Why is "<:" used in the spec?

[Persola]

I believe unist is using "<:" to indicate inheritance, but the WebIDL spec just asks for ":". Am I missing something?

[wooorm]

I believe it was used in the original spidermonkey estree ast, but unfortunately that link just started 404ing: https://developer.mozilla.org/en-US/docs/SpiderMonkey/Parser_API.

[wooorm]

@burdiyan Why are you wondering? If you want to create your own unist based format, you could choose how to write it. E.g., ntast uses TS I believe.

[burdiyan]

@wooorm I'm actually looking into consuming the syntax tree from another language (Go in my case), so I was wondering if there were any language-agnostic tools available, that could help me save some time keeping JS, Go and docs in sync.

[ChristianMurphy]

It depends on what you mean by "consuming".
If you mean sending an AST from one to another, the ASTs are generally JSON, and most languages have a JSON parser/stringifier implementation.
If you mean parsing in different languages, check out https://www.antlr.org
If you mean validation, since ASTs are generally JSON, JSON schema is a fairly portable validation format.

[wooorm]

Also: we do have types for unist/mdast/hast in definitelytyped. If you want the packages, they're published at @types/mdast and such!

[burdiyan]

I'm still trying to figure out all the requirements between interop across languages. This discussion helped to clarify things. Thank you!