1/* SPDX-License-Identifier: MIT OR Apache-2.0 */
2//! IEEE 754-2011 `maxNum`. This has been superseded by IEEE 754-2019 `maximumNumber`.
3//!
4//! Per the spec, returns the canonicalized result of:
5//! - `x` if `x > y`
6//! - `y` if `y > x`
7//! - The other number if one is NaN
8//! - Otherwise, either `x` or `y`, canonicalized
9//! - -0.0 and +0.0 may be disregarded (unlike newer operations)
10//!
11//! Excluded from our implementation is sNaN handling.
12//!
13//! More on the differences: [link].
14//!
15//! [link]: https://grouper.ieee.org/groups/msc/ANSI_IEEE-Std-754-2019/background/minNum_maxNum_Removal_Demotion_v3.pdf
16
17use super::super::Float;
18
19#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
20pub fn fmax<F: Float>(x: F, y: F) -> F {
21 let res: F = if x.is_nan() || x < y { y } else { x };
22 // Canonicalize
23 res * F::ONE
24}
25
26#[cfg(test)]
27mod tests {
28 use super::*;
29 use crate::support::{Hexf, Int};
30
31 fn spec_test<F: Float>() {
32 let cases = [
33 (F::ZERO, F::ZERO, F::ZERO),
34 (F::ONE, F::ONE, F::ONE),
35 (F::ZERO, F::ONE, F::ONE),
36 (F::ONE, F::ZERO, F::ONE),
37 (F::ZERO, F::NEG_ONE, F::ZERO),
38 (F::NEG_ONE, F::ZERO, F::ZERO),
39 (F::INFINITY, F::ZERO, F::INFINITY),
40 (F::NEG_INFINITY, F::ZERO, F::ZERO),
41 (F::NAN, F::ZERO, F::ZERO),
42 (F::ZERO, F::NAN, F::ZERO),
43 (F::NAN, F::NAN, F::NAN),
44 ];
45
46 for (x, y, res) in cases {
47 let val = fmax(x, y);
48 assert_biteq!(val, res, "fmax({}, {})", Hexf(x), Hexf(y));
49 }
50 }
51
52 #[test]
53 #[cfg(f16_enabled)]
54 fn spec_tests_f16() {
55 spec_test::<f16>();
56 }
57
58 #[test]
59 fn spec_tests_f32() {
60 spec_test::<f32>();
61 }
62
63 #[test]
64 fn spec_tests_f64() {
65 spec_test::<f64>();
66 }
67
68 #[test]
69 #[cfg(f128_enabled)]
70 fn spec_tests_f128() {
71 spec_test::<f128>();
72 }
73}
74