GridSearch.hs

dim mat = (length mat, length (head mat))

subMats mat (height, width) =
    [trimmed | r <- [0..rows]
      , c <- [0..columns]
      , let vertTrimmed = take height (drop r mat)
            trimmed = map (take width . drop c) vertTrimmed
      , length trimmed == height
      , length (head trimmed) == width]
    where (rows, columns) = dim mat

matContains mat p = elem p subs
    where subs = subMats mat $ dim p