>>22
That's cool, but sometimes you need to know more about the data in the input parameters. You might need to know the number of inversions in an array, together with its length for example. Or the number of overlapping polygons in a quad tree, and maybe some extra information about their positions. In cases like that, it is less intuitive to work with a function defined only on the natural numbers, although you could do it indirectly by encoding the discrete structures as natural numbers.