mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-23 01:33:36 +08:00
55eb99e9a9
C23 adds various <math.h> function families originally defined in TS 18661-4. Add the log10p1 functions (log10(1+x): like log1p, but for base-10 logarithms). This is directly analogous to the log2p1 implementation (except that whereas log2p1 has a smaller underflow range than log1p, log10p1 has a larger underflow range). The test inputs are copied from those for log1p and log2p1, plus a few more inputs in that wider underflow range. Tested for x86_64 and x86, and with build-many-glibcs.py.
50 lines
1.7 KiB
C
50 lines
1.7 KiB
C
/* Return base-10 logarithm of 1 + X.
|
|
Copyright (C) 2024 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-narrow-eval.h>
|
|
#include <math-underflow.h>
|
|
|
|
FLOAT
|
|
M_DECL_FUNC (__log10p1) (FLOAT x)
|
|
{
|
|
if (__glibc_unlikely (islessequal (x, M_LIT (-1.0))))
|
|
{
|
|
if (x == -1)
|
|
__set_errno (ERANGE);
|
|
else
|
|
__set_errno (EDOM);
|
|
}
|
|
if (isless (M_FABS (x), M_EPSILON / 4))
|
|
{
|
|
/* Ensure appropriate underflows (a wider range than for log1p,
|
|
with potential for zero results from nonzero arguments, in
|
|
which case errno should be set based on the result with any
|
|
excess range and precision removed) even if the result of
|
|
multiplying by M_MLIT (M_LOG10E) is exact. */
|
|
FLOAT ret = math_narrow_eval (M_MLIT (M_LOG10E) * x);
|
|
math_check_force_underflow (ret);
|
|
if (x != 0 && ret == 0)
|
|
__set_errno (ERANGE);
|
|
return ret;
|
|
}
|
|
return M_MLIT (M_LOG10E) * M_SUF (__log1p) (x);
|
|
}
|
|
declare_mgen_alias (__log10p1, log10p1);
|