57 lines
1.4 KiB
Python
57 lines
1.4 KiB
Python
from dataclasses import dataclass
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from typing import Union
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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: Union[int, float, None] = None
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def tokenize(src: str) -> list:
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tokens = []
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i = 0
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n = len(src)
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while i < n:
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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 < n and src[j].isdigit():
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j += 1
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if j < n and src[j] == '.':
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j += 1
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while j < n and src[j].isdigit():
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j += 1
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tokens.append(Token('NUMBER', float(src[i:j])))
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else:
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tokens.append(Token('NUMBER', int(src[i:j])))
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i = j
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elif ch == '+':
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tokens.append(Token('PLUS'))
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i += 1
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elif ch == '-':
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tokens.append(Token('MINUS'))
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i += 1
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elif ch == '*':
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tokens.append(Token('STAR'))
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i += 1
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elif ch == '/':
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tokens.append(Token('SLASH'))
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i += 1
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elif ch == '(':
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tokens.append(Token('LPAREN'))
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i += 1
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elif ch == ')':
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tokens.append(Token('RPAREN'))
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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'))
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return tokens
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