Scott Turner wrote:
It's a valid approach. Rather than declare an Updateable class, I'd just have the update function be a parameter of ins_in_tree. Also, the key and value types can be independent parameters of BinTree.
I started to refactor my code as you suggested. I inserted update function in the middle of parameter list of ins_in_tree function. Just because this order seemed to be logical to me. ins_in_tree :: (Ord a) => BinTree a -> (a->a) -> a -> BinTree a But soon I found that i need partial parametrization in order to rewrite old ins_list: ins_list lst = foldl ins_in_tree Leaf (map wrap lst) So i had to change parameter order in ins_in_tree: ins_in_tree :: (Ord a) => (a->a) -> BinTree a -> a -> BinTree a and then wrote: ins_list lst = foldl (ins_in_tree update_stat) Leaf (map wrap lst) update_stat (Word_stat s i) = Word_stat s (i+1) That worked, but what if i would need another order somethere further? Will I have to write some kind of wrapper like ins_in_tree' a b c = ins_in_tree b a c Does better solution exist?