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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] =
"$NetBSD: s_atan.c,v 1.8 1995/05/10 20:46:45 jtc Exp $";
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#endif
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#include "math.h"
00038
#include "mathP.h"
00039
00040
#ifdef __STDC__
00041
static const double atanhi[] = {
00042
#else
00043 static double atanhi[] = {
00044
#endif
00045
4.63647609000806093515e-01,
00046 7.85398163397448278999e-01,
00047 9.82793723247329054082e-01,
00048 1.57079632679489655800e+00,
00049 };
00050
00051
#ifdef __STDC__
00052
static const double atanlo[] = {
00053
#else
00054 static double atanlo[] = {
00055
#endif
00056
2.26987774529616870924e-17,
00057 3.06161699786838301793e-17,
00058 1.39033110312309984516e-17,
00059 6.12323399573676603587e-17,
00060 };
00061
00062
#ifdef __STDC__
00063
static const double aT[] = {
00064
#else
00065 static double aT[] = {
00066
#endif
00067
3.33333333333329318027e-01,
00068 -1.99999999998764832476e-01,
00069 1.42857142725034663711e-01,
00070 -1.11111104054623557880e-01,
00071 9.09088713343650656196e-02,
00072 -7.69187620504482999495e-02,
00073 6.66107313738753120669e-02,
00074 -5.83357013379057348645e-02,
00075 4.97687799461593236017e-02,
00076 -3.65315727442169155270e-02,
00077 1.62858201153657823623e-02,
00078 };
00079
00080
#ifdef __STDC__
00081
static const double
00082
#else
00083
static double
00084
#endif
00085 one = 1.0,
00086 huge = 1.0e300;
00087
00088
#ifdef __STDC__
00089
double atan(
double x)
00090 #
else
00091 double atan(x)
00092 double x;
00093 #endif
00094 {
00095
double w,s1,s2,z;
00096 int32_t ix,hx,
id;
00097
00098
GET_HIGH_WORD(hx,x);
00099 ix = hx&0x7fffffff;
00100
if(ix>=0x44100000) {
00101 u_int32_t low;
00102
GET_LOW_WORD(low,x);
00103
if(ix>0x7ff00000||
00104 (ix==0x7ff00000&&(low!=0)))
00105
return x+x;
00106
if(hx>0)
return atanhi[3]+
atanlo[3];
00107
else return -
atanhi[3]-
atanlo[3];
00108 }
if (ix < 0x3fdc0000) {
00109
if (ix < 0x3e200000) {
00110
if(huge+x>
one)
return x;
00111 }
00112
id = -1;
00113 }
else {
00114 x =
fabs(x);
00115
if (ix < 0x3ff30000) {
00116
if (ix < 0x3fe60000) {
00117
id = 0; x = (2.0*x-
one)/(2.0+x);
00118 }
else {
00119
id = 1; x = (x-
one)/(x+
one);
00120 }
00121 }
else {
00122
if (ix < 0x40038000) {
00123
id = 2; x = (x-1.5)/(
one+1.5*x);
00124 }
else {
00125
id = 3; x = -1.0/x;
00126 }
00127 }}
00128
00129 z = x*x;
00130 w = z*z;
00131
00132 s1 = z*(
aT[0]+w*(
aT[2]+w*(
aT[4]+w*(
aT[6]+w*(
aT[8]+w*
aT[10])))));
00133 s2 = w*(
aT[1]+w*(
aT[3]+w*(
aT[5]+w*(
aT[7]+w*
aT[9]))));
00134
if (
id<0)
return x - x*(s1+s2);
00135
else {
00136 z =
atanhi[
id] - ((x*(s1+s2) -
atanlo[
id]) - x);
00137
return (hx<0)? -z:z;
00138 }
00139 }