possible

Three valued Data.Maybe

https://github.com/tolysz/possible

Latest on Hackage:0.1.0.6

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BSD-3-Clause licensed by Marcin Tolysz
Maintained by [email protected]

Maybe lacks the information if Nothing represents missing or empty value. The idea is to have http://en.wikipedia.org/wiki/Three-valued_logic for values. Depends on Aeson having missing value.