Christian Maeder wrote:
If anyone is off tweaking the Data.Map library, I have a simple request (which I sometimes end up implementing in hacked up versions of Data.Map). There should be some way to extract an implicitly defined interval from the map, i.e.
interval :: (k -> v -> Ordering) -> Map k v -> Map k v
I'm not quite sure what you are asking for here. Why does the first argument take both a key and a value, and what is the Ordering saying? From your description I was expecting something more like: interval :: k -> k -> Map k v -> Map k v Are you saying that if the Ordering is "EQ" then the key is within the range? Take a look at my Ranged Sets library (on Hackage) for a complete treatment of the concept of ranges within an ordered type. I can imagine something like rangedSetMap :: RSet k -> Map k v -> Map k v where the resulting Map only contains the keys that are in the RSet. At present you would have to do that by iterating through the Map, but I can imagine a more efficient method. Alternatively the Boundary type defined in that library might be used: it splits an ordered type into values above and below a boundary. (Two Boundary values make a Range, and an ordered list of non-overlapping Ranges is an RSet). Paul.