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      1 /* e_acoshf.c -- float version of e_acosh.c.
      2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian (at) cygnus.com.
      3  */
      4 
      5 /*
      6  * ====================================================
      7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      8  *
      9  * Developed at SunPro, a Sun Microsystems, Inc. business.
     10  * Permission to use, copy, modify, and distribute this
     11  * software is freely granted, provided that this notice
     12  * is preserved.
     13  * ====================================================
     14  */
     15 
     16 #include <sys/cdefs.h>
     17 #if defined(LIBM_SCCS) && !defined(lint)
     18 __RCSID("$NetBSD: e_acoshf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $");
     19 #endif
     20 
     21 #include "math.h"
     22 #include "math_private.h"
     23 
     24 static const float
     25 one	= 1.0,
     26 ln2	= 6.9314718246e-01;  /* 0x3f317218 */
     27 
     28 float
     29 __ieee754_acoshf(float x)
     30 {
     31 	float t;
     32 	int32_t hx;
     33 	GET_FLOAT_WORD(hx,x);
     34 	if(hx<0x3f800000) {		/* x < 1 */
     35 	    return (x-x)/(x-x);
     36 	} else if(hx >=0x4d800000) {	/* x > 2**28 */
     37 	    if(hx >=0x7f800000) {	/* x is inf of NaN */
     38 	        return x+x;
     39 	    } else
     40 		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
     41 	} else if (hx==0x3f800000) {
     42 	    return 0.0;			/* acosh(1) = 0 */
     43 	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
     44 	    t=x*x;
     45 	    return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
     46 	} else {			/* 1<x<2 */
     47 	    t = x-one;
     48 	    return log1pf(t+sqrtf((float)2.0*t+t*t));
     49 	}
     50 }
     51