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unnamed-faq-90
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     To: "Dmitriy Goldobin" <gold@ems.chel.su>
     Subject: Re: FLEX trouble
     In-reply-to: Your message of Mon, 31 May 1999 18:44:49 PDT.
     Date: Tue, 01 Jun 1999 00:15:07 PDT
     From: Vern Paxson <vern>
     
     >   I have a trouble with FLEX. Why rule "/*".*"*/" work properly,=20
     > but rule "/*"(.|\n)*"*/" don't work ?
     
     The second of these will have to scan the entire input stream (because
     "(.|\n)*" matches an arbitrary amount of any text) in order to see if
     it ends with "*/", terminating the comment.  That potentially will overflow
     the input buffer.
     
     >   More complex rule "/*"([^*]|(\*/[^/]))*"*/ give an error
     > 'unrecognized rule'.
     
     You can't use the '/' operator inside parentheses.  It's not clear
     what "(a/b)*" actually means.
     
     >   I now use workaround with state <comment>, but single-rule is
     > better, i think.
     
     Single-rule is nice but will always have the problem of either setting
     restrictions on comments (like not allowing multi-line comments) and/or
     running the risk of consuming the entire input stream, as noted above.
     
     		Vern