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13 # tokenizer is an iterator that returns type, value pairs |
13 # tokenizer is an iterator that returns type, value pairs |
14 # elements is a mapping of types to binding strength, prefix and infix actions |
14 # elements is a mapping of types to binding strength, prefix and infix actions |
15 # an action is a tree node name, a tree label, and an optional match |
15 # an action is a tree node name, a tree label, and an optional match |
16 # __call__(program) parses program into a labelled tree |
16 # __call__(program) parses program into a labelled tree |
17 |
17 |
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18 import error |
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19 |
18 class parser(object): |
20 class parser(object): |
19 def __init__(self, tokenizer, elements, methods=None): |
21 def __init__(self, tokenizer, elements, methods=None): |
20 self._tokenizer = tokenizer |
22 self._tokenizer = tokenizer |
21 self._elements = elements |
23 self._elements = elements |
22 self._methods = methods |
24 self._methods = methods |
29 pass |
31 pass |
30 return t |
32 return t |
31 def _match(self, m): |
33 def _match(self, m): |
32 'make sure the tokenizer matches an end condition' |
34 'make sure the tokenizer matches an end condition' |
33 if self.current[0] != m: |
35 if self.current[0] != m: |
34 raise SyntaxError(self.current) |
36 raise error.ParseError("unexpected token: %s" % self.current[2], |
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37 pos) |
35 self._advance() |
38 self._advance() |
36 def _parse(self, bind=0): |
39 def _parse(self, bind=0): |
37 token, value = self._advance() |
40 token, value, pos = self._advance() |
38 # handle prefix rules on current token |
41 # handle prefix rules on current token |
39 prefix = self._elements[token][1] |
42 prefix = self._elements[token][1] |
40 if not prefix: |
43 if not prefix: |
41 raise SyntaxError("not a prefix: %s" % token) |
44 raise error.ParseError("not a prefix: %s" % token, pos) |
42 if len(prefix) == 1: |
45 if len(prefix) == 1: |
43 expr = (prefix[0], value) |
46 expr = (prefix[0], value) |
44 else: |
47 else: |
45 if len(prefix) > 2 and prefix[2] == self.current[0]: |
48 if len(prefix) > 2 and prefix[2] == self.current[0]: |
46 self._match(prefix[2]) |
49 self._match(prefix[2]) |
49 expr = (prefix[0], self._parse(prefix[1])) |
52 expr = (prefix[0], self._parse(prefix[1])) |
50 if len(prefix) > 2: |
53 if len(prefix) > 2: |
51 self._match(prefix[2]) |
54 self._match(prefix[2]) |
52 # gather tokens until we meet a lower binding strength |
55 # gather tokens until we meet a lower binding strength |
53 while bind < self._elements[self.current[0]][0]: |
56 while bind < self._elements[self.current[0]][0]: |
54 token, value = self._advance() |
57 token, value, pos = self._advance() |
55 e = self._elements[token] |
58 e = self._elements[token] |
56 # check for suffix - next token isn't a valid prefix |
59 # check for suffix - next token isn't a valid prefix |
57 if len(e) == 4 and not self._elements[self.current[0]][1]: |
60 if len(e) == 4 and not self._elements[self.current[0]][1]: |
58 suffix = e[3] |
61 suffix = e[3] |
59 expr = (suffix[0], expr) |
62 expr = (suffix[0], expr) |
63 if len(infix) == 3 and infix[2] == self.current[0]: |
66 if len(infix) == 3 and infix[2] == self.current[0]: |
64 self._match(infix[2]) |
67 self._match(infix[2]) |
65 expr = (infix[0], expr, (None)) |
68 expr = (infix[0], expr, (None)) |
66 else: |
69 else: |
67 if not infix[0]: |
70 if not infix[0]: |
68 raise SyntaxError("not an infix") |
71 raise error.ParseError("not an infix: %s" % token, pos) |
69 expr = (infix[0], expr, self._parse(infix[1])) |
72 expr = (infix[0], expr, self._parse(infix[1])) |
70 if len(infix) == 3: |
73 if len(infix) == 3: |
71 self._match(infix[2]) |
74 self._match(infix[2]) |
72 return expr |
75 return expr |
73 def parse(self, message): |
76 def parse(self, message): |