[Ometa] matching parameter values as literals

[Mark J. Nelson]

Hi all,

This might be something obvious I'm overlooking, but I wasn't able to 
figure out how to do it:

Is there a way for a rule to take a parameter and match its value 
against the input stream? I know apply(param) will take the parameter 
and match the rule *named* param, but how do I match the actual value of 
param as if it were a literal?

For example, take the following contrived rule schema:
num42toA = 42 -> 'A'
num43toB = 43 -> 'B'

If some function literal(x) existed, one might generalize a higher-order 
rule:
num integer:x char:result = literal(x) -> result

Of course, this particular example could be rewritten in more of a 
generate-and-test style, with a match against integer:y followed by ?(y 
== x), but I'm wondering if there's a way to do it directly. The 
built-in 'token' function looks like it must do this for strings, but 
alas, it's hand-coded in Javascript in parser.js, not in OMeta syntax.

If my literal() function existed, I'd imagine 'token' would be defined as:
token string:t = spaces* literal(t) -> t

Does such a function exist and I'm just missing it? Or am I on the wrong 
track here?

Thanks,
Mark

P.S. - Apart from still working out all the details, and attempting to 
get somewhat proficient at debugging grammars (i.e. more proficient than 
not at all), I'm quite liking OMeta so far.

-- 
Mark J. Nelson | http://www.cc.gatech.edu/~mnelson/
Researcher, Expressive Intelligence Studio, UC Santa Cruz
PhD student, School of Interactive Computing, Georgia Tech