% Blocks in our "block world" b3 b4 b7 blb5 b8 Block Stacking on (b1,b2) on (b3, b4) on (b4,b5) on (b5,b6) on (b7,b8) on (b8,b9) % stack order left (b2,b6) left (b6,b9) % Generalize "above" above (Above,Below):-on (Above,Below) above (Above, Below):- on (Above, AnyBlock), above (AnyBlock, Below). Show an implementation of leftof (X, Y) such that leftof (X, Y) resolves % to true if x is a block left of any block Y leftof (b1 ,b7) leftof (b2,b6) produces true leftof (b4,b5) produces false leftof (b9,b3) produces false findall (x, leftof (X,b8), 2) yields 2-[b3,b4,b5,b6,b1,b2] % For Example: produces true (in any order)