Re: [Haskell-beginners] Could not deduce (Matrix m (Maybe a)) from the context (Matrix m a)

Ah, yes. That might be just what I'm after!

However, having a look, none of the methods in the class look like they depend on the actual type a, so it might be better to have

class Matrix m where    fromRows :: [[a]] -> m a    toList :: m a -> [a]    rows :: m a -> Integer    columns :: m a -> Integer    row :: m a -> Integer -> [a]    column :: m a -> Integer -> [a]    at :: m a -> Integer -> Integer -> a    (!!!) :: m a -> Integer -> Integer -> a    vicinityRows :: m a -> Integer -> Integer -> [[Maybe a]]    vicinityMatrix :: m a -> Integer -> Integer -> m (Maybe a)    -- No constraint needed!!    neighbours :: m a -> Integer -> Integer -> [a]