41 lines
954 B
Python
41 lines
954 B
Python
from dataclasses import dataclass
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from typing import Any
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class LexError(Exception):
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pass
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@dataclass
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class Token:
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kind: str
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value: Any
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_SINGLE = {'+': 'PLUS', '-': 'MINUS', '*': 'STAR', '/': 'SLASH',
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'(': 'LPAREN', ')': 'RPAREN'}
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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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elif ch.isdigit() or ch == '.':
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j = i
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while j < len(src) and (src[j].isdigit() or src[j] == '.'):
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j += 1
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raw = src[i:j]
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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 = j
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elif ch in _SINGLE:
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tokens.append(Token(_SINGLE[ch], ch))
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i += 1
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else:
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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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