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 #include <sys/cdefs.h> 16 /* 17 * See e_atanh.c for complete comments. 18 * 19 * Converted to long double by David Schultz <das@FreeBSD.ORG> and 20 * Bruce D. Evans. 21 */ 22 23 #include <float.h> 24 #ifdef __i386__ 25 #include <ieeefp.h> 26 #endif 27 28 #include "fpmath.h" 29 #include "math.h" 30 #include "math_private.h" 31 32 /* EXP_TINY is the threshold below which we use atanh(x) ~= x. */ 33 #if LDBL_MANT_DIG == 64 34 #define EXP_TINY -34 35 #elif LDBL_MANT_DIG == 113 36 #define EXP_TINY -58 37 #else 38 #error "Unsupported long double format" 39 #endif 40 41 #if LDBL_MAX_EXP != 0x4000 42 /* We also require the usual expsign encoding. */ 43 #error "Unsupported long double format" 44 #endif 45 46 #define BIAS (LDBL_MAX_EXP - 1) 47 48 static const double one = 1.0, huge = 1e300; 49 static const double zero = 0.0; 50 51 long double 52 atanhl(long double x) 53 { 54 long double t; 55 uint16_t hx, ix; 56 57 ENTERI(); 58 GET_LDBL_EXPSIGN(hx, x); 59 ix = hx & 0x7fff; 60 if (ix >= 0x3fff) /* |x| >= 1, or NaN or misnormal */ 61 RETURNI(fabsl(x) == 1 ? x / zero : (x - x) / (x - x)); 62 if (ix < BIAS + EXP_TINY && (huge + x) > zero) 63 RETURNI(x); /* x is tiny */ 64 SET_LDBL_EXPSIGN(x, ix); 65 if (ix < 0x3ffe) { /* |x| < 0.5, or misnormal */ 66 t = x+x; 67 t = 0.5*log1pl(t+t*x/(one-x)); 68 } else 69 t = 0.5*log1pl((x+x)/(one-x)); 70 RETURNI((hx & 0x8000) == 0 ? t : -t); 71 } 72