gh-141004: Document Py_RETURN_NAN and Py_RETURN_INF (GH-141029)

ZeroIntensity · skirpichev · web-flow · commit 5b02c6e920aa · 2025-11-05T17:00:26.000-05:00
Co-authored-by: Sergey B Kirpichev &lt;skirpichev@gmail.com&gt;
diff --git a/Doc/c-api/float.rst b/Doc/c-api/float.rst
@@ -78,6 +78,23 @@ Floating-Point Objects
    Return the minimum normalized positive float *DBL_MIN* as C :c:expr:`double`.
 
 
+.. c:macro:: Py_RETURN_NAN
+
+   Return :data:`math.nan` from a function.
+
+   On most platforms, this is equivalent to ``return PyFloat_FromDouble(NAN)``.
+
+
+.. c:macro:: Py_RETURN_INF(sign)
+
+   Return :data:`math.inf` or :data:`-math.inf <math.inf>` from a function,
+   depending on the sign of *sign*.
+
+   On most platforms, this is equivalent to the following::
+
+      return PyFloat_FromDouble(copysign(INFINITY, sign));
+
+
 Pack and Unpack functions
 -------------------------
 
