[Haskell-cafe] Suitable structure to represents lots of similar lists

Dan Piponi dpiponi at gmail.com
Wed Apr 7 18:22:48 EDT 2010

I have a situation where I have a bunch of lists and I'll frequently
be making new lists from the old ones by applying map and filter. The
map will be applying a function that's effectively the identity on
most elements of the list, and filter will be using a function that
usually gives True. This means that there is potential for a large
amount of sharing between these lists that could be exploited,
something that ordinary lists would do badly. Does anyone have a
recommendation for a pure functional data structure for this case?

(It reminds me a bit of my own antidiagonal type, but that's not well
adapted to the highly dynamic situation I'm describing.)

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