On Fri, Sep 03, 2010 at 11:21:27AM -0400, Tom Murphy wrote:
I am not sure I understand what you are asking. Do you want something like this?
data Range = Range Integer Integer
toRanges :: [Integer] -> [Range] toRanges = ...
toRanges should not be too hard to write but nothing like that exists as far as I know.
I don't quite understand the functionality of toRanges. When I say "range," I mean a list containing an enumeration, in the form:
[2..300]
[2..300] is just syntactic sugar for the list [2,3,4,5,6,7,8,9,......,300]. It isn't actually a real "thing" in Haskell. That's why I made a new data type to represent it: data Range = Range Integer Integer toList (Range x y) = [x..y] So for example (Range 2 300) represents the list [2..300].
The record would actually be coming from an SQL database. I would like to be able to store a large list in SQL records, without having to store every element.
I see. So the question seems more about database design than about Haskell. Toby has suggested a more relational way to model the data, but his solution does end up storing every element. But you could do something more like CREATE TABLE tv_show ( id INTEGER NOT NULL, -- etc title VARCHAR(80), PRIMARY KEY (id) ); CREATE TABLE episode_ranges ( tv_show_id INTEGER NOT NULL, start_episode INTEGER, end_episode INTEGER PRIMARY KEY (tv_show_id, start_episode) ); Or something like that (it's been a while since I've used SQL). The data would then be more like tv_show (30, "The Simpsons") episode_ranges (30,1,4), (30,14,14), (30,18,21), (30,23,25) -Brent