1 /* from: FreeBSD: head/lib/msun/src/e_atanh.c 176451 2008-02-22 02:30:36Z das */ 2 3 /* @(#)e_atanh.c 1.3 95/01/18 */ 4 /* 5 * ==================================================== 6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7 * 8 * Developed at SunSoft, a Sun Microsystems, Inc. business. 9 * Permission to use, copy, modify, and distribute this 10 * software is freely granted, provided that this notice 11 * is preserved. 12 * ==================================================== 13 * 14 */ 15 16 #include <sys/cdefs.h> 17 /* 18 * See e_atanh.c for complete comments. 19 * 20 * Converted to long double by David Schultz <das@FreeBSD.ORG> and 21 * Bruce D. Evans. 22 */ 23 24 #include <float.h> 25 #ifdef __i386__ 26 #include <ieeefp.h> 27 #endif 28 29 #include "fpmath.h" 30 #include "math.h" 31 #include "math_private.h" 32 33 /* EXP_TINY is the threshold below which we use atanh(x) ~= x. */ 34 #if LDBL_MANT_DIG == 64 35 #define EXP_TINY -34 36 #elif LDBL_MANT_DIG == 113 37 #define EXP_TINY -58 38 #else 39 #error "Unsupported long double format" 40 #endif 41 42 #if LDBL_MAX_EXP != 0x4000 43 /* We also require the usual expsign encoding. */ 44 #error "Unsupported long double format" 45 #endif 46 47 #define BIAS (LDBL_MAX_EXP - 1) 48 49 static const double one = 1.0, huge = 1e300; 50 static const double zero = 0.0; 51 52 long double 53 atanhl(long double x) 54 { 55 long double t; 56 uint16_t hx, ix; 57 58 ENTERI(); 59 GET_LDBL_EXPSIGN(hx, x); 60 ix = hx & 0x7fff; 61 if (ix >= 0x3fff) /* |x| >= 1, or NaN or misnormal */ 62 RETURNI(fabsl(x) == 1 ? x / zero : (x - x) / (x - x)); 63 if (ix < BIAS + EXP_TINY && (huge + x) > zero) 64 RETURNI(x); /* x is tiny */ 65 SET_LDBL_EXPSIGN(x, ix); 66 if (ix < 0x3ffe) { /* |x| < 0.5, or misnormal */ 67 t = x+x; 68 t = 0.5*log1pl(t+t*x/(one-x)); 69 } else 70 t = 0.5*log1pl((x+x)/(one-x)); 71 RETURNI((hx & 0x8000) == 0 ? t : -t); 72 } 73