# JOURNAL-parse

## Design decisions

- **Grammar**: classic 3-level recursive descent:
  - `expr → term (('+' | '-') term)*` (lowest precedence)
  - `term → unary (('*' | '/') unary)*` (medium)
  - `unary → '-' unary | primary` (right-recursive for stacked unary)
  - `primary → NUMBER | '(' expr ')'`
- Left associativity falls out naturally from the `while` loops in `_expr` and `_term`.
- Unary is right-recursive (`-` `-` 5 → nested Unary) as is conventional.
- Empty input detected early at `parse()` entry before any descent.
- Trailing tokens detected after `_expr()` returns, before EOF check.

## Test count: 31 (20 parser + 11 existing lexer)