Wumpus

Copperbox revision 924.

I've implemented hspace and vspace combinators for the picture language. Their implementation justifies adding Blank as a picture constructor.

The following simple definition of hspace is invalid:

-- > hspace n a b = a ->- (moveH n b)

The movement due to moveH n is annulled by the (->-) operator which moves relative to the bounding box. Somehow changing the bounding box of picture b seems more complicated than sandwiching a blank picture between them:

-- > hspace n a b = a ->- blankH n ->- b