src/test/ui/traits/typeclasses-eq-example.rs

   1 // run-pass
   2
   3 #![allow(non_camel_case_types)]
   4 #![allow(non_snake_case)]
   5 #![allow(dead_code)]
   6
   7 // Example from lkuper's intern talk, August 2012.
   8 use Color::{cyan, magenta, yellow, black};
   9 use ColorTree::{leaf, branch};
  10
  11 trait Equal {
  12     fn isEq(&self, a: &Self) -> bool;
  13 }
  14
  15 #[derive(Clone, Copy)]
  16 enum Color { cyan, magenta, yellow, black }
  17
  18 impl Equal for Color {
  19     fn isEq(&self, a: &Color) -> bool {
  20         match (*self, *a) {
  21           (cyan, cyan)       => { true  }
  22           (magenta, magenta) => { true  }
  23           (yellow, yellow)   => { true  }
  24           (black, black)     => { true  }
  25           _                  => { false }
  26         }
  27     }
  28 }
  29
  30 #[derive(Clone)]
  31 enum ColorTree {
  32     leaf(Color),
  33     branch(Box<ColorTree>, Box<ColorTree>)
  34 }
  35
  36 impl Equal for ColorTree {
  37     fn isEq(&self, a: &ColorTree) -> bool {
  38         match (self, a) {
  39           (&leaf(ref x), &leaf(ref y)) => { x.isEq(&(*y).clone()) }
  40           (&branch(ref l1, ref r1), &branch(ref l2, ref r2)) => {
  41             (*l1).isEq(&(**l2).clone()) && (*r1).isEq(&(**r2).clone())
  42           }
  43           _ => { false }
  44         }
  45     }
  46 }
  47
  48 pub fn main() {
  49     assert!(cyan.isEq(&cyan));
  50     assert!(magenta.isEq(&magenta));
  51     assert!(!cyan.isEq(&yellow));
  52     assert!(!magenta.isEq(&cyan));
  53
  54     assert!(leaf(cyan).isEq(&leaf(cyan)));
  55     assert!(!leaf(cyan).isEq(&leaf(yellow)));
  56
  57     assert!(branch(Box::new(leaf(magenta)), Box::new(leaf(cyan)))
  58         .isEq(&branch(Box::new(leaf(magenta)), Box::new(leaf(cyan)))));
  59
  60     assert!(!branch(Box::new(leaf(magenta)), Box::new(leaf(cyan)))
  61         .isEq(&branch(Box::new(leaf(magenta)), Box::new(leaf(magenta)))));
  62
  63     println!("Assertions all succeeded!");
  64 }