This is useful for making easy and human to write definition files for whatever use. For example, lets say you are writing a simulator and you need an easy, human way to define parts about a given world like light sources, obstacles, and dimensions. see the discussion for this example fleshed out in code.
Python, 13 lines
For the example above, You might write something like the following:
If you were to then call something like World(file) in the runtime of your program where file is as follows:
dimensions(4, 5) newlightsource(1, 2) newlightsource(2, 3) newobstacle(0, 1)
You will end up with an instance of class World with the appropriate data, thus it is simple to create new ways to specify data for your program