e_atan2l.c revision 181074
1 2/* @(#)e_atan2.c 1.3 95/01/18 */ 3/* FreeBSD: head/lib/msun/src/e_atan2.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 16#include <sys/cdefs.h> 17__FBSDID("$FreeBSD: head/lib/msun/src/e_atan2l.c 181074 2008-07-31 22:41:26Z das $"); 18 19/* 20 * See comments in e_atan2.c. 21 * Converted to long double by David Schultz <das@FreeBSD.ORG>. 22 */ 23 24#include <float.h> 25 26#include "invtrig.h" 27#include "math.h" 28#include "math_private.h" 29 30static volatile long double 31tiny = 1.0e-300; 32static const long double 33zero = 0.0, 34pi = 3.14159265358979323846264338327950280e+00L; 35 36long double 37atan2l(long double y, long double x) 38{ 39 union IEEEl2bits ux, uy; 40 long double z; 41 int32_t k,m; 42 int16_t exptx, expsignx, expty, expsigny; 43 44 uy.e = y; 45 expsigny = uy.xbits.expsign; 46 expty = expsigny & 0x7fff; 47 ux.e = x; 48 expsignx = ux.xbits.expsign; 49 exptx = expsignx & 0x7fff; 50 51 if ((exptx==BIAS+LDBL_MAX_EXP && 52 ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)!=0) || /* x is NaN */ 53 (expty==BIAS+LDBL_MAX_EXP && 54 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* y is NaN */ 55 return x+y; 56 if (expsignx==BIAS && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0) 57 return atanl(y); /* x=1.0 */ 58 m = ((expsigny>>15)&1)|((expsignx>>14)&2); /* 2*sign(x)+sign(y) */ 59 60 /* when y = 0 */ 61 if(expty==0 && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)==0) { 62 switch(m) { 63 case 0: 64 case 1: return y; /* atan(+-0,+anything)=+-0 */ 65 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 66 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 67 } 68 } 69 /* when x = 0 */ 70 if(exptx==0 && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0) 71 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny; 72 73 /* when x is INF */ 74 if(exptx==BIAS+LDBL_MAX_EXP) { 75 if(expty==BIAS+LDBL_MAX_EXP) { 76 switch(m) { 77 case 0: return pio2_hi*0.5+tiny;/* atan(+INF,+INF) */ 78 case 1: return -pio2_hi*0.5-tiny;/* atan(-INF,+INF) */ 79 case 2: return 1.5*pio2_hi+tiny;/*atan(+INF,-INF)*/ 80 case 3: return -1.5*pio2_hi-tiny;/*atan(-INF,-INF)*/ 81 } 82 } else { 83 switch(m) { 84 case 0: return zero ; /* atan(+...,+INF) */ 85 case 1: return -zero ; /* atan(-...,+INF) */ 86 case 2: return pi+tiny ; /* atan(+...,-INF) */ 87 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 88 } 89 } 90 } 91 /* when y is INF */ 92 if(expty==BIAS+LDBL_MAX_EXP) 93 return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny; 94 95 /* compute y/x */ 96 k = expty-exptx; 97 if(k > LDBL_MANT_DIG+2) z=pio2_hi+pio2_lo; /* |y/x| huge */ 98 else if(expsignx<0&&k<-LDBL_MANT_DIG-2) z=0.0; /* |y/x| tiny, x<0 */ 99 else z=atanl(fabsl(y/x)); /* safe to do y/x */ 100 switch (m) { 101 case 0: return z ; /* atan(+,+) */ 102 case 1: return -z ; /* atan(-,+) */ 103 case 2: return pi-(z-pi_lo);/* atan(+,-) */ 104 default: /* case 3 */ 105 return (z-pi_lo)-pi;/* atan(-,-) */ 106 } 107} 108