From d5e9f8780abb2cb8de30b32a0246d20cad5d4dd3 Mon Sep 17 00:00:00 2001
From: Lafrite <lafrite@poneyworld.net>
Date: Thu, 18 Jul 2013 16:30:45 +0200
Subject: [PATCH] Basic calculus. Parenthesis are not perfect

---
 .gitignore  |   1 +
 calculus.py | 201 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 202 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 calculus.py

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c18dd8d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__/
diff --git a/calculus.py b/calculus.py
new file mode 100644
index 0000000..0f6402e
--- /dev/null
+++ b/calculus.py
@@ -0,0 +1,201 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+
+
+
+
+class Stack(object):
+	"""Docstring for Stack """
+
+	def __init__(self):
+		"""@todo: to be defined1 """
+		self.items = []
+
+	def isEmpty(self):
+		""" Says if the stack is empty
+		:returns: @todo
+
+		"""
+		return self.items == []
+
+	def push(self,  item):
+		"""Push an item in the stack
+
+		:param item: @todo
+		:returns: @todo
+
+		"""
+		self.items.append(item)
+
+	def pop(self):
+		"""Getting the last item and remove it
+		:returns: @todo
+
+		"""
+		return self.items.pop()
+
+	def peek(self):
+		"""Getting the last item
+		:returns: @todo
+
+		"""
+		return self.items[-1]
+
+	def size(self):
+		"""Lenght of the stack
+		:returns: @todo
+
+		"""
+		return len(self.items)
+
+	def __str__(self):
+		return str(self.items)
+
+	def __add__(self, addList):
+		return self.items + addList
+
+
+def infixToPostfix(infixExp):
+	"""Transform an infix expression into postfix expression
+
+	:param infixExp: an infix expression (caracters must be separate by a space)
+	:returns: the corresponding postfix expression
+
+	"""
+	priority = {"*" : 3, "/": 3, "+": 2, "-":2, "(": 1}
+	
+	opStack = Stack()
+	postfixList = []
+
+	tokenList = infixExp.split(" ")
+
+	for token in tokenList:
+		if token == "(":
+			opStack.push(token)
+		elif token == ")":
+			topToken = opStack.pop()
+			while topToken != "(":
+				postfixList.append(topToken)
+				topToken = opStack.pop()
+		elif token in "+-*/":
+			while (not opStack.isEmpty()) and (priority[opStack.peek()] >= priority[token]):
+				postfixList.append(opStack.pop())
+			opStack.push(token)
+		else:
+			postfixList.append(token)
+
+	while not opStack.isEmpty():
+		postfixList.append(opStack.pop())
+
+	return " ".join(postfixList)
+
+def computePostfix(postfixExp):
+	"""Compute a postfix expression
+
+	:param postfixExp: a postfix expression
+	:returns: the result of the expression
+
+	"""
+    # where to save numbers or 
+	operandeStack = Stack()
+
+	tokenList = postfixExp.split(" ")
+
+	for (i,token) in enumerate(tokenList):
+		if token in "+-*/":
+			op2 = operandeStack.pop()
+			op1 = operandeStack.pop()
+			res = doMath(token, op1, op2)
+			operandeStack.push(res)
+
+			#print("Operation: {op1} {op} {op2}".format(op1 = op1, op = token, op2 = op2))
+			#print(operandeStack)
+			#print(tokenList[i+1:])
+			newPostfix = " ".join(operandeStack + tokenList[i+1:])
+			print(postfixToInfix(newPostfix))
+
+		else:
+			operandeStack.push(token)
+
+	return operandeStack.pop()
+
+def doMath(op, op1, op2):
+	"""Compute "op1 op op2"
+
+	:param op: operator
+	:param op1: first operande
+	:param op2: second operande
+	:returns: string representing the result
+
+	"""
+	return str(eval(op1 + op + op2))
+
+
+def postfixToInfix(postfixExp):
+	"""Transforme postfix expression into infix expression
+
+	:param postfixExp: a postfix expression
+	:returns: the corresponding infix expression
+
+	"""
+	priority = {"*" : 3, "/": 3, "+": 2, "-":2}
+	operandeStack = Stack()
+
+	tokenList = postfixExp.split(" ")
+
+	for (i,token) in enumerate(tokenList):
+		if token in "+-*/":
+			op2 = operandeStack.pop()
+			op1 = operandeStack.pop()
+			res = "{op1} {op} {op2}".format(op1 = op1, op = token, op2 = op2)
+			
+			if i+1 < len(tokenList):
+				if tokenList[i+1] in "+-*/":
+					if priority[token] < priority[tokenList[i+1]]:
+						res = "( " + res + " )"
+
+			operandeStack.push(res)
+
+			#print("new token: {token}".format(token = token))
+			#print(" ".join(operandeStack +["!!"]+ tokenList[i+1:]))
+
+		else:
+			operandeStack.push(token)
+
+	return operandeStack.pop()
+
+
+def test(exp):
+	"""Make various test on an expression
+
+	"""
+	print("-------------")
+	print(exp)
+	postfix = infixToPostfix(exp)
+	#print(postfix)
+	print(computePostfix(postfix))
+	#print(postfixToInfix(postfix))
+
+
+if __name__ == '__main__':
+	exp = "1 + 3 * 5"
+	test(exp)
+
+	exp = "2 * 3 + 3 * 5"
+	test(exp)
+
+	exp = "2 * ( 3 + 4 ) + 3 * 5"
+	test(exp)
+	
+	exp = "2 * ( 3 + 4 ) + ( 3 - 4 ) * 5"
+	test(exp)
+	
+	exp = "2 * ( 2 - ( 3 + 4 ) ) + ( 3 - 4 ) * 5"
+	test(exp)
+
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del