Phlex:
Hello all,
I'm coming from the OO world, and there's something i don't quite understand in the way haskellers manipulate data (as all functional programmers i guess).
Let's say i have a deep nested data structure. Universe containing galaxies, containing solar systems, containing planets, containing countries, containing inhabitants, containing ...whatever.
Using the OO paradigm, once i get a reference to an inhabitant, i can update it quite easily (say by changing it's age), and that's the end of it.
On the other side, using the functional paradigm, it seems to me that the function i use in order to create a _new_ inhabitant with a different age will need to have knowledge of the country over it, the planet ..and so on up to the universe...as i need to update all these structures to reflect the change. This is pretty bad and most probably doesn't need to be like this.
So here I am hoping for you all to give me some pointers on how this is done "the functional way".
Nope, its not done like that. You share as much of the original structure as you can, as a general principle. Imagine updating a node in a tree by just detaching and reattaching a pointer. [1] [1] / \ / \ [2] [3] update node 5 [2] [3] / \ with value 7 / \ [4] [5] [4] * and share the rest of the structure. Since the rest isn't mutable anyway, you can share all over. -- Don