@YueLiPicasso tutorial

[IgorErin]

• It feels like the wrong type (In tutorial / in OCanren)

• And what is the project and where should it come from (here, here and here) By the way, I couldn't run the example. Is it even correct?

• From time to time I encounter unification of both (==) and (===). What is it correct? There is only one option in the first chapter of the tutorial.

• I didn't find this type in Logic.mli.