Updated exceptions to be more fitting, fixed a parse bug in the tokenizer and added the start of the calc engine.

calc_engine.py

@@ -0,0 +1,25 @@
+import token
+
+def calculate_results(tokens):
+	
+	return 0
+
+def peek_list(tokens):
+    if tokens:
+        return tokens[-1]
+    else:
+        raise IndexError("The token list is empty.", tokens)
+
+def operate(n1, n2, tokenType):
+	if tokenType == token.TokenType.add:
+		print("Adding %d and %d to get %d." %(n1, n2, n1 + n2))
+	elif tokenType == token.TokenType.subtract:
+		print("Subtracting %d and %d to get %d." %(n1, n2, n1 - n2))
+	elif tokenType == token.TokenType.multiply:
+		print("Multiplying %d and %d to get %d" %(n1, n2, n1 * n2))
+	elif tokenType == token.TokenType.divide:
+		print("Dividing %d and %d to get %d" %(n1, n2, n1 / n2))
+	elif tokenType == token.TokenType.power:
+		print("Raising %d to the power of %d to get %d" %(n1, n2, n1**n2))
+	else:
+		raise TypeError("Invalid operator value " + str(tokenType) + ".", tokenType)