55 lines
1.2 KiB
Python
55 lines
1.2 KiB
Python
import re
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_NUMBER_RE = re.compile(r'\d+\.?\d*|\.\d+')
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_SINGLE = {
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'+': 'PLUS',
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'-': 'MINUS',
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'*': 'STAR',
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'/': 'SLASH',
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'(': 'LPAREN',
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')': 'RPAREN',
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}
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class LexError(Exception):
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pass
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class Token:
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__slots__ = ('kind', 'value')
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def __init__(self, kind: str, value):
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self.kind = kind
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self.value = value
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def __repr__(self):
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return f'Token({self.kind}, {self.value!r})'
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def __eq__(self, other):
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return isinstance(other, Token) and self.kind == other.kind and self.value == other.value
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def tokenize(src: str) -> list:
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tokens = []
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i = 0
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while i < len(src):
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ch = src[i]
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if ch in ' \t':
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i += 1
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continue
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if ch in _SINGLE:
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tokens.append(Token(_SINGLE[ch], ch))
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i += 1
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continue
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m = _NUMBER_RE.match(src, i)
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if m:
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raw = m.group()
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value = float(raw) if '.' in raw else int(raw)
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tokens.append(Token('NUMBER', value))
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i = m.end()
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continue
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raise LexError(f"unexpected character {ch!r} at position {i}")
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tokens.append(Token('EOF', None))
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return tokens
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