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annotate lib/hypot.c @ 17363:5a51fb7777a9

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sys_select, sys_time: port 2013-01-30 Solaris 2.6 fix to Cygwin Problem reported by Marco Atzeri in <http://lists.gnu.org/archive/html/bug-gnulib/2013-03/msg00000.html>. * lib/sys_select.in.h [HAVE_SYS_SELECT_H && _CYGWIN_SYS_TIME_H]: Simply delegate to the system <sys/select.h> in this case too. Also, pay attention to _GL_SYS_SELECT_H_REDIRECT_FROM_SYS_TIME_H only if OSF/1, since otherwise Cygwin breaks, and it doesn't seem to be needed on Solaris either. * lib/sys_time.in.h [_CYGWIN_SYS_TIME_H]: Simply delgate to the system <sys/time.h> in this case.
author Paul Eggert <eggert@cs.ucla.edu>
date Tue, 19 Mar 2013 09:08:47 -0700
parents e542fd46ad6f
children 344018b6e5d7
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1 /* Hypotenuse of a right-angled triangle.
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2 Copyright (C) 2012-2013 Free Software Foundation, Inc.
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3
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4 This program is free software: you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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16
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17 /* Written by Bruno Haible <bruno@clisp.org>, 2012. */
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18
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19 #include <config.h>
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20
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21 /* Specification. */
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22 #include <math.h>
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23
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24 double
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25 hypot (double x, double y)
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26 {
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27 if (isfinite (x) && isfinite (y))
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28 {
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29 /* Determine absolute values. */
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30 x = fabs (x);
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31 y = fabs (y);
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32
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33 {
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34 /* Find the bigger and the smaller one. */
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35 double a;
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36 double b;
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37
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38 if (x >= y)
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39 {
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40 a = x;
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41 b = y;
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42 }
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43 else
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44 {
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45 a = y;
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46 b = x;
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47 }
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48 /* Now 0 <= b <= a. */
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49
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50 {
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51 int e;
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52 double an;
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53 double bn;
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54
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55 /* Write a = an * 2^e, b = bn * 2^e with 0 <= bn <= an < 1. */
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56 an = frexp (a, &e);
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57 bn = ldexp (b, - e);
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58
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59 {
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60 double cn;
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61
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62 /* Through the normalization, no unneeded overflow or underflow
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63 will occur here. */
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64 cn = sqrt (an * an + bn * bn);
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65 return ldexp (cn, e);
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66 }
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67 }
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68 }
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69 }
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70 else
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71 {
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72 if (isinf (x) || isinf (y))
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73 /* x or y is infinite. Return +Infinity. */
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74 return HUGE_VAL;
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75 else
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76 /* x or y is NaN. Return NaN. */
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77 return x + y;
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78 }
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79 }