contracts 0.6.10

Design-by-contract attributes
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

use contracts::*;

#[contract_trait]
trait Scale {
    #[requires(factor > 0)]
    #[ensures(ret >= self.base())]
    fn scale(&self, factor: u32) -> u32;

    fn base(&self) -> u32;
}

struct Multiplier(u32);

#[contract_trait]
impl Scale for Multiplier {
    fn scale(&self, factor: u32) -> u32 {
        self.0 * factor
    }

    fn base(&self) -> u32 {
        self.0
    }
}

fn main() {
    let multiplier = Multiplier(4);

    assert_eq!(multiplier.scale(2), 8);
}