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Merged
norvig merged 4 commits into from
Sep 7, 2016
Merged

Planning #253

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fdcc55b
Minor docstring changes
opensourceware Aug 21, 2016
83e32c1
Added Spare Tire Problem
opensourceware Aug 21, 2016
d6b1946
Fixed a bug in substitute method of class Action
opensourceware Aug 21, 2016
1d257fd
Fixed minor typo in comment
opensourceware Aug 21, 2016
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51 changes: 47 additions & 4 deletions planning.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@

class PDLL:
"""
PDLL used to deine a search problem
PDLL used to define a search problem
It stores states in a knowledge base consisting of first order logic statements
The conjunction of these logical statements completely define a state
"""
Expand Down Expand Up @@ -61,7 +61,11 @@ def __call__(self, kb, args):

def substitute(self, e, args):
"""Replaces variables in expression with their respective Propostional symbol"""
new_args = [args[i] for x in e.args for i in range(len(self.args)) if self.args[i] == x]
new_args = list(e.args)
for num, x in enumerate(e.args):
for i in range(len(self.args)):
if self.args[i] == x:
new_args[num] = args[i]
return Expr(e.op, *new_args)

def check_precond(self, kb, args):
Expand Down Expand Up @@ -123,12 +127,51 @@ def goal_test(kb):
effect_rem = [expr("In(c, p)")]
unload = Action(expr("Unload(c, p, a)"), [precond_pos, precond_neg], [effect_add, effect_rem])

# Load
# Used used 'f' instead of 'from' because 'from' is a python keyword and expr uses eval() function
# Fly
# Used 'f' instead of 'from' because 'from' is a python keyword and expr uses eval() function
precond_pos = [expr("At(p, f)"), expr("Plane(p)"), expr("Airport(f)"), expr("Airport(to)")]
precond_neg = []
effect_add = [expr("At(p, to)")]
effect_rem = [expr("At(p, f)")]
fly = Action(expr("Fly(p, f, to)"), [precond_pos, precond_neg], [effect_add, effect_rem])

return PDLL(init, [load, unload, fly], goal_test)


def spare_tire():
init = [expr('Tire(Flat)'),
expr('Tire(Spare)'),
expr('At(Flat, Axle)'),
expr('At(Spare, Trunk)')]

def goal_test(kb):
required = [expr('At(Spare, Axle)'), expr('At(Flat, Ground)')]
for q in required:
if kb.ask(q) is False:
return False
return True

##Actions
#Remove
precond_pos = [expr("At(obj, loc)")]
precond_neg = []
effect_add = [expr("At(obj, Ground)")]
effect_rem = [expr("At(obj, loc)")]
remove = Action(expr("Remove(obj, loc)"), [precond_pos, precond_neg], [effect_add, effect_rem])

#PutOn
precond_pos = [expr("Tire(t)"), expr("At(t, Ground)")]
precond_neg = [expr("At(Flat, Axle)")]
effect_add = [expr("At(t, Axle)")]
effect_rem = [expr("At(t, Ground)")]
put_on = Action(expr("PutOn(t, Axle)"), [precond_pos, precond_neg], [effect_add, effect_rem])

#LeaveOvernight
precond_pos = []
precond_neg = []
effect_add = []
effect_rem = [expr("At(Spare, Ground)"), expr("At(Spare, Axle)"), expr("At(Spare, Trunk)"),
expr("At(Flat, Ground)"), expr("At(Flat, Axle)"), expr("At(Flat, Trunk)")]
leave_overnight = Action(expr("LeaveOvernight"), [precond_pos, precond_neg], [effect_add, effect_rem])

return PDLL(init, [remove, put_on, leave_overnight], goal_test)