Module Reason_graph.Reason

module Reason: Datatype.S_with_collections 
  with type t = PdgTypes.Node.t * PdgTypes.Node.t * reason_type

Reasons for impact are expressed as sets (n', n, reason)

include Datatype.S

module Set: Datatype.Set  with type elt = t

module Map: Datatype.Map  with type key = t

module Hashtbl: Datatype.Hashtbl  with type key = t