# JOURNAL — phase lex

## Build session

### Design decisions
- `Token` is a `dataclass` with `kind: str` and `value: Union[int, float, None]`. Operator tokens have `value=None`; `NUMBER` tokens carry their parsed numeric value (int for integers, float when `.` present).
- `LexError` is a plain `Exception` subclass defined in the module.
- Used `re` module with `_NUMBER_RE = re.compile(r'\d+\.?\d*|\.\d+')` to match integers, floats-with-integer-part, and leading-dot floats.
- `_SINGLE` dict maps single chars to token kinds.

### Test run output
```
python -m unittest -q
----------------------------------------------------------------------
Ran 17 tests in 0.000s

OK
```

### Verify command outputs
```
python -c "from calc.lexer import tokenize; print([(t.kind,t.value) for t in tokenize('3.5*(1-2)')])"
[('NUMBER', 3.5), ('STAR', None), ('LPAREN', None), ('NUMBER', 1), ('MINUS', None), ('NUMBER', 2), ('RPAREN', None), ('EOF', None)]

python -c "from calc.lexer import tokenize; tokenize('1 @ 2')"
Traceback (most recent call last):
  ...
calc.lexer.LexError: unexpected character '@' at position 2
```