92 lines
2.2 KiB
Python
92 lines
2.2 KiB
Python
from collections import deque
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from tokens import NumberTokenParser, OperatorTokenParser
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class ParsingException(Exception):
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pass
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class Parser(object):
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def __init__(self, token_stream):
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self._token_stream = token_stream
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self._stack = deque()
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self._current_list = deque()
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def parse(self):
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state = 0
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while True:
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token = self._token_stream.get_token()
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if(token == "("):
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if(state == 1):
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raise ParsingException(
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"expected operator, not parenthesis: {} (near '{}')".format(
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self._token_stream._offset
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, token))
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self._stack.append(self._current_list)
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continue
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if(NumberTokenParser.can_parse(token)):
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if(state == 1):
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raise ParsingException(
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"expected operator, not number: {} (near '{}')".format(
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self._token_stream._offset
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, token))
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self._current_list.append(NumberTokenParser(token).parse())
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state = 1
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continue
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if(OperatorTokenParser.can_parse(token)):
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if(state != 1):
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raise ParsingException(
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"expected number or parenthesis, not operator: {} (near '{}')".format(
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self._token_stream._offset
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, token))
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self._current_list.append(OperatorTokenParser(token).parse())
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state = 0
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continue
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if(token == ")"):
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#if(state == 1):
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# raise ParsingException(
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# "expected operator, not parenthesis: {} (near '{}')".format(
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# self._token_stream._offset
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# , token))
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state = 1
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result = self.execute_branch(self._current_list)
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self._current_list = self._stack.pop()
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continue
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if(not token):
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if(self._stack):
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raise ParsingException("unexpected EOF while parsing")
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return self.execute_branch(self._current_list)
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raise ParsingException("unknown token: {} (near '{}')".format(self._token_stream._offset, token))
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return self.execute_branch(self._current_list)
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def execute_branch(self, branch):
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result = None
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current_operator = None
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for element in branch:
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if(result is None):
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result = element
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continue
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if(not isinstance(element, (float, int, complex))):
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# Operator
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current_operator = element
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continue
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if(current_operator):
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result = current_operator(result, element)
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current_operator = None
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return result
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