Re: Flex: token value more than what regexp matches
On 7 Jul 2005, at 23:53, Frans Englich wrote:
I have the problem that the value of a token appears to be more
than what the
regexp matches.
When parsing the expression "fn:false()", I get a QNAME token with
the value
"fn:false" -- what I expect & want.
However, when parsing the expression "false()", I get the token
NCNAME with
the value "false(". The token is right, but I don't want the
parantese to be
included.
This is frequently asked question: The Flex lexer merely provides a
pointer to the identified text in a buffer, temporarily '0'-
terminated, and in order to preserve that in subsequent lexer calls,
you need to copy it over. The Bison parser does indeed make several
calls to the lexer before the rule action is invoked.
Hans Aberg
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RE: Flex: token value more than what regexp matches
Frans Englich wrote:
> The relevant parts in my Bison is:
>
> %union
> {
> int ival;
> char *sval;
> KDOM::XPath::ExpressionImpl *expr;
> KDOM::XPath::ExpressionImpl::List *expressionList;
> QPSingleType *singleType; KDOM::XPath::SharedQName *qName;
> bool emptyAllowed;
> }
> However, when parsing the expression "false()", I get the
> token NCNAME with
> the value "false(". The token is right, but I don't want the
> parantese to be included.
>
> Why is the parantese included in the value, and how do I fix
> it? The regexp
> "[a-zA-Z-]+" really shouldn't match it, right?
This is really a FAQ.
Flex overwrites the '(' with a null character when it
passes the token to bison.
Your bison rule stores only the pointer to the string.
By the time the bison parser gets around to printing
your token (one token later), flex has restored the
'(' character (and overwritten the ')' character).
To fix, save the contents of the string instead of only
the pointer to it.
Vincent Zweije
Development
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Re: Flex: token value more than what regexp matches
Hans, Vincent, Thanks for your suggestions -- it of course solved my problem. Cheers, Frans ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
