[Haskell-beginners] 2 Questions: mutable data and copying results

[Daniel Fischer]

On Tuesday 17 August 2010 16:08:49, C Gosch wrote:
> >
> > Since the graph is immutable most of the nodes in the new graph are
> > shared with nodes in the old graph. This is know as path copying and
> > is everywhere persistent ("immutable") data structures are used.
> > Updating a data structure (e.g. a tree) typically requires O(log n)
> > nodes to be copied.
>
> So that means the compiler figures this out for my own data structures,
> or do I have to take care that copying is done this way?
> Sorry for my ignorance, I'm still learning :)

It's done automatically (and, if your nodes contain huge data, you'll be 
happy to learn tha the data isn't copied at all, only the pointers to it).