decimax 0.2.0

Fast, fixed-size, floating-point decimal 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

use decimax::{Dec32, Dec64, Dec128, Decimal, UnderlyingInt};

fn test_add<I: UnderlyingInt>(a: Decimal<I, true>, b: Decimal<I, true>, r: Decimal<I, true>) {
    dbg!(a, b, r);
    assert_eq!(a + -b, a - b);
    assert_eq!(-a + b, b - a);
    assert_eq!(-a + -b, -(b + a));
    assert_eq!(-a + -b, -r);

    assert_eq!(a + b, r);
    assert_eq!(b + a, r);
    assert_eq!(r - a, b);
    assert_eq!(r - b, a);
}

#[test]
fn add128() {
    // normal
    let a = Dec128::from_parts(1000, 10);
    let b = Dec128::from_parts(2000, 10);
    let c = Dec128::from_parts(3000, 10);
    test_add(a, a, b);
    test_add(a, b, c);

    // zero
    test_add(a, Dec128::ZERO, a);
    test_add(a, -Dec128::ZERO, a);

    // different scales
    let d = Dec128::from_parts(1000, 13);
    let e = Dec128::from_parts(1001000, 13);
    test_add(a, d, e);

    let max_mantissa = (1_i128 << 122) - 1;

    // different scales with big mantissa
    let big1 = Dec128::from_parts(max_mantissa - 1, 7);
    let big2 = Dec128::from_parts(max_mantissa, 7);
    test_add(a, big1, big2);

    // overflow in addition, so reduce scale
    let big1 = Dec128::from_parts(max_mantissa - 3, 10);
    let big2 = Dec128::from_parts(max_mantissa / 5, 9);
    test_add(big1, big1, big2);

    // overflow without scale to reduced
    let big1 = Dec128::from_parts(max_mantissa, 0);
    assert!(big1.checked_add(big1).is_none());
}

#[test]
fn add64() {
    // normal
    let a = Dec64::from_parts(1000, 10);
    let b = Dec64::from_parts(2000, 10);
    let c = Dec64::from_parts(3000, 10);
    test_add(a, a, b);
    test_add(a, b, c);

    // zero
    test_add(a, Dec64::ZERO, a);
    test_add(a, -Dec64::ZERO, a);

    // different scales
    let d = Dec64::from_parts(1000, 13);
    let e = Dec64::from_parts(1001000, 13);
    test_add(a, d, e);

    let max_mantissa = (1_i64 << 59) - 1;

    // different scales with big mantissa
    let big1 = Dec64::from_parts(max_mantissa - 1, 7);
    let big2 = Dec64::from_parts(max_mantissa, 7);
    test_add(a, big1, big2);

    // overflow in addition, so reduce scale
    let big1 = Dec64::from_parts(max_mantissa - 7, 10);
    let big2 = Dec64::from_parts(max_mantissa / 5 - 1, 9);
    test_add(big1, big1, big2);

    // overflow without scale to reduced
    let big1 = Dec64::from_parts(max_mantissa, 0);
    assert!(big1.checked_add(big1).is_none());
}

#[test]
fn add32() {
    // normal
    let a = Dec32::from_parts(1000, 4);
    let b = Dec32::from_parts(2000, 4);
    let c = Dec32::from_parts(3000, 4);
    test_add(a, a, b);
    test_add(a, b, c);

    // zero
    test_add(a, Dec32::ZERO, a);
    test_add(a, -Dec32::ZERO, a);

    // different scales
    let d = Dec32::from_parts(1000, 7);
    let e = Dec32::from_parts(1001000, 7);
    test_add(a, d, e);

    let max_mantissa = (1_i32 << 28) - 1;

    // different scales with big mantissa
    let big1 = Dec32::from_parts(max_mantissa - 1, 1);
    let big2 = Dec32::from_parts(max_mantissa, 1);
    test_add(a, big1, big2);

    // overflow in addition, so reduce scale
    let big1 = Dec32::from_parts(max_mantissa - 5, 5);
    let big2 = Dec32::from_parts(max_mantissa / 5 - 1, 4);
    test_add(big1, big1, big2);

    // overflow without scale to reduced
    let big1 = Dec32::from_parts(max_mantissa, 0);
    assert!(big1.checked_add(big1).is_none());
}