I was playing around with the idea of using rebol to convert EBNF to Rebol parse rules. A strange occupation maybe, but I thought it might be useful one day. Anyway, I found a rule in EBNF, as described in XML1.0 - http://www.w3.org/TR/REC-xml.html, for which I believe there is no equivalent in Rebol - and I cannot see how it can be worked around. It is the A - B rule which says "matches any string that matches A but does not match B". I looked into the use of this rule in the xml spec and found that it does not relate simply to characters, so I cannot just do something with "complement". Is there a way, or no? Thanks, Brett.
