9 Jan
2007
9 Jan
'07
11:46 p.m.
Misha, This feels like you would compose dictionary types in heterogeneous lists and then have a type-driven lookup from the dictionary list; this would be very similar to the lookup operation for TICs in the HList lib, only that the driving type is of kind *->* and that the traversing instances eventually need to be constrained by the Sat constraint for the driving type. Do you think, this could work? Best, Ralf
f :: (Contains cxt ShowCxt) => Box cxt -> String f (Box a) = show a
The type is meant to say that the context of the box must contain Show as one of the classes. I would imagine the Contains class to be something like
class Contains cxt subCxt where subDict :: cxt a -> subCxt a