presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/isNaN
class MathFunctions:    @Description("test if value is not-a-number")
    @ScalarFunction("is_nan")
    @SqlType(StandardTypes.BOOLEAN)
    public static boolean isNaN(@SqlType(StandardTypes.DOUBLE) double num)
    {
        return Double.isNaN(num);
    }