On 8/22/2011 11:56 AM, Simon Hoerder wrote:
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Hi,
I'm fairly new to boost libraries but searched the documentation and googled for an answer to my problem but couldn't come up with something. Please bear with me.
I am using boost::regex (version 1.42.0 on debian amd64 machine) to parse a vhdl-like file. To this end, I am trying to use the regular expression boost::regex("^SIGNAL ([A-Z0-9_]*?): STD_LOGIC_VECTOR\( ([0-9]*?) DOWNTO ([0-9]*?)\);$"); to match strings like: SIGNAL W07: STD_LOGIC_VECTOR( 255 DOWNTO 0);
My problem is that matching those parantheses in the string doesn't work - - I've tested the regexp under perl and it works fine but boost::regexp and C++ works only if I remove the brackets from the string and from the regular expression.
' what(): Found a closing ) with no corresponding openening
' what(): Unmatched marking parenthesis ( or \(. The error occured while parsing the regular expression fragment: '[0-9]*?);$>>>HERE>>>'.
Issues I observed& tested: 1) '\(' ... '\)' no match but g++ complains about an unknown escape sequence '\)'. 1a) Using '\(' ... ')' doesn't match. (I would have expected an exception to be thrown but none whatsoever.) 2) '0x28' ... '0x29' doesn't match. (0x28 = ASCII '(', 0x29 = ASCII ')') 3) '\Q(\E' ... '\Q)\E' no match but g++ complains about an unknown escape sequence '\Q'. 4) If I try to match only one of the brackets and remove the other from the string& regex I get one of the following: '\(' ... gives me: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::regex_error> parenthesis. The error occured while parsing the regular expression fragment: '?([0-9]*?)>>>HERE>>>);$'. ... '\)' gives me: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::regex_error> 5) Even boost::regex("^SIGNAL W07: STD_LOGIC_VECTOR\( 255 DOWNTO 0\);$"); fails to match SIGNAL W07: STD_LOGIC_VECTOR( 255 DOWNTO 0);
Points 1a and 4 suggests that boost::regex treats even escaped parantheses as special characters which is quite surprising to me. I am sure a lot of people successfully used boost::regex to match parantheses so I do wonder which part of the documentation I have missed.
I'd be happy to provide more debugging information if you tell me how to produce it.
Many thanks, Simon Hoerder
You need to escape the slash character for normal C++ processing, i.e. double slash. It should be "\\(" and "\\)" to catch a parentheses. -- Bill