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[glibc/history.git] / math / divtc3.c
blobd974ae6454bf7570218d3b40129fe38820701763
1 /* Copyright (C) 2005, 2006 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Richard Henderson <rth@redhat.com>, 2005.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18 02111-1307 USA. */
20 #include <stdbool.h>
21 #include <math.h>
22 #include <complex.h>
24 attribute_hidden
25 long double _Complex
26 __divtc3 (long double a, long double b, long double c, long double d)
28 long double denom, ratio, x, y;
30 /* ??? We can get better behavior from logarithmic scaling instead of
31 the division. But that would mean starting to link libgcc against
32 libm. We could implement something akin to ldexp/frexp as gcc builtins
33 fairly easily... */
34 if (fabsl (c) < fabsl (d))
36 ratio = c / d;
37 denom = (c * ratio) + d;
38 x = ((a * ratio) + b) / denom;
39 y = ((b * ratio) - a) / denom;
41 else
43 ratio = d / c;
44 denom = (d * ratio) + c;
45 x = ((b * ratio) + a) / denom;
46 y = (b - (a * ratio)) / denom;
49 /* Recover infinities and zeros that computed as NaN+iNaN; the only cases
50 are nonzero/zero, infinite/finite, and finite/infinite. */
51 if (isnan (x) && isnan (y))
53 if (denom == 0.0 && (!isnan (a) || !isnan (b)))
55 x = __copysignl (INFINITY, c) * a;
56 y = __copysignl (INFINITY, c) * b;
58 else if ((isinf (a) || isinf (b)) && isfinite (c) && isfinite (d))
60 a = __copysignl (isinf (a) ? 1 : 0, a);
61 b = __copysignl (isinf (b) ? 1 : 0, b);
62 x = INFINITY * (a * c + b * d);
63 y = INFINITY * (b * c - a * d);
65 else if ((isinf (c) || isinf (d)) && isfinite (a) && isfinite (b))
67 c = __copysignl (isinf (c) ? 1 : 0, c);
68 d = __copysignl (isinf (d) ? 1 : 0, d);
69 x = 0.0 * (a * c + b * d);
70 y = 0.0 * (b * c - a * d);
74 return x + I * y;