pub fn balance_of(bank: &Bank, account: &BankAccount) -> Option<(Date, Money)>Expand description
A bank account’s balance known, and its day: the newest of its exports’,
whatever name each gave it (BankAccount::exports: its number, its IBAN,
none). Each name is the same account, so their balances are one balance
at different days, never added: an export first read without a number,
later with one, counted the same money twice (review of 5 October 2026).
Two real accounts are two cards.