lib/libm/src/w_exp.c

   1 /* @(#)w_exp.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #include <sys/cdefs.h>
  14 #if defined(LIBM_SCCS) && !defined(lint)
  15 __RCSID("$NetBSD: w_exp.c,v 1.10 2007/08/20 16:01:40 drochner Exp $");
  16 #endif
  17
  18 /*
  19  * wrapper exp(x)
  20  */
  21
  22 #include "namespace.h"
  23 #include "math.h"
  24 #include "math_private.h"
  25
  26 #ifdef __weak_alias
  27 __weak_alias(exp, _exp)
  28 #endif
  29
  30 static const double
  31 o_threshold=  7.09782712893383973096e+02,  /* 0x40862E42, 0xFEFA39EF */
  32 u_threshold= -7.45133219101941108420e+02;  /* 0xc0874910, 0xD52D3051 */
  33
  34 double
  35 exp(double x)           /* wrapper exp */
  36 {
  37 #ifdef _IEEE_LIBM
  38         return __ieee754_exp(x);
  39 #else
  40         double z;
  41         z = __ieee754_exp(x);
  42         if(_LIB_VERSION == _IEEE_) return z;
  43         if(finite(x)) {
  44             if(x>o_threshold)
  45                 return __kernel_standard(x,x,6); /* exp overflow */
  46             else if(x<u_threshold)
  47                 return __kernel_standard(x,x,7); /* exp underflow */
  48         }
  49         return z;
  50 #endif
  51 }