Added proper AST display to term.py

term.py

@@ -63,6 +63,7 @@ def lex(text):
         c = next(it,END)
 
 class OperatorNode:
+    operator = "?"
     def __init__(self, left, right):
         self.left = left
         self.right = right
@@ -73,19 +74,28 @@ class OperatorNode:
     def __repr__(self):
         return "%s < %s, %s >" % (self.__class__.__name__, repr(self.left), repr(self.right))
 
+    def printAST(self,tab=0):
+        self.left.printAST(tab+1)
+        print("\t"*tab,self.operator)
+        self.right.printAST(tab+1)
+
 class AdditionNode(OperatorNode):
+    operator = "+"
     def calculate(self):
         return self.left.calculate() + self.right.calculate()
 
 class SubtractionNode(OperatorNode):
+    operator = "-"
     def calculate(self):
         return self.left.calculate() - self.right.calculate()
 
 class MultiplicationNode(OperatorNode):
+    operator = "*"
     def calculate(self):
         return self.left.calculate() * self.right.calculate()
 
 class DivisionNode(OperatorNode):
+    operator = "/"
     def calculate(self):
         right = self.right.calculate()
         if right == 0:
@@ -102,6 +112,9 @@ class NumNode:
     def __repr__(self):
         return "NumNode < %d >" % self.value
 
+    def printAST(self,tab=0):
+        print("\t"*tab,self.value)
+
 # 1. S -> E
 # 2. E -> E+T
 # 3. E -> E-T
@@ -270,6 +283,6 @@ if __name__ == '__main__':
     print('"%s"' % l)
     print(list(lex(l)))
     ast = parse(l)
-    print(repr(ast))
+    ast.printAST()
     print(l," = ",ast.calculate())