There's two problems with currencies: 1. So many languages don't have a native "decimal" type to build off of, so somewhere in the data's lifecycle, a "1.75"

There's two problems with currencies: 1. So many languages don't have a native "decimal" type to build off of, so somewhere in the data's lifecycle, a "1.75" turns into "1.7499999999997". 2. The rules around exchange rates, number of decimals, coding and symbols. The first problem should be solved as a first-class language feature. This will discourage hacks with a "fixed point" type, where you store integer "175 cents" instead of decimal "$1.75"-- inviting huge confusion if the currency ever drops or restructures its minor unit, and supports non-money use cases where floating point inaccuracy is risky. Item 2 makes more sense as a library. You can record that there's a 1000:1 ratio between pre-1998 and current roubles, that the symbol for the Baht will inevitably confuse Bitcoin enthusiasts, and that the Korean won no longer has any decimal places, in dynamic fields.