1 /* Complex square root of float value.
2 Copyright (C) 1997, 1998 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
6
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
11
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
16
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, write to the Free
19 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
20 02111-1307 USA. */
21
22 #include <complex.h>
23 #include <math.h>
24
25 #include "math_private.h"
26
27
28 __complex__ float
__csqrtf(__complex__ float x)29 __csqrtf (__complex__ float x)
30 {
31 __complex__ float res;
32 int rcls = fpclassify (__real__ x);
33 int icls = fpclassify (__imag__ x);
34
35 if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
36 {
37 if (icls == FP_INFINITE)
38 {
39 __real__ res = HUGE_VALF;
40 __imag__ res = __imag__ x;
41 }
42 else if (rcls == FP_INFINITE)
43 {
44 if (__real__ x < 0.0)
45 {
46 __real__ res = icls == FP_NAN ? __nanf ("") : 0;
47 __imag__ res = __copysignf (HUGE_VALF, __imag__ x);
48 }
49 else
50 {
51 __real__ res = __real__ x;
52 __imag__ res = (icls == FP_NAN
53 ? __nanf ("") : __copysignf (0.0, __imag__ x));
54 }
55 }
56 else
57 {
58 __real__ res = __nanf ("");
59 __imag__ res = __nanf ("");
60 }
61 }
62 else
63 {
64 if (icls == FP_ZERO)
65 {
66 if (__real__ x < 0.0)
67 {
68 __real__ res = 0.0;
69 __imag__ res = __copysignf (__ieee754_sqrtf (-__real__ x),
70 __imag__ x);
71 }
72 else
73 {
74 __real__ res = fabsf (__ieee754_sqrtf (__real__ x));
75 __imag__ res = __copysignf (0.0, __imag__ x);
76 }
77 }
78 else if (rcls == FP_ZERO)
79 {
80 float r = __ieee754_sqrtf (0.5 * fabsf (__imag__ x));
81
82 __real__ res = __copysignf (r, __imag__ x);
83 __imag__ res = r;
84 }
85 else
86 {
87 float d, r, s;
88
89 d = __ieee754_hypotf (__real__ x, __imag__ x);
90 /* Use the identity 2 Re res Im res = Im x
91 to avoid cancellation error in d +/- Re x. */
92 if (__real__ x > 0)
93 {
94 r = __ieee754_sqrtf (0.5f * d + 0.5f * __real__ x);
95 s = (0.5f * __imag__ x) / r;
96 }
97 else
98 {
99 s = __ieee754_sqrtf (0.5f * d - 0.5f * __real__ x);
100 r = fabsf ((0.5f * __imag__ x) / s);
101 }
102
103 __real__ res = r;
104 __imag__ res = __copysignf (s, __imag__ x);
105 }
106 }
107
108 return res;
109 }
110 weak_alias (__csqrtf, csqrtf)
111