# JOURNAL — phase parse

## 2026-06-15 — Initial implementation

### Approach
Recursive-descent parser with three precedence levels:
- `_expr`: handles `+` and `-` (lowest)
- `_term`: handles `*` and `/` (medium)
- `_unary`: handles unary `-` (right-associative by recursion)
- `_primary`: handles `NUMBER` and `(expr)` (highest)

Left associativity falls out naturally from the while-loop pattern in `_expr` and `_term`.

### Test run
```
python -m unittest -q
Ran 31 tests in 0.001s
OK
```

### AST shape verification
```
D1 1+2*3: BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
D2 8-3-2: BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
D2 8/4/2: BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
D3 (1+2)*3: BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
D4 -5: Unary('-', Num(5))
D4 -(1+2): Unary('-', BinOp('+', Num(1), Num(2)))
D4 3*-2: BinOp('*', Num(3), Unary('-', Num(2)))
D5 '1 +': ParseError: unexpected token 'EOF' (None); expected number or '('
D5 '(1': ParseError: expected 'RPAREN' but got 'EOF' (None)
D5 '1 2': ParseError: unexpected token 'NUMBER' (2) after expression
D5 ')(': ParseError: unexpected token 'RPAREN' (')'); expected number or '('
D5 '': ParseError: empty input
```