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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [mathfp/] [sf_atangent.c] - Rev 301
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/* @(#)z_atangentf.c 1.0 98/08/13 */ /****************************************************************** * The following routines are coded directly from the algorithms * and coefficients given in "Software Manual for the Elementary * Functions" by William J. Cody, Jr. and William Waite, Prentice * Hall, 1980. ******************************************************************/ /****************************************************************** * Arctangent * * Input: * x - floating point value * * Output: * arctangent of x * * Description: * This routine calculates arctangents. * *****************************************************************/ #include <float.h> #include "fdlibm.h" #include "zmath.h" static const float ROOT3 = 1.732050807; static const float a[] = { 0.0, 0.523598775, 1.570796326, 1.047197551 }; static const float q[] = { 0.1412500740e+1 }; static const float p[] = { -0.4708325141, -0.5090958253e-1 }; float _DEFUN (atangentf, (float, float, float, int), float x _AND float v _AND float u _AND int arctan2) { float f, g, R, P, Q, A, res; int N; int branch = 0; int expv, expu; /* Preparation for calculating arctan2. */ if (arctan2) { if (u == 0.0) if (v == 0.0) { errno = ERANGE; return (z_notanum_f.f); } else { branch = 1; res = __PI_OVER_TWO; } if (!branch) { int e; /* Get the exponent values of the inputs. */ g = frexpf (v, &expv); g = frexpf (u, &expu); /* See if a divide will overflow. */ e = expv - expu; if (e > FLT_MAX_EXP) { branch = 1; res = __PI_OVER_TWO; } /* Also check for underflow. */ else if (e < FLT_MIN_EXP) { branch = 2; res = 0.0; } } } if (!branch) { if (arctan2) f = fabsf (v / u); else f = fabsf (x); if (f > 1.0) { f = 1.0 / f; N = 2; } else N = 0; if (f > (2.0 - ROOT3)) { A = ROOT3 - 1.0; f = (((A * f - 0.5) - 0.5) + f) / (ROOT3 + f); N++; } /* Check for values that are too small. */ if (-z_rooteps_f < f && f < z_rooteps_f) res = f; /* Calculate the Taylor series. */ else { g = f * f; P = (p[1] * g + p[0]) * g; Q = g + q[0]; R = P / Q; res = f + f * R; } if (N > 1) res = -res; res += a[N]; } if (arctan2) { if (u < 0.0) res = __PI - res; if (v < 0.0) res = -res; } else if (x < 0.0) { res = -res; } return (res); }
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