On Sat, Aug 15, 2009 at 5:12 PM, Ian Duncan
Hello all,
I'm trying to build a function that takes a string such as "123" and gives me permutations including permutations with lesser list lengths. I'm not sure how to phrase it, but here is what the output could look like:
foo "123" => ["123","213","321","231","312","132", "12", "13", "21", "23", "31", "32", "1", "2", "3", ""]
The ordering doesn't matter, and that null list at the end doesn't particularly matter, but I don't really know the mathematical phrasing of what I'm asking for. I'm trying to build a scrabble helper that can find the optimal score given a set of letters to work with.
Thanks for your help,
Ian Duncan _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners
Import Data.List, then the function you want is concatMap permutations . subsequences subsequences returns a list of all subsequences of the original list in order. permutations returns a list of all possible orderings of the list. concatMap applies permutations to every member of the subsequence list and then flattens the list down to a single list again. Hope that helps, Alex