How to Implement Syntax Lists?

Question

Hi,

I am, so far, very impressed with the toolset provided by the OSLO project. I had been working with ANTLR to date, and found that OSLO is far simpler to implement - and do hope that this will go to a production release.

Firstly I would like to say that I'm not an expert in language design, so please forgive me if this is a little fundamental. Here goes ...

When implementing lists (such as argument lists), this is the common template which appears to be used ...

syntax  ArgList
        =   a:Argument=> [a]
        |   list:ArgList "," a:Argument => {valuesof(list), a }    
        ;

However, I have started to use this template ...

syntax  ArgList
       = a:Argument b:("," b:Argument=> b)* => {a,valuesof(b)}
       ;

They both return the same AST, but I was wondering if there is any difference "under-the-covers" ?

Your comments are welcome.

Answer 1

The "M" team says that the second version is better because it invokes "valuesof" only once whereas the first version invokes it multiple times. THe second version is what's generally used within the product team's work.

.Kraig