Monetary Amount Support

[dselman]

Define how monetary amounts/currencies should be modeled in CML and executed in Ergo. Do we need arbitrary precision math or fixed-point math for example? How many bits?

Existing CTO Model
https://github.com/accordproject/models/blob/master/money.cto

JS Libraries
https://scurker.github.io/currency.js/
https://github.com/MikeMcl/bignumber.js/

Java Libraries
JavaMoney_Specification_1.0-final.pdf
http://javadox.com/javax.money/money-api/1.0/javax/money/MonetaryAmount.html
https://github.com/JavaMoney/jsr354-api/blob/master/src/main/java/javax/money/MonetaryAmount.java

Solidity
ethereum/EIPs#724
https://rangeshsripathi.com/2017/12/13/4-dealing-with-fractions-in-solidity-smart-contract/

[jeromesimeon]

Adding Corda's financial model to the list: https://docs.corda.net/financial-model.html

[jeromesimeon]

Useful info, if we use Double as representation https://stackoverflow.com/questions/732612/whats-the-first-double-that-deviates-from-its-corresponding-long-by-delta

[jeromesimeon]

Another useful bit of info: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER

So, assuming we want to keep a precision on monetary amounts based on cents, in theory we could stick to doubles between -(2^51 - 1) and (2^51 - 1) -- those are already quite large numbers!