Comment by kazinator | Hacker News Reader

Comment by kazinator | Hacker News Reader

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Paul Graham is not a complete idiot, and you are not disproving his statement "hard to implement properly in a language without turning it into a dialect of Lisp".

If you have to parse anything, it's not a Lisp-like macro, which is always an object arising from a production in the language.

Parsing can be hard, so he is right there too. If we take out some subset of Rust that has a significant syntax, and implement it in macros, that sounds like being up to the elbows in parsing.

You're not up to your elbows if somebody else has already done the work for you. If the input to your macro is a valid production in Rust, then all the parsing work that's incumbent on the macro author is to write

    let ast = parse_macro_input!(input as Foo);

Where foo is some type defined by the `syn` crate and there's one for every production in Rust's grammar. But neither are you limited to those. You can also extend or replace that grammar as you see fit, but in that case the added parsing is on you.

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