sysdeps/libm-ieee754/e_coshf.c

   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 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: e_coshf.c,v 1.6 1996/04/08 15:43:41 phil Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float huge = 1.0e30;
  25 static const float one = 1.0, half=0.5;
  26 #else
  27 static float one = 1.0, half=0.5, huge = 1.0e30;
  28 #endif
  29
  30 #ifdef __STDC__
  31         float __ieee754_coshf(float x)
  32 #else
  33         float __ieee754_coshf(x)
  34         float x;
  35 #endif
  36 {
  37         float t,w;
  38         int32_t ix;
  39
  40         GET_FLOAT_WORD(ix,x);
  41         ix &= 0x7fffffff;
  42
  43     /* x is INF or NaN */
  44         if(ix>=0x7f800000) return x*x;
  45
  46     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
  47         if(ix<0x3eb17218) {
  48             t = __expm1f(fabsf(x));
  49             w = one+t;
  50             if (ix<0x24000000) return w;        /* cosh(tiny) = 1 */
  51             return one+(t*t)/(w+w);
  52         }
  53
  54     /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
  55         if (ix < 0x41b00000) {
  56                 t = __ieee754_expf(fabsf(x));
  57                 return half*t+half/t;
  58         }
  59
  60     /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
  61         if (ix < 0x42b17180)  return half*__ieee754_expf(fabsf(x));
  62
  63     /* |x| in [log(maxdouble), overflowthresold] */
  64         if (ix<=0x42b2d4fc) {
  65             w = __ieee754_expf(half*fabsf(x));
  66             t = half*w;
  67             return t*w;
  68         }
  69
  70     /* |x| > overflowthresold, cosh(x) overflow */
  71         return huge*huge;
  72 }