Cleaned up with hlint.
Fixed type inconsistency.
Separated domain definitions.
Use Domain instead of Set explicitly.
Fixed to use lazy ST monads.
Do not depend representation of Domain in tests.
Add a test for laziness of FD monad.
Reorganize import lists.
Add tests.
Modify comments.
Refactoring

Wrap FD monad with newdata.
Refactor lifting.
Stylished with stylish-haskell
Stylished
Merge pull request #21 from notae/wip/tests

Fixed to use lazy ST monads and cleaned up