MGrammar - Unordered and optional multi-projections?

Fri, 26 Jun 2009 15:40:41 Z

Given this grammar:

module test
{
    language test
    {
        syntax Main = OneTwo*;
        
        syntax OneTwo
            =  o:One t:Two "\r\n"
            => Result { One => true, Two => true }
            |  Two One "\r\n"
            => Result { One => true, Two => true }
            |  One "\r\n"
            => Result { One => true, Two => false }
            |  Two "\r\n"
            => Result { One => false, Two => true };
                
        token One = "one";
        token Two = "two";
        
        interleave Ignore = " ";
    }
}

How could I refactor the syntax "OneTwo" to have only a single projection? In my real language I have a bunch of other tokens before and after the two optional and unordered items and the | list can be quite extensive and long if I have to enumerate every possible combination. Furthermore if you have a third item ("OneTwoThree" for example) then your | list can get exponentially grow.

Is there a trick to defining unordered and optional items in the middle of a complex syntax?

MGrammar - Unordered and optional multi-projections?

Sat, 27 Jun 2009 13:28:15 Z

Hi. Had the same issue last year. Gio promised to fix it :-)

http://social.msdn.microsoft.com/Forums/en-US/oslo/thread/3d5cb0ce-ac57-47e0-a17c-55e977f2b56b

Giovanni Della-Libera : "Hi! I'm on the dev team for MGrammar and we've been thinking about this scenario, so I'm glad to see a customer hitting it. We'd like to make this easy to indicate in the language. Will let you know once we've made progress here."

MGrammar - Unordered and optional multi-projections?

Sat, 27 Jun 2009 15:53:06 Z

Yup that appears to be the exact same problem.