/* Domain: objects are not equivalent, some of them (frozen) are to be 
	   taken as late as possible.
*/

(define (domain briefcase)
(:requirements :typing )
(:types normal frozen - obj)
(:fluents (atRobby ?x - loc)	
	(at ?x - obj ?l -loc)	
	(in ?x - obj) )
(:static (normal ?x - obj)(frozen ?x - obj))
(:constants (home - loc))

(:theory (forall (?x - frozen)(frozen ?x))
         (forall (?x - normal)(normal ?x)))
	
(:action go
	:parameters (?from ?to - loc)
	:precondition (atRobby ?from)
	:effect (atRobby ?to) (not(atRobby ?from))
	:only-if ; either go to the robot's destination
                 ; or go to a place where an object can be taken
                 ; or dropped
		 (or (exists (?x - obj) 
			  (and (initially (at ?x ?to))(at ?x ?to)))
		     (exists (?x - obj) 
			  (and (goal (at ?x ?to))(in ?x)))
		     (goal (atRobby ?to)) )
		; move from home or from a place where initially
                ; there is something or something has to be dropped
		(or (exists (?x - obj)(initially (at ?x ?from)))
		    (exists (?x - obj)(goal(at ?x ?from)))
		    (initially (atRobby ?from))) 
	:next ; either do something in the place where you get
              ; or there is nothing left to do
	  (or 
	    (exists (?x - obj)
		(or (take ?x ?to)(drop ?x ?to)))
	    (forall (?x - obj ?y -loc)
		    (implies (goal(at ?x ?y)) (at ?x ?y)))) )
	            
(:action take
	:parameters (?x - obj ?room - loc)
	:precondition (atRobby ?room)(at ?x ?room)
	:effect (in ?x)(not(at ?x ?room))
	:only-if (initially(at ?x ?room)) (not(goal(at ?x ?room)))
               ; if x is normal, then 
               ; there are no frozen objects in the briefcase
	       (implies (normal ?x)
                    (or (exists (?y - frozen)(take ?y ?room))
	                (forall (?y - frozen)(not(in ?y)))))
	:s-asap )

(:action drop
	:parameters (?x - obj ?room -loc)
	:precondition (in ?x)(atRobby ?room)
	:effect (not(in ?x)) (at ?x ?room)
	:only-if (goal(at ?x ?room))
             ; drop all objects together in the room
             ; i.e. do not go, take, drop here several times
		(forall (?y - obj)
		  (implies(goal(at ?y ?room))(in ?y)))
	:s-asap )
)