Shen (in particular its type system) is an executable Sequent Calculus system [0] written with a small portable lisp. This derives from a propositional logic system, not H-M over typed lambda calculus.<p>[0] - <a href="http:&#x2F;&#x2F;www.shenlanguage.org&#x2F;learn-shen&#x2F;types&#x2F;types_sequent_calculus.html" rel="nofollow">http:&#x2F;&#x2F;www.shenlanguage.org&#x2F;learn-shen&#x2F;types&#x2F;types_sequent_c...</a>