nuttx/libs/libc/math/lib_pow.c
2022-09-03 21:19:10 +08:00

63 lines
2.0 KiB
C

/****************************************************************************
* libs/libc/math/lib_pow.c
*
* This file is a part of NuttX:
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Ported by: Darcy Gong
*
* It derives from the Rhombus OS math library by Nick Johnson which has
* a compatible, MIT-style license:
*
* Copyright (C) 2009, 2010 Nick Johnson <nickbjohnson4224 at gmail.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/compiler.h>
#include <math.h>
/****************************************************************************
* Public Functions
****************************************************************************/
#ifdef CONFIG_HAVE_DOUBLE
double pow(double b, double e)
{
if (b > 0)
{
return exp(e * log(b));
}
else if (b < 0 && e == (int)e)
{
if ((int)e % 2 == 0)
{
return exp(e * log(fabs(b)));
}
else
{
return -exp(e * log(fabs(b)));
}
}
return 0;
}
#endif