Spaces replaced by tabs (like in the other modules).
starting csp alg. implementation
tabs instead of repeated spaces
addEdgeConstraint
Digraph now exports Digraph data constructor
TypedDigraph imports Data.Map
Match imports List (for 'find'); removed rewrite from Match.hs
corrected inconsistences
rewritten with foldM and expanded
save

before separating constraint constructors from addEdgeConstraint
major rewrite of Match.hs
major clean up in Match.hs
Match shouldn't rely on details from Digraph.hs

some functions in Match.hs relied on the internal definitions
from other Modules; particulary there were some pattern matches
over Edge and Digraph structures. They were changed to call
appropriated functions (source, target) over those structures.