[Haskell-cafe] Reconstructing a tree from a list of its paths (to leaves)

Twan van Laarhoven twanvl at gmail.com
Tue Apr 10 12:26:34 CEST 2012

On 10/04/12 09:55, Arnaud Bailly wrote:
> Hello,
> I am manipulating labeled multiway trees, some kind of "lightweight"
> XML notation. One thing I would like to be able to do is manipulating
> a tree as a list of (Path, Value). Generating such a list is easy but
> I am a little bit surprised to find it harder to reconstruct a tree,
> given such a list assuming some sensible properties (list is ordered,
> for example).
> I got the intuition this has already been tackled in one way or
> another in a functional setting in Haskell (I code in Java but using
> mostly functional constructs), but don't know where to look.

The haskell solution would be to consider first how to turn a single 
(Path,Value) into a tree. Then you just combine these trees for all the 
paths by taking their union. I attached some code.

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