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 __FBSDID("$FreeBSD$"); 18 19 /* 20 * See e_atanh.c for complete comments. 21 * 22 * Converted to long double by David Schultz <das@FreeBSD.ORG> and 23 * Bruce D. Evans. 24 */ 25 26 #include <float.h> 27 #ifdef __i386__ 28 #include <ieeefp.h> 29 #endif 30 31 #include "fpmath.h" 32 #include "math.h" 33 #include "math_private.h" 34 35 /* EXP_TINY is the threshold below which we use atanh(x) ~= x. */ 36 #if LDBL_MANT_DIG == 64 37 #define EXP_TINY -34 38 #elif LDBL_MANT_DIG == 113 39 #define EXP_TINY -58 40 #else 41 #error "Unsupported long double format" 42 #endif 43 44 #if LDBL_MAX_EXP != 0x4000 45 /* We also require the usual expsign encoding. */ 46 #error "Unsupported long double format" 47 #endif 48 49 #define BIAS (LDBL_MAX_EXP - 1) 50 51 static const double one = 1.0, huge = 1e300; 52 static const double zero = 0.0; 53 54 long double 55 atanhl(long double x) 56 { 57 long double t; 58 uint16_t hx, ix; 59 60 ENTERI(); 61 GET_LDBL_EXPSIGN(hx, x); 62 ix = hx & 0x7fff; 63 if (ix >= 0x3fff) /* |x| >= 1, or NaN or misnormal */ 64 RETURNI(fabsl(x) == 1 ? x / zero : (x - x) / (x - x)); 65 if (ix < BIAS + EXP_TINY && (huge + x) > zero) 66 RETURNI(x); /* x is tiny */ 67 SET_LDBL_EXPSIGN(x, ix); 68 if (ix < 0x3ffe) { /* |x| < 0.5, or misnormal */ 69 t = x+x; 70 t = 0.5*log1pl(t+t*x/(one-x)); 71 } else 72 t = 0.5*log1pl((x+x)/(one-x)); 73 RETURNI((hx & 0x8000) == 0 ? t : -t); 74 } 75