Two parameter memoization in Haskell

Question

I\'m trying to memoize the following function:

gridwalk x y
    | x == 0 = 1
    | y == 0 = 1
    | otherwise = (gridwalk (x - 1) y) + (gridwalk x (y - 1))
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Answer 1

Use the data-memocombinators package from hackage. It provides easy to use memorization techniques and provides an easy and breve way to use them:

import Data.MemoCombinators (memo2,integral)

gridwalk = memo2 integral integral gridwalk' where
  gridwalk' x y
    | x == 0 = 1
    | y == 0 = 1
    | otherwise = (gridwalk (x - 1) y) + (gridwalk x (y - 1))