Mercurial > hg > octave-kai > gnulib-hg
annotate lib/hypotl.c @ 17342:c75939cb6254
merge with default branch
| author | Michael Goffioul <michael.goffioul@gmail.com> |
|---|---|
| date | Thu, 21 Feb 2013 14:57:31 +0000 |
| parents | e542fd46ad6f |
| children |
| rev | line source |
|---|---|
| 16519 | 1 /* Hypotenuse of a right-angled triangle. |
|
17249
e542fd46ad6f
maint: update all copyright year number ranges
Eric Blake <eblake@redhat.com>
parents:
16519
diff
changeset
|
2 Copyright (C) 2012-2013 Free Software Foundation, Inc. |
| 16519 | 3 |
| 4 This program is free software: you can redistribute it and/or modify | |
| 5 it under the terms of the GNU General Public License as published by | |
| 6 the Free Software Foundation; either version 3 of the License, or | |
| 7 (at your option) any later version. | |
| 8 | |
| 9 This program is distributed in the hope that it will be useful, | |
| 10 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 12 GNU General Public License for more details. | |
| 13 | |
| 14 You should have received a copy of the GNU General Public License | |
| 15 along with this program. If not, see <http://www.gnu.org/licenses/>. */ | |
| 16 | |
| 17 /* Written by Bruno Haible <bruno@clisp.org>, 2012. */ | |
| 18 | |
| 19 #include <config.h> | |
| 20 | |
| 21 /* Specification. */ | |
| 22 #include <math.h> | |
| 23 | |
| 24 #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE | |
| 25 | |
| 26 long double | |
| 27 hypotl (long double x, long double y) | |
| 28 { | |
| 29 return hypot (x, y); | |
| 30 } | |
| 31 | |
| 32 #else | |
| 33 | |
| 34 long double | |
| 35 hypotl (long double x, long double y) | |
| 36 { | |
| 37 if (isfinite (x) && isfinite (y)) | |
| 38 { | |
| 39 /* Determine absolute values. */ | |
| 40 x = fabsl (x); | |
| 41 y = fabsl (y); | |
| 42 | |
| 43 { | |
| 44 /* Find the bigger and the smaller one. */ | |
| 45 long double a; | |
| 46 long double b; | |
| 47 | |
| 48 if (x >= y) | |
| 49 { | |
| 50 a = x; | |
| 51 b = y; | |
| 52 } | |
| 53 else | |
| 54 { | |
| 55 a = y; | |
| 56 b = x; | |
| 57 } | |
| 58 /* Now 0 <= b <= a. */ | |
| 59 | |
| 60 { | |
| 61 int e; | |
| 62 long double an; | |
| 63 long double bn; | |
| 64 | |
| 65 /* Write a = an * 2^e, b = bn * 2^e with 0 <= bn <= an < 1. */ | |
| 66 an = frexpl (a, &e); | |
| 67 bn = ldexpl (b, - e); | |
| 68 | |
| 69 { | |
| 70 long double cn; | |
| 71 | |
| 72 /* Through the normalization, no unneeded overflow or underflow | |
| 73 will occur here. */ | |
| 74 cn = sqrtl (an * an + bn * bn); | |
| 75 return ldexpl (cn, e); | |
| 76 } | |
| 77 } | |
| 78 } | |
| 79 } | |
| 80 else | |
| 81 { | |
| 82 if (isinf (x) || isinf (y)) | |
| 83 /* x or y is infinite. Return +Infinity. */ | |
| 84 return HUGE_VALL; | |
| 85 else | |
| 86 /* x or y is NaN. Return NaN. */ | |
| 87 return x + y; | |
| 88 } | |
| 89 } | |
| 90 | |
| 91 #endif |