# JOURNAL — eval phase

## Build log

1. Read `calc/parser.py` to understand AST node types: `Num`, `BinOp`, `Unary`.
2. Created `calc/evaluator.py`:
   - `EvalError` exception for API-safe error surface.
   - `evaluate(node)` walks AST recursively.
   - Division uses true division (`/`); div-by-zero raises `EvalError`.
   - Whole-valued float results are returned as `int` (D3 rule).
3. Created `calc/test_evaluator.py`:
   - `TestArithmetic` covers all D1 expressions.
   - `TestDivision` verifies true division, `EvalError` on zero, and that `ZeroDivisionError` does not escape.
   - `TestResultType` checks int/float return types.
   - `TestCLI` uses subprocess to verify D4 (exit codes, stderr output).
4. Created top-level `calc.py` CLI:
   - Accepts one argument, runs the full pipeline.
   - Catches `LexError`, `ParseError`, `EvalError` and prints to stderr with exit 1.
   - No traceback on error.
5. Ran `python -m unittest -q` → 49 tests, 0 failures.
6. Ran all 8 CLI checks from the plan — all match expected output.