int-interval 0.8.0

A small, no_std half-open interval algebra library for primitive integer types.
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
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142

use super::*;

#[cfg(test)]
mod unit_tests {
    use super::*;

    #[test]
    fn test_minkowski_add_basic() {
        let a = I8CO::try_new(1, 5).unwrap();
        let b = I8CO::try_new(-3, 2).unwrap();
        let res = a.checked_minkowski_add(b).unwrap();
        // start = 1 + -3 = -2
        assert_eq!(res.start(), -2);
        // end_excl = (4 + 1 + 1) = 6 (a.end_incl + b.end_incl + 1)
        assert_eq!(res.end_excl(), 6);
    }

    #[test]
    fn test_minkowski_sub_basic() {
        let a = I8CO::try_new(5, 10).unwrap();
        let b = I8CO::try_new(2, 4).unwrap();
        let res = a.checked_minkowski_sub(b).unwrap();
        assert_eq!(res.start(), 2); // 5 - 3
        assert_eq!(res.end_excl(), 8); // 9 - 2 + 1
    }

    #[test]
    fn test_minkowski_mul_basic() {
        let a = I8CO::try_new(-2, 3).unwrap(); // [-2,3)
        let b = I8CO::try_new(-1, 2).unwrap(); // [-1,2)
        let res = a.checked_minkowski_mul_hull(b).unwrap();
        // 四个组合: -2*-1=2, -2*1=-2, 2*-1=-2, 2*1=2 -> min=-2, max=2
        assert_eq!(res.start(), -2);
        assert_eq!(res.end_excl(), 3); // max+1=2+1
    }

    #[test]
    fn test_minkowski_div_basic() {
        let a = I8CO::try_new(-4, 10).unwrap();
        let b = I8CO::try_new(2, 5).unwrap();
        let res = a.checked_minkowski_div_hull(b).unwrap();
        // 四个组合：-4/2=-2, -4/4=-1, 9/2=4, 9/4=2 -> min=-2, max=4
        assert_eq!(res.start(), -2);
        assert_eq!(res.end_excl(), 5); // max+1=4+1
    }

    #[test]
    fn test_minkowski_div_by_zero() {
        let a = I8CO::try_new(1, 5).unwrap();
        let b = I8CO::try_new(0, 3).unwrap();
        assert!(a.checked_minkowski_div_hull(b).is_none());
    }
}

#[cfg(test)]
mod prop_tests {
    use super::*;
    use proptest::prelude::*;

    fn interval_strategy() -> impl Strategy<Value = I8CO> {
        prop_oneof![
            Just(I8CO::try_new(i8::MIN, i8::MIN + 1).unwrap()), // [-128, -127)
            Just(I8CO::try_new(i8::MIN, i8::MAX).unwrap()),     // [-128, 127)
            Just(I8CO::try_new(i8::MAX - 1, i8::MAX).unwrap()), // [126, 127)
            (i8::MIN..=i8::MAX, i8::MIN..=i8::MAX)
                .prop_filter_map("valid interval", |(s, e)| I8CO::try_new(s, e))
        ]
    }

    proptest! {
        #[test]
        fn prop_add_containment(a in interval_strategy(), b in interval_strategy()) {
            if let Some(c) = a.checked_minkowski_add(b) {
                let xs = [a.start(), a.end_excl()-1];
                let ys = [b.start(), b.end_excl()-1];
                for &x in &xs {
                    for &y in &ys {
                        let sum = x.wrapping_add(y);
                        prop_assert!(c.start() <= sum && sum < c.end_excl());
                    }
                }
            }
        }

        #[test]
        fn prop_sub_containment(a in interval_strategy(), b in interval_strategy()) {
            if let Some(c) = a.checked_minkowski_sub(b) {
                let xs = [a.start(), a.end_excl()-1];
                let ys = [b.start(), b.end_excl()-1];
                for &x in &xs {
                    for &y in &ys {
                        let diff = x.wrapping_sub(y);
                        prop_assert!(c.start() <= diff && diff < c.end_excl());
                    }
                }
            }
        }

        #[test]
        fn prop_mul_containment(a in interval_strategy(), b in interval_strategy()) {
            if let Some(c) = a.checked_minkowski_mul_hull(b) {
                let xs = [a.start(), a.end_excl()-1];
                let ys = [b.start(), b.end_excl()-1];
                for &x in &xs {
                    for &y in &ys {
                        let prod = x.wrapping_mul(y);
                        prop_assert!(c.start() <= prod && prod < c.end_excl());
                    }
                }
            }
        }

        #[test]
        fn prop_div_containment(a in interval_strategy(), b in interval_strategy()
            .prop_filter("non-zero start", |b| b.start() != 0)) {
            if let Some(c) = a.checked_minkowski_div_hull(b) {
                let xs = [a.start(), a.end_excl()-1];
                let ys = [b.start(), b.end_excl()-1];
                for &x in &xs {
                    for &y in &ys {
                        let div = x / y;
                        prop_assert!(c.start() <= div && div < c.end_excl());
                    }
                }
            }
        }

        #[test]
        fn prop_add_commutative(a in interval_strategy(), b in interval_strategy()) {
            let res1 = a.checked_minkowski_add(b);
            let res2 = b.checked_minkowski_add(a);
            prop_assert_eq!(res1, res2);
        }

        #[test]
        fn prop_mul_commutative(a in interval_strategy(), b in interval_strategy()) {
            let res1 = a.checked_minkowski_mul_hull(b);
            let res2 = b.checked_minkowski_mul_hull(a);
            prop_assert_eq!(res1, res2);
        }
    }
}