lex rules

"Blake Stone" <brian@NOSPAMibc.com.au>
30 Nov 2000 13:46:27 -0500

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lex rules brian@NOSPAMibc.com.au (Blake Stone) (2000-11-30)
Re: lex rules fjh@cs.mu.OZ.AU (2000-12-01)
Re: lex rules esmond.pitt@bigpond.com (Esmond Pitt) (2000-12-01)
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From: "Blake Stone" <brian@NOSPAMibc.com.au>
Newsgroups: comp.compilers
Date: 30 Nov 2000 13:46:27 -0500
Organization: Customer of Telstra Big Pond Direct
Keywords: lex, question
Posted-Date: 30 Nov 2000 13:46:27 EST

Hi All,

        Sorry if this isn't the right place. Are there any lex/yacc specific

I have some lex code below:

ws [ \t\r\n]+
eq {ws}?"="{ws}?
dq "\""
sq "'"

VersionNum [a-zA-Z0-9_.:]+
EncName [A-Za-z][A-Za-z0-9._]*

VersionInfo {ws}"version"{eq}({dq}|{sq}){VersionNum}({dq}|{sq})
EncodingDecl {ws}"encoding"{eq}({dq}|{sq}){EncName}({dq}|{sq})
StandaloneDecl {ws}"standalone"{eq}({dq}|{sq})("yes"|"no")({dq}|{sq})
XmlDecl "<?xml"{VersionInfo}{EncodingDecl}?{StandaloneDecl}?{ws}?"?>"

{XmlDecl} { return XMLDECL; }

Note that the EncodingDecl and StandaloneDecl should be optional. Yet, when
I have
<?xml version="1.0" ?> as input it does not match {XmlDecl}. If I
remove{EncodingDecl} and {StandaloneDecl} then it works fine (or if I expand
the input to use them). Why is this and how do I fix it?


[I think I've seen bugs before in nested named patterns. -John]

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