adjust nested data structure

nested_data_structure.hs

module Test where

import qualified Data.Vector as V
import qualified Data.HashMap.Strict as M
import Data.Hashable (Hashable)

type MyData k v = V.Vector (M.HashMap k v)

adjustVec :: Int -> (a -> a) -> V.Vector a -> V.Vector a
adjustVec ix f vec =
    let v = vec V.! ix
    in  vec V.// [(ix, f v)]

modify :: (Eq k, Hashable k) => Int -> k -> v -> MyData k v -> MyData k v
modify idx k v = adjustVec idx (M.insert k v)