Daniel@0: /* Part of DML (Digital Music Laboratory)
Daniel@0: 	Copyright 2014-2015 Samer Abdallah, University of London
Daniel@0: 	 
Daniel@0: 	This program is free software; you can redistribute it and/or
Daniel@0: 	modify it under the terms of the GNU General Public License
Daniel@0: 	as published by the Free Software Foundation; either version 2
Daniel@0: 	of the License, or (at your option) any later version.
Daniel@0: 
Daniel@0: 	This program is distributed in the hope that it will be useful,
Daniel@0: 	but WITHOUT ANY WARRANTY; without even the implied warranty of
Daniel@0: 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
Daniel@0: 	GNU General Public License for more details.
Daniel@0: 
Daniel@0: 	You should have received a copy of the GNU General Public
Daniel@0: 	License along with this library; if not, write to the Free Software
Daniel@0: 	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
Daniel@0: */
Daniel@0: 
Daniel@0: :- module(state, [set_state/2, get_state/2, with_state/3, retract_state/1]).
Daniel@0: 
Daniel@0: :- meta_predicate
Daniel@0:       with_state(:,+,0),
Daniel@0:       retract_state(:),
Daniel@0:       set_state(:,+),
Daniel@0:       get_state(:,-).
Daniel@0: 
Daniel@0: :- use_module(insist).
Daniel@0: :- dynamic state/3.
Daniel@0: 
Daniel@0: get_state(M:Key,Value) :- state(M,Key,Value).
Daniel@0: set_state(M:Key,Value) :-
Daniel@0:    retractall(state(M,Key,_)),
Daniel@0:    assert(state(M,Key,Value)).
Daniel@0: 
Daniel@0: with_state(M:Key,Value,Goal) :-
Daniel@0:    insist(\+state(M,Key,_),state_exists(M:Key)),
Daniel@0:    setup_call_cleanup( 
Daniel@0:       assert(state(M,Key,Value)), Goal,
Daniel@0:       retract_state(M:Key)).
Daniel@0: 
Daniel@0: retract_state(M:Key) :- retractall(state(M,Key,_)).
Daniel@0: 
Daniel@0: