Mapytex/pymath/str2tokens.py

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#!/usr/bin/env python
# encoding: utf-8
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from .operator import Operator
from .generic import Stack, isOperator, isNumber
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def str2tokens(exp):
""" Parse the string into tokens then turn it into postfix form
>>> str2tokens('2+3*4')
[2, 3, 4, '*', '+']
>>> str2tokens('2*3+4')
[2, 3, '*', 4, '+']
"""
in_tokens = str2in_tokens(exp)
post_tokens = in2post_fix(in_tokens)
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return post_tokens
def str2in_tokens(exp):
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""" Parse the expression, ie tranform a string into a list of tokens
/!\ float are not availiable yet!
:param exp: The expression (a string)
:returns: list of token
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>>> str2tokens('2+3*4')
['2', '+', '3', '*', '4']
>>> str2tokens('2*3+4')
['2', '*', '3', '+', '4']
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"""
tokens = ['']
for character in exp:
if character.isdigit():
# for "big" numbers (like 2345)
if type(tokens[-1]) == int:
if tokens[-1] > 0:
tokens[-1] = tokens[-1]*10 + int(character)
else:
tokens[-1] = tokens[-1]*10 - int(character)
# Special case for "-" at the begining of an expression or before "("
elif tokens[-1] == "-" and \
str(tokens[-2]) in " (+-*/:":
tokens[-1] = - int(character)
else:
tokens.append(int(character))
elif character in "+-*/:^":
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tokens.append(Operator(character))
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elif character == ")":
tokens.append(character)
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elif character in "(":
# If "3(", ")("
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if isNumber(tokens[-1]) \
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or tokens[-1] == ")" :
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#tokens.append(Operator("*"))
tokens.append(Operator("*"))
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tokens.append(character)
elif character == ".":
raise ValueError("No float number please")
elif character != " ":
raise ValueError("{} is an unvalid character".format(character))
return tokens[1:]
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def in2post_fix(infix_tokens):
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""" From the infix_tokens list compute the corresponding postfix_tokens list
@param infix_tokens: the infix list of tokens to transform into postfix form.
@return: the corresponding postfix list of tokens.
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>>> a, s, m, d, p = Operator("+"), Operator("-"), Operator("*"), Operator("/"), Operator("^")
>>> in2post_fix(['(', 2, '+', 5, '-', 1, ')', '/', '(', 3, '*', 4, ')'])
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[2, 5, '+', 1, '-', 3, 4, '*', '/']
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>>> in2post_fix(['-', '(', '-', 2, ')'])
[2, '-', '-']
>>> in2post_fix(['-', '(', '-', 2, '+', 3, '*', 4, ')'])
[2, '-', 3, 4, '*', '+', '-']
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"""
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# Stack where operator will be stocked
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opStack = Stack()
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# final postfix list of tokens
postfix_tokens = []
# stack with the nbr of tokens still to compute in postfix_tokens
arity_Stack = Stack()
arity_Stack.push(0)
for (pos_token,token) in enumerate(infix_tokens):
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## Pour voir ce qu'il se passe dans cette procédure
#print(str(postfix_tokens), " | ", str(opStack), " | ", str(infix_tokens[(pos_token+1):]), " | ", str(arity_Stack))
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if token == "(":
opStack.push(token)
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# Set next arity counter
arity_Stack.push(0)
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elif token == ")":
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op = opStack.pop()
while op != "(":
postfix_tokens.append(op)
op = opStack.pop()
# Go back to old arity
arity_Stack.pop()
# Raise the arity
arity = arity_Stack.pop()
arity_Stack.push(arity + 1)
elif isOperator(token):
while (not opStack.isEmpty()) and (opStack.peek().priority >= token.priority):
op = opStack.pop()
postfix_tokens.append(op)
arity = arity_Stack.pop()
token.arity = arity + 1
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opStack.push(token)
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# print("--", token, " -> ", str(arity + 1))
# Reset arity to 0 in case there is other operators (the real operation would be "-op.arity + 1")
arity_Stack.push(0)
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else:
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postfix_tokens.append(token)
arity = arity_Stack.pop()
arity_Stack.push(arity + 1)
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while not opStack.isEmpty():
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op = opStack.pop()
postfix_tokens.append(op)
# # Pour voir ce qu'il se passe dans cette procédure
# print(str(postfix_tokens), " | ", str(opStack), " | ", str(infix_tokens[(pos_token+1):]), " | ", str(arity_Stack))
if arity_Stack.peek() != 1:
raise ValueError("Unvalid expression. The arity Stack is ", str(arity_Stack))
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return postfix_tokens
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if __name__ == '__main__':
#a, s, m, d, p = Operator("+"), Operator("-"), Operator("*"), Operator("/"), Operator("^")
#in_tokens = str2in_tokens("2+3*4")
#print("\t in_tokens :" + str(in_tokens))
#
#print(in2post_fix(in_tokens))
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import doctest
doctest.testmod()
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# -----------------------------
# Reglages pour 'vim'
# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
# cursor: 16 del