Hi, I've just begun experimenting with Haskell, and I'm having a lot of fun, but my first semi-serious program is in need of some optimization, and based on the results of profiling I think a really good start is to memoize one particular function which is called many, many times (and currently consumes over 80% of the program run time). The function takes a two-dimensional range and a location within that range and returns a list of the locations vertically and horizontally adjacent to that location and within the bounds type Bounds = ((Int,Int),(Int,Int)) type Location = (Int,Int) adjacentCells :: Bounds -> Location -> [Location] adjacentCells bounds (col, row) = filter valid cells where valid loc = inRange bounds loc neighborLoc' = [(col-1,row),(col+1,row),(col,row-1),(col,row+1)] The ranges are fairly small -- certainly no more than 10x10, and each location has an associated list of at most 4 neighbors (edge locations have less). During a given run of the program, the bounds are fixed. So, any tips on how I can memoize this function? I have read the Memoization page on the wiki, and I understand (I think) the recursive memoization section, but it's not clear to me how to apply that approach. Section one on non-recursive memoization seems like what I want, but I don't understand the section and the links provided haven't shed any light for me. The section uses the following notation to describe how to construct a map to be used to hold the keys and values: Map () b := b Map (Either a a') b := (Map a b, Map a' b) Map (a,a') b := Map a (Map a' b) but I'm not sure what that notation is. It's not Haskell code, I don't think. Any and all suggestions appreciated. Thanks, Shawn.