# JOURNAL — Phase `parse` (Builder)

## 2026-06-15 — Implementation

### Design decisions
- Grammar: `expr → term ((+|-) term)*`, `term → unary ((*|/) unary)*`, `unary → - unary | primary`, `primary → NUMBER | ( expr )`. Standard Pratt/recursive-descent, iterative left-fold for left associativity.
- Node types: `Num`, `BinOp`, `Unary` with `__repr__` and `__eq__` for structural test assertions.
- `ParseError` defined in `parser.py`.

### Test run output
```
$ python -m unittest -q
Ran 44 tests in 0.001s
OK
```

### Cold-verify commands verified locally
```
$ 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 +'))"
calc.parser.ParseError: unexpected token 'EOF' (None)
(exit 1)

$ python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('8-3-2')))"
BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))

$ python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('8/4/2')))"
BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))

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

$ python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('-5')))"
Unary('-', Num(5))

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

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