memo-map

Utility for memoizing an effectful function (e.g. database query) using a map.

Example

import MemoMap

For demonstration, a silly little function that performs an effect and returns a value:

f :: Int -> IO Int
f x = do
  putStrLn ("f " <> show x)
  pure (x * 10)

If f may be applied to the same argument repeatedly, perhaps it would be advantageous to save the results from a previous application rather than repeating the action.

Create a MemoMap

Turn f into a MemoMap.

  mm <- newMemoMap f

Use the memoized function

Use runMemoMap mm instead of f to run a memoized version of f.

  print =<< runMemoMap mm 2
  print =<< runMemoMap mm 2
  print =<< runMemoMap mm 3

Output:

f 2
20
20
f 3
30

Inspect the cache

You can also use getMemoMap to inspect the stored values.

  print =<< getMemoMap mm

Output:

fromList [(2,20),(3,30)]

CHANGELOG | LICENSE