%	Domain knowledge for WARPLAN - stacking blocks.
%	execute using 'run!' - solves Sussman's anomoly.

add(on(U,W),	move(U,V,W)).
add(clear(V),	move(U,V,W)).

del(on(U,V),	move(U,V,W)).
del(clear(W),	move(U,V,W)).

can(move(U,V,floor),	on(U,V) & V /= floor & clear(U)).
can(move(U,V,W),	clear(W) & on(U,V) & U /= W & clear(U)).

imposs(on(X,Y) & clear(Y)).
imposs(on(X,Y) & on(X,Z) & Y /= Z).
imposs(on(X,X)).
imposs(on(X, Z) & on(Y, Z) & X /= Y).

always(X) :- X.

given(start,on(a,floor)).
given(start,on(b,floor)).
given(start,on(c,a)).
given(start,on(d,floor)).
given(start,on(e,d)).
given(start,clear(b)).
given(start,clear(c)).
given(start,clear(e)).

run:- plans(on(a, b) & on(b, c), start).