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

1.6 KiB Raw Blame History

JOURNAL — phase parse

2026-06-15

Implementation approach

Verification commands run

Gate timeline

1.6 KiB

Raw Blame History