pro1 expo added

Author: yyl

unit3/input.txt

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+5.5 9 + 2 * 6 1.5 * + =
+5.5 5 + = 
+5.5 2 / 4 + 5 * = 
+5 2 ^ = 

unit3/output.txt

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+38.0
+10.5
+33.75
+25.0

unit3/pro1.py

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+'''
+RPN Calculator
+'''
+
+from opus7.stackAsLinkedList import StackAsLinkedList
+
+class Algorithms(object):
+
+  @staticmethod
+  def calculator(input, output):
+    stack = StackAsLinkedList()
+    for line in input.readlines():
+      for word in line.split():
+        if word == "+":
+          print "it is +"
+          arg2 = stack.pop()
+          arg1 = stack.pop()
+          stack.push(arg1 + arg2)
+        elif word == "*":
+          print "it is *"
+          arg2 = stack.pop()
+          arg1 = stack.pop()
+          stack.push(arg1 * arg2)
+        elif word == "-":
+          print "it is -"
+          arg2 = stack.pop()
+          arg1 = stack.pop()
+          stack.push(arg1 - arg2)
+        elif word == "/":
+          print "it is /"
+          arg2 = stack.pop()
+          arg1 = stack.pop()
+          stack.push(arg1 / arg2)
+        # exponential expression
+        elif word == "^":
+          print "it is ^"
+          arg2 = stack.pop()
+          arg1 = stack.pop()
+          stack.push(arg1 ** arg2)
+        elif word == "=":
+          print "it is ="
+          arg = stack.pop()
+          output.write(str(arg) + "\n")
+          print "ans is ", arg
+        else:
+          print "it is number"
+          # make it double
+          stack.push(float(word))
+
+
+Algorithms.calculator(open("input.txt", 'r'), open("output.txt", 'w+'))