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103 lines
3.2 KiB
103 lines
3.2 KiB
/************************************************************************ |
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* libc/math/lib_libexpi.c |
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* |
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* This file is a part of NuttX: |
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* |
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* Copyright (C) 2012 Gregory Nutt. All rights reserved. |
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* Ported by: Darcy Gong |
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* |
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* It derives from the Rhombs OS math library by Nick Johnson which has |
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* a compatibile, MIT-style license: |
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* |
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* Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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* |
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************************************************************************/ |
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/************************************************************************ |
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* Included Files |
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************************************************************************/ |
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#include <nuttx/config.h> |
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#include <nuttx/compiler.h> |
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#include <sys/types.h> |
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#include <math.h> |
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/************************************************************************ |
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* Public Functions |
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************************************************************************/ |
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/************************************************************************ |
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* Pre-processor Definitions |
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************************************************************************/ |
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#define M_E2 (M_E * M_E) |
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#define M_E4 (M_E2 * M_E2) |
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#define M_E8 (M_E4 * M_E4) |
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#define M_E16 (M_E8 * M_E8) |
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#define M_E32 (M_E16 * M_E16) |
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#define M_E64 (M_E32 * M_E32) |
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#define M_E128 (M_E64 * M_E64) |
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#define M_E256 (M_E128 * M_E128) |
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#define M_E512 (M_E256 * M_E256) |
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#define M_E1024 (M_E512 * M_E512) |
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/************************************************************************ |
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* Private Data |
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************************************************************************/ |
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static double _expi_square_tbl[11] = |
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{ |
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M_E, // e^1 |
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M_E2, // e^2 |
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M_E4, // e^4 |
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M_E8, // e^8 |
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M_E16, // e^16 |
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M_E32, // e^32 |
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M_E64, // e^64 |
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M_E128, // e^128 |
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M_E256, // e^256 |
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M_E512, // e^512 |
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M_E1024, // e^1024 |
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}; |
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/************************************************************************ |
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* Public Functions |
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************************************************************************/ |
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double lib_expi(size_t n) |
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{ |
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size_t i; |
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double val; |
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if (n > 1024) |
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{ |
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return INFINITY; |
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} |
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val = 1.0; |
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for (i = 0; n; i++) |
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{ |
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if (n & (1 << i)) |
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{ |
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n &= ~(1 << i); |
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val *= _expi_square_tbl[i]; |
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} |
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} |
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return val; |
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} |
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