| /* origin: FreeBSD /usr/src/lib/msun/src/s_atanf.c */ |
| /* |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| use super::fabsf; |
| |
| const ATAN_HI: [f32; 4] = [ |
| 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ |
| 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ |
| 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ |
| 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ |
| ]; |
| |
| const ATAN_LO: [f32; 4] = [ |
| 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ |
| 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ |
| 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ |
| 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ |
| ]; |
| |
| const A_T: [f32; 5] = [ |
| 3.3333328366e-01, |
| -1.9999158382e-01, |
| 1.4253635705e-01, |
| -1.0648017377e-01, |
| 6.1687607318e-02, |
| ]; |
| |
| #[inline] |
| pub fn atanf(mut x: f32) -> f32 { |
| let x1p_120 = f32::from_bits(0x03800000); // 0x1p-120 === 2 ^ (-120) |
| |
| let z: f32; |
| |
| let mut ix = x.to_bits(); |
| let sign = (ix >> 31) != 0; |
| ix &= 0x7fffffff; |
| |
| if ix >= 0x4c800000 { |
| /* if |x| >= 2**26 */ |
| if x.is_nan() { |
| return x; |
| } |
| z = ATAN_HI[3] + x1p_120; |
| return if sign { -z } else { z }; |
| } |
| let id = if ix < 0x3ee00000 { |
| /* |x| < 0.4375 */ |
| if ix < 0x39800000 { |
| /* |x| < 2**-12 */ |
| if ix < 0x00800000 { |
| /* raise underflow for subnormal x */ |
| force_eval!(x * x); |
| } |
| return x; |
| } |
| -1 |
| } else { |
| x = fabsf(x); |
| if ix < 0x3f980000 { |
| /* |x| < 1.1875 */ |
| if ix < 0x3f300000 { |
| /* 7/16 <= |x| < 11/16 */ |
| x = (2. * x - 1.) / (2. + x); |
| 0 |
| } else { |
| /* 11/16 <= |x| < 19/16 */ |
| x = (x - 1.) / (x + 1.); |
| 1 |
| } |
| } else { |
| if ix < 0x401c0000 { |
| /* |x| < 2.4375 */ |
| x = (x - 1.5) / (1. + 1.5 * x); |
| 2 |
| } else { |
| /* 2.4375 <= |x| < 2**26 */ |
| x = -1. / x; |
| 3 |
| } |
| } |
| }; |
| /* end of argument reduction */ |
| z = x * x; |
| let w = z * z; |
| /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ |
| let s1 = z * (A_T[0] + w * (A_T[2] + w * A_T[4])); |
| let s2 = w * (A_T[1] + w * A_T[3]); |
| if id < 0 { |
| return x - x * (s1 + s2); |
| } |
| let id = id as usize; |
| let z = ATAN_HI[id] - ((x * (s1 + s2) - ATAN_LO[id]) - x); |
| if sign { |
| -z |
| } else { |
| z |
| } |
| } |