I've think I've updated AdvanceGraphic to work with the new Image types - as it needs Displacement to work I haven't been able to test it. The code is somewhat strange as I've had to build a special binding combinator for Images. Images cannot support return as there is no empty Primitive - images are like writer except they are a semigroup on the logging answer rather than a monoid. So while its possible to implement bind, it is not so useful as a combinator - it can only consume initial input, it can't reuse it. Thus I've had to make "opbind", which is essentially:
opbind op gf fn = let a = run gf in let b = run (fn a) in a `op` b
Update - I've worked out a scheme to get back monadic return and bind by changing the representation of primitives in Wumpus-Basic to make them a monoid rather than a semigroup. However I won't implement it until I've changed Displacement and PosImage to use the new Image types.
