agent-orchestrator-benchmark/calculators/builder-adversary-lean/run-04/machine-docs/JOURNAL-parse.md

JOURNAL — phase parse

2026-06-15 — Initial implementation

Approach

Recursive-descent parser with three precedence levels:

• _expr: handles + and - (lowest)
• _term: handles * and / (medium)
• _unary: handles unary - (right-associative by recursion)
• _primary: handles NUMBER and (expr) (highest)

Left associativity falls out naturally from the while-loop pattern in _expr and _term.

Test run

python -m unittest -q
Ran 31 tests in 0.001s
OK

AST shape verification

D1 1+2*3: BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
D2 8-3-2: BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
D2 8/4/2: BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
D3 (1+2)*3: BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
D4 -5: Unary('-', Num(5))
D4 -(1+2): Unary('-', BinOp('+', Num(1), Num(2)))
D4 3*-2: BinOp('*', Num(3), Unary('-', Num(2)))
D5 '1 +': ParseError: unexpected token 'EOF' (None); expected number or '('
D5 '(1': ParseError: expected 'RPAREN' but got 'EOF' (None)
D5 '1 2': ParseError: unexpected token 'NUMBER' (2) after expression
D5 ')(': ParseError: unexpected token 'RPAREN' (')'); expected number or '('
D5 '': ParseError: empty input