1 2 /* @(#)e_acos.c 1.3 95/01/18 */ 3 /* FreeBSD: head/lib/msun/src/e_acos.c 176451 2008-02-22 02:30:36Z das */ 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 #include <sys/cdefs.h> 16 __FBSDID("$FreeBSD$"); 17 18 /* 19 * See comments in e_acos.c. 20 * Converted to long double by David Schultz <das@FreeBSD.ORG>. 21 */ 22 23 #include <float.h> 24 25 #include "invtrig.h" 26 #include "math.h" 27 #include "math_private.h" 28 29 static const long double 30 one= 1.00000000000000000000e+00, 31 pi = 3.14159265358979323846264338327950280e+00L; 32 33 long double 34 acosl(long double x) 35 { 36 union IEEEl2bits u; 37 long double z,p,q,r,w,s,c,df; 38 int16_t expsign, expt; 39 u.e = x; 40 expsign = u.xbits.expsign; 41 expt = expsign & 0x7fff; 42 if(expt >= BIAS) { /* |x| >= 1 */ 43 if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0) { 44 if (expsign>0) return 0.0; /* acos(1) = 0 */ 45 else return pi+2.0*pio2_lo; /* acos(-1)= pi */ 46 } 47 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 48 } 49 if(expt<BIAS-1) { /* |x| < 0.5 */ 50 if(expt<ACOS_CONST) return pio2_hi+pio2_lo;/*x tiny: acosl=pi/2*/ 51 z = x*x; 52 p = P(z); 53 q = Q(z); 54 r = p/q; 55 return pio2_hi - (x - (pio2_lo-x*r)); 56 } else if (expsign<0) { /* x < -0.5 */ 57 z = (one+x)*0.5; 58 p = P(z); 59 q = Q(z); 60 s = sqrtl(z); 61 r = p/q; 62 w = r*s-pio2_lo; 63 return pi - 2.0*(s+w); 64 } else { /* x > 0.5 */ 65 z = (one-x)*0.5; 66 s = sqrtl(z); 67 u.e = s; 68 u.bits.manl = 0; 69 df = u.e; 70 c = (z-df*df)/(s+df); 71 p = P(z); 72 q = Q(z); 73 r = p/q; 74 w = r*s+c; 75 return 2.0*(df+w); 76 } 77 } 78