[Haskell-cafe] Re: I just don't get it (data structures and OO)

[Donald Bruce Stewart]

apfelmus:
> Phlex wrote:
> > Donald Bruce Stewart wrote:
> >>
> >> 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.
> > 
> > That's precisely the thing i don't understand.
> > In order to update node 3 with a new pointer, i need to mutate it, so i
> > need to recreate it, and so on up to node 1.
> 
> Yes, that's correct, I think Dons shared a bit too much here :)

Spent too much time with zippers lately ;)

-- Don