Added math.isinf() and math.isnan()

4 files changed, 69 insertions, 6 deletions

diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index f92610f..d0b03ed 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -66,6 +66,23 @@ Number-theoretic and representation functions:
    apart" the internal representation of a float in a portable way.
 
 
+.. function:: isinf(x)
+
+   Checks if the float *x* is positive or negative infinite.
+
+   ..versionadded:: 2.6
+
+
+.. function:: isnan(x)
+
+   Checks if the float *x* is a NaN (not a number). NaNs are part of the
+   IEEE 754 standards. Operation like but not limited to ``inf * 0``, 
+   ``inf / inf`` or any operation involving a NaN, e.g. ``nan * 1``, return
+   a NaN.
+
+   ..versionadded:: 2.6
+
+
 .. function:: ldexp(x, i)
 
    Return ``x * (2**i)``.  This is essentially the inverse of function
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 98e4623..d2da59b 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -229,6 +229,22 @@ class MathTests(unittest.TestCase):
         self.ftest('tanh(0)', math.tanh(0), 0)
         self.ftest('tanh(1)+tanh(-1)', math.tanh(1)+math.tanh(-1), 0)
 
+    def testIsnan(self):
+        self.assert_(math.isnan(float("nan")))
+        self.assert_(math.isnan(float("inf")* 0.))
+        self.failIf(math.isnan(float("inf")))
+        self.failIf(math.isnan(0.))
+        self.failIf(math.isnan(1.))
+
+    def testIsinf(self):
+        self.assert_(math.isinf(float("inf")))
+        self.assert_(math.isinf(float("-inf")))
+        self.assert_(math.isinf(1E400))
+        self.assert_(math.isinf(-1E400))
+        self.failIf(math.isinf(float("nan")))
+        self.failIf(math.isinf(0.))
+        self.failIf(math.isinf(1.))
+
     # RED_FLAG 16-Oct-2000 Tim
     # While 2.0 is more consistent about exceptions than previous releases, it
     # still fails this part of the test on some platforms.  For now, we only
diff --git a/Misc/NEWS b/Misc/NEWS
index 3e3f074..95845b6 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@ What's New in Python 2.6 alpha 1?
 Core and builtins
 -----------------
 
+- Issue #1640: Added math.isinf() and math.isnan() functions.
+
 - Issue #1726: Remove Python/atof.c from PCBuild/pythoncore.vcproj
 
 - Removed PCbuild8/ directory and added a new build directory for VS 2005
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 431590c..7540b5d 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -315,9 +315,8 @@ math_log10(PyObject *self, PyObject *arg)
 PyDoc_STRVAR(math_log10_doc,
 "log10(x) -> the base 10 logarithm of x.");
 
-/* XXX(nnorwitz): Should we use the platform M_PI or something more accurate
-   like: 3.14159265358979323846264338327950288 */
-static const double degToRad = 3.141592653589793238462643383 / 180.0;
+static const double degToRad = Py_MATH_PI / 180.0;
+static const double radToDeg = 180.0 / Py_MATH_PI;
 
 static PyObject *
 math_degrees(PyObject *self, PyObject *arg)
@@ -325,7 +324,7 @@ math_degrees(PyObject *self, PyObject *arg)
 	double x = PyFloat_AsDouble(arg);
 	if (x == -1.0 && PyErr_Occurred())
 		return NULL;
-	return PyFloat_FromDouble(x / degToRad);
+	return PyFloat_FromDouble(x * radToDeg);
 }
 
 PyDoc_STRVAR(math_degrees_doc,
@@ -343,6 +342,33 @@ math_radians(PyObject *self, PyObject *arg)
 PyDoc_STRVAR(math_radians_doc,
 "radians(x) -> converts angle x from degrees to radians");
 
+static PyObject *
+math_isnan(PyObject *self, PyObject *arg)
+{
+	double x = PyFloat_AsDouble(arg);
+	if (x == -1.0 && PyErr_Occurred())
+		return NULL;
+	return PyBool_FromLong((long)Py_IS_NAN(x));
+}
+
+PyDoc_STRVAR(math_isnan_doc,
+"isnan(x) -> bool\n\
+Checks if float x is not a number (NaN)");
+
+static PyObject *
+math_isinf(PyObject *self, PyObject *arg)
+{
+	double x = PyFloat_AsDouble(arg);
+	if (x == -1.0 && PyErr_Occurred())
+		return NULL;
+	return PyBool_FromLong((long)Py_IS_INFINITY(x));
+}
+
+PyDoc_STRVAR(math_isinf_doc,
+"isinf(x) -> bool\n\
+Checks if float x is infinite (positive or negative)");
+
+
 static PyMethodDef math_methods[] = {
 	{"acos",	math_acos,	METH_O,		math_acos_doc},
 	{"asin",	math_asin,	METH_O,		math_asin_doc},
@@ -358,6 +384,8 @@ static PyMethodDef math_methods[] = {
 	{"fmod",	math_fmod,	METH_VARARGS,	math_fmod_doc},
 	{"frexp",	math_frexp,	METH_O,		math_frexp_doc},
 	{"hypot",	math_hypot,	METH_VARARGS,	math_hypot_doc},
+	{"isinf",	math_isinf,	METH_O,		math_isinf_doc},
+	{"isnan",	math_isnan,	METH_O,		math_isnan_doc},
 	{"ldexp",	math_ldexp,	METH_VARARGS,	math_ldexp_doc},
 	{"log",		math_log,	METH_VARARGS,	math_log_doc},
 	{"log10",	math_log10,	METH_O,		math_log10_doc},
@@ -389,13 +417,13 @@ initmath(void)
 	if (d == NULL)
 		goto finally;
 
-        if (!(v = PyFloat_FromDouble(atan(1.0) * 4.0)))
+        if (!(v = PyFloat_FromDouble(Py_MATH_PI)))
                 goto finally;
 	if (PyDict_SetItemString(d, "pi", v) < 0)
                 goto finally;
 	Py_DECREF(v);
 
-        if (!(v = PyFloat_FromDouble(exp(1.0))))
+        if (!(v = PyFloat_FromDouble(Py_MATH_E)))
                 goto finally;
 	if (PyDict_SetItemString(d, "e", v) < 0)
                 goto finally;