/* @(#)w_pow.c 5.2 93/10/01 */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

/*
FUNCTION
	<<pow>>, <<powf>>---x to the power y
INDEX
	pow
INDEX
	powf


ANSI_SYNOPSIS
	#include <math.h>
	double pow(double <[x]>, double <[y]>);
	float pow(float <[x]>, float <[y]>);

TRAD_SYNOPSIS
	#include <math.h>
	double pow(<[x]>, <[y]>);
	double <[x]>, <[y]>;

	float pow(<[x]>, <[y]>);
	float <[x]>, <[y]>;

DESCRIPTION
	<<pow>> and <<powf>> calculate <[x]> raised to the exp1.0nt <[y]>.
	@tex
	(That is, $x^y$.)
	@end tex

RETURNS
	On success, <<pow>> and <<powf>> return the value calculated.

	When the argument values would produce overflow, <<pow>>
	returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>.  If the
	argument <[x]> passed to <<pow>> or <<powf>> is a negative
	noninteger, and <[y]> is also not an integer, then <<errno>>
	is set to <<EDOM>>.  If <[x]> and <[y]> are both 0, then
	<<pow>> and <<powf>> return <<1>>.

	You can modify error handling for these functions using <<matherr>>.

PORTABILITY
	<<pow>> is ANSI C. <<powf>> is an extension.  */

/* 
 * wrapper pow(x,y) return x**y
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
double
pow (double x, double y)	/* wrapper pow */
#else
double
pow (x, y)			/* wrapper pow */
     double x, y;
#endif
{
#ifdef _IEEE_LIBM
  return __ieee754_pow (x, y);
#else
  double z;
#ifndef HUGE_VAL
#define HUGE_VAL inf
  double inf = 0.0;

  SET_HIGH_WORD (inf, 0x7ff00000);	/* set inf to infinite */
#endif
  struct exception exc;
  z = __ieee754_pow (x, y);
  if (_LIB_VERSION == _IEEE_ || isnan (y))
    return z;
  if (isnan (x))
    {
      if (y == 0.0)
	{
	  /* pow(NaN,0.0) */
	  /* error only if _LIB_VERSION == _SVID_ & _XOPEN_ */
	  exc.type = DOMAIN;
	  exc.name = "pow";
	  exc.err = 0;
	  exc.arg1 = x;
	  exc.arg2 = y;
	  exc.retval = x;
	  if (_LIB_VERSION == _IEEE_ || _LIB_VERSION == _POSIX_)
	    exc.retval = 1.0;
	  else if (!matherr (&exc))
	    {
	      errno = EDOM;
	    }
	  if (exc.err != 0)
	    errno = exc.err;
	  return exc.retval;
	}
      else
	return z;
    }
  if (x == 0.0)
    {
      if (y == 0.0)
	{
	  /* pow(0.0,0.0) */
	  /* error only if _LIB_VERSION == _SVID_ */
	  exc.type = DOMAIN;
	  exc.name = "pow";
	  exc.err = 0;
	  exc.arg1 = x;
	  exc.arg2 = y;
	  exc.retval = 0.0;
	  if (_LIB_VERSION != _SVID_)
	    exc.retval = 1.0;
	  else if (!matherr (&exc))
	    {
	      errno = EDOM;
	    }
	  if (exc.err != 0)
	    errno = exc.err;
	  return exc.retval;
	}
      if (finite (y) && y < 0.0)
	{
	  /* 0**neg */
	  exc.type = DOMAIN;
	  exc.name = "pow";
	  exc.err = 0;
	  exc.arg1 = x;
	  exc.arg2 = y;
	  if (_LIB_VERSION == _SVID_)
	    exc.retval = 0.0;
	  else
	    exc.retval = -HUGE_VAL;
	  if (_LIB_VERSION == _POSIX_)
	    errno = EDOM;
	  else if (!matherr (&exc))
	    {
	      errno = EDOM;
	    }
	  if (exc.err != 0)
	    errno = exc.err;
	  return exc.retval;
	}
      return z;
    }
  if (!finite (z))
    {
      if (finite (x) && finite (y))
	{
	  if (isnan (z))
	    {
	      /* neg**non-integral */
	      exc.type = DOMAIN;
	      exc.name = "pow";
	      exc.err = 0;
	      exc.arg1 = x;
	      exc.arg2 = y;
	      if (_LIB_VERSION == _SVID_)
		exc.retval = 0.0;
	      else
		exc.retval = 0.0 / 0.0;	/* X/Open allow NaN */
	      if (_LIB_VERSION == _POSIX_)
		errno = EDOM;
	      else if (!matherr (&exc))
		{
		  errno = EDOM;
		}
	      if (exc.err != 0)
		errno = exc.err;
	      return exc.retval;
	    }
	  else
	    {
	      /* pow(x,y) overflow */
	      exc.type = OVERFLOW;
	      exc.name = "pow";
	      exc.err = 0;
	      exc.arg1 = x;
	      exc.arg2 = y;
	      if (_LIB_VERSION == _SVID_)
		{
		  exc.retval = HUGE;
		  y *= 0.5;
		  if (x < 0.0 && rint (y) != y)
		    exc.retval = -HUGE;
		}
	      else
		{
		  exc.retval = HUGE_VAL;
		  y *= 0.5;
		  if (x < 0.0 && rint (y) != y)
		    exc.retval = -HUGE_VAL;
		}
	      if (_LIB_VERSION == _POSIX_)
		errno = ERANGE;
	      else if (!matherr (&exc))
		{
		  errno = ERANGE;
		}
	      if (exc.err != 0)
		errno = exc.err;
	      return exc.retval;
	    }
	}
    }
  if (z == 0.0 && finite (x) && finite (y))
    {
      /* pow(x,y) underflow */
      exc.type = UNDERFLOW;
      exc.name = "pow";
      exc.err = 0;
      exc.arg1 = x;
      exc.arg2 = y;
      exc.retval = 0.0;
      if (_LIB_VERSION == _POSIX_)
	errno = ERANGE;
      else if (!matherr (&exc))
	{
	  errno = ERANGE;
	}
      if (exc.err != 0)
	errno = exc.err;
      return exc.retval;
    }
  return z;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */