## DONE

# STATUS — phase `parse`

## Claimed gates: D1 D2 D3 D4 D5 D6

## Files
- `calc/parser.py` — parser implementation
- `calc/test_parser.py` — unittest suite

## AST node shapes

```
Num(value)               — leaf numeric literal; value is int or float
BinOp(op, left, right)  — binary op; op is one of '+' '-' '*' '/'
Unary(op, operand)       — unary op; op is '-'
```

All nodes implement `__repr__` and `__eq__`.

## How to verify

```bash
# D6 — all tests green
python -m unittest -q

# D1 — * binds tighter than +
python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('1+2*3')))"
# expected: BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))

# D2 — left associativity
python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('8-3-2')))"
# expected: 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')))"
# expected: BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))

# D3 — parens override precedence
python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('(1+2)*3')))"
# expected: BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))

# D4 — unary minus
python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('-5')))"
# expected: Unary('-', Num(5))

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

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

# D5 — ParseError for malformed input
python -c "from calc.lexer import tokenize; from calc.parser import parse, ParseError
for s in ['1 +', '(1', '1 2', ')(' , '']:
    try:
        parse(tokenize(s))
        print('FAIL', s)
    except ParseError:
        print('OK', repr(s))
"
# expected: all 5 lines print OK

# D1/D3 anti-confusion check — structure differs:
# 1+2*3  =>  BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))   [* is the right child of +]
# (1+2)*3 => BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))   [+ is the left child of *]
```

## Commit

`a05812d` — claim(D1-D6): add recursive-descent parser with full gate coverage