1  /* e_acoshf.c -- float version of e_acosh.c.
       2   */
       3  
       4  /*
       5   * ====================================================
       6   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       7   *
       8   * Developed at SunPro, 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  #if defined(LIBM_SCCS) && !defined(lint)
      16  static char rcsid[] = "$NetBSD: e_acoshf.c,v 1.5 1995/05/12 04:57:20 jtc Exp $";
      17  #endif
      18  
      19  #include <math.h>
      20  #include <math_private.h>
      21  #include <libm-alias-finite.h>
      22  
      23  static const float
      24  one	= 1.0,
      25  ln2	= 6.9314718246e-01;  /* 0x3f317218 */
      26  
      27  float __ieee754_acoshf(float x)
      28  {
      29  	float t;
      30  	int32_t hx;
      31  	GET_FLOAT_WORD(hx,x);
      32  	if(hx<0x3f800000) {		/* x < 1 */
      33  	    return (x-x)/(x-x);
      34  	} else if(hx >=0x4d800000) {	/* x > 2**28 */
      35  	    if(hx >=0x7f800000) {	/* x is inf of NaN */
      36  		return x+x;
      37  	    } else
      38  		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
      39  	} else if (hx==0x3f800000) {
      40  	    return 0.0;			/* acosh(1) = 0 */
      41  	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
      42  	    t=x*x;
      43  	    return __ieee754_logf((float)2.0*x-one/(x+sqrtf(t-one)));
      44  	} else {			/* 1<x<2 */
      45  	    t = x-one;
      46  	    return __log1pf(t+sqrtf((float)2.0*t+t*t));
      47  	}
      48  }
      49  libm_alias_finite (__ieee754_acoshf, __acoshf)