# STATUS — phase `eval`

## DONE

## Claims

Gates D1–D5 are implemented and verified at commit `b1369091c751655df8925685b6a2187123aeb6ff`.

### D1 — arithmetic

**What:** `evaluate(parse(tokenize(s)))` returns correct integer results for `+`, `-`, `*`, `/` with precedence and parens.

**Verify:**
```bash
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('2+3*4'))))"
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('(2+3)*4'))))"
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('8-3-2'))))"
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('-2+5'))))"
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('2*-3'))))"
```
**Expected:** `14`, `20`, `3`, `3`, `-6`

### D2 — division

**What:** `/` is true division; division by zero raises `EvalError`, not bare `ZeroDivisionError`.

**Verify:**
```bash
python -c "from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(evaluate(parse(tokenize('7/2'))))"
python -c "
from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate, EvalError
try:
    evaluate(parse(tokenize('1/0')))
    print('FAIL: no exception')
except EvalError as e:
    print('PASS: EvalError:', e)
except ZeroDivisionError:
    print('FAIL: bare ZeroDivisionError')
"
```
**Expected:** `3.5` then `PASS: EvalError: division by zero`

### D3 — result type

**What:** Whole-valued results print without `.0`; non-whole print as float. Rule in `evaluator.format_result`.

**Verify:**
```bash
python -c "from calc.evaluator import format_result; from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(repr(format_result(evaluate(parse(tokenize('4/2'))))))"
python -c "from calc.evaluator import format_result; from calc.lexer import tokenize; from calc.parser import parse; from calc.evaluator import evaluate; print(repr(format_result(evaluate(parse(tokenize('7/2'))))))"
```
**Expected:** `'2'` and `'3.5'`

### D4 — CLI

**What:** `python calc.py <expr>` evaluates expression; invalid expressions print to stderr and exit non-zero.

**Verify:**
```bash
python calc.py "2+3*4"    # prints: 14, exit 0
python calc.py "(2+3)*4"  # prints: 20, exit 0
python calc.py "7/2"      # prints: 3.5, exit 0
python calc.py "4/2"      # prints: 2, exit 0
python calc.py "1/0"; echo "exit: $?"   # error on stderr, exit 1
python calc.py "1 +"; echo "exit: $?"   # error on stderr, exit 1
```

### D5 — tests green

**What:** Full unittest suite (lex + parse + eval) passes with 0 failures.

**Verify:**
```bash
python -m unittest -q
```
**Expected:** `Ran 44 tests in ... OK` (0 failures)

## Files

- `calc/evaluator.py` — `EvalError`, `evaluate(node)`, `format_result(value)`
- `calc.py` — CLI entry point
- `calc/test_evaluator.py` — unittest suite covering D1–D5