mirror of
https://github.com/python/cpython.git
synced 2024-11-25 01:20:47 +01:00
26 lines
760 B
C
26 lines
760 B
C
/* log1p(x) = log(1+x). The log1p function is designed to avoid the
|
|
significant loss of precision that arises from direct evaluation when x is
|
|
small. Use the substitute from _math.h on all platforms: it includes
|
|
workarounds for buggy handling of zeros.
|
|
*/
|
|
|
|
static double
|
|
_Py_log1p(double x)
|
|
{
|
|
/* Some platforms (e.g. MacOS X 10.8, see gh-59682) supply a log1p function
|
|
but don't respect the sign of zero: log1p(-0.0) gives 0.0 instead of
|
|
the correct result of -0.0.
|
|
|
|
To save fiddling with configure tests and platform checks, we handle the
|
|
special case of zero input directly on all platforms.
|
|
*/
|
|
if (x == 0.0) {
|
|
return x;
|
|
}
|
|
else {
|
|
return log1p(x);
|
|
}
|
|
}
|
|
|
|
#define m_log1p _Py_log1p
|