/rust/registry/src/index.crates.io-1949cf8c6b5b557f/libm-0.2.11/src/math/cosf.rs
Line | Count | Source |
1 | | /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */ |
2 | | /* |
3 | | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
4 | | * Optimized by Bruce D. Evans. |
5 | | */ |
6 | | /* |
7 | | * ==================================================== |
8 | | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
9 | | * |
10 | | * Developed at SunPro, a Sun Microsystems, Inc. business. |
11 | | * Permission to use, copy, modify, and distribute this |
12 | | * software is freely granted, provided that this notice |
13 | | * is preserved. |
14 | | * ==================================================== |
15 | | */ |
16 | | |
17 | | use core::f64::consts::FRAC_PI_2; |
18 | | |
19 | | use super::{k_cosf, k_sinf, rem_pio2f}; |
20 | | |
21 | | /* Small multiples of pi/2 rounded to double precision. */ |
22 | | const C1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */ |
23 | | const C2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */ |
24 | | const C3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */ |
25 | | const C4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */ |
26 | | |
27 | | /// The cosine of `x` (f32). |
28 | | /// |
29 | | /// `x` is specified in radians. |
30 | | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
31 | 0 | pub fn cosf(x: f32) -> f32 { |
32 | 0 | let x64 = x as f64; |
33 | | |
34 | 0 | let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120 |
35 | | |
36 | 0 | let mut ix = x.to_bits(); |
37 | 0 | let sign = (ix >> 31) != 0; |
38 | 0 | ix &= 0x7fffffff; |
39 | | |
40 | 0 | if ix <= 0x3f490fda { |
41 | | /* |x| ~<= pi/4 */ |
42 | 0 | if ix < 0x39800000 { |
43 | | /* |x| < 2**-12 */ |
44 | | /* raise inexact if x != 0 */ |
45 | 0 | force_eval!(x + x1p120); |
46 | 0 | return 1.; |
47 | 0 | } |
48 | 0 | return k_cosf(x64); |
49 | 0 | } |
50 | 0 | if ix <= 0x407b53d1 { |
51 | | /* |x| ~<= 5*pi/4 */ |
52 | 0 | if ix > 0x4016cbe3 { |
53 | | /* |x| ~> 3*pi/4 */ |
54 | 0 | return -k_cosf(if sign { x64 + C2_PIO2 } else { x64 - C2_PIO2 }); |
55 | 0 | } else if sign { |
56 | 0 | return k_sinf(x64 + C1_PIO2); |
57 | | } else { |
58 | 0 | return k_sinf(C1_PIO2 - x64); |
59 | | } |
60 | 0 | } |
61 | 0 | if ix <= 0x40e231d5 { |
62 | | /* |x| ~<= 9*pi/4 */ |
63 | 0 | if ix > 0x40afeddf { |
64 | | /* |x| ~> 7*pi/4 */ |
65 | 0 | return k_cosf(if sign { x64 + C4_PIO2 } else { x64 - C4_PIO2 }); |
66 | 0 | } else if sign { |
67 | 0 | return k_sinf(-x64 - C3_PIO2); |
68 | | } else { |
69 | 0 | return k_sinf(x64 - C3_PIO2); |
70 | | } |
71 | 0 | } |
72 | | |
73 | | /* cos(Inf or NaN) is NaN */ |
74 | 0 | if ix >= 0x7f800000 { |
75 | 0 | return x - x; |
76 | 0 | } |
77 | | |
78 | | /* general argument reduction needed */ |
79 | 0 | let (n, y) = rem_pio2f(x); |
80 | 0 | match n & 3 { |
81 | 0 | 0 => k_cosf(y), |
82 | 0 | 1 => k_sinf(-y), |
83 | 0 | 2 => -k_cosf(y), |
84 | 0 | _ => k_sinf(y), |
85 | | } |
86 | 0 | } |