On Sun, Sep 9, 2012 at 1:46 AM, Milan Straka <f...@ucw.cz> wrote: > Hi all, > > is there any way to perform a destructive update on a plain ADT? > Imagine I have a simple > data Tree a = Nil | Node a (Tree a) (Tree a) > I would like to be able to modify right subtree of an existing tree. > > I can do that for example when using IORefs by changing the datatype to > data Tree a = Nil | Node a (IORef (Tree a)) (IORef (Tree a)) > and use unsafePerformIO + writeIORef. But the IORefs cause additional > complexity when working with the data type. > > > At the moment I am interested in any GHC solution, be it non-portable or > version specific. I would like just to run some benchmarks and see the > results. > > Cheers, > Milan
You can do it if you refer to the children using Array#s. That's what I do in unordered-containers to implement a more efficient fromList. For arbitrary field types I don't think there's a way (although it would be useful when birthing persistent data structures). -- Johan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
