On 8/4/2010 5:09 PM, Daniel Bradburn wrote:
I'm not sure without seeing exactly what you are trying to do, but perhaps
http://www.boost.org/doc/libs/1_43_0/libs/preprocessor/doc/ref/tuple_rem.htm...
or
http://www.boost.org/doc/libs/1_43_0/libs/preprocessor/doc/ref/tuple_rem_cto...
Could help you.
Except that: 1) I do not know ( or normally care ) how many commas are in the parenthesized value ( ie. size of the tuple ) 2) The value can be passed without any parentheses and therefore not be a tuple. For this second problem I can force the end-user always to put parentheses around the passed value, even if it does not need it to form a single macro value. But 1) would still remain a problem. Of course I could solve 1) by forcing the end-user to also pass the number of commas in the parenthesized value as a separate template parameter, but I think that is too much of a burden for the end-user. I just want the end-user to pass the value as a single macro parameter, and to use the value without the outer parentheses if the value contains commas. But perhaps this is just impossible to do with C++'s macro facilities. The preprocessing library is so great I was hoping it could even solve this problem. In reality I may not need to strip off the parentheses from the value ( which in my particular case forms part of a C++ declaration ), since redundant parentheses almost ( possibly ) never causes a syntax error in C++. It does seems as if the preprocessor library should have the functionality I require since it is able to extract a value from a sequence via BOOST_PP_SEQ_ELEM, and a sequence can be in the simple form of '(value)'. However my tests show that if I pass a non-sequence, such as just 'value' to BOOST_PP_SEQ_ELEM, the compiler gives a warning and the result is bogus.
To: boost-users@lists.boost.org From: eldiener@tropicsoft.com Date: Wed, 4 Aug 2010 16:05:57 -0400 Subject: [Boost-users] [preprocessor] removing parentheses
I have a single macro parameter which allows its passed value to contain commas. Therefore the user of the macro needs parentheses around the parameter if it contains one or more commas ( to does not have to ). When processing this parameter in a macro I would like to remove the outer parentheses if they are there before passing the value on for further processing. Is there a way to do this using some preprocessor library macro ?
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users