blocks world augmented with probabilistic faststack operator

(operator pickup
  (params (<x> OBJECT))
  (preconds (clear <x>) (on-table <x>) (arm-empty))
  (effects (1.0 (del (on-table <x>)) (del (clear <x>)) (del (arm-empty))
		(add (holding <x>)))))

(operator putdown
  (params (<x> OBJECT))
  (preconds (holding <x>))
  (effects (1.0  (add (clear <x>)) (add (arm-empty)) (del (holding <x>))
		(add (on-table <x>)))))

(operator faststack
  (params (<x> OBJECT) (<y> OBJECT))
  (preconds (clear <x>) (clear <y>) (on-table <x>) (arm-empty))
  (effects (0.7 (del (on-table <x>)) (add (on <x> <y>)) (del (clear <y>)))
	   (0.3)))

(operator stack
  (params (<x> OBJECT) (<y> OBJECT))
  (preconds (clear <y>) (holding <x>))
  (effects (1.0 (add (arm-empty)) (add (clear <x>)) (add (on <x> <y>))
		(del (holding <x>)) (del (clear <y>)))))

(operator unstack
  (params (<x> OBJECT) (<y> OBJECT))
  (preconds (on <x> <y>) (clear <x>) (arm-empty))
  (effects (1.0 (add (holding <x>)) (add (clear <y>))
		(del (on <x> <y>)) (del (clear <x>)) (del (arm-empty)))))