.. highlightlang:: us .. _nan: nan === .. index:: nan .. us.tag nan ENGLISH oldfunc Changed593 :ref:`nan` (Not a Number) returns the number 0/0. .. function:: r = nan() .. us.return **Return Value** *r* is 0/0. .. us.history **History** .. list-table:: :header-rows: 1 * - Version - Description * - 5.9.3 - This function is obsolete. .. seealso:: :ref:`isnan` :sub:`id-852090`