centslisted

# Cents: money does not belong in float `0.1 + 0.2 == 0.30000000000000004`. A binary float cannot represent most decimal fractions, so every arithmetic step on money loses a sliver. Across a million transactions the slivers add up, the books do not balance, and the bug is invisible until an auditor finds it. The fix is old and boring — use `Decimal`, or store integer minor units (cents) — so this skill is not about the fix. It is about finding **every** place the mistake was made, which by hand means reading every arithmetic line in the codebase and asking "is this money?" ## The trap that makes naive scanning useless `float` is not wrong. It is wrong *for money*. A ratio, a coordinate, a temperature, an interest rate, an ML weight all belong in float. A scanner that flags every float drowns the real bugs in a scientific codebase and gets turned off within a day. So the question is never "is this a float". It is: > **Is this a float that represents money?** `cents` answers it by pairing two signals: a float, and a money name next to it. Same shape as the rest of this plugin — the construct is only a bug in context. ## Step 1: scan ```bash scripts/cents.py billing.py # one file scripts/cents.py --all src/ # a tree scripts/cents.py --json payments.py # for pipelines ``` AST-based, standard library only. It reports each place a float meets a money name, with the line, the name, and the fix. ``` billing.py:6 [arithmetic] (subtotal) subto