haskell - Why there's not mapKeys in Data.Hashmap? -


i want use function such mapkeys map on keys. there namely function mapkeys in data.map, no analogues in data.hashmap. moreover, in data.hashmap have found nothing manipulating keys. there incompleteness of data.hashmap module or exists ideological reasons don't it?

a hashmap achieves performance determining location of value applying hash function on key. mapping on keys involve pulling each element out of map , reinserting using hash of new key. doable, of course, quite lot of work, , possibly best avoided.


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