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Re-implement ShuntingYard.infix_to_postfix()
The previous implementation had no concept of associativity. Signed-off-by: Jan Lindemann <jan@janware.com>
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81ca793a6e
commit
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1 changed files with 118 additions and 29 deletions
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@ -1,7 +1,9 @@
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from collections import namedtuple
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import re
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Operator = namedtuple("Operator", [ "func", "nargs" , "prec" ])
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Operator = namedtuple("Operator", [ "func", "nargs" , "prec", "assoc" ]) # export
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L, R = 'Left Right'.split()
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ARG, KEYW, LPAREN, RPAREN = 'arg kw ( )'.split()
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class Stack:
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@ -25,10 +27,22 @@ class Stack:
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class ShuntingYard(object): # export
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def __init__(self, operators):
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def __init__(self, operators = None):
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self.debug = True
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self.__ops = {}
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if operators is not None:
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for k, v in operators.iteritems():
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self.add_operator(k, v.func, v.nargs, v.prec)
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self.add_operator(k, v.func, v.nargs, v.prec, v.assoc)
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def token_string():
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for k, v in self.__ops:
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buf = ", " + k
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if v.nargs > 1:
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buf += "xxx"
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r = r + buf
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if len(r):
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return r[2:]
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return r
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def tokenize(self, spec):
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@ -46,25 +60,96 @@ class ShuntingYard(object): # export
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tokens, remainder = scanner.scan(spec)
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if len(remainder)>0:
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raise Expression("Failed to tokenize " + spec + ", remaining bit is ", remainder)
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raise Exception("Failed to tokenize " + spec + ", remaining bit is ", remainder)
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print tokens
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#print tokens
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return tokens
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r = []
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for e in tokens:
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r.append(e[1])
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return r
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def add_operator(self, name, func, nargs, precedence):
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self.__ops[name] = Operator(func, nargs, precedence)
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def add_operator(self, name, func, nargs, precedence, assoc):
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self.__ops[name] = Operator(func, nargs, precedence, assoc)
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def infix_to_postfix(self, infix):
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tokenized = self.tokenize(infix)
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print "tokenized = ", tokenized
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outq, stack = [], []
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table = ['TOKEN,ACTION,RPN OUTPUT,OP STACK,NOTES'.split(',')]
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for toktype, token in tokenized:
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print "Checking token", token
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note = action = ''
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if toktype == ARG:
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action = 'Add arg to output'
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outq.append(token)
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table.append( (token, action, ' '.join(outq), ' '.join(s[0] for s in stack), note) )
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elif toktype == KEYW:
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val = self.__ops[token]
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t1, (f1, n1, p1, a1) = token, val
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v = t1
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note = 'Pop ops from stack to output'
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while stack:
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t2, (f2, n2, p2, a2) = stack[-1]
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if (a1 == L and p1 <= p2) or (a1 == R and p1 < p2):
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if t1 != RPAREN:
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if t2 != LPAREN:
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stack.pop()
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action = '(Pop op)'
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outq.append(t2)
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else:
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break
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else:
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if t2 != LPAREN:
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stack.pop()
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action = '(Pop op)'
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outq.append(t2)
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else:
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stack.pop()
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action = '(Pop & discard "(")'
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table.append( (v, action, ' '.join(outq), ' '.join(s[0] for s in stack), note) )
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break
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table.append( (v, action, ' '.join(outq), ' '.join(s[0] for s in stack), note) )
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v = note = ''
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else:
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note = ''
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break
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note = ''
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note = ''
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if t1 != RPAREN:
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stack.append((token, val))
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action = 'Push op token to stack'
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else:
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action = 'Discard ")"'
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table.append( (v, action, ' '.join(outq), ' '.join(s[0] for s in stack), note) )
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note = 'Drain stack to output'
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while stack:
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v = ''
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t2, (f2, n2, p2, a2) = stack[-1]
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action = '(Pop op)'
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stack.pop()
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outq.append(t2)
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table.append( (v, action, ' '.join(outq), ' '.join(s[0] for s in stack), note) )
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v = note = ''
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if self.debug:
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maxcolwidths = [len(max(x, key=len)) for x in zip(*table)]
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row = table[0]
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print( ' '.join('{cell:^{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
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for row in table[1:]:
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print( ' '.join('{cell:<{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
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return table[-1][2].split()
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def infix_to_postfix_orig(self, infix):
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s = Stack()
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r = []
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tokens = self.tokenize(infix)
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for token in tokens:
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for tokinfo in tokens:
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print tokinfo
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toktype, token = tokinfo[0], tokinfo[1]
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print "Checking token ", token
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@ -105,16 +190,18 @@ class ShuntingYard(object): # export
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for token in postfixexpr:
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print "Checking token %s" % (token)
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if token not in self.__ops.keys():
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vals.push(token)
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continue
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op = self.__ops[token]
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args = []
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#print "Adding %d arguments" % (op.nargs)
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print "Adding %d arguments" % (op.nargs)
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for i in range(0, op.nargs):
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#print "Adding argument %d" % (i)
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print "Adding argument %d" % (i)
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args.append(vals.pop())
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#print "running %s(%s)" % (token, ', '.join(reversed(args)))
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val = op.func(*reversed(args))
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print "%s(%s) = %s" % (token, ', '.join(reversed(args)), val)
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vals.push(val)
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@ -134,8 +221,8 @@ if __name__ == '__main__':
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class Calculator(ShuntingYard):
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def tokenize(self, string):
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return string.split()
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#def tokenize(self, string):
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# return string.split()
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def f_mult(self, a, b):
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return str(atof(a) * atof(b));
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@ -152,16 +239,18 @@ if __name__ == '__main__':
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def __init__(self):
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Op = Operator
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operators = {
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'/': Op(self.f_div, 2, 3),
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'*': Op(self.f_mult, 2, 3),
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'+': Op(self.f_add, 2, 2),
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'-': Op(self.f_sub, 2, 2),
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'(': Op(None, 2, 1),
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')': Op(None, 2, 1)
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'^': Op(None, 2, 4, R),
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'*': Op(self.f_mult, 2, 3, L),
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'/': Op(self.f_div, 2, 3, L),
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'+': Op(self.f_add, 2, 2, L),
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'-': Op(self.f_sub, 2, 2, L),
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'(': Op(None, 0, 9, L),
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')': Op(None, 0, 0, L),
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}
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super(Calculator, self).__init__(operators)
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print Calculator().eval("( 2 * 3 + 4 * 5 ) / ( 5 - 3 )")
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rr = Calculator().eval("( 2 * 3 + 4 * 5 ) / ( 5 - 3 )")
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print "Result =", rr
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# ------------- testbed match object
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@ -182,7 +271,7 @@ if __name__ == '__main__':
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def f_is_not(self, a):
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if a == "True":
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return "False"
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return "False"
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return "True"
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def f_and(self, a_, b_):
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a = a_ == "True"
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@ -194,14 +283,14 @@ if __name__ == '__main__':
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def __init__(self, obj):
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Op = Operator
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operators = {
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'(': Op(None, 2, 1),
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')': Op(None, 2, 1),
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'name=': Op(self.f_is_name, 1, 3),
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'and': Op(self.f_and, 2, 3),
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'label~=': Op(self.f_matches_label, 1, 3),
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'False': Op(None, 0, 3),
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'True': Op(None, 0, 3),
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'not': Op(self.f_is_not, 1, 3),
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'(': Op(None, 2, 9, L),
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')': Op(None, 2, 0, L),
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'name=': Op(self.f_is_name, 1, 3, R),
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'and': Op(self.f_and, 2, 3, L),
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'label~=': Op(self.f_matches_label, 1, 3, R),
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'False': Op(None, 0, 3, L),
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'True': Op(None, 0, 3, L),
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'not': Op(self.f_is_not, 1, 3, R),
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}
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super(Matcher, self).__init__(operators)
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