[Haskell-cafe] Help wanted: Lazy multiway zipper with mismached intervals

Rene de Visser rene_de_visser at hotmail.com
Tue Sep 27 10:42:40 EDT 2005

Many thanks to all for the replies
>From: ChrisK <chrisk at MIT.EDU>

>Could the interval for element x of List xList overlap with more than
>one element of another list?  It does not matter too much, but is
>something you did not clarify.  In general, how may the intervals for
>all the lists overlap?  (The answer may be too complex, in which case
>you can just ignore me).

Yes, unlimited overlap is possible. e.g. Infinite interval in one list, and 
infinitely many small intervals in another list.

>I would start by merging, perhaps in stages, into an intermediate list
>with elements of its own "data FooIntermediate = A _ [_]| B  _ [(_,_)] |
>C _ _ _ | ..." types.
Yes, I'll probably use this suggestion, maybe with records to make partial 
update easier.

>If you need to change the semantics of merging the streams then it may
>help when you refactor that the types of events are now types of
>constructors and the compiler is checking your code.
Originally I had thought that I could treat the merge symetrically, but I 
now think this is not the case. Still I am not sure if I will use different 
types for different types of merge.


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