mainloop: Change the code such that the main loop is able to count up and down

[seletz]

Problem

The main loop currently can either count up or down, depending on the if in the mainloop function.

That's not good. We want the main loop to work in both cases.

Requirements

The main loop must work with all combinations of start, increment and stop parameters. You may -- for now -- ignore pathological cases.

Deliverable

• Working code
• Documented Function
• Test examples

  Hints

For the second task:

• You will need to pass more than one parameter to the new function
• You will need to return something from the new function

  Tasks

• [x] Change the code in the main loop which tests if the loop should stop
• [x] Extract ("refactor") the code such that the decision to stop is made in a function called ist_simulation_fertig. See the hints