JOURNAL-eval — Builder

Build log

Approach

AST walker in calc/evaluator.py:

Num → return _coerce(node.value)
Unary('-', ...) → _coerce(-evaluate(operand))
BinOp → evaluate both sides; for /, check right == 0 before dividing; apply _coerce to result

_coerce(value): if isinstance(value, float) and value == int(value) → int(value), else pass-through. This keeps the API return clean (no 2.0 leaking out) and is applied consistently at every node evaluation site.

Test run (local)

python -m unittest -v 2>&1
...
Ran 68 tests in 0.270s
OK

All 68 tests pass:

18 lexer tests (unchanged)
26 parser tests (unchanged)
24 evaluator + CLI tests (new)

CLI spot-check

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)

D3 rule rationale

Python / always returns float. Applying _coerce at every evaluate site means:

4/2 → 2.0 → int(2) = 2
7/2 → 3.5 (not whole → stays float)
2+3 → 5 (int arithmetic → already int, _coerce is a no-op)

This is documented in calc/evaluator.py module docstring.

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