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math.atan2 is misbehaving on Windows; this patch

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should fix the problem in the same way that
the cmath.phase problems were fixed.
This commit is contained in:
Mark Dickinson 2008-04-20 21:39:04 +00:00
parent eac43afdc9
commit 92483cd8da
1 changed files with 37 additions and 1 deletions
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38
Modules/mathmodule.c
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@ -95,6 +95,42 @@ is_error(double x)
return result; return result;
} }
/*
wrapper for atan2 that deals directly with special cases before
delegating to the platform libm for the remaining cases. This
is necessary to get consistent behaviour across platforms.
Windows, FreeBSD and alpha Tru64 are amongst platforms that don't
always follow C99.
*/
static double
m_atan2(double y, double x)
{
if (Py_IS_NAN(x) || Py_IS_NAN(y))
return Py_NAN;
if (Py_IS_INFINITY(y)) {
if (Py_IS_INFINITY(x)) {
if (copysign(1., x) == 1.)
/* atan2(+-inf, +inf) == +-pi/4 */
return copysign(0.25*Py_MATH_PI, y);
else
/* atan2(+-inf, -inf) == +-pi*3/4 */
return copysign(0.75*Py_MATH_PI, y);
}
/* atan2(+-inf, x) == +-pi/2 for finite x */
return copysign(0.5*Py_MATH_PI, y);
}
if (Py_IS_INFINITY(x) || y == 0.) {
if (copysign(1., x) == 1.)
/* atan2(+-y, +inf) = atan2(+-0, +x) = +-0. */
return copysign(0., y);
else
/* atan2(+-y, -inf) = atan2(+-0., -x) = +-pi. */
return copysign(Py_MATH_PI, y);
}
return atan2(y, x);
}
/* /*
math_1 is used to wrap a libm function f that takes a double math_1 is used to wrap a libm function f that takes a double
arguments and returns a double. arguments and returns a double.
@ -236,7 +272,7 @@ FUNC1(asinh, asinh, 0,
"asinh(x)\n\nReturn the hyperbolic arc sine (measured in radians) of x.") "asinh(x)\n\nReturn the hyperbolic arc sine (measured in radians) of x.")
FUNC1(atan, atan, 0, FUNC1(atan, atan, 0,
"atan(x)\n\nReturn the arc tangent (measured in radians) of x.") "atan(x)\n\nReturn the arc tangent (measured in radians) of x.")
FUNC2(atan2, atan2, FUNC2(atan2, m_atan2,
"atan2(y, x)\n\nReturn the arc tangent (measured in radians) of y/x.\n" "atan2(y, x)\n\nReturn the arc tangent (measured in radians) of y/x.\n"
"Unlike atan(y/x), the signs of both x and y are considered.") "Unlike atan(y/x), the signs of both x and y are considered.")
FUNC1(atanh, atanh, 0, FUNC1(atanh, atanh, 0,