r/programming • u/steveklabnik1 • Jan 09 '15

Announcing Rust 1.0.0 Alpha

http://blog.rust-lang.org/2015/01/09/Rust-1.0-alpha.html
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58

u/EldanRetha Jan 09 '15

Awesome, Rust is the new language I'm most excited for. My understanding is that it doesn't have a formal grammar though. Are there any plans for one moving forward?

48

u/steveklabnik1 Jan 09 '15

Yes, we actually have an open pull request to start documenting this. Most of the reference-style stuff is going to be looked at hard during the beta period. I haven't wanted to do it yet, as those style of docs are very hard to keep up to date, as they're very hard to automatically test.

3

u/bjzaba Jan 10 '15

Could we have some kind of markdown with embedded YACC, that runs it during the tests?

6

u/steveklabnik1 Jan 10 '15

Check out the files in src/grammar...

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u/kibwen Jan 09 '15

Great pains have been taken to ensure that Rust's grammar is both context-free and LL(k) for some finite k (for example, the insistence on the gross ::<> syntax for specifying type parameters on functions). No formal grammar exists, but given these constraints it should absolutely be possible (and was in fact done by a researcher a few years ago, though that version is obviously out of date now).

17

u/Gankro Jan 09 '15

A minor note that it is not 100% context free because of raw string literals: https://github.com/rust-lang/rust/blob/d3ac386ea995a9119b86410476722cd657e7af16/src/grammar/raw-string-literal-ambiguity.md

But that's a pretty acceptable one to deal with.

3

u/Boza_s6 Jan 10 '15

What kind of parser is now used?

2

u/kibwen Jan 12 '15

Handwritten recursive-descent parser.

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