Parsing strings to chords

[mainrs]

Hey! I have a simple use-case where I want to parse strings into the correct chords:

D#maj7
C# (implies major)
C#min/m/minor

Can this be done with this crate?

[henryksloan]

Hi! The library provides from_regex functions for most domains, including chords and scales. The general form of the regex is <root> <quality> <number>, where quality and number are optional. That means that C# will work as you indicate. To get D# major 7, you would have to pass D# major seventh or D# maj seventh, as the number must be fully spelled out (though number and quality are case insensitive, and number can be omitted). C# minor can be retrieved by passing C# minor or C# min.

It wouldn't be a huge modification to allow abbreviations. In fact, the regex parses are already case insensitive, and effectively ignore whitespace. One would just have to extend the regexes in number.rs and quality.rs in such a way that accounts for overlaps. For example, the regex for maj(or)?\s*(seventh | 7) should come before seventh | 7 (meaning dominant)`.

[mainrs]

Good to hear that this is indeed possible. I can open a PR if you're fine with regex extensions.

[henryksloan]

I think that would be great, though it'll be up to @ozankasikci's approval. But I think everyone would be in favor of more permissive regexes! If you get a chance, the tests of number and quality regex parsing (test_number.rs and test_quality.rs respectively) could use some more tests, so feel free to add tests relevant to your changes.

[ozankasikci]

@henryksloan thanks for the detailed reply!

This is indeed possible and would be a nice improvement for the regex parser. Feel free to work on that @sirwindfield if you want 👍

[XBagon]

By the way, I'm planning to split up the parsing in the CLI with my structopt rewrite. PitchClass, Mode, etc. are ready independently and put together afterwards, that would make for a more strict, straightforward API, while also not having to rely on regex too heavily. The from_regex functions of Chord and Scale would still be useful for library purposes probably, and I could also add a --regex flag to the CLI.