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       ---
       e_coshf.c (1598B)
       ---
            1 /* e_coshf.c -- float version of e_cosh.c.
            2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@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_coshf.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, half=0.5, huge = 1.0e30;
           24 
           25 float
           26 __ieee754_coshf(float x)
           27 {
           28         float t,w;
           29         int32_t ix;
           30 
           31         GET_FLOAT_WORD(ix,x);
           32         ix &= 0x7fffffff;
           33 
           34     /* x is INF or NaN */
           35         if(ix>=0x7f800000) return x*x;
           36 
           37     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
           38         if(ix<0x3eb17218) {
           39             t = expm1f(fabsf(x));
           40             w = one+t;
           41             if (ix<0x24000000) return w;        /* cosh(tiny) = 1 */
           42             return one+(t*t)/(w+w);
           43         }
           44 
           45     /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
           46         if (ix < 0x41b00000) {
           47                 t = __ieee754_expf(fabsf(x));
           48                 return half*t+half/t;
           49         }
           50 
           51     /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
           52         if (ix < 0x42b17180)  return half*__ieee754_expf(fabsf(x));
           53 
           54     /* |x| in [log(maxdouble), overflowthresold] */
           55         if (ix<=0x42b2d4fc) {
           56             w = __ieee754_expf(half*fabsf(x));
           57             t = half*w;
           58             return t*w;
           59         }
           60 
           61     /* |x| > overflowthresold, cosh(x) overflow */
           62         return huge*huge;
           63 }