CODEWITHSUNDEEP
haskelldictionary
AdelNick
AdelNick

Reputation: 993

modifying Map of Maps in Haskell

What would be a proper way of working with a map of maps in Haskell? Assuming that I want to have something like

import qualified Data.Map as M

type Key1   = String
type MyMap1 = M.Map Key1 Int
type Key    = String
type MyMap  = M.Map Key MyMap1

how am I supposed to implement the function which adds elements into the map? The best I can think of is

addE :: Key -> Key1 -> Int -> MyMap -> MyMap
addE k k1 v = M.insertWith M.union k (M.singleton k1 v)

but M.union gives me O(n) complexity instead of expected O(log n)

Is there a better way to do this or another data structure that should be used instead?

Upvotes: 2

Views: 252

Answers (1)

Louis Wasserman
Louis Wasserman

Reputation: 198211

addE :: Key -> Key1 -> Int -> MyMap -> MyMap
addE k k1 v = M.alter (Just . M.insert k1 v . fromMaybe M.empty) k

Upvotes: 3

Related Questions