Issue 23229: add cmath.inf, cmath.nan, cmath.infj and cmath.nanj.

Doc/library/cmath.rst

@@ -259,6 +259,34 @@ Constants
 
    .. versionadded:: 3.6
 
+.. data:: inf
+
+   Floating-point positive infinity. Equivalent to ``float('inf')``.
+
+   .. versionadded:: 3.6
+
+.. data:: infj
+
+   Complex number with zero real part and positive infinity imaginary
+   part. Equivalent to ``complex(0.0, float('inf'))``.
+
+   .. versionadded:: 3.6
+
+.. data:: nan
+
+   A floating-point "not a number" (NaN) value.  Equivalent to
+   ``float('nan')``.
+
+   .. versionadded:: 3.6
+
+.. data:: nanj
+
+   Complex number with zero real part and NaN imaginary part. Equivalent to
+   ``complex(0.0, float('nan'))``.
+
+   .. versionadded:: 3.6
+
+
 .. index:: module: math
 
 Note that the selection of functions is similar, but not identical, to that in