# JOURNAL — phase parse

## 2026-06-15

### Implementation approach

Built a standard recursive-descent parser with two levels of precedence:

```
expr   : term (('+' | '-') term)*       # low precedence, left-assoc
term   : factor (('*' | '/') factor)*   # high precedence, left-assoc
factor : NUMBER
       | '-' factor                      # unary minus (right-recursive)
       | '(' expr ')'
```

The left-associativity is inherent in the `while` loop pattern: each
iteration wraps the current `left` in a new BinOp, so `8-3-2` naturally
produces `BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))`.

Unary minus in `factor` uses right-recursion so `--5` gives
`Unary('-', Unary('-', Num(5)))` and `3 * -2` gives
`BinOp('*', Num(3), Unary('-', Num(2)))` — the unary binds only to
what follows it, not to the whole expression.

### Verification commands run

```
$ python -m unittest -q
Ran 50 tests in 0.001s
OK

$ python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('1+2*3')))"
BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))

$ python -c "from calc.lexer import tokenize; from calc.parser import parse; parse(tokenize('1 +'))"
# ParseError: unexpected token 'EOF' (None)  [raised, not crash]
```

All five mandatory error cases (`1 +`, `(1`, `1 2`, `)(`, `""`) raise
`ParseError` — not `IndexError`, `KeyError`, or any other exception.

### Gate timeline

- feat commit `c78a0d7` — parser + tests + STATUS
- D1 claimed `49beb26`, pushed
- D2 claimed `73f747d`, pushed
- D3 claimed `3c97bfc`, pushed
- D4 claimed `686695b`, pushed
- D5 claimed `66d75f1`, pushed
- D6 claimed `272fbac`, pushed
- Awaiting Adversary verdict