Repeat generation of macro

Question

I would like to generate the following preprocessor pragmas

#pragma blabla column("0030")
#pragma blabla column("0130")
#pragma blabla column("0230")
...
#pragma blabla column("2330")

the hour changing from 0 to 23

Is that possible with BOOST_PP_LOCAL_LIMITS/ITERATE?

Answer 1

Yeah.

#include <boost/preprocessor/repeat.hpp>
#include <boost/preprocessor/stringize.hpp>
#include <boost/preprocessor/control/if.hpp>
#include <boost/preprocessor/comparison/greater.hpp>

#define blabla(z, n, data)                          \
    _Pragma(BOOST_PP_STRINGIZE(                     \
        blabla column(                              \
            BOOST_PP_STRINGIZE(                     \
                BOOST_PP_CAT(                       \
                    BOOST_PP_CAT(                   \
                        BOOST_PP_IF(                \
                            BOOST_PP_GREATER(n, 9), \
                            ,                       \
                            0                       \
                        ),                          \
                        n                           \
                    ),                              \
                    30                              \
                )                                   \
            )                                       \
        )                                           \
    ))

BOOST_PP_REPEAT(24, blabla, ~)

_Pragma saved us there because there is no way to generate preprocessor directives such as #pragma, however it is very picky about what it accepts. In particular, it doesn't do string concatenation, so _Pragma("some" "thing") does not work, we have to concatenate everything in token-land then stringize as the last step.