https://github.com/norfairking/really-safe-money

Uncompromisingly safe money library
https://github.com/norfairking/really-safe-money

Last synced: about 2 months ago
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Uncompromisingly safe money library

• Host: GitHub
• URL: https://github.com/norfairking/really-safe-money
• Owner: NorfairKing
• Created: 2022-07-30T15:23:56.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2024-08-15T16:15:54.000Z (4 months ago)
• Last Synced: 2024-08-15T18:19:27.871Z (4 months ago)
• Language: Haskell
• Homepage: https://cs-syd.eu/posts/2022-08-22-how-to-deal-with-money-in-software
• Size: 416 KB
• Stars: 44
• Watchers: 4
• Forks: 2
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml

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README

        
# Really safe money

## Status

Ready to try out!

This is not used in production anywhere yet, and the docs are incomplete, so try it out with the appropriate amount of caution.

## Features

* No partial functions.

* No silently incorrect functions.

* Compile errors for instances that must not exist

* Batteries included, otherwise users will write their own batteries, incorrectly

## Comparison

|  | Really Safe Money | [Safe Money](https://github.com/k0001/safe-money) | [Dollaridoos](https://github.com/qfpl/dollaridoos) | [Plutus values](https://playground.plutus.iohkdev.io/doc/haddock/plutus-ledger-api/html/Plutus-V1-Ledger-Value.html#t:Value) | [Simple Amount](https://hackage.haskell.org/package/simple-amount-0.2.0) | [Safe Decimal](https://hackage.haskell.org/package/safe-decimal-0.2.1.0) | [Money](https://github.com/jpvillaisaza/money) | [Simple Money](https://hackage.haskell.org/package/simple-money) |

|--|--|--|--|--|--|--|--|--|

| Explicitly meant for money                        | ✔️  | ✔️  | ✔️     | ✔️ | ✖️ | ✖️ | ✔️    | ✔️ |

| Cannot create or destroy money through errors     | ✔️  | ✔️  | C     | ✔️ | ✔️ | ✔️ | ✔️    | ✖️ |

| No silent overflow or underflow                   | ✔️  | ✔️  | C     | ✔️ | ✔️ | ✔️ | ✔️    | ✖️ |

| Cannot represent nonsense values of money         | ✔️  | ✔️  | C     | ✔️ | ✖️ | C | ✔️    | ✖️ |

| Computations use constant time and space          | ✔️  | ✖️  | C     | ✖️ | ✖️ | C | ✖️    | ✔️ |

| Cannot represent amounts that are too granular    | ✔️  | ✖️  | C     | ✔️ | ✖️ | C | ✖️    | ✖️ |

| No-floating-point representation                  | ✔️  | ✔️  | C     | ✔️ | ✔️ | ✔️ | ✔️    | ✖️ |

| Fixed-sized representation                        | ✔️  | ✖️  | C     | ✖️ | ✖️ | C | ✖️    | ✔️ |

| Amounts with    type-level currency               | ✔️  | ✔️  | C [1] | ✖️ | ✔️ | ✖️ | ✔️[2] | ✔️ |

| Amounts without type-level currency               | ✔️  | ✖️  | C     | ✔️ | ✖️ | ✔️ | ✖️    | ✖️ |

| A type for positive-only amounts                  | ✔️  | ✖️  | C     | ✖️ | ✖️ | ✔️ | ✔️    | ✖️ |

| A type for positive or negative amounts           | ✔️  | ✔️  | C     | ✔️ | ✔️ | ✔️ | ✖️    | ✔️ |

| No 'Num' instance for amounts                     | ✔️  | ✖️  | ✖️     | ✔️ | ✖️ | ✖️ | ✖️    | ✔️ |

| Type-errors for instances that must not exist     | ✔️  | ✔️  | ✖️     | ✖️ | ✖️ | ✖️ | ✖️    | ✖️ |

| Multi-amounts                                     | ✔️  | ✖️  | ✖️     | ? | ✖️ | ✖️ | ✖️    | ✖️ |

| Multi-accounts                                    | ✔️  | ✖️  | ✖️     | ? | ✖️ | ✖️ | ✖️    | ✖️ |

| Addition                                          | ✔️  | ✔️  | ✔️     | ✖️ | ✔️ | ✔️ | ✔️    | ✔️ |

| Subtraction                                       | ✔️  | ✔️  | ✔️     | ✖️ | ✔️ | ✔️ | ✔️    | ✔️ |

| Negation                                          | ✔️  | ✔️  | ✔️     | ✖️ | ✔️ | ✔️ | ✔️    | ✖️ |

| Integer scalar multiplication                     | ✔️  | ✔️  | ✔️     | ✖️ | ✖️ | ✖️ | ✔️    | ✔️ |

| Distribution                                      | ✔️  | ✖️  | ✖️     | ✖️ | ✔️ | ✖️ | ✖️    | ✖️ |

| Fractional multiplication                         | ✔️  | ✔️  | ✔️     | ✖️ | ✔️ | ✔️ | ✔️    | ✔️ |

| Fractional multiplication with correct accounting | ✔️  | ✖️  | ✖️     | ✖️ | ✖️ | ✖️ | ✖️    | ✖️ |

[1]: Dollaridoos technically supports multiple currencies, but [its `Show` instance](https://github.com/qfpl/dollaridoos/blob/fd0686edad9fee855f4651cb9494a9214f570e6a/src/Data/Money.hs) always uses `$`.

[2]: [Money technically supports multiple currencies, but only the three that it defines](https://github.com/jpvillaisaza/money/blob/fbfac3dbc585749035d46e31ca6c9b4b53c978ef/src/Data/Money.hs#L48-L51).

(I will happily correct any errors in this table if you see I have made any.)

* ✔️: Supported

* C: Possible but you have to write some code yourself. This is not good enough for a money library.

* 🚧: Under development

* ✖️: Not supported

* ?: I don't know.

## License

All rights reserved.

Contact me if you would like to use this library.