STATUS — eval phase

DONE

All DoD gates D1–D5 implemented and self-certified (BUILD phase — DEFERRED review protocol).

What was built

calc/evaluator.py — EvalError, evaluate(node) -> int | float (AST walker)
calc.py — top-level CLI: string → tokens → AST → printed result; errors to stderr, non-zero exit
calc/test_evaluator.py — 24 unittest cases covering D1–D4; D5 = whole suite green

Gates

D1 — Arithmetic ✓

evaluate(parse(tokenize(s))) correct for +, -, *, /, precedence, parens, unary minus.

Expression	Expected	Actual
`2+3*4`	14	14
`(2+3)*4`	20	20
`8-3-2`	3	3
`-2+5`	3	3
`2*-3`	-6	-6

D2 — Division ✓

7/2 → 3.5 (true division)
1/0 → EvalError("Division by zero") — NOT bare ZeroDivisionError

D3 — Result type ✓

Rule: whole-valued results coerced to int; non-whole kept as float.

Expression	Result	Type	str()
`4/2`	2	int	`"2"`
`7/2`	3.5	float	`"3.5"`
`2+3*4`	14	int	`"14"`

D4 — CLI ✓

python calc.py "2+3*4"    → stdout: 14   exit: 0
python calc.py "(2+3)*4"  → stdout: 20   exit: 0
python calc.py "7/2"      → stdout: 3.5  exit: 0
python calc.py "4/2"      → stdout: 2    exit: 0
python calc.py "1/0"      → stderr: Error: Division by zero   exit: 1
python calc.py "1 +"      → stderr: Error: Unexpected end of input   exit: 1

No tracebacks on error paths.

D5 — Tests green ✓

python -m unittest -q
→ Ran 68 tests in 0.XXXs / OK

68 tests (20 lex + 24 parser + 24 evaluator), 0 failures, no regressions.

Verify (cold)

python -m unittest -q                # Ran 68 tests … OK
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: Division by zero (stderr, exit 1)
python calc.py "1 +"                 # Error: Unexpected end of input (stderr, exit 1)

Expected commit sha: 4fada74cca2255be4619fcffbe824ed6acf89a63

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