ex/PL0.ML

minor cleanup, added 'axclass', 'instance', 'syntax', 'defs' sections;

(*  Title: 	HOL/ex/pl0.ML
    ID:         $Id$
    Author: 	Tobias Nipkow
    Copyright   1994  TU Muenchen

Inductive definition of propositional logic formulae.
*)

structure PL0 = DeclaredDatatype
(val base = PL0.thy
 val data = "'a pl = false | var('a) | \"op->\"('a pl,'a pl)"
);