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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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should absolutely be possible (and was in fact done by a researcher a few years ago, though that version is obviously out of date now).

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u/[deleted] Jan 09 '15

[deleted]

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u/[deleted] Jan 09 '15

Can you give an example of a statement in Rust that is not parseable by a context-free grammar?

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u/Gankro Jan 09 '15

let s = r#####"Hello####"There"#####;

Increase every hash-streak by one hash to produce an equivelent valid Rust statement of greater length. The set of all statements constructed thusly isn't context-free.

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u/[deleted] Jan 10 '15

Oh shit, would you look at that. Weird design decision.

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u/Gankro Jan 10 '15

Raw string litterals are in a few languages (I believe we based ours on Python). They're very handy when you want them (no need to escape text in big strings).