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      1 /* e_atanhf.c -- float version of e_atanh.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 #ifndef lint
     17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_atanhf.c,v 1.6 2002/05/28 17:03:12 alfred Exp $";
     18 #endif
     19 
     20 #include "math.h"
     21 #include "math_private.h"
     22 
     23 static const float one = 1.0, huge = 1e30;
     24 
     25 static const float zero = 0.0;
     26 
     27 float
     28 __ieee754_atanhf(float x)
     29 {
     30 	float t;
     31 	int32_t hx,ix;
     32 	GET_FLOAT_WORD(hx,x);
     33 	ix = hx&0x7fffffff;
     34 	if (ix>0x3f800000) 		/* |x|>1 */
     35 	    return (x-x)/(x-x);
     36 	if(ix==0x3f800000)
     37 	    return x/zero;
     38 	if(ix<0x31800000&&(huge+x)>zero) return x;	/* x<2**-28 */
     39 	SET_FLOAT_WORD(x,ix);
     40 	if(ix<0x3f000000) {		/* x < 0.5 */
     41 	    t = x+x;
     42 	    t = (float)0.5*log1pf(t+t*x/(one-x));
     43 	} else
     44 	    t = (float)0.5*log1pf((x+x)/(one-x));
     45 	if(hx>=0) return t; else return -t;
     46 }
     47