simplified make_option/dest_option;
added make_variant/dest_variant -- usual representation of datatypes;
(* Title: Sequents/ROOT.ML
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1991 University of Cambridge
Classical Sequent Calculus based on Pure Isabelle.
*)
use_thys ["LK", "ILL", "ILL_predlog", "Washing", "Modal0", "T", "S4", "S43"];