Created
August 5, 2015 21:06
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| fn main() { | |
| type One = Succ<Zero>; | |
| type Two = Succ<One>; | |
| type Three = Succ<Two>; | |
| type Five = <Two as Add<Three>>::Result; | |
| type Four = <One as Sub<Five>>::Result; | |
| println!("Zero: {}", Zero::fmt()); | |
| println!("One: {}", One::fmt()); | |
| println!("Two: {}", Two::fmt()); | |
| println!("Three: {}", Three::fmt()); | |
| println!("Four: {}", Four::fmt()); | |
| println!("Five: {}", Five::fmt()); | |
| } | |
| trait Peano { | |
| fn fmt() -> String; | |
| } | |
| struct Zero; | |
| impl Peano for Zero { | |
| fn fmt() -> String { | |
| "Zero".to_string() | |
| } | |
| } | |
| struct Succ<T> { | |
| t: T, | |
| } | |
| impl<T: Peano> Peano for Succ<T> { | |
| fn fmt() -> String { | |
| format!("Succ<{}>", T::fmt()) | |
| } | |
| } | |
| trait Add<T> { | |
| type Result: Peano; | |
| } | |
| impl<T: Peano> Add<T> for Zero { | |
| type Result = T; | |
| } | |
| impl<T, U> Add<T> for Succ<U> | |
| where U: Add<Succ<T>>, | |
| { | |
| type Result = <U as Add<Succ<T>>>::Result; | |
| } | |
| trait Sub<T> { | |
| type Result: Peano; | |
| } | |
| impl<T: Peano> Sub<T> for Zero { | |
| type Result = T; | |
| } | |
| impl<T, U> Sub<Succ<T>> for Succ<U> | |
| where T: Peano, | |
| U: Peano, | |
| U: Sub<T>, | |
| { | |
| type Result = <U as Sub<T>>::Result; | |
| } |
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