1 /* s_atanhl.c -- long double version of s_atan.c.
2 * Conversion to long double by Ulrich Drepper,
3 * Cygnus Support, drepper@cygnus.com.
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
14 * ====================================================
17 /* __ieee754_atanhl(x)
19 * 1.Reduced x to positive by atanh(-x) = -atanh(x)
22 * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
26 * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
29 * atanhl(x) is NaN if |x| > 1 with signal;
30 * atanhl(NaN) is that NaN with no signal;
31 * atanhl(+-1) is +-INF with signal.
36 #include "math_private.h"
38 static const long double one
= 1.0L, huge
= 1e4900L
;
40 static const long double zero
= 0.0L;
43 __ieee754_atanhl(long double x
)
47 ieee854_long_double_shape_type u
;
53 if (ix
>= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */
60 if(ix
<0x3fc60000 && (huge
+x
)>zero
) return x
; /* x < 2^-57 */
62 if(ix
<0x3ffe0000) { /* x < 0.5 */
64 t
= 0.5*__log1pl(t
+t
*u
.value
/(one
-u
.value
));
66 t
= 0.5*__log1pl((u
.value
+u
.value
)/(one
-u
.value
));
67 if(jx
& 0x80000000) return -t
; else return t
;
69 strong_alias (__ieee754_atanhl
, __atanhl_finite
)