Of course!  Lookahead non-gobbling.  A lesson learned.

Thanks mightily,

Bob Schaaf


On Jun 10, 2009, at 12:40 AM, Clifford Heath wrote:

> Robert Schaaf wrote:
>> But the empty string passes!
>
> It's not a general solution, but you can require that *something*
> follows, using &.
>
> rule roman_numeral
> &. ( stuff )
> end
>
> There's no better way to write M{0,3}
>
> Clifford Heath.
>