63 lines
1.6 KiB
Python
63 lines
1.6 KiB
Python
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#!/usr/bin/env python3
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import tokenizer
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class Parser:
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def __init__(self):
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self.token = None
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self.remained_token = None
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def parse(self, token_list):
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none_token = tokenizer.Token(val=None, type=None, line=None,column=None)
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# remove comment, whitespace and newline tokens
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token_list = list(filter(lambda x: not x.type in ['CMT', 'WS', 'NL'], token_list))
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token_list += [none_token]
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if token_list[0] == None:
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print("The compiled content is empty. Stop parsing.")
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return None
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self.token = token_list[0]
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self.remained_token = token_list[1:]
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result = self.expr_star()
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if self.token.val != None:
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raise Exception("The S-expression is not well-formed.")
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return result
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def advance(self):
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self.token = self.remained_token[0]
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self.remained_token = self.remained_token[1:]
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'''
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Grammar:
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expr_star = [None] | expr+
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expr = atom | ( expr_star )
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'''
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def expr(self):
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if self.token.val == "(":
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self.advance()
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result = self.expr_star()
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if self.token.val != ")":
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raise Exception("The S-expression is not well-formed.")
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else:
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self.advance()
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return result
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else:
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result = self.token
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self.advance()
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return result
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def expr_star(self):
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result = []
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while not self.token.val in [")", None]:
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result_item = self.expr()
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result.append(result_item)
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return result
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