luhncalc 1.1.0

Validate digit sequences with the Luhn algorithm and calculate the next check digit.
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# luhncalc

[![crates.io version][1]][2] [![CI][3]][4]
[![downloads][5]][6] [![docs.rs docs][7]][8]

`luhncalc` is a small crate that works both as a command-line utility and as a Rust library for validating digit sequences with the Luhn algorithm and calculating the next check digit.

# Command line usage

Validate the following invalid digit sequence `1234567890`:

```bash
> luhncalc 1234567890

Sequence:       1234567890
Valid sequence: false
Next digit:     3
```

Validate the following valid digit sequence `12345678903`:

```bash
> luhncalc 12345678903

Sequence:       12345678903
Valid sequence: true
Next digit:     1
```

# Library usage

Add the crate to your project:

```toml
[dependencies]
luhncalc = "1"
```

Use one of the public functions from Rust code:

```rust
use luhncalc::{analyze, calculate_check_digit, validate};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    assert_eq!(validate("12345678903")?, true);
    assert_eq!(calculate_check_digit("1234567890")?, '3');

    let analysis = analyze("12345678903")?;
    assert_eq!(analysis.valid, true);
    assert_eq!(analysis.next_check_digit, '1');

    Ok(())
}
```

The library returns an error when the digit sequence is empty or contains anything other than ASCII digits `0-9`.

# License

This project is licensed under either of

- [the Apache License, Version 2.0](./LICENSE-APACHE)
- [the MIT license](./LICENSE-MIT)

at your option.

## Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-20 license, shall be dual licensed as above, without any additional terms or conditions.

[1]: https://img.shields.io/crates/v/luhncalc.svg?style=flat-square
[2]: https://crates.io/crates/luhncalc
[3]: https://img.shields.io/github/actions/workflow/status/Poremski/luhncalc/ci.yml?branch=main&style=flat-square
[4]: https://github.com/Poremski/luhncalc/actions/workflows/ci.yml
[5]: https://img.shields.io/crates/d/luhncalc.svg?style=flat-square
[6]: https://crates.io/crates/luhncalc
[7]: https://img.shields.io/badge/docs-latest-blue.svg?style=flat-square
[8]: https://docs.rs/luhncalc

[releases]: https://github.com/Poremski/luhncalc/releases