> > I have a question for those of you who are familiar with lex and yacc. > Obviously, if the literal strings "|", "^", etc. are treated as > otherwise uninterpreted tokens, an HL7 v2 message cannot be parsed with > any context free grammar, but if after reading the first 5 characters, > we make them the tokens FIELD_SEP, COMP_SEP, etc., then token stream > can easily be parsed with a CFG. But is it possible to use a tool like > lex (of flex) to implement a scanner for HL7 messages? I can't thtink > of any way of doing this. I know yacc can be used with hand coded > scanners, but scanning the message is already 80% of the work!
To my knowledge, you could do what you are suggesting. Tokenizing in Yacc/Bison is of course, tricky. I assume you are talking about HL7 2.0 since HL7 3.0 is supposed to be a subset of XML (according to what I read). You will probably have to "un-tokenize" in cases where the first 5 characters appear in comments, which is reasonable. Just as a warning of the wierdness you get when you have "flexible" token to character associations. Another possibility would be to use Terence Parr's ANTLR (http://www.antlr.org/) which allows for grammars for the scanner as well as a grammar for the parser. Best Regards, David > > ===== > A practical man is a man who practices the errors of his forefathers. > --Benjamin Disraeli > ==== > Greg Woodhouse > [EMAIL PROTECTED] > [EMAIL PROTECTED] > > > > > > ------------------------------------------------------- > The SF.Net email is sponsored by: Beat the post-holiday blues > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > _______________________________________________ > Hardhats-members mailing list > Hardhats-members@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/hardhats-members > ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Hardhats-members mailing list Hardhats-members@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/hardhats-members
