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author | The Android Open Source Project <initial-contribution@android.com> | 2008-10-21 07:00:00 -0700 |
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committer | The Android Open Source Project <initial-contribution@android.com> | 2008-10-21 07:00:00 -0700 |
commit | 8771baa10b2dc5bbedb08231d99c72cfd6abcb5b (patch) | |
tree | 87dbea36a0e5ed0f2f8e2a499b9c1014af6a38b5 /e_acosh.c | |
download | fdlibm-8771baa10b2dc5bbedb08231d99c72cfd6abcb5b.tar.gz |
Initial Contributionandroid-1.0release-1.0cdma-import
Diffstat (limited to 'e_acosh.c')
-rw-r--r-- | e_acosh.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/e_acosh.c b/e_acosh.c new file mode 100644 index 0000000..d98e81a --- /dev/null +++ b/e_acosh.c @@ -0,0 +1,65 @@ + +/* @(#)e_acosh.c 1.3 95/01/18 */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunSoft, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + * + */ + +/* __ieee754_acosh(x) + * Method : + * Based on + * acosh(x) = log [ x + ieee_sqrt(x*x-1) ] + * we have + * acosh(x) := ieee_log(x)+ln2, if x is large; else + * acosh(x) := ieee_log(2x-1/(ieee_sqrt(x*x-1)+x)) if x>2; else + * acosh(x) := ieee_log1p(t+ieee_sqrt(2.0*t+t*t)); where t=x-1. + * + * Special cases: + * acosh(x) is NaN with signal if x<1. + * acosh(NaN) is NaN without signal. + */ + +#include "fdlibm.h" + +#ifdef __STDC__ +static const double +#else +static double +#endif +one = 1.0, +ln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */ + +#ifdef __STDC__ + double __ieee754_acosh(double x) +#else + double __ieee754_acosh(x) + double x; +#endif +{ + double t; + int hx; + hx = __HI(x); + if(hx<0x3ff00000) { /* x < 1 */ + return (x-x)/(x-x); + } else if(hx >=0x41b00000) { /* x > 2**28 */ + if(hx >=0x7ff00000) { /* x is inf of NaN */ + return x+x; + } else + return __ieee754_log(x)+ln2; /* acosh(huge)=ieee_log(2x) */ + } else if(((hx-0x3ff00000)|__LO(x))==0) { + return 0.0; /* acosh(1) = 0 */ + } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ + t=x*x; + return __ieee754_log(2.0*x-one/(x+ieee_sqrt(t-one))); + } else { /* 1<x<2 */ + t = x-one; + return ieee_log1p(t+ieee_sqrt(2.0*t+t*t)); + } +} |