src/math/e_atanhf.c


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/* e_atanhf.c -- float version of e_atanh.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include <math.h>
#include "math_private.h"

static const float one = 1.0, huge = 1e30;

static const float zero = 0.0;

float
atanhf(float x)
{
        float t;
        int32_t hx,ix;
        GET_FLOAT_WORD(hx,x);
        ix = hx&0x7fffffff;
        if (ix>0x3f800000)              /* |x|>1 */
            return (x-x)/(x-x);
        if(ix==0x3f800000)
            return x/zero;
        if(ix<0x31800000&&(huge+x)>zero) return x;      /* x<2**-28 */
        SET_FLOAT_WORD(x,ix);
        if(ix<0x3f000000) {             /* x < 0.5 */
            t = x+x;
            t = (float)0.5*log1pf(t+t*x/(one-x));
        } else
            t = (float)0.5*log1pf((x+x)/(one-x));
        if(hx>=0) return t; else return -t;
}