283 lines
6.4 KiB
Python
283 lines
6.4 KiB
Python
#!/usr/bin/env python
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# encoding: utf-8
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from generic import Stack
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def infixToPostfix(infixExp):
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"""Transform an infix expression into postfix expression
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:param infixExp: an infix expression (caracters must be separate by a space)
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:returns: the corresponding postfix expression
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"""
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priority = {"*" : 3, "/": 3, "+": 2, "-":2, "(": 1}
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opStack = Stack()
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postfixList = []
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tokenList = infixExp.split(" ")
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for token in tokenList:
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if token == "(":
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opStack.push(token)
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elif token == ")":
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topToken = opStack.pop()
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while topToken != "(":
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postfixList.append(topToken)
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topToken = opStack.pop()
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elif token in "+-*/":
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while (not opStack.isEmpty()) and (priority[opStack.peek()] >= priority[token]):
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postfixList.append(opStack.pop())
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opStack.push(token)
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else:
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postfixList.append(token)
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while not opStack.isEmpty():
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postfixList.append(opStack.pop())
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return " ".join(postfixList)
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def computePostfix(postfixExp):
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"""Compute a postfix expression
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:param postfixExp: a postfix expression
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:returns: the result of the expression
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"""
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print(postfixToInfix(postfixExp))
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# where to save numbers or
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operandeStack = Stack()
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tokenList = postfixExp.split(" ")
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for (i,token) in enumerate(tokenList):
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if token in "+-*/":
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op2 = operandeStack.pop()
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op1 = operandeStack.pop()
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res = doMath(token, op1, op2)
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operandeStack.push(res)
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#print("Operation: {op1} {op} {op2}".format(op1 = op1, op = token, op2 = op2))
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#print(operandeStack)
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#print(tokenList[i+1:])
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newPostfix = " ".join(operandeStack + tokenList[i+1:])
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print(postfixToInfix(newPostfix))
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else:
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operandeStack.push(token)
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return operandeStack.pop()
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def computePostfixBis(postfixExp):
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"""Compute a postfix expression like a good student
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:param postfixExp: a postfix expression
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:returns: the result of the expression
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"""
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print(postfixToInfix(postfixExp))
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# where to save numbers or
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operandeStack = Stack()
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tokenList = postfixExp.split(" ")
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# On fait le calcul jusqu'à n'avoir plus qu'un élément
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while len(tokenList) > 1:
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tmpTokenList = []
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# on va chercher les motifs du genre A B + pour les calculer
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while len(tokenList) > 2:
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if isNumber(tokenList[0]) and isNumber(tokenList[1]) and tokenList[2] in "+-*/":
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# S'il y a une opération à faire
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op1 = tokenList[0]
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op2 = tokenList[1]
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token = tokenList[2]
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res = doMath(token, op1, op2)
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tmpTokenList.append(res)
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# Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
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del tokenList[0:3]
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else:
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tmpTokenList.append(tokenList[0])
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del tokenList[0]
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tmpTokenList += tokenList
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tokenList = tmpTokenList.copy()
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print(postfixToInfix(" ".join(tokenList)))
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return tokenList[0]
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def isNumber(exp):
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"""Check if the expression can be a number
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:param exp: an expression
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:returns: True if the expression can be a number and false otherwise
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"""
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tokenList = exp.split(" ")
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if len(tokenList) != 1:
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# Ici l'expression est trop longue
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return 0
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return exp.isdigit() or (exp[0] == "-" and exp[1:].isdigit())
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pass
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def doMath(op, op1, op2):
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"""Compute "op1 op op2"
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:param op: operator
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:param op1: first operande
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:param op2: second operande
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:returns: string representing the result
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"""
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return str(eval(op1 + op + op2))
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def postfixToInfix(postfixExp):
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"""Transforme postfix expression into infix expression
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:param postfixExp: a postfix expression
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:returns: the corresponding infix expression
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"""
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operandeStack = Stack()
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tokenList = postfixExp.split(" ")
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for (i,token) in enumerate(tokenList):
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if token in "+-*/":
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op2 = operandeStack.pop()
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if needPar(op2, token, "after"):
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op2 = "( " + op2 + " )"
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op1 = operandeStack.pop()
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if needPar(op1, token, "before"):
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op1 = "( " + op1 + " )"
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res = "{op1} {op} {op2}".format(op1 = op1, op = token, op2 = op2)
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operandeStack.push(res)
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else:
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operandeStack.push(token)
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return operandeStack.pop()
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def needPar(operande, operator, posi = "after"):
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"""Says whether or not the operande needs parenthesis
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:param operande: the operande
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:param operator: the operator
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:param posi: "after"(default) if the operande will be after the operator, "before" othewise
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:returns: bollean
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"""
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priority = {"*" : 3, "/": 3, "+": 2, "-":2}
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if isNumber(operande) and "-" in operande:
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return 1
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elif not isNumber(operande):
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# Si c'est une grande expression ou un chiffre négatif
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stand_alone = get_main_op(operande)
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# Si la priorité de l'operande est plus faible que celle de l'opérateur
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minor_priority = priority[get_main_op(operande)] < priority[operator]
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# Si l'opérateur est -/ pour after ou juste / pour before
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special = (operator in "-/" and posi == "after") or (operator in "/" and posi == "before")
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return stand_alone and (minor_priority or special)
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else:
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return 0
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def get_main_op(exp):
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"""Getting the main operation of th expression
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:param exp: the expression
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:returns: the main operation (+, -, * or /) or 0 if the expression is only one element
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"""
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priority = {"*" : 3, "/": 3, "+": 2, "-":2}
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parStack = Stack()
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tokenList = exp.split(" ")
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if len(tokenList) == 1:
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# Si l'expression n'est qu'un élément
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return 0
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main_op = []
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for token in tokenList:
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if token == "(":
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parStack.push(token)
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elif token == ")":
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parStack.pop()
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elif token in "+-*/" and parStack.isEmpty():
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main_op.append(token)
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return min(main_op, key = lambda s: priority[s])
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def test(exp):
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"""Make various test on an expression
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"""
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print("-------------")
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print("Expression ",exp)
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postfix = infixToPostfix(exp)
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#print("Postfix " , postfix)
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#print(computePostfix(postfix))
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#print("Bis")
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print(computePostfixBis(postfix))
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#print(postfixToInfix(postfix))
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#print(get_main_op(exp))
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if __name__ == '__main__':
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exp = "1 + 3 * 5"
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test(exp)
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exp = "2 * 3 * 3 * 5"
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test(exp)
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exp = "2 * 3 + 3 * 5"
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test(exp)
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exp = "2 * ( 3 + 4 ) + 3 * 5"
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test(exp)
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exp = "2 * ( 3 + 4 ) + ( 3 - 4 ) * 5"
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test(exp)
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exp = "2 * ( 2 - ( 3 + 4 ) ) + ( 3 - 4 ) * 5"
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test(exp)
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exp = "2 * ( 2 - ( 3 + 4 ) ) + 5 * ( 3 - 4 )"
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test(exp)
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exp = "2 + 5 * ( 3 - 4 )"
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test(exp)
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exp = "( 2 + 5 ) * ( 3 - 4 )"
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test(exp)
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exp = "( 2 + 5 ) * ( 3 * 4 )"
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test(exp)
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exp = "( 2 + 5 ) / ( 3 * 4 )"
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test(exp)
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## Ce denier pose un soucis. Pour le faire marcher il faudrai implémenter le calcul avec les fractions
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#exp = "( 2 + 5 ) / 3 * 4"
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#test(exp)
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# -----------------------------
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# Reglages pour 'vim'
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# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
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# cursor: 16 del
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