How to model functions in an object or a class diagram


I would like to know how Can I model a function in an object diagram.
In the diagram I have classes, instances and there are some helper functions that will do some operations on these instances. I could not find any function object to be used and there is only operations inside the classes but not as an independent object, so how can this be done in visual paradigm? thanks

If you use function style modeling or programming, you use operations as a name of functions and method as function procedures. For modeling a detailed function procedure you use an activity diagram (actions). See little more here: