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Diffstat (limited to 'nuttx/libc/math/lib_sinf.c')
-rw-r--r-- | nuttx/libc/math/lib_sinf.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/nuttx/libc/math/lib_sinf.c b/nuttx/libc/math/lib_sinf.c new file mode 100644 index 000000000..9e493d8ef --- /dev/null +++ b/nuttx/libc/math/lib_sinf.c @@ -0,0 +1,104 @@ +/************************************************************************ + * libc/math/lib_sinf.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 <sys/types.h> +#include <math.h> + +/************************************************************************ + * Private Data + ************************************************************************/ + +static float _flt_inv_fact[] = +{ + 1.0 / 1.0, // 1 / 1! + 1.0 / 6.0, // 1 / 3! + 1.0 / 120.0, // 1 / 5! + 1.0 / 5040.0, // 1 / 7! + 1.0 / 362880.0, // 1 / 9! + 1.0 / 39916800.0, // 1 / 11! +}; + +/************************************************************************ + * Public Functions + ************************************************************************/ + +float sinf(float x) +{ + float x_squared; + float sin_x; + size_t i; + + /* Move x to [-pi, pi) */ + + x = fmodf(x, 2 * M_PI); + if (x >= M_PI) + { + x -= 2 * M_PI; + } + + if (x < -M_PI) + { + x += 2 * M_PI; + } + + /* Move x to [-pi/2, pi/2) */ + + if (x >= M_PI_2) + { + x = M_PI - x; + } + + if (x < -M_PI_2) + { + x = -M_PI - x; + } + + x_squared = x * x; + sin_x = 0.0; + + /* Perform Taylor series approximation for sin(x) with six terms */ + + for (i = 0; i < 6; i++) + { + if (i % 2 == 0) + { + sin_x += x * _flt_inv_fact[i]; + } + else + { + sin_x -= x * _flt_inv_fact[i]; + } + + x *= x_squared; + } + + return sin_x; +} |