# JOURNAL — phase parse

## Build notes

Implemented a classic recursive-descent parser.

Grammar (precedence lowest → highest):
```
expr   → term   (('+' | '-') term)*
term   → unary  (('*' | '/') unary)*
unary  → '-' unary | primary
primary→ NUMBER | '(' expr ')'
```

The `while` loops in `_expr` and `_term` produce left-associative trees naturally: each iteration wraps the accumulated left subtree as the new `node`, so 8-3-2 folds as ((8-3)-2).

Unary minus recurses right (`_unary` calls itself) to allow `--5` to parse as `Unary('-', Unary('-', Num(5)))`.

Empty input is caught by checking for EOF before entering `_expr`. Trailing tokens (e.g. `1 2`) are caught by the EOF check after `_expr` returns. Unclosed parens are caught in `_primary` when expecting RPAREN but finding EOF.

36 tests: 3 precision, 3 left-assoc, 3 paren, 4 unary, 5 error, plus 18 from lexer phase.