bpo-39310: Add math.ulp(x) (GH-17965)

Add math.ulp(): return the value of the least significant bit
of a float.

1 files changed, 40 insertions, 1 deletions

diff --git a/Modules/clinic/mathmodule.c.h b/Modules/clinic/mathmodule.c.h
index f34633c..f95d291 100644
--- a/Modules/clinic/mathmodule.c.h
+++ b/Modules/clinic/mathmodule.c.h
@@ -856,4 +856,43 @@ math_nextafter(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=e4ed1a800e4b2eae input=a9049054013a1b77]*/
+
+PyDoc_STRVAR(math_ulp__doc__,
+"ulp($module, x, /)\n"
+"--\n"
+"\n"
+"Return the value of the least significant bit of the float x.");
+
+#define MATH_ULP_METHODDEF    \
+    {"ulp", (PyCFunction)math_ulp, METH_O, math_ulp__doc__},
+
+static double
+math_ulp_impl(PyObject *module, double x);
+
+static PyObject *
+math_ulp(PyObject *module, PyObject *arg)
+{
+    PyObject *return_value = NULL;
+    double x;
+    double _return_value;
+
+    if (PyFloat_CheckExact(arg)) {
+        x = PyFloat_AS_DOUBLE(arg);
+    }
+    else
+    {
+        x = PyFloat_AsDouble(arg);
+        if (x == -1.0 && PyErr_Occurred()) {
+            goto exit;
+        }
+    }
+    _return_value = math_ulp_impl(module, x);
+    if ((_return_value == -1.0) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyFloat_FromDouble(_return_value);
+
+exit:
+    return return_value;
+}
+/*[clinic end generated code: output=9b51d215dbcac060 input=a9049054013a1b77]*/