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/* Return sine of pi * X.
Copyright (C) 2024-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <math.h>
#include <math-underflow.h>
FLOAT
M_DECL_FUNC (__sinpi) (FLOAT x)
{
if (isless (M_FABS (x), M_EPSILON))
{
FLOAT ret = M_MLIT (M_PI) * x;
math_check_force_underflow (ret);
return ret;
}
if (__glibc_unlikely (isinf (x)))
__set_errno (EDOM);
FLOAT y = x - M_LIT (2.0) * M_SUF (round) (M_LIT (0.5) * x);
FLOAT absy = M_FABS (y);
if (absy == M_LIT (0.0) || absy == M_LIT (1.0))
return M_COPYSIGN (M_LIT (0.0), x);
else if (islessequal (absy, M_LIT (0.25)))
return M_SUF (__sin) (M_MLIT (M_PI) * y);
else if (islessequal (absy, M_LIT (0.75)))
return M_COPYSIGN (M_SUF (__cos) (M_MLIT (M_PI) * (M_LIT (0.5) - absy)),
y);
else
return M_COPYSIGN (M_SUF (__sin) (M_MLIT (M_PI) * (M_LIT (1.0) - absy)),
y);
}
declare_mgen_alias (__sinpi, sinpi);
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