Attachment 53970 Details for Bug 97562

gcc testcase

mathmodule.c (text/plain), 1.65 KB, created by Jan Matejek on 2005-10-13 18:12:21 UTC

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Creator: Jan Matejek

Created: 2005-10-13 18:12:21 UTC

Size: 1.65 KB

patch

obsolete

>/* Math module -- standard C math library functions, pi and e */
>
>#include "Python.h"
>#include "longintrepr.h"
>
>/* A decent logarithm is easy to compute even for huge longs, but libm can't
>   do that by itself -- loghelper can.  func is log or log10, and name is
>   "log" or "log10".  Note that overflow isn't possible:  a long can contain
>   no more than INT_MAX * SHIFT bits, so has value certainly less than
>   2**(2**64 * 2**16) == 2**2**80, and log2 of that is 2**80, which is
>   small enough to fit in an IEEE single.  log and log10 are even smaller.
>*/
>static PyObject*
>loghelper(PyObject* args, double (*func)(double), char *format, PyObject *arg)
>{
>	/* If it is long, do it ourselves. */
>	if (PyLong_Check(arg)) {
>		double x;
>		int e;
>		x = _PyLong_AsScaledDouble(arg, &e);
>		x = func(x) + (e * (double)SHIFT) * func(2.0);
>		return PyFloat_FromDouble(x);
>	}
>
>	/* Else let libm handle it by itself. */
>	return PyFloat_FromDouble(2.302585);
>}
>
>static PyObject *
>math_log(PyObject *self, PyObject *args)
>{
>	PyObject *arg;
>	PyObject *base = NULL;
>	PyObject *num, *den;
>	PyObject *ans;
>	PyObject *newargs;
>
>	PyArg_UnpackTuple(args, "log", 1, 2, &arg, &base);
>
>	newargs = PyTuple_Pack(1, arg);
>	num = loghelper(newargs, log, "d:log", arg);
>
>
>	Py_DECREF(newargs);
>	newargs = PyTuple_Pack(1, base);
>	den = loghelper(newargs, log, "d:log", base);
>
>
>	Py_DECREF(newargs);
>
>	ans = PyNumber_Divide(num, den);
>	Py_DECREF(num);
>	Py_DECREF(den);
>	return ans;
>}
>
>static PyMethodDef math_methods[] = {
>	{"log",		math_log,	METH_VARARGS,	NULL},
>	{NULL,		NULL}		/* sentinel */
>};
>
>PyMODINIT_FUNC
>initmath(void)
>{
>	PyObject *m;
>
>	m = Py_InitModule3("math", math_methods, NULL);
>	PyModule_GetDict(m);
>}

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Attachments on bug 97562: 53970