> However, no mainstream language has a first-class data type for representing money...

I beg to differ. Java has "Decimal" class which guarantees to be safe from IEEE754 floating number side effects, and specially created to handle cases like money and financial calculations.

In these days it's used as BigDecimal, it seems [1].

[0]: https://docs.oracle.com/javase/8/docs/api/java/text/DecimalF... [1]: https://docs.oracle.com/en/java/javase/23/docs/api/java.base...