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Diffstat (limited to 'nuttx/libc/math/lib_erfl.c')
-rw-r--r-- | nuttx/libc/math/lib_erfl.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/nuttx/libc/math/lib_erfl.c b/nuttx/libc/math/lib_erfl.c new file mode 100644 index 000000000..594e9183b --- /dev/null +++ b/nuttx/libc/math/lib_erfl.c @@ -0,0 +1,72 @@ +/************************************************************************ + * libc/math/lib_erfl.c + * + * Copyright (C) 2015 Brennan Ashton. All rights reserved. + * Author: Brennan Ashton <bashton@brennanashton.com> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/************************************************************************ + * Included Files + ************************************************************************/ + +#include <nuttx/config.h> +#include <nuttx/compiler.h> + +#include <math.h> + +/************************************************************************ + * Public Functions + ************************************************************************/ + +#ifdef CONFIG_HAVE_LONG_DOUBLE +long double erfl(long double x) +{ + /* This implementation comes from the Handbook of Mathmatical Functions + * The implementations in this book are not protected by copyright. + * erf comes from formula 7.1.26 + */ + + char sign; + long double t; + long double a1, a2, a3, a4, a5, p; + + a1 = 0.254829592; + a2 = -0.284496736; + a3 = 1.421413741; + a4 = -1.453152027; + a5 = 1.061405429; + p = 0.3275911; + + sign = (x >= 0 ? 1 : -1); + t = 1.0/(1.0 + p*x); + return sign * (1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * expf(-x * x)); +} +#endif |