color) -> bool { + match (*self, *a) { + (cyan, cyan) => { true } + (magenta, magenta) => { true } + (yellow, yellow) => { true } + (black, black) => { true } + _ => { false } + } + } +} + +#[derive(Clone)] +enum ColorTree { + leaf(Color), + branch(Box<ColorTree>, Box<ColorTree>) +} + +impl Equal for ColorTree { + fn isEq(&self, a: &ColorTree) -> bool { + match (self, a) { + (&leaf(ref x), &leaf(ref y)) => { x.isEq(&(*y).clone()) } + (&branch(ref l1, ref r1), &branch(ref l2, ref r2)) => { + (*l1).isEq(&(**l2).clone()) && (*r1).isEq(&(**r2).clone()) + } + _ => { false } + } + } +} + +pub fn main() { + assert!(cyan.isEq(&cyan)); + assert!(magenta.isEq(&magenta)); + assert!(!cyan.isEq(&yellow)); + assert!(!magenta.isEq(&cyan)); + + assert!(leaf(cyan).isEq(&leaf(cyan))); + assert!(!leaf(cyan).isEq(&leaf(yellow))); + + assert!(branch(Box::new(leaf(magenta)), Box::new(leaf(cyan))) + .isEq(&branch(Box::new(leaf(magenta)), Box::new(leaf(cyan))))); + + assert!(!branch(Box::new(leaf(magenta)), Box::new(leaf(cyan))) + .isEq(&branch(Box::new(leaf(magenta)), Box::new(leaf(magenta))))); + + println!("Assertions all succeeded!"); +} |