is_nan Finds whether a value is not a number &reftitle.description; boolis_nan floatval Checks whether val is 'not a number', like the result of acos(1.01). &reftitle.parameters; val The value to check &reftitle.returnvalues; Returns &true; if val is 'not a number', else &false;. &reftitle.examples; ]]> &example.outputs; &reftitle.seealso; is_finite is_infinite