atan2l.c raw

   1  /* origin: FreeBSD /usr/src/lib/msun/src/e_atan2l.c */
   2  /*
   3   * ====================================================
   4   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5   *
   6   * Developed at SunSoft, a Sun Microsystems, Inc. business.
   7   * Permission to use, copy, modify, and distribute this
   8   * software is freely granted, provided that this notice
   9   * is preserved.
  10   * ====================================================
  11   *
  12   */
  13  /*
  14   * See comments in atan2.c.
  15   * Converted to long double by David Schultz <das@FreeBSD.ORG>.
  16   */
  17  
  18  #include "libm.h"
  19  
  20  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
  21  long double atan2l(long double y, long double x)
  22  {
  23  	return atan2(y, x);
  24  }
  25  #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
  26  #include "__invtrigl.h"
  27  
  28  long double atan2l(long double y, long double x)
  29  {
  30  	union ldshape ux, uy;
  31  	long double z;
  32  	int m, ex, ey;
  33  
  34  	if (isnan(x) || isnan(y))
  35  		return x+y;
  36  	if (x == 1)
  37  		return atanl(y);
  38  	ux.f = x;
  39  	uy.f = y;
  40  	ex = ux.i.se & 0x7fff;
  41  	ey = uy.i.se & 0x7fff;
  42  	m = 2*(ux.i.se>>15) | uy.i.se>>15;
  43  	if (y == 0) {
  44  		switch(m) {
  45  		case 0:
  46  		case 1: return y;           /* atan(+-0,+anything)=+-0 */
  47  		case 2: return  2*pio2_hi;  /* atan(+0,-anything) = pi */
  48  		case 3: return -2*pio2_hi;  /* atan(-0,-anything) =-pi */
  49  		}
  50  	}
  51  	if (x == 0)
  52  		return m&1 ? -pio2_hi : pio2_hi;
  53  	if (ex == 0x7fff) {
  54  		if (ey == 0x7fff) {
  55  			switch(m) {
  56  			case 0: return  pio2_hi/2;   /* atan(+INF,+INF) */
  57  			case 1: return -pio2_hi/2;   /* atan(-INF,+INF) */
  58  			case 2: return  1.5*pio2_hi; /* atan(+INF,-INF) */
  59  			case 3: return -1.5*pio2_hi; /* atan(-INF,-INF) */
  60  			}
  61  		} else {
  62  			switch(m) {
  63  			case 0: return  0.0;        /* atan(+...,+INF) */
  64  			case 1: return -0.0;        /* atan(-...,+INF) */
  65  			case 2: return  2*pio2_hi;  /* atan(+...,-INF) */
  66  			case 3: return -2*pio2_hi;  /* atan(-...,-INF) */
  67  			}
  68  		}
  69  	}
  70  	if (ex+120 < ey || ey == 0x7fff)
  71  		return m&1 ? -pio2_hi : pio2_hi;
  72  	/* z = atan(|y/x|) without spurious underflow */
  73  	if ((m&2) && ey+120 < ex)  /* |y/x| < 0x1p-120, x<0 */
  74  		z = 0.0;
  75  	else
  76  		z = atanl(fabsl(y/x));
  77  	switch (m) {
  78  	case 0: return z;               /* atan(+,+) */
  79  	case 1: return -z;              /* atan(-,+) */
  80  	case 2: return 2*pio2_hi-(z-2*pio2_lo); /* atan(+,-) */
  81  	default: /* case 3 */
  82  		return (z-2*pio2_lo)-2*pio2_hi; /* atan(-,-) */
  83  	}
  84  }
  85  #endif
  86