simple_money 0.3.0

Down-to-earth money and currency implementation written in Rust.
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# Brief description
"Down-to-earth" (explained further below) money [^fowler] and currency implementation written in Rust.

See further below for more detailed design considerations.
[^fowler]: Money consists of an amount and a Currency,
as described by Martin Fowler in his [Money EAA Pattern](https://martinfowler.com/eaaCatalog/money.html).


# Usage

```rust
// You create a Currency either with a string code ...
let eur = Currency::new("EUR", 2)?;
// ... or a byte array ...
let kwt = Currency::new_using_bytes(b"KWD", 2)?;
// ... you need a byte array also to create a constant (compiler doesn't allow unwrap) ...
const EUR: Currency = Currency::new_using_bytes_const(b"EUR", 2);

// ... and use either to instantiate Money instances:
let money1 = Money { full_amount_as_minor: 12_95, currency: eur };
let money2 = Money { full_amount_as_minor: 15_99, currency: EUR };
let result =  money1 + money2;
```


# Other implementations

Simple Money has similar implementations in other programming languages.
There's a [_Simple Money_ project page on BitBucket](https://bitbucket.org/afischl/workspace/projects/MONEY), but I haven't published all of them.


# Features and design considerations

Features in common with all implementations: see [Design Considerations](DESIGN.md)


# Comparison to similar libraries
Here are two alternatives I've found:
- [steel-cent](https://crates.io/crates/steel-cent)
  - uses an i64 for the amount, just like this implementation
  - has the same precision as the minor amount allows (no "half Cents")
  - its currency has the `Copy` trait and is as small as mine
  - the ISO currencies are provided, but IntelliJ's Rust plugin fails to see them (works in the terminal though)
- [rusty-money](https://crates.io/crates/rusty-money):
  - uses its own 128 representation for the amount
  - has more precision than available by the minor amount
  - its currency...
    - has lots of fields, ...
    - ... but the ISO currencies are provided ready to use
    - has the `Copy` trait, but is eighty bytes in size
  - is bristling with features (e.g. exchange rates?)