pxfm/rounding/
rint.rs

1/*
2 * // Copyright (c) Radzivon Bartoshyk 9/2025. All rights reserved.
3 * //
4 * // Redistribution and use in source and binary forms, with or without modification,
5 * // are permitted provided that the following conditions are met:
6 * //
7 * // 1.  Redistributions of source code must retain the above copyright notice, this
8 * // list of conditions and the following disclaimer.
9 * //
10 * // 2.  Redistributions in binary form must reproduce the above copyright notice,
11 * // this list of conditions and the following disclaimer in the documentation
12 * // and/or other materials provided with the distribution.
13 * //
14 * // 3.  Neither the name of the copyright holder nor the names of its
15 * // contributors may be used to endorse or promote products derived from
16 * // this software without specific prior written permission.
17 * //
18 * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
22 * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#[inline]
31pub const fn rint(x: f64) -> f64 {
32    /* Use generic implementation.  */
33    static TWO52: [f64; 2] = [
34        4.50359962737049600000e+15,  /* 0x43300000, 0x00000000 */
35        -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
36    ];
37    let mut i0: i64 = x.to_bits() as i64;
38    let sx = (i0 >> 63) & 1;
39    let j0: i32 = (((i0 >> 52) & 0x7ff) - 0x3ff) as i32;
40    if j0 < 52 {
41        if j0 < 0 {
42            let w = TWO52[sx as usize] + x;
43            let t = w - TWO52[sx as usize];
44            i0 = t.to_bits() as i64;
45            let u = (i0 & (0x7fffffffffffffffu64 as i64)) | (sx << 63);
46            return f64::from_bits(u as u64);
47        }
48    } else {
49        return if j0 == 0x400 {
50            x + x /* inf or NaN  */
51        } else {
52            x /* x is integral  */
53        };
54    }
55    let w = TWO52[sx as usize] + x;
56    w - TWO52[sx as usize]
57}
58
59#[cfg(test)]
60mod tests {
61    use super::*;
62    #[test]
63    fn test_rintf() {
64        assert_eq!(rint(0f64), 0.0f64.round());
65        assert_eq!(rint(1f64), 1.0f64.round());
66        assert_eq!(rint(1.2f64), 1.2f64.round());
67        assert_eq!(rint(-1.2f64), (-1.2f64).round());
68        assert_eq!(rint(-1.6f64), (-1.6f64).round());
69        assert_eq!(rint(-1.5f64), (-1.5f64).round());
70        assert_eq!(rint(1.6f64), 1.6f64.round());
71        assert_eq!(rint(1.5f64), 1.5f64.round());
72        assert_eq!(rint(2.5f64), 2.0f64);
73        assert_eq!(rint(3.5f64), 4.0f64);
74        assert_eq!(rint(-2.5f64), -2.0f64);
75        assert_eq!(rint(-3.5f64), -4.0f64);
76        assert_eq!(rint(f64::INFINITY), f64::INFINITY);
77        assert_eq!(rint(f64::NEG_INFINITY), f64::NEG_INFINITY);
78        assert!(rint(f64::NAN).is_nan());
79    }
80}
pxfm/rounding/rint.rs

pxfm/rounding/
rint.rs
