malachite_nz/integer/logic/
significant_bits.rs

1// Copyright © 2025 Mikhail Hogrefe
2//
3// This file is part of Malachite.
4//
5// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
6// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
7// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
8
9use crate::integer::Integer;
10use malachite_base::num::logic::traits::SignificantBits;
11
12impl SignificantBits for &Integer {
13    /// Returns the number of significant bits of an [`Integer`]'s absolute value.
14    ///
15    /// $$
16    /// f(n) = \\begin{cases}
17    ///     0 & \text{if} \\quad n = 0, \\\\
18    ///     \lfloor \log_2 |n| \rfloor + 1 & \\text{otherwise}.
19    /// \\end{cases}
20    /// $$
21    ///
22    /// # Worst-case complexity
23    /// Constant time and additional memory.
24    ///
25    /// # Examples
26    /// ```
27    /// use malachite_base::num::basic::traits::Zero;
28    /// use malachite_base::num::logic::traits::SignificantBits;
29    /// use malachite_nz::integer::Integer;
30    ///
31    /// assert_eq!(Integer::ZERO.significant_bits(), 0);
32    /// assert_eq!(Integer::from(100).significant_bits(), 7);
33    /// assert_eq!(Integer::from(-100).significant_bits(), 7);
34    /// ```
35    fn significant_bits(self) -> u64 {
36        self.abs.significant_bits()
37    }
38}
malachite_nz/integer/logic/significant_bits.rs

malachite_nz/integer/logic/
significant_bits.rs
