acme-omitted: purely functional omitted content for Haskell

Standard Haskell lacks the ability to express the notion of "omitted content", making it impossible to distinguish the truly "undefined" and the merely "omitted".

acme-omitted provides

• a universal definition of "omitted"; and
• functions to observe the difference between omitted and undefined.

The library is standards-compliant, type-safe, and user-friendly.