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[Radu Mereuta <headness13 AT gmail.com>]

Hi,

"_" in K is viewed as an anonymous variable, and it can't be renamed.

It is fine to use it in your programs, but not in rules, so you need to separate them.

What you could do, is to split your modules: COMMON -> RUST-SYNTAX, RUST

Put most of the syntax in the common module, and only the stuff that looks like variables in the syntax module. (usually Ids and nullable productions).

Then in your semantics module, you can work with the labeled form.

If you really need to match on such an identifier, you can use the labeled form: #token("_", "Id"). (really not sure about the format here, it changed from version to version).

Radu

On Sat, Jul 28, 2018 at 6:47 PM, <wang_feng_bro AT 163.com> wrote:

Hi all,

I am working on Rust now. In Rust, we have “_” ( like default in C++ ) in match. For instance, 

let x = 1;

match x {

   1 => println!(“one”),

   2 => println!(“two”),

   _ => (),

}

In my implementation, "_ "will be recognized as type of Id in K I think and K will try to evaluate it. However,I already defined a rule:

 rule <k> X:Id => V ...</k> 

        <env>... X |-> L ...</env> 

        <store>... L |-> V ...</store> 

So, “_” can not be evaluated. I tried to defined “_” as a special token, but it didn’t work because many rules use “_”. Anyway, there are always conflicts. 

Any ideas ?

Jerry