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/************************************************************************
* lib/math/lib_libexpi.c
*
* This file is a part of NuttX:
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Ported by: Darcy Gong
*
* It derives from the Rhombs OS math library by Nick Johnson which has
* a compatibile, MIT-style license:
*
* Copyright (C) 2009-2011 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 <sys/types.h>
#include <math.h>
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Pre-processor Definitions
************************************************************************/
#define M_E2 (M_E * M_E)
#define M_E4 (M_E2 * M_E2)
#define M_E8 (M_E4 * M_E4)
#define M_E16 (M_E8 * M_E8)
#define M_E32 (M_E16 * M_E16)
#define M_E64 (M_E32 * M_E32)
#define M_E128 (M_E64 * M_E64)
#define M_E256 (M_E128 * M_E128)
#define M_E512 (M_E256 * M_E256)
#define M_E1024 (M_E512 * M_E512)
/************************************************************************
* Private Data
************************************************************************/
static double _expi_square_tbl[11] =
{
M_E, // e^1
M_E2, // e^2
M_E4, // e^4
M_E8, // e^8
M_E16, // e^16
M_E32, // e^32
M_E64, // e^64
M_E128, // e^128
M_E256, // e^256
M_E512, // e^512
M_E1024, // e^1024
};
/************************************************************************
* Public Functions
************************************************************************/
double lib_expi(size_t n)
{
size_t i;
double val;
if (n > 1024)
{
return INFINITY;
}
val = 1.0;
for (i = 0; n; i++)
{
if (n & (1 << i))
{
n &= ~(1 << i);
val *= _expi_square_tbl[i];
}
}
return val;
}
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