fixed-bigint 0.6.1

Fixed-size big integer implementation for Rust
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
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238

use crate::harness::*;

// Identity (`one`) and the width bounds (`min`/`max`). At the pinned 32-bit
// width, min is zero and max is the 32-bit max on every backing.
#[test]
fn one_and_bounds() {
    fn body<C: Carrier>() {
        assert_eq!(C::one(), C::from_u32(1));
        assert!(One::is_one(&C::from_u32(1)));
        assert!(!One::is_one(&C::from_u32(0)));

        assert_eq!(C::min_value(), C::from_u32(0));
        assert_eq!(C::max_value(), C::from_u32(MAX32));
    }
    for_both_carriers!(body);
}

// `num_integer::Roots` and `num_integer::Integer` are compiled only under the
// `num-traits` feature (which pulls in `num-integer`), so their shared coverage
// is gated to match — unlike the always-available const-num-traits surface.
#[cfg(feature = "num-traits")]
#[test]
fn roots_and_integer() {
    fn body<C: Carrier + num_integer::Roots + num_integer::Integer>() {
        use num_integer::{Integer, Roots};

        // Roots truncate toward zero, including at the width extremes.
        assert_eq!(Roots::sqrt(&C::from_u32(0)), C::from_u32(0));
        assert_eq!(Roots::sqrt(&C::from_u32(144)), C::from_u32(12));
        assert_eq!(Roots::sqrt(&C::from_u32(145)), C::from_u32(12));
        // floor(sqrt(2^32 - 1)) = 0xFFFF.
        assert_eq!(Roots::sqrt(&C::max_value()), C::from_u32(0xFFFF));
        assert_eq!(Roots::cbrt(&C::from_u32(0)), C::from_u32(0));
        assert_eq!(Roots::cbrt(&C::from_u32(27)), C::from_u32(3));
        // floor(cbrt(2^32 - 1)) = 1625 (1625^3 <= max < 1626^3).
        assert_eq!(Roots::cbrt(&C::max_value()), C::from_u32(1625));
        assert_eq!(Roots::nth_root(&C::from_u32(81), 4), C::from_u32(3));

        // Integer: gcd / lcm / floored div-mod / div_rem / parity, with the
        // zero-operand identities pinned (gcd(x,0)=x, lcm anything-0 = 0).
        assert_eq!(
            Integer::gcd(&C::from_u32(0), &C::from_u32(0)),
            C::from_u32(0)
        );
        assert_eq!(
            Integer::gcd(&C::from_u32(10), &C::from_u32(0)),
            C::from_u32(10)
        );
        assert_eq!(
            Integer::gcd(&C::max_value(), &C::from_u32(0)),
            C::max_value()
        );
        assert_eq!(
            Integer::gcd(&C::from_u32(48), &C::from_u32(36)),
            C::from_u32(12)
        );
        assert_eq!(
            Integer::lcm(&C::from_u32(0), &C::from_u32(0)),
            C::from_u32(0)
        );
        assert_eq!(
            Integer::lcm(&C::from_u32(10), &C::from_u32(0)),
            C::from_u32(0)
        );
        assert_eq!(
            Integer::lcm(&C::from_u32(4), &C::from_u32(6)),
            C::from_u32(12)
        );
        assert_eq!(
            Integer::div_floor(&C::from_u32(17), &C::from_u32(5)),
            C::from_u32(3)
        );
        assert_eq!(
            Integer::mod_floor(&C::from_u32(17), &C::from_u32(5)),
            C::from_u32(2)
        );
        assert_eq!(
            Integer::div_rem(&C::from_u32(17), &C::from_u32(5)),
            (C::from_u32(3), C::from_u32(2))
        );
        assert!(Integer::is_even(&C::from_u32(10)));
        assert!(Integer::is_odd(&C::from_u32(7)));
    }
    for_both_carriers!(body);
}

#[test]
fn euclid_absdiff_midpoint() {
    fn body<C: Carrier>() {
        // Euclid: unsigned, so == ordinary div/rem.
        assert_eq!(
            Euclid::div_euclid(C::from_u32(17), C::from_u32(5)),
            C::from_u32(3)
        );
        assert_eq!(
            Euclid::rem_euclid(C::from_u32(17), C::from_u32(5)),
            C::from_u32(2)
        );
        assert_eq!(
            Euclid::div_rem_euclid(C::from_u32(17), C::from_u32(5)),
            (C::from_u32(3), C::from_u32(2))
        );
        assert_eq!(
            CheckedEuclid::checked_rem_euclid(C::from_u32(17), C::from_u32(5)),
            Some(C::from_u32(2))
        );
        assert_eq!(
            CheckedEuclid::checked_div_euclid(C::from_u32(17), C::from_u32(0)),
            None
        );
        assert_eq!(
            CheckedEuclid::checked_rem_euclid(C::from_u32(17), C::from_u32(0)),
            None
        );
        // checked_div_rem_euclid carries its own zero guard — pin both paths.
        assert_eq!(
            CheckedEuclid::checked_div_rem_euclid(C::from_u32(17), C::from_u32(5)),
            Some((C::from_u32(3), C::from_u32(2)))
        );
        assert_eq!(
            CheckedEuclid::checked_div_rem_euclid(C::from_u32(17), C::from_u32(0)),
            None
        );

        // abs_diff, both orders.
        assert_eq!(
            AbsDiff::abs_diff(C::from_u32(10), C::from_u32(3)),
            C::from_u32(7)
        );
        assert_eq!(
            AbsDiff::abs_diff(C::from_u32(3), C::from_u32(10)),
            C::from_u32(7)
        );

        // midpoint averages without overflow.
        assert_eq!(
            Midpoint::midpoint(C::from_u32(10), C::from_u32(20)),
            C::from_u32(15)
        );
        let max = C::from_u32(MAX32);
        assert_eq!(Midpoint::midpoint(max, max), max); // (max + max) / 2 = max
    }
    for_both_carriers!(body);
}

#[test]
fn power_of_two_and_multiples() {
    fn body<C: Carrier>() {
        // is_power_of_two.
        assert!(!IsPowerOfTwo::is_power_of_two(C::from_u32(0)));
        for p in [1u32, 2, 4, 8, 128, 256, 0x8000_0000] {
            assert!(IsPowerOfTwo::is_power_of_two(C::from_u32(p)));
        }
        for np in [3u32, 5, 6, 7, 100, 255] {
            assert!(!IsPowerOfTwo::is_power_of_two(C::from_u32(np)));
        }

        // next_power_of_two.
        assert_eq!(
            NextPowerOfTwo::next_power_of_two(C::from_u32(0)),
            C::from_u32(1)
        );
        assert_eq!(
            NextPowerOfTwo::next_power_of_two(C::from_u32(5)),
            C::from_u32(8)
        );
        assert_eq!(
            NextPowerOfTwo::next_power_of_two(C::from_u32(128)),
            C::from_u32(128)
        );
        assert_eq!(
            NextPowerOfTwo::checked_next_power_of_two(C::from_u32(100)),
            Some(C::from_u32(128))
        );
        // 2^31 + 1 rounds up to 2^32, which overflows the 32-bit width.
        assert_eq!(
            NextPowerOfTwo::checked_next_power_of_two(C::from_u32(0x8000_0001)),
            None
        );
        assert_eq!(
            NextPowerOfTwo::wrapping_next_power_of_two(C::from_u32(0x8000_0001)),
            C::from_u32(0)
        );

        // MultipleOf: zero divisor is false (const-num-traits convention).
        assert!(MultipleOf::is_multiple_of(C::from_u32(10), C::from_u32(5)));
        assert!(!MultipleOf::is_multiple_of(C::from_u32(11), C::from_u32(5)));
        assert!(!MultipleOf::is_multiple_of(C::from_u32(10), C::from_u32(0)));

        // NextMultipleOf.
        assert_eq!(
            NextMultipleOf::next_multiple_of(C::from_u32(11), C::from_u32(5)),
            C::from_u32(15)
        );
        assert_eq!(
            NextMultipleOf::next_multiple_of(C::from_u32(10), C::from_u32(5)),
            C::from_u32(10)
        );
        // rhs greater than self: the next multiple is rhs itself.
        assert_eq!(
            NextMultipleOf::next_multiple_of(C::from_u32(3), C::from_u32(10)),
            C::from_u32(10)
        );
        assert_eq!(
            NextMultipleOf::checked_next_multiple_of(C::from_u32(10), C::from_u32(0)),
            None
        );
        // self + (rhs - rem) overflows the 32-bit width.
        assert_eq!(
            NextMultipleOf::checked_next_multiple_of(C::from_u32(MAX32), C::from_u32(10)),
            None
        );
    }
    for_both_carriers!(body);
}

#[test]
fn isqrt_and_ilogs() {
    fn body<C: Carrier>() {
        // isqrt: floor square root.
        assert_eq!(Isqrt::isqrt(C::from_u32(0)), C::from_u32(0));
        assert_eq!(Isqrt::isqrt(C::from_u32(15)), C::from_u32(3));
        assert_eq!(Isqrt::isqrt(C::from_u32(16)), C::from_u32(4));
        assert_eq!(Isqrt::isqrt(C::from_u32(1_000_000)), C::from_u32(1000));
        assert_eq!(Isqrt::isqrt(C::from_u32(MAX32)), C::from_u32(0xFFFF));

        // ilog2 / ilog10 / ilog.
        assert_eq!(Ilog2::ilog2(C::from_u32(8)), 3);
        assert_eq!(Ilog2::ilog2(C::from_u32(0x8000_0000)), 31);
        assert_eq!(Ilog2::checked_ilog2(C::from_u32(0)), None);
        assert_eq!(Ilog10::ilog10(C::from_u32(9999)), 3);
        assert_eq!(Ilog10::ilog10(C::from_u32(1_000_000_000)), 9);
        assert_eq!(Ilog10::checked_ilog10(C::from_u32(0)), None);
        assert_eq!(Ilog::ilog(C::from_u32(27), C::from_u32(3)), 3);
        assert_eq!(Ilog::checked_ilog(C::from_u32(10), C::from_u32(1)), None);
    }
    for_both_carriers!(body);
}