Cleaning
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lafrite
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81725a6104
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#!/usr/bin/env python
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# encoding: utf-8
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from generic import Stack
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from calculus import isNumber, doMath
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class Expression(object):
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"""An arithmetic expression"""
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priority = {"*" : 3, "/": 3, "+": 2, "-":2, "(": 1}
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def __init__(self, exp, fix = "infix"):
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"""Initiate the expression.
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:param exp: the string representing the expression (infx form by default)
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:param fix: form of the expression infix (default) - postfix - prefix
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"""
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if fix == "infix":
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self._exp_infix = exp
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self._token_infix = exp.split(" ")
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elif fix == "postfix":
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self._token_postfix = exp
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else:
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print("Pas encore fait!")
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def infixToPostfix(self):
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"""Convert the infix expression into postfix expression.
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"""
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#@todo importer les exemples
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opStack = Stack()
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postfixList = []
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for token in self._token_infix:
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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 (self.priority[opStack.peek()] >= self.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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self._token_postfix = postfixList
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self._exp_postfix = " ".join(postfixList)
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def computePostfix(self):
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"""Compute a postfix expression like a good student
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:returns: list of steps to reach the result (postfix form)
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"""
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tokenList = self._token_postfix.copy()
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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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#print(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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if len(tmpTokenList) > 1:
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next_steps = Expression(tmpTokenList, fix = "postfix").computePostfix()
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else:
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next_steps = tmpTokenList
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print(self._exp_postfix)
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return [self._exp_postfix] + next_steps
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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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expression = Expression(exp)
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expression.infixToPostfix()
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print(expression.computePostfix())
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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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# -----------------------------
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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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@ -1,191 +0,0 @@
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#!/usr/bin/env python
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# encoding: utf-8
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class Expression(object):
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"""A calculus expression. Today it can andle only expression with numbers later it will be able to manipulate unknown"""
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priority = {"*" : 3, "/": 3, "+": 2, "-":2, "(": 1}
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def __init__(self, exp):
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""" Initiate the expression.
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:param exp: the expression. It can be a string or a list of tokens. It can be infix or postfix expression
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"""
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self._tokens = {}
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self._strings = {}
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if type(exp) == list:
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fix = self.get_fix(exp)
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self._tokens[fix] = exp
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elif type(exp) == str:
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tokens = self.parseExp(exp)
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fix = self.get_fix(tokens)
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self._tokens[fix] = tokens
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self._strings[fix] = exp
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else:
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raise ValueError("The expression needs to be a string or a list of token")
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# ---------------------
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# String parsing
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# @classmethod ????
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def parseExp(self, exp):
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""" Parse the expression, ie tranform a string into a list of tokens
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:param exp: The expression (a string)
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:returns: list of token
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"""
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return exp.split(" ")
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# ---------------------
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# "fix" recognition
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def get_fix(self, tokens):
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""" Give the "fix" of an expression
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infix -> A + B
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prefix -> + A B
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postfix -> A B +
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:param exp: the expression (list of token)
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:returns: the "fix" (infix, postfix, prefix)
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"""
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if tokens[0] in "+-*/":
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return "prefix"
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elif token[0] not in "+-*/" ans token[1] not in "+-*/":
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return "postfix"
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else:
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return "infix"
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# ----------------------
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# Expressions - tokens getters
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def tokens(self, fix = "infix"):
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"""Get the list of tokens with the wanted fix
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:param fix: the fix wanted (infix default)
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:returns: list of tokens
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"""
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# Si ce fix n'a pas encore été enregistré
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if fix not in self._tokens:
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# Il peut venir de la version string
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if fix in self._string:
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self._tokens[fix] = self.parseExp(self._string[fix])
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# Sinon il faut le calculer à partir d'une autre forme
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else:
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fix_transfo = "to" + fix.capitalize()
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getattr(self,fix_transfo)()
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return self._tokens[fix]
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##### On en est là,il faudra faire attention à bien vérifier ce que les "to..." enregistre (string ou tokens)
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def string(self, fix = "infix"):
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"""Get the string with the wanted fix
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:param fix: the fix wanted (infix default)
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:returns: the string representing the expression
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"""
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# Si ce fix n'a pas encore été enregistré
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if fix not in self._string:
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# Il peut venir de la version string
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if fix in self._tokens:
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self._string[fix] = self.parseExp(self._string[fix])
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# Sinon il faut le calculer à partir d'une autre forme
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else:
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fix_transfo = "to" + fix.capitalize()
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getattr(self,fix_transfo)()
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return self._string[fix]
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# ----------------------
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# "fix" tranformations
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def toPostfix(self):
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""" Transorm the expression into postfix form using the infix form"""
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pass
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def toInfix(self):
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""" Tranform the expression into infix form using postfix form"""
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pass
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# ---------------------
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# Tools for placing parenthesis in infix notation
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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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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 = self.priority[get_main_op(operande)] < self.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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# J'aime pas bien cette endroit faudrait que ce soit une méthode qui s'applique uniquement à l'expression en question (self) pas à n'importe quel string, ça serait plus propre.
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def get_main_op(exp):
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""" Gives the main operation of the 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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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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# ---------------------
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# Computing the expression
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def compute(self):
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""" Recursive method for computing as a student the expression
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:returns: list of steps needed to reach the result
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"""
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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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# -----------------------------
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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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