Mapytex/pymath/expression.py

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#!/usr/bin/env python
# encoding: utf-8
from .generic import Stack, flatten_list, expand_list, isNumber, isOperator
from .render import txt, tex
from .str2tokens import str2tokens
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__all__ = ['Expression']
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class Expression(object):
"""A calculus expression. Today it can andle only expression with numbers later it will be able to manipulate unknown"""
STR_RENDER = tex
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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 postfix tokens.
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"""
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if type(exp) == str:
self._exp = exp
self.postfix_tokens = str2tokens(exp) # les tokens seront alors stockés dans self.tokens temporairement
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elif type(exp) == list:
self.postfix_tokens = exp
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def __str__(self):
"""
Overload str
If you want to changer render set Expression.RENDER
"""
return self.STR_RENDER(self.postfix_tokens)
def render(self, render = lambda x:str(x)):
""" Same as __str__ but accept render as argument
:param render: function which render the list of token (postfix form) to string
"""
# TODO: I don't like the name of this method |ven. janv. 17 12:48:14 CET 2014
return render(self.postfix_tokens)
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## ---------------------
## Mechanism functions
def simplify(self):
""" Generator which return steps for computing the expression """
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if not self.can_go_further():
yield self.STR_RENDER(self.postfix_tokens)
else:
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self.compute_exp()
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old_s = ''
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for s in self.steps:
new_s = self.STR_RENDER(s)
# Astuce pour éviter d'avoir deux fois la même étape (par exemple pour la transfo d'une division en fraction)
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if new_s != old_s:
old_s = new_s
yield new_s
for s in self.child.simplify():
if old_s != s:
yield s
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def can_go_further(self):
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"""Check whether it's a last step or not. If not create self.child the next expression.
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:returns: 1 if it's not the last step, 0 otherwise
"""
if len(self.postfix_tokens) == 1:
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return 0
else:
return 1
def compute_exp(self):
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""" Create self.child with self.steps to go up to it """
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self.steps = [self.postfix_tokens]
tokenList = self.postfix_tokens.copy()
tmpTokenList = []
while len(tokenList) > 2:
# on va chercher les motifs du genre A B +, quand l'operateur est d'arité 2, pour les calculer
if isNumber(tokenList[0]) and isNumber(tokenList[1]) \
and isOperator(tokenList[2]) and tokenList[2].arity == 2 :
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# S'il y a une opération à faire
op1 = tokenList[0]
op2 = tokenList[1]
operator = tokenList[2]
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res = operator(op1, op2)
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tmpTokenList.append(res)
# Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
del tokenList[0:3]
# Et les motifs du gens - A, quand l'operateur est d'arité 1
elif isNumber(tokenList[0]) \
and isOperator(tokenList[1]) and tokenList[2].arity == 1:
# S'il y a une opération à faire
op1 = tokenList[0]
operator = tokenList[1]
res = operator(op1)
tmpTokenList.append(res)
# Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
del tokenList[0:2]
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else:
tmpTokenList.append(tokenList[0])
del tokenList[0]
tmpTokenList += tokenList
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steps = expand_list(tmpTokenList)
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if len(steps[:-1]) > 0:
self.steps += [flatten_list(s) for s in steps[:-1]]
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self.child = Expression(steps[-1])
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def test(exp):
a = Expression(exp)
for i in a.simplify():
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print(i)
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print("\n")
if __name__ == '__main__':
Expression.STR_RENDER = txt
exp = "2 ^ 3 * 5"
test(exp)
exp = "1 + 3 * 5"
test(exp)
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#exp = "2 * 3 * 3 * 5"
#test(exp)
#exp = "2 * 3 + 3 * 5"
#test(exp)
#exp = "2 * ( 3 + 4 ) + 3 * 5"
#test(exp)
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#exp = "2 * ( 3 + 4 ) + ( 3 - 4 ) * 5"
#test(exp)
#
#exp = "2 * ( 2 - ( 3 + 4 ) ) + ( 3 - 4 ) * 5"
#test(exp)
#
#exp = "2 * ( 2 - ( 3 + 4 ) ) + 5 * ( 3 - 4 )"
#test(exp)
#
#exp = "2 + 5 * ( 3 - 4 )"
#test(exp)
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#exp = "( 2 + 5 ) * ( 3 - 4 )^4"
#test(exp)
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#exp = "( 2 + 5 ) * ( 3 * 4 )"
#test(exp)
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#exp = "( 2 + 5 - 1 ) / ( 3 * 4 )"
#test(exp)
#exp = "( 2 + 5 ) / ( 3 * 4 ) + 1 / 12"
#test(exp)
#exp = "( 2+ 5 )/( 3 * 4 ) + 1 / 2"
#test(exp)
#exp="(-2+5)/(3*4)+1/12+5*5"
#test(exp)
#exp="-2*4(12 + 1)(3-12)"
#test(exp)
#exp="(-2+5)/(3*4)+1/12+5*5"
#test(exp)
# TODO: The next one doesn't work |ven. janv. 17 14:56:58 CET 2014
#exp="-2*(-a)(12 + 1)(3-12)"
#e = Expression(exp)
#print(e)
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## Can't handle it yet!!
#exp="-(-2)"
#test(exp)
#import doctest
#doctest.testmod()
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# -----------------------------
# Reglages pour 'vim'
# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
# cursor: 16 del