Added implementation of the cake problem, tests for cake and three towers problem (aimacode#265)

* Added implementation of the cake problem

* Added test for three_block_tower and fixed a bug in three_block_tower code

Author: opensourceware

planning.py

@@ -175,7 +175,7 @@ def goal_test(kb):
     leave_overnight = Action(expr("LeaveOvernight"), [precond_pos, precond_neg], [effect_add, effect_rem])
 
     return PDLL(init, [remove, put_on, leave_overnight], goal_test)
-    
+
 def three_block_tower():
     init = [expr('On(A, Table)'),
             expr('On(B, Table)'),
@@ -195,18 +195,44 @@ def goal_test(kb):
 
     ## Actions
     #  Move
-    precond_pos = [expr('On(b, x)'), expr('Clear(b)'), expr('Clear(y)'), expr('Block(b)'),
-                   expr('Block(y)'), expr('b != x'), expr('b != y'), expr('x != y')]
+    precond_pos = [expr('On(b, x)'), expr('Clear(b)'), expr('Clear(y)'), expr('Block(b)'), expr('Block(y)')]
     precond_neg = []
     effect_add = [expr('On(b, y)'), expr('Clear(x)')]
     effect_rem = [expr('On(b, x)'), expr('Clear(y)')]
     move = Action(expr('Move(b, x, y)'), [precond_pos, precond_neg], [effect_add, effect_rem])
 
     #  MoveToTable
-    precond_pos = [expr('On(b, x)'), expr('Clear(b)'), expr('Block(b)'), expr('b != x')]
+    precond_pos = [expr('On(b, x)'), expr('Clear(b)'), expr('Block(b)')]
     precond_neg = []
     effect_add = [expr('On(b, Table)'), expr('Clear(x)')]
     effect_rem = [expr('On(b, x)')]
     moveToTable = Action(expr('MoveToTable(b, x)'), [precond_pos, precond_neg], [effect_add, effect_rem])
 
     return PDLL(init, [move, moveToTable], goal_test)
+
+def have_cake_and_eat_cake_too():
+    init = [expr('Have(Cake)')]
+
+    def goal_test(kb):
+        required = [expr('Have(Cake)'), expr('Eaten(Cake)')]
+        for q in required:
+            if kb.ask(q) is False:
+                return False
+        return True
+
+    ##Actions
+    # Eat cake
+    precond_pos = [expr('Have(Cake)')]
+    precond_neg = []
+    effect_add = [expr('Eaten(Cake)')]
+    effect_rem = [expr('Have(Cake)')]
+    eat_cake = Action(expr('Eat(Cake)'), [precond_pos, precond_neg], [effect_add, effect_rem])
+
+    #Bake Cake
+    precond_pos = []
+    precond_neg = [expr('Have(Cake)')]
+    effect_add = [expr('Have(Cake)')]
+    effect_rem = []
+    bake_cake = Action(expr('Bake(Cake)'), [precond_pos, precond_neg], [effect_add, effect_rem])
+
+    return PDLL(init, [eat_cake, bake_cake], goal_test)

tests/test_planning.py

@@ -46,3 +46,26 @@ def test_spare_tire():
         p.act(action)
 
     assert p.goal_test()
+
+def test_three_block_tower():
+    p = three_block_tower()
+    assert p.goal_test() is False
+    solution = [expr("MoveToTable(C, A)"),
+                expr("Move(B, Table, C)"),
+                expr("Move(A, Table, B)")]
+
+    for action in solution:
+        p.act(action)
+        
+    assert p.goal_test()
+
+def test_have_cake_and_eat_cake_too():
+    p = have_cake_and_eat_cake_too()
+    assert p.goal_test() is False
+    solution = [expr("Eat(Cake)"),
+                expr("Bake(Cake)")]
+
+    for action in solution:
+        p.act(action)
+
+    assert p.goal_test()