pro3 solved

Author: yyl

unit4/pro3.py

@@ -0,0 +1,39 @@
+'''
+Consider the Polynomial class given in Program . Implement a method that computes the value of a polynomial, say p(x), for a given value of x. Hint: Use a visitor that visits all the terms in the polynomial and accumulates the result.
+'''
+
+from opus7.polynomialAsOrderedList import PolynomialAsOrderedList
+from opus7.visitor import Visitor
+
+class MyPoly(PolynomialAsOrderedList):
+
+  def poly(self, x):
+    poly_visitor = PolyVisitor(x)
+    self.accept(poly_visitor)
+    return poly_visitor.sum
+
+  
+class PolyVisitor(Visitor):
+
+  def __init__(self, x):
+    self._x = x 
+    self._sum = 0
+
+  def visit(self, obj):
+    self._sum += obj.coefficient * self._x ** obj.exponent
+
+  def getSum(self):
+    return self._sum
+
+  sum = property(
+      fget = lambda self: self.getSum())
+
+my_poly = MyPoly()
+# test polynomial 1 + 2x + x^2
+term1 = MyPoly.Term(1, 0)
+term2 = MyPoly.Term(2, 1)
+term3 = MyPoly.Term(1, 2)
+my_poly.addTerm(term1)
+my_poly.addTerm(term2)
+my_poly.addTerm(term3)
+print my_poly.poly(6)