agent-orchestrator-benchmark/calculators/builder-adversary-lean/run-01/machine-docs/JOURNAL-eval.md

JOURNAL — Phase eval (Builder)

2026-06-15 — Implementation

Built evaluator, CLI, and test suite in one pass.

AST walk in calc/evaluator.py:

• Num: return node.value (int or float as stored by lexer)
• Unary('-'): negate result of recursive evaluate
• BinOp('+'/'-'/'*'): straightforward arithmetic on evaluated children
• BinOp('/'): true division; guard right == 0 → EvalError; if result is float and whole, return int(result) (D3 rule)

D3 result type rule: evaluate() returns int for whole-valued results, float for non-whole. This means 4/2 → int(2) (prints 2), 7/2 → float(3.5) (prints 3.5). Pure integer arithmetic stays int throughout (Python int + int = int).

CLI calc.py: catches LexError, ParseError, EvalError → stderr + exit 1. No traceback exposed.

Test run: 46 tests pass (15 lexer + 20 parser + 11 evaluator). No regressions.

Verified all plan cases:

python calc.py "2+3*4"   → 14
python calc.py "(2+3)*4" → 20
python calc.py "7/2"     → 3.5
python calc.py "4/2"     → 2
python calc.py "1/0"     → error to stderr, exit 1
python calc.py "1 +"     → error to stderr, exit 1