Dinero is a Rust port of Dinero.js (unstable)

List of things to do before v1 release:

• [ ] Determine finite list of features to port from https://v2.dinerojs.com/docs
• [ ] Write all selected functions
• [ ] Test all selected functions
• [ ] Refactor code outside of core/src/lib.rs to make it easier to maintain
• [ ] Add CI (lint, build, coverage, etc...)
• [ ] Write docs for docs.rs
• [ ] Make a doc landing page + ReadMe with more user-friendly guides
• [ ] ???

List of selected functions

• [ ] allocate
• [ ] trim_scale
• [ ] transform_scale
• [ ] normalize_scale
• [ ] add
• [ ] subtract
• [ ] multiply
• [ ] is_zero
• [ ] is_negative
• [ ] is_positive
• [ ] have_same_amount
• [ ] have_same_currency
• [ ] ???

Post release to do:

• [ ] Setup auto-release and contribution guides
• [ ] Setup contrib list
• [ ] Setup issue templates
• [ ] ???

Explore the idea of transforming Currency to a trait.

Current implementation

Today the Dinero struct looks like this:

#[derive(Debug, Clone, Copy, Eq)]
pub struct Dinero {
    pub amount: i128,
    pub currency: Currency, // <-- 
    pub scale: u32,
}

Goals

When doing operations on Dinero we often check if they have the same currency at run-time.

Example:

let a = Dinero::new(1, EUR, None);
let b = Dinero::new(2, USD, None);

let z = add(x,y); // <-- This will return an `UnequalCurrencyError`

Possible implementation

Using Bounds this can be done at compile time.

pub trait Currency {
    const CODE: CountryCode;
    const BASE: u32;
    const EXPONENT: u32;
}

Then maybe the Dinero struct can look something like this?

#[derive(Debug, Clone, Copy)]
pub struct Dinero<Currency> { // <-- Not sure how to reference the currency here?
    pub amount: i128,
    pub scale: u32,
}

// A constructor would look like this?
impl Dinero<dyn Currency> {
    pub fn new(amount: i128, scale: Option<u32>) -> Dinero<dyn Currency> {
        Dinero {
            scale: scale.unwrap_or_else(|| self::Currency::EXPONENT.to_owned()),
            amount,
        }
    }
}


let d = Dinero::<USD>::new(42, Some(2));

I'm still not sure how to make this work synthetically. So any help is more than welcome!