-- Smith, Ramsey, Holloway - PLDI 2004.
--
type Triv k cls color
- = cls -- ^ the class of the node we're trying to color.
- -> UniqSet k -- ^ the node's neighbors.
- -> UniqSet color -- ^ the node's exclusions.
+ = cls -- the class of the node we're trying to color.
+ -> UniqSet k -- the node's neighbors.
+ -> UniqSet color -- the node's exclusions.
-> Bool