1#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
2pub fn nextafter(x: f64, y: f64) -> f64 {
3 if x.is_nan() || y.is_nan() {
4 return x + y;
5 }
6
7 let mut ux_i = x.to_bits();
8 let uy_i = y.to_bits();
9 if ux_i == uy_i {
10 return y;
11 }
12
13 let ax = ux_i & (!1_u64 / 2);
14 let ay = uy_i & (!1_u64 / 2);
15 if ax == 0 {
16 if ay == 0 {
17 return y;
18 }
19 ux_i = (uy_i & (1_u64 << 63)) | 1;
20 } else if ax > ay || ((ux_i ^ uy_i) & (1_u64 << 63)) != 0 {
21 ux_i -= 1;
22 } else {
23 ux_i += 1;
24 }
25
26 let e = (ux_i >> 52) & 0x7ff;
27 // raise overflow if ux.f is infinite and x is finite
28 if e == 0x7ff {
29 force_eval!(x + x);
30 }
31 let ux_f = f64::from_bits(ux_i);
32 // raise underflow if ux.f is subnormal or zero
33 if e == 0 {
34 force_eval!(x * x + ux_f * ux_f);
35 }
36 ux_f
37}
38