1 /* from: FreeBSD: head/lib/msun/src/e_atanh.c 176451 2008-02-22 02:30:36Z das */ 2 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 * 13 */ 14 15 /* 16 * See e_atanh.c for complete comments. 17 * 18 * Converted to long double by David Schultz <das@FreeBSD.ORG> and 19 * Bruce D. Evans. 20 */ 21 22 #include <float.h> 23 #ifdef __i386__ 24 #include <ieeefp.h> 25 #endif 26 27 #include "fpmath.h" 28 #include "math.h" 29 #include "math_private.h" 30 31 /* EXP_TINY is the threshold below which we use atanh(x) ~= x. */ 32 #if LDBL_MANT_DIG == 64 33 #define EXP_TINY -34 34 #elif LDBL_MANT_DIG == 113 35 #define EXP_TINY -58 36 #else 37 #error "Unsupported long double format" 38 #endif 39 40 #if LDBL_MAX_EXP != 0x4000 41 /* We also require the usual expsign encoding. */ 42 #error "Unsupported long double format" 43 #endif 44 45 #define BIAS (LDBL_MAX_EXP - 1) 46 47 static const double one = 1.0, huge = 1e300; 48 static const double zero = 0.0; 49 50 long double 51 atanhl(long double x) 52 { 53 long double t; 54 uint16_t hx, ix; 55 56 ENTERI(); 57 GET_LDBL_EXPSIGN(hx, x); 58 ix = hx & 0x7fff; 59 if (ix >= 0x3fff) /* |x| >= 1, or NaN or misnormal */ 60 RETURNI(fabsl(x) == 1 ? x / zero : (x - x) / (x - x)); 61 if (ix < BIAS + EXP_TINY && (huge + x) > zero) 62 RETURNI(x); /* x is tiny */ 63 SET_LDBL_EXPSIGN(x, ix); 64 if (ix < 0x3ffe) { /* |x| < 0.5, or misnormal */ 65 t = x+x; 66 t = 0.5*log1pl(t+t*x/(one-x)); 67 } else 68 t = 0.5*log1pl((x+x)/(one-x)); 69 RETURNI((hx & 0x8000) == 0 ? t : -t); 70 } 71