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Working HW2 #2 extra after review in class #14

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40 changes: 40 additions & 0 deletions hw02/homework2.py
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Original file line number Diff line number Diff line change
Expand Up @@ -291,6 +291,46 @@ def substitute (self,id,new_e):
self._e2.substitute(id,new_e))


class ECache (Exp):
def __init__ (self, e):
self._e = e
self._v = None

def eval (self, prim_dict, fun_dict=FUNC_DICT):
if self._v == None:
self._v = self._e.eval(prim_dict)
return self._v

def substitute (self, id, new_e):
self._e.substitute(id, new_e)
return self


class ELetN (Exp):
# "memoized" local binding

def __init__ (self, id, e1, e2):
self._id = id
self._e1 = ECache(e1)
self._e2 = e2

def __str__ (self):
return "ELetN({},{},{})".format(id, self._e1, self._e2)

def eval(self, prim_dict, fun_dict=FUNC_DICT):
new_e2 = self._e2.substitute(self._id, self._e1)
return new_e2.eval(prim_dict)

def substitute (self, id, new_e):
if id == self._id:
return ELetN(self._id,
self._e1.substitute(id,new_e),
self._e2)
return ELetN(self._id,
self._e1.substitute(id,new_e),
self._e2.substitute(id,new_e))


class EId (Exp):
# identifier

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12 changes: 12 additions & 0 deletions hw02/homework2_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,18 @@ def test_ELetS(self):
("b",EId("a"))],
EPrimCall("-",[EId("a"),EId("b")]))).expand().eval(INITIAL_PRIM_DICT).value, 0)

def test_ELetN(self):
self.assertEqual(ELetN("a",EInteger(10),EId("a")).eval(INITIAL_PRIM_DICT).value, 10)
self.assertEqual(ELetN("a",EInteger(10),
ELetN("b",EInteger(20),EId("a"))).eval(INITIAL_PRIM_DICT).value, 10)
self.assertEqual(ELetN("a",EInteger(10),
ELetN("a",EInteger(20),EId("a"))).eval(INITIAL_PRIM_DICT).value, 20)
self.assertEqual(ELetN("a",EPrimCall("+",[EInteger(10),EInteger(20)]),
ELetN("b",EInteger(20),EId("a"))).eval(INITIAL_PRIM_DICT).value, 30)
self.assertEqual(ELetN("a",EPrimCall("+",[EInteger(10),EInteger(20)]),
ELetN("b",EInteger(20),
EPrimCall("*",[EId("a"),EId("a")]))).eval(INITIAL_PRIM_DICT).value, 900)

def test_EDef(self):
EDef("add1", ["x"], EPrimCall("+", [EInteger(1), EId("x")])).eval(INITIAL_PRIM_DICT)
EDef("add2", "x", EPrimCall("+", [EInteger(2), EId("x")])).eval(INITIAL_PRIM_DICT)
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