1+ import itertools
2+ import re
3+ from typing import Dict
4+
5+
16class CalcParseError (Exception ):
27 pass
38
@@ -43,7 +48,7 @@ class CalcNode:
4348
4449 def __init__ (self , formula = None ):
4550 if formula :
46- root = parse_to_calc_node (formula )
51+ root = _parse (formula )
4752 self .content = root .content
4853 self .lch = root .lch
4954 self .rch = root .rch
@@ -70,29 +75,52 @@ def __ne__(self, other):
7075 return not self .__eq__ (other )
7176
7277 def __str__ (self , depth = 0 ):
73- if self .operator is not None :
74- lv = self .lch .__str__ (depth = depth + 1 )
75- rv = self .rch .__str__ (depth = depth + 1 )
76- res = "%s%s%s" % (lv , _operator_to_string (self .operator ), rv )
77- if depth > 0 and (self .operator == add or self .operator == sub ):
78- res = "(%s)" % res
79- return res
80- elif isinstance (self .content , int ):
81- return str (self .content )
82- else :
83- return self .content
78+ opens = [] # Position list of open brackets
79+ cands = []
80+ original_formula = self .to_string_strictly ()
81+ for i , c in enumerate (original_formula ):
82+ if c == '(' :
83+ opens .append (i )
84+ elif c == ')' :
85+ assert len (opens ) > 0
86+ cands .append ((opens [- 1 ], i ))
87+ opens .pop ()
88+ pass
89+
90+ values_for_identity_check = [3 , 14 , 15 , 92 ]
91+
92+ def likely_identical (formula : str ):
93+ node = CalcNode (formula )
94+ vars = node .get_all_variables ()
95+ for combination in itertools .product (values_for_identity_check , repeat = len (vars )):
96+ val_dict = dict (zip (vars , list (combination )))
97+ if self .evaluate (val_dict ) != node .evaluate (val_dict ):
98+ return False
99+ return True
100+
101+ # Remove parentheses greedy
102+ res_formula = list (original_formula )
103+ for op , cl in cands :
104+ tmp = res_formula .copy ()
105+ tmp [op ] = ''
106+ tmp [cl ] = ''
107+ if likely_identical ("" .join (tmp )):
108+ res_formula = tmp
109+ simplified_form = "" .join (res_formula )
110+
111+ return simplified_form
84112
85113 def get_all_variables (self ):
86- if self .operator is not None :
114+ if self .is_operator_node () :
87115 lv = self .lch .get_all_variables ()
88116 rv = self .rch .get_all_variables ()
89117 return lv + rv
90- elif isinstance ( self .content , int ):
118+ elif self .is_constant_node ( ):
91119 return []
92120 else :
93121 return [self .content ]
94122
95- def evaluate (self , variables = None ):
123+ def evaluate (self , variables : Dict [ str , int ] = None ):
96124 if variables is None :
97125 variables = {}
98126 if self .is_operator_node ():
@@ -103,10 +131,42 @@ def evaluate(self, variables=None):
103131 return int (self .content )
104132 else :
105133 if self .content not in variables :
106- raise EvaluateError
134+ raise EvaluateError (
135+ "Found an unknown variable '{}'" .format (self .content ))
107136 else :
108137 return variables [self .content ]
109138
139+ def simplify (self ):
140+ current_formula = str (self )
141+
142+ # Really stupid heuristics but covers the major case.
143+ while True :
144+ next_formula = re .sub (r"-1\+1$" , "" , current_formula )
145+ next_formula = re .sub (r"\+0$" , "" , next_formula )
146+ next_formula = re .sub (r"-0$" , "" , next_formula )
147+ if next_formula == current_formula :
148+ break
149+ current_formula = next_formula
150+
151+ return CalcNode (current_formula )
152+
153+ def to_string_strictly (self ):
154+ if self .is_operator_node ():
155+ return "({lch}{op}{rch})" .format (
156+ lch = self .lch .to_string_strictly (),
157+ op = _operator_to_string (self .operator ),
158+ rch = self .rch .to_string_strictly ()
159+ )
160+ else :
161+ return str (self .content )
162+
163+
164+ def _parse (formula : str ):
165+ res , pos = _expr (formula + "$" , 0 ) # $ is put as a terminal character
166+ if pos != len (formula ):
167+ raise CalcParseError
168+ return res
169+
110170
111171def _expr (formula , pos ):
112172 res , pos = _term (formula , pos )
@@ -179,19 +239,5 @@ def _factor(formula, pos):
179239 raise CalcParseError
180240
181241
182- def parse_to_calc_node (formula ):
183- """
184- 入力
185- formula # str : 式
186- 出力
187- #CalcNode : 構文木の根ノード
188-
189- """
190- res , pos = _expr (formula + "$" , 0 ) # $は使わないことにする
191- if pos != len (formula ):
192- raise CalcParseError
193- return res
194-
195-
196- if __name__ == '__main__' :
197- print (CalcNode ("N-1-1+1000*N*N" ).evaluate ({"N" : 10 }))
242+ def parse_to_calc_node (formula : str ) -> CalcNode :
243+ return CalcNode (formula )
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