On 6/15/07, Arkadiy Vertleyb <vertleyb@hotmail.com> wrote:
"Server Levent Yilmaz" <leventyilmaz@gmail.com> wrote
I have a related, simpler question:
Given a tuple (or any other container) with arbitrary elements, is there a way to determine if an element is SPECIAL_TEXT or some other text. For example given, ( a, b, SPECIAL_TEXT, c, d ), can we construct (0, 0, 1, 0, 0)?
If you know all the possibilities in advance, you can do something like:
#define LOOKING_FOR_SPECIAL_TEXT 1 #define LOOKING_FOR_a 0 #define LOOKING_FOR_b 0 #define LOOKING_FOR_c 0 #define LOOKING_FOR_d 0
and then transform the sequence using concatination LOOKING_FOR_ with the current item.
Nope, I don't know in advance. In fact, those (a,b,...) are not really single character text, but rather comma separated formal arguments to a function such as (real *, const char[], etc... ), so concat wouldnt work even if I knew the types a priori. I did somehow come up with this dirty trick, though it doesn't quite cut it: #include <boost/preprocessor/seq/elem.hpp> #define SPECIAL_TYPE ~)(1 #define IS_SPECIAL(x) BOOST_PP_SEQ_ELEM(1, (x)(0)) IS_SPECIAL( real*& ) // would give 0 IS_SPECIAL( SPECIAL_TYPE ) // would give 1 However, the whole question is not quite answered by this: #include <boost/preprocessor/enum.hpp> #include <boost/preprocessor/array/elem.hpp> #include <boost/preprocessor/punctuation/paren.hpp> #define ArgumentList1 (3, (int, real*, char[])) #define ArgumentList2 (4, (int, real*, SPECIAL_TYPE, char[])) #define OP(z,i,arr) IS_SPECIAL( BOOST_PP_ARRAY_ELEM(i,arr) ) ( BOOST_PP_ENUM( 3, OP, ArgumentList1) ) // would give (0,0,0) ( BOOST_PP_ENUM( 4, OP, ArgumentList2) ) // obviously fails with warnings // instead of spitting (0,0,1,0) any ideas? Levent. -- Server Levent Yilmaz Mechanical Engineering University of Pittsburgh