action(move(R,From,To)):- rocket(R),place(From),place(To),From \== To.
action(unload(R,P,C)):- rocket(R),place(P),cargo(C).
action(load(R,P,C)):- rocket(R),place(P),cargo(C).
action(persists(P)):- proposition(P).


proposition(at(R,P)):- rocket(R),place(P).
proposition(at(C,P)):- cargo(C),place(P).
proposition(in(C,R)):- cargo(C),rocket(R).


precond(move(R,From,To),[at(R,From)]).
delEffects(move(R,From,To),[at(R,From)]).
addEffects(move(R,From,To),[at(R,To)]).

precond(unload(R,P,C),[at(R,P),in(C,R)]).
delEffects(unload(R,P,C),[in(C,R)]).
addEffects(unload(R,P,C),[at(C,P)]).

precond(load(R,P,C),[at(R,P),at(C,P)]).
delEffects(load(R,P,C),[at(C,P)]).
addEffects(load(R,P,C),[in(C,R)]).

precond(persists(P),[P]).
delEffects(persists(P),[]).
addEffects(persists(P),[P]).

rocket(r1).
rocket(r2).
place(a).
place(b).
cargo(c1).
cargo(c2).

init([at(c1,b),at(c2,a),at(r1,a),at(r2,a)]).

goal([at(c1,a),at(c2,b)]).